CN110174185B

CN110174185B - Spatial scanning dual-wavelength Raman flashing method and device for representing substrate nanowire

Info

Publication number: CN110174185B
Application number: CN201910447409.0A
Authority: CN
Inventors: 张兴; 罗舒婷; 樊傲然; 胡玉东; 王海东
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2019-05-27
Filing date: 2019-05-27
Publication date: 2020-11-17
Anticipated expiration: 2039-05-27
Also published as: CN110174185A

Abstract

The invention discloses a space scanning dual-wavelength Raman flashing method and device for characterizing a substrate nanowire, wherein the method comprises the following steps: fixing continuous heating laser at the center position of the one-dimensional nanowire, heating the sample to a stable state, changing the position of the center of a continuous detection laser spot along the direction of the one-dimensional sample, and obtaining the temperature distribution along the length direction of the sample under the stable state; fixing pulse heating laser at the center of a one-dimensional nanowire, changing the position of the center of a pulse detection laser spot along the direction of a one-dimensional sample, measuring a curve of temperature change along with time in a pulse period, calculating to obtain phases at different positions, and obtaining the distribution of the phases along the spatial direction; and fitting parameters according to the temperature distribution in the steady-state process and the distribution of the phase in the transient process along the space direction to obtain thermophysical parameters. The method can realize the purposes of non-contact, higher measurement precision and higher sensitivity by double beams of non-concurrent lasers, and is simple and easy to realize.

Description

Spatial scanning dual-wavelength Raman flashing method and device for representing substrate nanowire

Technical Field

The invention relates to the technical field of micro-nano scale thermophysical property testing, in particular to a spatial scanning dual-wavelength Raman flashing method and device for characterizing a substrate nanowire.

Background

The nano-wire has wide application prospect in the fields of micro-electronics, thermoelectric conversion, photoelectric conversion and micro-nano sensors, and the application premise is that the thermophysical property of the nano-wire can be accurately represented. In practical applications, the nanowires are rarely in the form of suspensions and are usually placed on a substrate. Due to the existence of the scale effect and the interface, the thermal physical properties of the nano material and the bulk material, the base nano material and the suspension nano material are obviously different, so that the development of a simple and accurate thermal physical property measurement method for the micro-nano field is significant.

At present, there are two kinds of contact and non-contact measurement methods for one-dimensional nanowires. The contact type mainly comprises an electrical measurement method, including a 3 omega method, a direct current method, a suspension micro-device method, a T-shaped method and the like. The thermal physical properties of the platinum gold wire and the carbon nanotube bundle can be measured by using a 3 omega method, and the method is used by researchers for many times, but the method has the defects that the resistance of the wire to be measured and the temperature have a definite linear relation, and the nanowire is easy to damage by applying alternating current to the nanowire. In addition, the method has wide application range and does not depend on the measurement method of the property of the wire to be measured, namely the suspension micro-device method, but the sensor of the method has complex structure and difficult manufacture and the nanowire transfer has higher difficulty. The thermal conductivity of a single carbon nanotube is measured by using a T-shaped method in the related art, but the method is only suitable for suspending the nanowire, and the phenomenon that the sample is difficult to lap also exists. And the contact-type measurement method is difficult to avoid the destructiveness of the sample, and the in-situ characterization is difficult, so that the non-contact method has more advantages compared with the non-contact method.

For a non-contact measurement method, a Raman spectroscopy method is mostly used, and laser in the Raman spectroscopy method has dual functions of local heating and local temperature measurement. On the basis, people combine Raman and electrical measurement methods to develop suspension microdevices, namely a Raman method, a Raman T-shaped method and the like. In addition, the steady-state Raman measurement method is used for electrifying and heating the nanowire to be measured, measuring the temperature rise of the central point of the nanowire to be measured by Raman spectroscopy, and measuring the thermal conductivity of the platinum wire and the graphene carbon fiber. However, this method is performed in a steady state, and cannot measure thermal diffusivity, and still requires energization, and complete non-contact measurement cannot be achieved. On the basis, a Raman flash method is developed, a beam of pulse laser and a beam of continuous laser are used as a heating source and a temperature sensor, the elimination of the laser absorption coefficient is realized, and the thermal diffusivity of the nanowire is directly measured. The method has the disadvantages that the method is influenced by the rising edge of the square wave pulse, the time resolution is difficult to improve, and the measurement precision is not high. Furthermore, in the related art, a dual-wavelength raman flash method is used for measuring the thermal diffusivity of the one-dimensional substrate-containing nano material, but the method depends on accurate measurement of a temperature rise curve, the temperature rise and drop time of the nano material with the extremely small size, such as the carbon nano tube, is extremely short, the temperature rise curve is difficult to accurately measure, and the common-point measurement of two beams of laser cannot realize detection at the position with the highest sensitivity, so that the error is large and the sensitivity is low.

In summary, the existing methods all have certain limitations, and it is difficult to accurately characterize the thermophysical properties of the one-dimensional substrate nanowire, so that an accurate, simple and convenient in-situ measurement method is urgently needed to be developed.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.

Therefore, one objective of the present invention is to provide a spatial scanning dual-wavelength raman flash method for characterizing a substrate nanowire, which can achieve the purposes of non-contact, higher measurement accuracy and higher sensitivity by using a dual-beam non-common point laser, and is simple and easy to implement.

It is another object of the invention to propose a spatially scanning dual wavelength raman flash device featuring a substrate nanowire.

In order to achieve the above object, an embodiment of an aspect of the present invention provides a method for characterizing a spatial scanning dual-wavelength raman flash with a substrate nanowire, including the following steps: a steady state step: fixing heating laser at the center of a one-dimensional nanowire, heating a sample to a stable state, changing the position of the center of a detection laser spot along the direction of the one-dimensional sample, and obtaining the temperature distribution along the length direction of the sample under the stable state, wherein the heating laser and the detection laser both use continuous laser, and the wavelengths of the heating laser and the detection laser are different; transient state step: fixing the heating laser at the center of the one-dimensional nanowire, changing the position of the center of a spot of the detection laser along the direction of the one-dimensional sample, measuring a curve of temperature change along with time in a pulse period at different positions by using pulse lasers with different wavelengths and the same pulse period, and calculating to obtain phases at different positions to obtain the distribution of the phases along the spatial direction; constructing a heat conduction equation set: and fitting parameters according to the temperature distribution of the steady-state step and the distribution of the phase of the transient step along the space direction to obtain thermophysical parameters.

The spatial scanning dual-wavelength Raman flashing method for characterizing the nanowire with the substrate can accurately measure the thermophysical property parameters of the nanowire with the substrate in one dimension, is non-contact measurement, and compared with an electrical measurement method, the method does not need to plate electrodes, has no danger of electric leakage, does not need to contact with a sample, has no damage to the sample, and can measure the thermophysical property of the in-situ characterization one-dimensional nanowire material; compared with the existing non-contact method, namely the dual-wavelength flash Raman method, the temperature distribution on the space dimension can be measured, the temperature distribution is converted into the phase distribution, namely the fitting of the temperature rise curve is converted into the fitting of the space phase, so that the measurement precision and the sensitivity of the thermal diffusivity are greatly improved, and the purposes of non-contact, higher measurement precision and higher sensitivity are realized through the dual-beam non-common point laser, and the method is simple and easy to realize.

In addition, the spatially scanning two-wavelength raman flash method characterizing a substrate nanowire according to the above-described embodiments of the present invention may also have the following additional technical features:

further, in one embodiment of the present invention, the steady state step comprises: calibrating a sample to be detected, changing the temperature of the sample through a constant-temperature heating table, and fitting the characteristic peaks of the sample to be detected at different temperatures to obtain the one-to-one correspondence relationship between the temperature of the sample to be detected and the peak positions of the characteristic peaks; under the action of the heating laser, controlling the temperature T of the sample to be detected to be lower than the environmental temperature₀Rising to steady-state temperature T_stMoving the detection laser to a position x₁Obtaining the position x according to the corresponding relation₁Average steady-state temperature rise of Gaussian integration of position detection laser

Moving the probe laser to position x₂Obtaining the position x according to the corresponding relation₂Average steady-state temperature rise of Gaussian integration of position detection laser

Changing the spatial position of the detection laser to enable the spot center of the detection laser to be gradually far away from the spot center of the heating laser, and obtaining the temperature distribution along the direction of the one-dimensional sample under the stable state

Using the heating laser spotCentral steady state temperature rise

For the steady state temperature distribution

Carrying out normalization processing to obtain a dimensionless steady-state temperature distribution theta_st(x)。

Further, in one embodiment of the present invention, the step of transiently operating the battery includes: fixing the spot center position of the detection laser, and changing the time delay between the heating pulse laser and the detection pulse laser to obtain any position x₀Pulse width t of position detection_pAverage temperature rise over time curve of internal Gaussian integral

Utilizing the maximum temperature rise of the central position of the heating pulse laser facula

The obtained temperature change curve of the sample to be measured along with the time

Normalization processing is carried out to obtain a dimensionless temperature rise curve theta (x)₀T); dimensionless temperature rise curve theta (x) for measurement location₀T) performing phase locking processing to extract the phase difference between the center position of the detected laser spot and the center position of the heated laser spot

Moving the probe laser to position x₁Repeating the above steps to obtain the position x₁At the phase of the sample to be measured

And moving the probe laser to position x₂To obtain the position x₂At the phase of the sample to be measured

Continuously changing the position of the spot center of the detection laser to gradually get away from the spot center of the heating laser to obtain the variation curve of the phase along the direction of the one-dimensional nanowire along with the space position

Further, in an embodiment of the present invention, the sample to be detected is a one-dimensional nanomaterial with a substrate, wherein if the substrate is a non-metallic material, the probing laser simultaneously extracts the temperature rises of the sample and the substrate; if the substrate is a metallic material, the temperature rise of the substrate is ignored.

Further, in one embodiment of the present invention, the wavelength of the probe laser is different from the wavelength of the heating pulse laser, and the intensity of the probe laser irradiated on the surface of the sample is less than 1mW, and the heating pulse laser and the probe pulse laser are both formed by modulation of an electro-optical modulator and a signal generator by continuous laser.

Further, in an embodiment of the present invention, the step of constructing the thermal conductivity equations includes: establishing a heat conduction equation set in a steady state process to obtain a steady state temperature distribution T_st(x) And carrying out Gaussian integral averaging, and normalizing by using the steady-state temperature rise of the center of the heating laser spot to obtain dimensionless steady-state temperature distribution theta_st(x) (ii) a Establishing an unsteady state heat conduction equation set in the transient temperature rise process to obtain the temperature distribution T of the temperature rise section_h(x, t) at a detection pulse width t_pThe internal Gaussian integral is averaged to obtain

Establishing an unsteady state heat conduction equation set in the transient cooling process to obtain the temperature distribution T of the cooling section_c(x, t) at a detection pulse width t_pThe internal Gaussian integral is averaged to obtain

Obtaining said one dimensionPhase distribution of nanowires along length direction

Fitting by using non-dimensionalized steady-state temperature distribution and transient phase distribution to obtain thermal diffusivity alpha, thermal conductivity lambda and contact thermal resistance R_c。

To achieve the above object, another embodiment of the present invention provides a spatially scanning dual-wavelength raman flash device featuring a substrate nanowire, comprising: the steady-state module is used for fixing heating laser at the center position of the one-dimensional nanowire, heating the sample to a steady state, changing the position of the center of a detection laser spot along the direction of the one-dimensional sample, and acquiring temperature distribution along the length direction of the sample in the steady state, wherein the heating laser and the detection laser both use continuous laser, and the wavelengths of the heating laser and the detection laser are different; the transient module is used for fixing the heating laser at the center position of the one-dimensional nanowire, changing the position of the center of a spot of the detection laser along the direction of the one-dimensional sample, measuring a curve of temperature change along with time in a pulse period at different positions by using pulse lasers with different wavelengths and the same pulse period, and calculating to obtain phases at different positions to obtain the distribution of the phases along the spatial direction; and constructing a heat conduction equation set module for fitting parameters according to the temperature distribution of the steady-state module and the distribution of the phase of the transient module along the space direction to obtain thermophysical parameters.

The spatial scanning dual-wavelength Raman flash device for characterizing the nanowire with the substrate can accurately measure the thermophysical property parameters of the nanowire with the substrate in a non-contact manner, and compared with an electrical measurement method, the device does not need to be plated with an electrode, has no electric leakage danger, does not need to be contacted with a sample, has no damage to the sample, and can measure the thermophysical property of the in-situ characterization one-dimensional nanowire material; compared with the existing non-contact method, namely the dual-wavelength flash Raman method, the temperature distribution on the space dimension can be measured, the temperature distribution is converted into the phase distribution, namely the fitting of the temperature rise curve is converted into the fitting of the space phase, so that the measurement precision and the sensitivity of the thermal diffusivity are greatly improved, the two beams of laser non-common point measurement can realize the detection at the position with the highest sensitivity, and then the purposes of non-contact, higher measurement precision and higher sensitivity are realized through the two beams of non-common point laser, and the method is simple and easy to realize.

In addition, the spatially scanning dual wavelength raman flash device featuring a substrate nanowire according to the above-described embodiments of the present invention may also have the following additional technical features:

further, in one embodiment of the present invention, wherein,

the steady-state module is further used for calibrating a sample to be detected, changing the temperature of the sample through the constant-temperature heating table, and fitting the characteristic peaks of the sample to be detected at different temperatures to obtain the one-to-one correspondence relationship between the temperature of the sample to be detected and the peak positions of the characteristic peaks; under the action of the heating laser, controlling the temperature T of the sample to be detected to be lower than the environmental temperature₀Rising to steady-state temperature T_stMoving the detection laser to a position x₁Obtaining the position x according to the corresponding relation₁Average steady-state temperature rise of Gaussian integration of position detection laser

Utilizing the steady-state temperature rise of the center of the heating laser spot

For the steady state temperature distribution

Carrying out normalization processing to obtain a dimensionless steady-state temperature distribution theta_st(x)；

The transient module is further used for fixing the spot center position of the detection laser, changing the time delay between the heating pulse laser and the detection pulse laser, and obtaining any position x₀Pulse width t of position detection_pAverage temperature rise over time curve of internal Gaussian integral

The heat conduction equation set building module is further used for building a heat conduction equation set in a steady state process to obtain a steady state temperature distribution T_st(x) And carrying out Gaussian integral averaging, and normalizing by using the steady-state temperature rise of the center of the heating laser spot to obtain dimensionless steady-state temperature distribution theta_st(x) (ii) a Establishing an unsteady state heat conduction equation set in the transient temperature rise process to obtain the temperature distribution T of the temperature rise section_h(x, t) at a detection pulse width t_pThe internal Gaussian integral is averaged to obtain

Obtaining the phase distribution of the one-dimensional nanowire along the length direction

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a flow chart of a method of characterizing a spatially scanned two-wavelength Raman flash with a substrate nanowire according to one embodiment of the present invention;

FIG. 2 is a schematic flow chart of a characterization method step S100 according to one embodiment of the present invention;

FIG. 3 is a schematic flow chart of a characterization method step S200 according to one embodiment of the present invention;

FIG. 4 is a schematic flow chart of a characterization method step S300 according to one embodiment of the present invention;

FIG. 5 is a schematic view of a structural model of a one-dimensional substrate nanomaterial sample in accordance with an embodiment of the present invention;

FIG. 6 is a schematic diagram of a physical model of a one-dimensional substrate nanomaterial sample in accordance with one embodiment of the present invention;

FIG. 7 is a schematic diagram of the sequence of heating pulses and probe pulses, the variation of the temperature of the heating center and the probe center, according to one embodiment of the present invention;

FIG. 8 is a graph illustrating steady state process temperature distribution and sensitivity for different contact resistances, in accordance with an embodiment of the present invention;

FIG. 9 is a schematic diagram of the spatial phase distribution and sensitivity of the transient process at different contact resistances according to an embodiment of the present invention;

FIG. 10 is a graph illustrating temperature variation during the next pulse period for different contact resistances, in accordance with one embodiment of the present invention;

fig. 11 is a schematic structural diagram of a spatially scanning dual wavelength raman flash device featuring a substrate nanowire in accordance with one embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

The following describes a spatial scanning dual-wavelength raman flash method and apparatus for characterizing a substrate nanowire according to an embodiment of the present invention with reference to the accompanying drawings, and first, a spatial scanning dual-wavelength raman flash method for characterizing a substrate nanowire according to an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a flow chart of a method of characterizing a spatially-scanned two-wavelength Raman flash with a substrate nanowire according to one embodiment of the present invention.

As shown in fig. 1, the spatially scanning two-wavelength raman flash method characterizing a substrate nanowire comprises the steps of:

in step S100, a steady-state step: fixing heating laser at the center of a one-dimensional nanowire, heating a sample to a stable state, changing the position of the center of a detection laser spot along the direction of the one-dimensional sample, and obtaining the temperature distribution along the length direction of the sample under the stable state, wherein the heating laser and the detection laser both use continuous laser, and the wavelengths of the heating laser and the detection laser are different.

It can be understood that, in the embodiment of the invention, the sample to be detected is heated to a stable state by using the continuous heating laser, the central position of the continuous detection laser spot is changed along the length direction of the one-dimensional sample, the spatial temperature distribution of the sample to be detected is obtained by measurement, and the parameter lambada R is obtained by fitting according to the stable spatial temperature distribution_c. Wherein the power of the detection laser is far less than that of the heating laser, and the two laser beams have different wavelengths.

It should be noted that the temperature measurement principle of the raman spectrometer is as follows: the detection laser irradiates on a sample to be detected, a small part of laser generates Raman scattering and is collected by the objective lens, the laser frequency generating the Raman scattering is changed, the laser with the original frequency is filtered by the optical filter and enters the spectrometer analysis system, and the Raman spectrum is obtained. Each substance has a certain Raman characteristic peak, and the peak position shift of the substance characteristic peak has a certain relation with the temperature under different temperatures, so that the temperature of the substance can be obtained by Raman spectroscopy.

The Raman spectrometer has the characteristic of non-contact temperature measurement, cannot damage a sample, has a light spot radius reaching a submicron order, and is suitable for temperature measurement in the micro-nano field. Through improvement, the Raman spectrometer can be provided with two beams of laser, one beam of laser is heated, the other beam of laser is detected, the detection laser can move in three-dimensional space dimension relative to the heating laser, the experiment process is carried out in vacuum, and the vacuum degree of the vacuum environment is ensured to be less than 10^-3Pa, thereby avoiding the influence on the experimental result due to convection.

Further, in one embodiment of the present invention, the steady state step comprises: calibrating a sample to be detected, changing the temperature of the sample through a constant-temperature heating table, and fitting the characteristic peaks of the sample to be detected at different temperatures to obtain the one-to-one correspondence relationship between the temperature of the sample to be detected and the peak positions of the characteristic peaks; under the action of heating laser, controlling the temperature T of the sample to be measured from the environment₀Rising to steady-state temperature T_stMoving the detection laser to position x₁Obtaining the position x according to the corresponding relation₁Average steady-state temperature rise of Gaussian integration of position detection laser

Moving the detection laser to position x₂Obtaining the position x according to the corresponding relation₂Average steady-state temperature rise of Gaussian integration of position detection laser

Changing the spatial position of the detection laser to make the spot center of the detection laser gradually far away from the spot center of the heating laser to obtain the temperature distribution along the direction of the one-dimensional sample under the stable state

Steady temperature rise by heating laser spot center

For steady state temperature distribution

Specifically, as shown in fig. 2, step S100 may specifically include:

s110: and calibrating the temperature of the sample to be detected, and determining the one-to-one corresponding relation between the temperature and the characteristic peak deviation.

Different substances have different characteristic peak shifts, so the sample needs to be calibrated before the formal experiment. And placing the sample on a constant-temperature heating table, vacuumizing the constant-temperature heating table, gradually increasing the temperature of the constant-temperature heating table from the ambient temperature, and determining the upper limit of the temperature according to experimental conditions so as to obtain the one-to-one corresponding determined relationship between the Raman characteristic peaks and the temperature.

S120: and moving the central position of the detection light spot along the length direction of the sample, and measuring the space temperature distribution under the stable state.

Under the action of heating laser, the sample to be measured is heated from the environmental temperature T₀Rising to steady-state temperature T_stMoving the detection laser to position x₁Obtaining x according to the one-to-one correspondence relationship between the temperature and the characteristic peak of the Raman spectrum₁Average steady state temperature rise of one detection laser Gaussian integral at position

Moving the detection laser to position x₂Obtaining x according to the one-to-one correspondence relationship between the temperature and the characteristic peak of the Raman spectrum₂Average steady state temperature rise of one detection laser Gaussian integral at position

The space position of the detection laser is continuously changed to ensure that the spot center of the detection laser is gradually far away from the spot center of the heating laser, thereby obtaining the temperature distribution along the direction of the one-dimensional sample under the stable state

According to the embodiment of the invention, the wavelength of the detection laser and the wavelength of the heating laser are different, so that the detection laser signal is not influenced by the heating laser. In the experiment, the power of the detection laser is generally less than 1mW, and the temperature rise of the sample to be detected can be considered to be caused by the heating laser, so that the detection laser cannot cause the temperature rise of the nano material.

S130: and normalizing the steady-state temperature by using the central temperature of the heating laser spot.

Heating the temperature of the center of the laser spot in a steady state

The maximum temperature is used to adjust the steady-state space temperature distribution

Normalization processing is performed to eliminate the influence of laser absorption rate. The treatment method comprises the following steps:

in step S200, a transient step: fixing heating laser at the center of a one-dimensional nanowire, changing the center position of a detection laser spot along the direction of a one-dimensional sample, using pulse laser for both the heating laser and the detection laser, wherein the wavelengths of the heating laser and the detection laser are different, the pulse periods are the same, measuring the curve of temperature change along with time in one pulse period at different positions, calculating to obtain the phases at different positions, and obtaining the distribution of the phases along the spatial direction.

It is understood that the embodiment of the present invention may use a strong pulse laser to heat the sample, so that the temperature of the sample changes periodically. And (3) detecting the temperature by using weaker pulse laser, and measuring the temperature change curve of the sample to be detected in one pulse period by changing the time delay between two beams of laser. And fitting according to the temperature change curve to obtain the phase of the detection position. And changing the position of the center of the detection laser spot along the length direction of the nanowire to obtain the phase distribution of the sample to be detected on the spatial position.

Specifically, heating laser is fixed at the center position of a one-dimensional nanowire, the center position of a laser spot of detection laser is fixed, pulse laser is used for both the heating laser and the detection laser, the wavelengths of the heating laser and the detection laser are different, and the pulse periods are the same; and adjusting the time delay between the two beams of laser to obtain a curve of the temperature change along with the time of the sample to be detected in one pulse period of the central position of the detection laser spot, and calculating by using a phase formula to obtain the phase difference between the detection position and the heating position. And changing the central position of the detection laser spot along the length direction of the sample to be detected, and repeating the process to obtain the spatial distribution of the phase along the length direction of the sample.

Further, in one embodiment of the present invention, the step of transiently operating the memory further comprises: fixing the central position of the laser spot by dual-wavelength Raman flash method, and changing the time delay between the heating pulse laser and the detection pulse laser to obtain any position x₀Pulse width t of position detection_pAverage temperature rise over time curve of internal Gaussian integral

Maximum temperature rise by using heating pulse laser spot center position

Normalization processing is carried out to obtain a dimensionless temperature rise curve theta (x)₀T), thereby eliminating the influence of the unknown parameter of laser absorptivity on experimental data; dimensionless temperature rise curve theta (x) for measurement location₀T) performing phase locking processing to extract the phase difference between the center position of the detected laser spot and the center position of the heated laser spot

Moving the probe laser to position x₁Repeating the above steps to obtain a position x₁At the phase of the sample to be measured

And moving the probe laser to position x₂To obtain a position x₂At the phase of the sample to be measured

In one embodiment of the invention, the sample to be detected is a one-dimensional substrate nano material, preferably a non-metallic material with good Raman signals, such as a carbon nanotube, a silicon nanowire, a carbon fiber and the like; if the substrate is made of non-metal material, the temperature rise of the sample and the substrate can be extracted simultaneously by the detection laser; if the substrate is made of a metal material, although no Raman signal exists, the thermal diffusivity of the metal material is generally high, so that the temperature rise of the substrate is negligible. Both the heating pulse laser and the probe pulse laser are formed by modulation of a continuous laser by an electro-optical modulator and a signal generator. The wavelength of the detection laser is greater than the wavelength of the heating laser. The intensity of the probing laser irradiated on the upper surface of the sample is less than 1 mW.

It should be noted that the steady-state step of S100 and the transient step of S200 are performed in a vacuum environment, and the vacuum degree of the vacuum environment is less than 10^-3Pa。

Specifically, according to an embodiment of the present invention, referring to fig. 3, step S200 may specifically include:

s210: and heating the sample by using the heating pulse laser to ensure that the temperature of the sample is periodically changed.

In a pulse period t of the heating laser₀Is divided into a temperature rising section t_hAnd a cooling section t_c. Wherein in the temperature rise section, the temperature of the sample to be measured is controlled by the ambient temperature T₀Rising to the maximum temperature T at the end of the temperature rise section_mAt the cooling stage, the temperature of the sample to be measuredTemperature from the maximum temperature T_mDown to ambient temperature T₀。

According to the embodiment of the invention, the temperature control platform can control the environment temperature to be +/-0.1K, and if the temperature control platform with the accuracy higher than or equal to that of the environment temperature is adopted, the measurement accuracy can be further improved.

According to the embodiment of the invention, the electro-optical modulator and the signal generator can convert continuous laser into pulse laser, so that the temperature of the sample to be measured changes periodically, and a transient temperature field is constructed.

S220: and changing the time delay between the detection pulse lasers of the heating pulse lasers, measuring the temperature rise curve of the sample to be detected in one pulse period by using the detection pulse lasers, performing normalization and phase locking treatment, and calculating the phase difference between the detection point and the heating point.

Fixing the probe laser at position x₀At the pulse time t of the detection laser_pAnd internally detecting the sample to be detected to obtain the Raman spectrum of the sample, thereby obtaining the average temperature of Gaussian integration in one pulse time of the detection laser. Varying the time delay t between two lasers_dCan obtain the average temperature of the Gaussian integrals corresponding to different time delay times

Thereby obtaining a position x₀The temperature of the sample to be measured changes with time in a pulse period of the heating laser

In order to eliminate the influence of the unknown parameter of the laser absorption rate on experimental data, the obtained change curve of the temperature of the sample to be detected along with the time is obtained

Normalization is performed in a similar manner to that in steady state. Selecting the highest temperature in a pulse period at the center of the heating laser spot

I.e. the temperature at the centre of the laser spot at the end of the warm-up phase, using this temperature for position x₀The temperature rise curve is normalized,

the spatial position x can be obtained₀The transient temperature rise curve is dimensionless.

Phase difference between center position of detection laser spot and center position of heating laser spot is extracted by phase-locked principle

Will theta (x)₀And t) is respectively multiplied with sin ω t and cos ω t to obtain the phase difference between the detection laser and the heating laser as follows:

wherein, ω is 2 π/(t)_h+t_c) And the frequency of the heating pulse laser is shown, and n is the number of cycles of the temperature change of the sample to be measured.

In actual measurement, the number of time points measured in one pulse period is limited, and integral operation cannot be performed, so that the integral operation needs to be converted into series operation. I.e. using the formula:

wherein, t_iIs the time point measured in one pulse period, omega-2 pi/(t)_h+t_c) The frequency of the heating pulse laser is shown.

The detection pulse laser and the heating pulse laser are obtained by continuous laser through an electro-optical modulator and a signal generator, the wavelengths of the detection pulse laser and the heating pulse laser are different, and the pulse periods are the same. The wavelength of the detection pulse laser is different from that of the heating pulse laser, so that the detection pulse signal is not influenced by the heating pulse laser. In factIn the test, the power of the detection laser is generally less than 1mW, and the temperature rise of the sample to be detected can be considered to be caused by the heating laser, so that the detection laser cannot cause the temperature rise of the nano material. The pulse width of the detection pulse is much smaller than that of the heating pulse, and therefore it can be considered that the detection pulse width t is the detection pulse width_pThe average temperature of the inner gaussian integral is the temperature at time t.

In the embodiment of the present invention, since the raman is used to measure the temperature, it is necessary to ensure that the sample has a good raman signal, and therefore, a non-metallic one-dimensional nanomaterial, such as a silicon nanowire, a carbon nanotube, and a carbon fiber, is generally used. The more pronounced the raman peak position of the material used, the more pronounced the raman shift with respect to temperature, the higher the measurement accuracy.

S230: and changing the central position of the detection laser spot, and measuring temperature rise curves at different positions to obtain the spatial phase distribution along the length direction of the sample to be measured.

Fixing heating laser at the center of one-dimensional nanowire, and moving detection laser to position x₁Repeating the transient process S220 to obtain x₁At the phase of the sample to be measured

Moving the probe laser to position x₂Repeating the transient process S220 to obtain x₂At the phase of the sample to be measured

The position of the spot center of the detection laser is continuously changed to be gradually far away from the spot center of the heating laser, so that a change curve of the phase along the direction of the one-dimensional nanowire along with the space position is obtained

According to the embodiment of the present invention, specific test parameters of raman signal detection are not particularly limited, such as the spot diameter of the detection laser, and those skilled in the art can select the specific material according to the sample and the substrate, and will not be described herein again. To be explainedThat is, the "spot radius" means the attenuation of the laser spot power density to 1/e of the laser center power density²The radius of (d), i.e., the laser spot size.

In step S300, a heat conduction equation set construction step: and fitting parameters according to the temperature distribution of the steady-state step and the distribution of the phase of the transient step along the space direction to obtain thermophysical parameters.

It is understood that the embodiment of the present invention can obtain the parameter CR according to the phase distribution fitting_cWill be λ R_cAnd CR_cAnd (4) obtaining the thermal diffusivity of the sample to be detected by comparing. Knowing the specific volume heat capacity C of the material, the contact thermal resistance R can be obtained_cAnd thermal conductivity λ.

Further, in one embodiment of the present invention, the step of constructing the set of thermal conductivity equations comprises: establishing a heat conduction equation set in a steady state process to obtain a steady state temperature distribution T_st(x) And averaging by Gaussian integral to obtain

Normalization is carried out by utilizing the steady-state temperature rise of the center of the heating laser spot to obtain dimensionless steady-state temperature distribution theta_st(x) (ii) a Establishing an unsteady state heat conduction equation set in the transient temperature rise process to obtain the temperature distribution T of the temperature rise section_h(x, t) at a detection pulse width t_pThe internal Gaussian integral is averaged to obtain

Obtaining the phase distribution of one-dimensional nanowires along the length direction

Fitting by using non-dimensionalized steady-state temperature distribution and transient phase distribution to obtain thermal diffusivity alpha, thermal conductivity lambda and contact heatResistance R_c。

Specifically, as shown in fig. 4, step S300 may specifically include:

s310: and establishing a heat conduction equation set in a steady state process, and solving steady state temperature distribution.

The control equation and boundary conditions for the one-dimensional substrate-containing nanomaterial steady-state process are as follows:

wherein, T_stIs the steady state temperature rise of the sample; t is_s,stIs the steady-state temperature rise of the substrate; lambda is the thermal conductivity of the nanowire to be tested; lambda [ alpha ]_sIs the substrate thermal conductivity; c is specific volumetric heat capacity; r_cIs contact thermal resistance; a is the cross-sectional area of the nanowire; eta is the laser absorption rate of the nanowire; eta_sLaser absorptivity for the substrate; q. q.s₀Heating laser power; d is the nanowire diameter; l is the nanowire length; r is_eTo heat the laser spot radius.

Firstly, solving the steady-state temperature distribution T of the substrate_s,st(x, z), T obtained by the solution_s,stThe heat conduction differential equation of the (x, z) introduced into the nano material can be solved to obtain the steady-state temperature distribution T of the sample to be measured_st(x) In that respect For T_st(x) Performing Gaussian integral averaging according to formula

Can obtain

Wherein x' is the position of the center of the detection laser spot. Steady state temperature rise using heated laser spot center

To pair

Normalization is carried out according to the formula

Obtaining a dimensionless steady-state temperature distribution theta_st(x)。

If the substrate is a non-metal material, the probing laser can measure the temperature rise of the substrate and the sample at the same time. If the substrate is made of a metal material, although no Raman signal exists, the thermal diffusivity of the metal material is generally high, so that the temperature rise of the substrate is negligible.

S320: and establishing an unsteady state heat conduction equation set in the transient temperature rise process, and solving the temperature distribution of the temperature rise section.

According to an embodiment of the invention, the control equation and boundary conditions for the transient temperature rise section are as follows:

wherein, T_hRaising the temperature of the sample in a temperature raising section; t is_s,hThe temperature of the substrate is raised in a temperature raising section; lambda is the thermal conductivity of the nanowire to be tested; lambda [ alpha ]_sIs the substrate thermal conductivity; c is specific volumetric heat capacity; r_cIs contact thermal resistance; a is the cross-sectional area of the nanowire; eta is the laser absorption rate of the nanowire; eta_sLaser absorptivity for the substrate; q. q.s₀Heating laser power; d is the nanowire diameter; l is the nanowire length; r is_eTo heat the laser spot radius.

Firstly, the temperature change T of the temperature rise section of the substrate along with time and space is solved_s,h(x, z, T), T obtained by the solution_s,hThe heat conduction differential equation of the nano material is introduced into (x, z, T), and the temperature distribution T of the temperature rise section of the sample to be measured can be obtained by solving_h(x, t). If the substrate is a non-metal material, the probing laser can measure the temperature rise of the substrate and the sample at the same time. If the substrate is made of a metal material, although no Raman signal exists, the thermal diffusivity of the metal material is generally high, so that the temperature rise of the substrate is negligible.

The temperature T obtained above_h(x, t) at a detection pulse width t_pThe average is obtained by internal Gaussian integration, namely the temperature obtained by the measurement of the detection laser

The expression is as follows:

wherein x' is the heating laser spot center position. Using maximum temperature rise in the center of the heated laser spot

To pair

Carrying out normalization processing to obtain theta_h(x,t)，

Thereby eliminating the effect of laser absorption.

S330: and establishing an unsteady state heat conduction equation set in the transient cooling process, and solving the temperature distribution of the cooling section.

The control equation and boundary conditions for the transient cooling section are as follows:

wherein, T_cThe temperature rise of the sample is carried out in the sample cooling section; t is_s,cRaising the temperature of the substrate in the cooling section; lambda is the thermal conductivity of the nanowire to be tested; lambda [ alpha ]_sIs the substrate thermal conductivity; c is specific volumetric heat capacity; r_cIs contact thermal resistance; a is the cross-sectional area of the nanowire; eta is the laser absorption rate of the nanowire; eta_sLaser absorptivity for the substrate; q. q.s₀Heating laser power; d is the nanowire diameter; l is the nanowire length; r is_eTo heat the laser spot radius.

Firstly, the change T of the temperature of the cooling section of the substrate along with time and space is solved_s,c(x, z, T), T obtained by the solution_s,cThe heat conduction differential equation of the nano material is introduced into (x, z, T), and the temperature distribution T of the cooling section of the sample to be measured can be obtained by solving_c(x, t). If the substrate is a non-metal material, the probing laser can measure the temperature rise of the substrate and the sample at the same time. If the substrate is made of a metal material, although no Raman signal exists, the thermal diffusivity of the metal material is generally high, so that the temperature rise of the substrate is negligible.

The temperature T of the cooling section is measured by the same method as the transient temperature rise process_c(x, t) at a detection pulse width t_pThe average of the internal Gaussian integrals is calculated, then normalization is carried out, and the dimensionless temperature rise curve theta obtained by the detection laser measurement can be obtained_c(x,t)

S340: and calculating the phase distribution of the one-dimensional nanowires along the length direction.

Obtaining the above-obtained dimensionless temperature rise curve theta in the temperature rise and drop process_h(x, t) and θ_c(x, t) performing phase locking processing to obtain phase distribution of different spatial positions

Wherein, ω is 2 π/(t)_h+t_c) And the frequency of the heating pulse laser is shown, and n is the number of cycles of the temperature change of the sample to be measured. Also, since the measured points are discrete points, the continuous integration is converted into a summation of series, i.e.

S350: and fitting by utilizing the steady-state temperature distribution and the transient phase distribution to obtain thermophysical parameters.

Solving the steady state heat conduction equation set, finding that the steady state temperature distribution is lambada R_cAnd eta R_cAs a function of (c). Where λ is the thermal conductivity, R_cEta is the laser absorption rate of the sample. By subjecting the steady state temperature toThe degree is normalized, eliminating the influence of laser absorption rate, so that the dimensionless steady-state temperature distribution is only lambdar_cAs a function of (c). Under a steady state, the temperature of a limited number of space points is obtained through measurement, and fitting is carried out by utilizing a least square method to obtain a parameter lambda R_c。

Solving the transient heat conduction equation set to find that the transient temperature distribution is lambdar_c，ηR_cAnd CR_cAs a function of (c). Normalizing by using the highest point temperature rise of the center of the heating laser spot to eliminate eta R_cThe influence of (c). Parameter lambdar_cObtained in the steady state process, and the parameter CR is obtained by fitting the spatial phase distribution_c(ii) a Wherein C is the specific volumetric heat capacity, R_cIs contact thermal resistance;

will be lambda R_cAnd CR_cObtaining the thermal diffusivity alpha by calculating the ratio;

the specific volumetric heat capacity C of the material is known, according to the parameter CR_cThe contact thermal resistance R can be obtained_c；

Known contact thermal resistance R_cAccording to the parameter λ R_cThe thermal conductivity lambda can be obtained.

In summary, for a one-dimensional substrate nanomaterial sample, the dimensionless temperature distribution of the nanowire is measured in a steady state, and the phase distribution of the nanowire is measured in a transient state, so that the thermophysical property parameters of the sample can be obtained through fitting. Wherein, the heating laser power is far greater than the detection laser, so that the temperature rise of the nanowire can be considered to be caused only by the heating laser; normalizing the temperature may eliminate the effect of unknown laser absorption. The laser is adopted for heating, so that sample damage caused by contact measurement can be avoided; the phase obtained by temperature calculation is used for parameter fitting, so that errors caused by uncertainty of temperature measurement are reduced; by regulating and controlling the delay time between the two beams of laser, the limitation of the rising edge of the pulse laser to the time resolution is avoided, so that the time resolution is improved to 100 ps. Therefore, the one-dimensional nano material with the substrate obtained by the method has higher thermal physical property parameter precision, better accuracy and higher sensitivity.

The invention will now be described with reference to specific examples, which are intended to be illustrative only and not to be limiting in any way.

In this example, the thermophysical parameters of a one-dimensional substrate nanomaterial are determined.

The structural model and the physical model of the one-dimensional substrate nano material are shown in fig. 5 and 6. Firstly, fixing the center of a light spot of a heating laser at the center of a sample, and heating the sample to be detected to a stable state by using a continuous heating laser in accordance with Gaussian distribution. The selection of the heating laser power is determined according to the actual conditions of the sample, and the temperature rise of the sample is generally ensured to be about 50 ℃ to 100 ℃. The continuous detection laser with the power less than 1mW is used for temperature measurement, and the wavelength of the detection laser is greater than that of the heating laser, so that the influence of the heating laser on the detection laser is avoided. And continuously moving the center of the light spot of the detection laser along the length direction of the one-dimensional nanowire, thereby obtaining the steady-state spatial temperature distribution of the one-dimensional nanowire. In a vacuum environment, natural convection is negligible.

And establishing a one-dimensional steady-state heat conduction equation set, wherein the substrate is a bulk material, the sample is a one-dimensional nano material, the characteristic dimension of the sample is far smaller than the dimension of the substrate, the laser power irradiated on the substrate can be considered as the power of heating laser, and the part absorbed by the sample can be ignored. The control equation of the substrate satisfies the two-dimensional cylindrical coordinate heat conduction equation.

Obtaining the steady-state temperature distribution T of the nano wire by solving according to the heat conduction equation_st(x) In that respect From sodiumThe equation of control for the metric line can be found that the steady state temperature distribution is λ R_cAnd eta R_cSo that the steady-state temperature is normalized by the temperature at the center of the heating laser spot to obtain a non-dimensionalized steady-state temperature distribution theta_st(x) The influence of the laser absorptivity of the nanowire is eliminated. Performing least square fitting on the steady-state temperature distribution to obtain a parameter lambda R_c。

The continuous laser is converted into pulse laser by an electro-optical modulator and a signal generator, the wavelengths of the heating pulse laser and the detection pulse laser are different, and the pulse periods are the same. Referring to FIG. 7, a periodically varying temperature field of a nanowire is constructed using a heat pulse laser, and a pulse width t of a probing laser_pMuch smaller than the pulse width of the heating laser. By varying the time delay t between two lasers during a pulse period_dObtained at a pulse width t_pAverage temperature of internal Gaussian integral

Change over time. Moving the central position of the laser spot along the length direction of the nanowire to obtain the pulse widths t of different points in space_pInternal Gaussian integral average temperature

Change over time. Using formulas

Temperature rise curves for different points in space

And (4) normalizing to obtain a dimensionless temperature rise curve theta (x, t). Using formula of phase calculation

A spatial phase distribution is obtained.

Establishing a heat conduction equation set of a transient temperature rising section and a transient temperature falling section as follows:

wherein, T_hRaising the temperature of the sample in a temperature raising section; t is_cRaising the temperature of the sample in the temperature reduction section; t is_s,hThe temperature of the substrate is raised in a temperature raising section; t is_s,cRaising the temperature of the substrate in the cooling section; lambda is the thermal conductivity of the nanowire to be tested; lambda [ alpha ]_sIs the substrate thermal conductivity; c is specific volumetric heat capacity; r_cIs contact thermal resistance; a is the cross-sectional area of the nanowire; eta is the laser absorption rate of the nanowire; eta_sLaser absorptivity for the substrate; q. q.s₀Heating laser power; d is the nanowire diameter; l is the nanowire length; r is_eTo heat the laser spot radius.

The temperature distribution of the transient temperature rising section and the transient temperature falling section is lambda R obtained by solving the equation_c，ηR_cAnd CR_cAs a function of (c). Can eliminate eta R by dimensionless temperature rise curve_cThe influence of the parameters. Lambada R_cCan be obtained by a steady state process, so that the parameter CR can be obtained by fitting the phase distribution of the one-dimensional substrate nano material space by a least square method_c. The parameter lambdar_cAnd CR_cThe thermal diffusivity alpha can be obtained by taking the ratio. The specific volumetric heat capacity C of the material is known, according to the parameter CR_cThe contact thermal resistance R can be obtained_c(ii) a Known contact thermal resistance R_cAccording to the parameter λ R_cThe thermal conductivity lambda can be obtained.

The method selects the silver-based silicon nanowire with the diameter of 20nm and the length of 40 mu m to carry out sensitivity analysis. Silver is a metal material and has high thermal diffusivity, so the temperature rise of the silver substrate in the heating process is negligible. In a steady state, the sample was heated using a 10mW heating laser, and the temperature distribution and sensitivity of the sample in the spatial direction are shown in fig. 8. Thermal contact resistance R _c1 m.K/W, 10 m.K/W and 100 m.K/W are taken respectively, and it can be seen that the temperature decreases more and more slowly with the increase of the contact thermal resistance. Heat conductivity lambda is 14The plus and minus change of 8W/(m.K) is 20%, the average value of the absolute value of the plus and minus change of the steady-state temperature is taken to define the sensitivity, the sensitivity is found to have an extreme value, and the most sensitive point gradually shifts to a position far away from the heating center along with the increase of the thermal resistance.

For the transient process, the heating laser power is 10mW, the temperature change in one pulse period is shown in FIG. 9 under different contact thermal resistances, and the spatial phase distribution is shown in FIG. 10. It can be seen that the phase changes more and more significantly with spatial position as the contact resistance increases. The specific volumetric heat capacity C is 1.6543 multiplied by 10⁶J/(m³K) by 20%, it can be found that the greater the contact resistance, the further from the heating center, the higher the phase sensitivity.

The present invention is not limited to the above embodiments, and the principle of the space scanning dual-wavelength raman flash method for measuring the thermophysical properties of the one-dimensional substrate-containing nanomaterial, which is proposed in the present invention, can be widely applied to the field and other fields related thereto, and can be implemented in various other embodiments. In addition, the model can be degraded into a one-dimensional suspension nanometer material by removing the base term in the heat conduction equation set. Therefore, the design of the invention is within the protection scope of the invention, and the design of the invention can be changed or modified simply by adopting the design idea of the invention.

According to the space scanning dual-wavelength Raman flash method provided by the embodiment of the invention, compared with the existing electrical measurement method, the method does not need to plate electrodes, so that the danger of electric leakage of a sample with a substrate is avoided; the method does not need to be in direct contact with a sample, does not have any damage to the sample, and can represent the thermophysical property of the nanowire in situ; compared with the existing non-contact measurement method, the time resolution and the space resolution of the experimental system used by the method are obviously improved, the limitation of the rising edge of the pulse laser in the traditional method is broken through, and the time resolution is improved to 100 ps; for a nano sample with a smaller scale, the temperature rises and falls very fast in the transient process, and the temperature rise curve is difficult to accurately measure.

Next, a spatial scanning dual-wavelength raman flash apparatus proposed according to an embodiment of the present invention is described with reference to the accompanying drawings.

Fig. 11 is a schematic structural diagram of a spatial scanning dual-wavelength raman flash apparatus according to an embodiment of the present invention.

As shown in fig. 11, the spatial scanning dual wavelength raman flash device 10 includes: a steady state module 100, a transient module 200, and a build thermal conduction equations set module 300.

The steady-state module 100 is configured to fix heating laser at a center of a one-dimensional nanowire, heat a sample to a steady state, change a position of a center of a detection laser spot along a direction of the one-dimensional sample, and obtain temperature distribution along a length direction of the sample in the steady state, where the heating laser and the detection laser both use continuous laser and have different wavelengths; the transient module 200 is configured to fix the heating laser at a center of the one-dimensional nanowire, change a position of a center of a spot of the detection laser along a direction of the one-dimensional sample, use pulse lasers for both the heating laser and the detection laser, and measure curves of temperature change with time in a pulse period at different positions, where the wavelengths of the two are different and the pulse periods are the same, calculate phases at different positions, and obtain distribution of the phases along a spatial direction; the building thermal conductivity equation set module 300 is configured to fit parameters according to the temperature distribution of the steady-state module and the distribution of the phase of the transient module along the spatial direction, so as to obtain thermophysical parameters. The device provided by the embodiment of the invention can realize the purposes of non-contact type, higher measurement precision and higher sensitivity through double laser beams, and is simple and easy to realize.

Further, in one embodiment of the present invention, wherein,

the steady-state module 100 is further used for calibrating a sample to be measured, changing the temperature of the sample through the constant-temperature heating table, and fitting the characteristic peaks of the sample to be measured at different temperatures to obtain the one-to-one correspondence relationship between the temperature of the sample to be measured and the peak positions of the characteristic peaks; under the action of heating laser, controlling the temperature T of the sample to be measured from the environment₀Rising to steady-state temperature T_stMoving the detection laser to position x₁According to the corresponding relationshipTo position x₁Average steady-state temperature rise of Gaussian integration of position detection laser

Steady temperature rise by heating laser spot center

For steady state temperature distribution

Row normalization processing to obtain dimensionless steady-state temperature distribution theta_st(x)；

The transient module 200 is further configured to fix a spot center position of the detection laser, and change a time delay between the heating pulse laser and the detection pulse laser to obtain an arbitrary position x₀Pulse width t of position detection_pAverage temperature rise over time curve of internal Gaussian integral

Maximum temperature rise by using heating pulse laser spot center position

Normalization processing is carried out to obtain a dimensionless temperature rise curve theta (x)₀T); to measureDimensionless temperature rise curve of position theta (x)₀T) performing phase locking processing to extract the phase difference between the center position of the detected laser spot and the center position of the heated laser spot

The module 300 for establishing a heat conduction equation set is further used for establishing a heat conduction equation set in a steady state process to obtain a steady state temperature distribution T_st(x) And averaging by Gaussian integral to obtain

And the steady-state temperature rise of the center of the heating laser spot is utilized to carry out normalization to obtain dimensionless steady-state temperature distribution theta_st(x) (ii) a Establishing an unsteady state heat conduction equation set in the transient temperature rise process to obtain the temperature distribution T of the temperature rise section_h(x, t) at a detection pulse width t_pThe internal Gaussian integral is averaged to obtain

Further, in an embodiment of the present invention, the sample to be detected is a one-dimensional nanomaterial with a substrate, wherein if the substrate is a non-metallic material, the temperature rise of the sample and the substrate is extracted by the detection laser at the same time; if the substrate is a metal material, the temperature rise of the substrate is ignored.

Further, in one embodiment of the present invention, the wavelength of the probe laser is different from the wavelength of the heating pulse laser, and the intensity of the probe laser irradiated on the surface of the sample is less than 1mW, and the heating pulse laser and the probe pulse laser are both formed by modulation of a continuous laser by an electro-optical modulator and a signal generator.

It should be noted that the foregoing explanation on the embodiment of the spatial scanning dual-wavelength raman flash method is also applicable to the spatial scanning dual-wavelength raman flash apparatus of this embodiment, and details are not repeated here.

Compared with the existing electrical measurement method, the spatial scanning dual-wavelength Raman flash device provided by the embodiment of the invention does not need to be plated with an electrode, so that the danger of electric leakage of a sample with a substrate is avoided; the nanowire does not need to be in direct contact with a sample, does not damage the sample, and can represent the thermophysical property of the nanowire in situ; compared with the existing non-contact measurement method, the time resolution and the space resolution of the used experimental system are obviously improved, the limitation of the rising edge of the pulse laser in the traditional method is broken through, and the time resolution is improved to 100 ps; for a nano sample with a smaller scale, the temperature rises and falls very fast in the transient process, the temperature rise curve is difficult to measure accurately, the accurate measurement of the temperature rise curve is converted into the calculation of the phase, the sensitivity is higher, the uncertainty in experimental measurement is reduced, and the thermophysical property of the nano material with the substrate in one dimension can be measured and represented accurately.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims

1. A spatially scanning dual wavelength raman flash method for characterizing a substrate nanowire, comprising the steps of:

a steady state step: fixing heating laser at the center of the one-dimensional nanowire, heating the one-dimensional nanowire sample to a stable state, changing the position of the center of a detection laser spot along the length direction of the sample, and obtaining the temperature distribution along the length direction of the sample under the stable state, wherein the heating laser in the step of the stable state uses continuous heating laser,the detection laser uses continuous detection laser with different wavelengths, wherein the steady-state step comprises the following steps: calibrating a sample to be detected, changing the temperature of the sample through a constant-temperature heating table, and fitting the characteristic peaks of the sample to be detected at different temperatures to obtain the one-to-one correspondence relationship between the temperature of the sample to be detected and the peak positions of the characteristic peaks; under the action of the continuous heating laser, controlling the sample to be detected to be at the ambient temperature T₀Rising to steady-state temperature T_stMoving the continuous detection laser to a position x₁Obtaining the position x according to the corresponding relation₁Average steady-state temperature rise of Gaussian integration of continuous detection laser

Moving the continuous probe laser to position x₂Obtaining the position x according to the corresponding relation₂Average steady-state temperature rise of Gaussian integration of continuous detection laser

Changing the spatial position of the continuous detection laser to make the spot center of the continuous detection laser gradually far away from the spot center of the continuous heating laser to obtain the temperature distribution along the length direction of the sample under the stable state

Utilizing the steady-state temperature rise of the center of the continuously heated laser spot

For the steady state temperature distribution

Transient state step: fixing heating laser at the center of the one-dimensional nanowire, changing the position of the center of a detection laser spot along the length direction of the sample, and adding in the transient stepThe thermal laser uses pulse heating laser, the detection laser uses pulse detection laser, the two have different wavelengths and the same pulse period, at different positions, the curve of temperature change along with time in one pulse period is measured, the phases of different positions are obtained by calculation, and the distribution of the phases along the space direction is obtained, wherein the transient step comprises the following steps: fixing the spot center position of the pulse detection laser, and changing the time delay between the pulse heating laser and the pulse detection laser to obtain any position x₀Pulse width t of position detection_pAverage temperature rise over time curve of internal Gaussian integral

The highest temperature rise of the central position of the laser facula heated by the pulse

Normalization processing is carried out to obtain a dimensionless temperature rise curve theta (x)₀T); for the measurement position x₀Is a dimensionless temperature rise curve theta (x)₀T) performing phase-locking processing to extract the phase difference between the center position of the pulse detection laser spot and the center position of the pulse heating laser spot

Moving the pulsed detection laser to position x₁Repeating the above steps to obtain the position x₁At the phase of the sample to be measured

And moving the pulsed detection laser to position x₂To obtain the position x₂At the phase of the sample to be measured

Continuously changing the position of the spot center of the pulse detection laser to gradually keep away from the spot center of the pulse heating laser to obtain a change curve of the phase along the length direction of the one-dimensional nanowire along the space position

Constructing a heat conduction equation set: fitting by using non-dimensionalized steady-state temperature distribution and transient phase distribution to obtain thermal diffusivity alpha; wherein the steady state temperature distribution is λ R_cAnd eta R_cλ is the thermal conductivity, R_cIs contact thermal resistance, and eta is the laser absorption rate of the sample; elimination of η R by normalization of the steady-state temperature_cIs λ R, the dimensionless steady-state temperature distribution_cThe function of (a) is fitted by using a least square method under a steady state to obtain a parameter lambda R_c(ii) a The transient temperature distribution is λ R_c、ηR_cAnd CR_cC is the specific volumetric heat capacity; normalizing by using the highest point temperature rise of the heating laser spot center to eliminate eta R_cInfluence of, λ R_cHas been obtained by a steady-state process, by fitting the spatial phase distribution to obtain the parameter CR_c(ii) a According to λ R_cAnd CR_cObtaining the thermal diffusivity alpha according to the ratio of the thermal diffusivity values; knowing the specific volumetric heat capacity C, according to the parameter CR_cThe contact thermal resistance R can be obtained_cAnd further according to the parameter lambdar_cThe thermal conductivity λ is obtained.

2. The method of claim 1, wherein if the substrate is a non-metallic material, the probing laser simultaneously extracts the temperature rise of the sample and the substrate; if the substrate is a metallic material, the temperature rise of the substrate is ignored.

3. The method of claim 1, wherein the probing laser is irradiated on the sample surface at an intensity of less than 1mW, and wherein the pulsed laser light and the pulsed probing laser light are both formed by modulation of an electro-optic modulator and a signal generator.

4. A spatially scanning dual wavelength Raman flash device characterizing a nanowire having a substrate, comprising

The steady-state module is used for fixing heating laser at the center of the one-dimensional nanowire, heating the one-dimensional nanowire sample to a steady state, changing the position of the center of a detection laser spot along the length direction of the sample, and obtaining the temperature distribution along the length direction of the sample under the steady state, wherein the heating laser in the steady-state step uses continuous heating laser, the detection laser uses continuous detection laser, and the wavelengths of the heating laser and the detection laser are different, wherein the steady-state module is further used for calibrating the sample to be detected, changing the temperature of the sample through a constant-temperature heating table, fitting the characteristic peaks of the sample to be detected at different temperatures, and obtaining the one-to-one correspondence relationship between the temperature of the sample to be detected and; under the action of the continuous heating laser, controlling the sample to be detected to be at the ambient temperature T₀Rising to steady-state temperature T_stMoving the continuous detection laser to a position x₁Obtaining the position x according to the corresponding relation₁Average steady-state temperature rise of Gaussian integration of continuous detection laser

For the steady state temperature distribution

A transient module, configured to fix the heating laser at the center of the one-dimensional nanowire, change the position of the center of the detection laser spot along the length direction of the sample, where the heating laser in the transient step uses a pulse heating laser, the detection laser uses a pulse detection laser, the two have different wavelengths and the pulse period is the same, measure the curve of temperature change with time in one pulse period at different positions, calculate the phases at different positions, and obtain the distribution of the phases along the space direction, where the transient module is further configured to fix the position of the center of the pulse detection laser spot, change the time delay between the pulse heating laser and the pulse detection laser, and obtain the x-position at any position₀Pulse width t of position detection_pAverage temperature rise over time curve of internal Gaussian integral

Constructing a heat conduction equation set module, and fitting by using non-dimensionalized steady-state temperature distribution and transient phase distribution to obtain thermal diffusivity alpha; wherein the steady state temperature distribution is λ R_cAnd eta R_cλ is the thermal conductivity, R_cIs contact thermal resistance, and eta is the laser absorption rate of the sample; elimination of η R by normalization of the steady-state temperature_cIs λ R, the dimensionless steady-state temperature distribution_cThe function of (a) is fitted by using a least square method under a steady state to obtain a parameter lambda R_c(ii) a The transient temperature distribution is λ R_c、ηR_cAnd CR_cC is the specific volumetric heat capacity; normalizing by using the highest point temperature rise of the heating laser spot center to eliminate eta R_cInfluence of, λ R_cHas been obtained by a steady-state process, by fitting the spatial phase distribution to obtain the parameter CR_c(ii) a According to λ R_cAnd CR_cObtaining the thermal diffusivity alpha according to the ratio of the thermal diffusivity values; knowing the specific volumetric heat capacity C, according to the parameter CR_cThe contact thermal resistance R can be obtained_cAnd further according to the parameter lambdar_cThe thermal conductivity λ is obtained.

5. The apparatus of claim 4, wherein if the substrate is a non-metallic material, the probing laser simultaneously extracts the temperature rise of the sample and the substrate; if the substrate is a metallic material, the temperature rise of the substrate is ignored.

6. The apparatus of claim 4, wherein the probing laser is irradiated on the sample surface at an intensity of less than 1mW, and wherein the pulsed laser light and the pulsed probing laser light are both formed by modulation of an electro-optic modulator and a signal generator.