CN112179972A - PSD (phase-sensitive Detector) method-based polymer material trap parameter characterization device and method - Google Patents
PSD (phase-sensitive Detector) method-based polymer material trap parameter characterization device and method Download PDFInfo
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Abstract
The application discloses a device and a method for representing trap parameters of a polymer material based on a PSD (phase-sensitive Detector) method, which are used for solving the problem that the trap parameters of the polymer material at a specific temperature cannot be accurately represented in the prior art. The device comprises: the excitation light guide-in module is used for guiding in an excitation light source; the excitation light source is used for exciting the trapped charge of the sample to be detected; the direct-current voltage leading-in module is used for leading direct-current voltage into a front electrode of a sample to be detected; the temperature regulation and control module is used for regulating and controlling the temperature of the sample to be detected; the current signal derivation module is used for collecting a current signal formed by detrapping charges of a sample to be detected; the temperature regulation and control module mainly comprises a heating plate, a heating controller, a red copper cold head, a liquid nitrogen bottle, a liquid nitrogen transmission pipe and a circulating pump. The method and the device can realize the large-scale characterization of the trap parameters of the polymer material at a specific temperature, can ensure the accuracy of the characterization of the trap parameters, and can be widely applied to the test and research of the polymer material in a special use environment.
Description
Technical Field
The application relates to the technical field of polymer trap parameter measurement, in particular to a device and a method for representing trap parameters of a polymer material based on a PSD method.
Background
The polymer insulating material has the advantages of excellent electrical insulating property, heat resistance, mechanical property, easy processing and forming, low price, light weight and the like, and is widely applied to the fields of electronics and electricity, nuclear reactors, aerospace and the like. In recent years, researches show that the polymer material inevitably introduces impurities such as additives and intrinsic defects of the material in the production and manufacturing process, and local states with energy levels in forbidden bands are formed in the polymer material, so that defect points allowing carriers to stay appear in the material, and conditions are provided for the accumulation of space charges. The action of space charge in polymer such as trap, trap and migration can induce local electric field concentration, thereby leading to the aging of polymer material and even breakdown (volume penetration and surface flashover), and seriously threatening the safety of polymer insulation material. The existence of traps in the polymer directly influences the actions of space charge trapping, detrapping, migration and the like. Therefore, the trap parameters for accurately characterizing the polymer material have important guiding values for material selection, new material development and material insulation performance evaluation.
Photo-stimulated discharge (PSD) is a commonly used method for measuring trap parameters in polymer insulation materials. However, the existing PSD method is only characterized under room temperature, and is affected by the ambient temperature during the actual use of the polymer material, thereby affecting the change of trap parameters of the polymer material. Therefore, only the trap parameter of the polymer material under the room temperature environment is researched, the trap parameter of the polymer material under the specific temperature cannot be accurately characterized, and the actual use condition of the polymer material cannot be truly reflected.
Disclosure of Invention
The embodiment of the application provides a device and a method for representing trap parameters of a polymer material based on a PSD (phase-sensitive Detector) method, which are used for solving the technical problems that the prior art cannot accurately represent the trap parameters of the polymer material at a specific temperature and cannot truly reflect the actual use condition of the polymer material.
In one aspect, an embodiment of the present application provides a PSD-based polymer material trap parameter characterization apparatus, where the apparatus includes: the excitation light guide-in module is used for guiding in an excitation light source; the excitation light source is used for exciting the trapped charge of the sample to be detected; the direct-current voltage leading-in module is used for leading direct-current voltage into a front electrode of a sample to be detected; the temperature regulation and control module is used for regulating and controlling the temperature of the sample to be detected; the current signal derivation module is used for collecting a current signal formed by detrapping charges of a sample to be detected; the temperature regulation and control module mainly comprises a heating plate, a heating controller, a red copper cold head, a liquid nitrogen bottle, a liquid nitrogen transmission pipe and a circulating pump.
According to the polymer material trap parameter characterization device based on the PSD method, the excitation light source and the direct-current voltage are introduced into the sample to be tested through the excitation light introduction module and the direct-current voltage introduction module, and the sample to be tested is excited to generate an excitation current signal, so that the effects of high test precision, short test period, wide measurable energy level range, simplicity and easiness in implementation of the device and the like can be achieved on the premise of not damaging the sample to be tested; in addition, the temperature of the sample to be tested is regulated and controlled by the temperature regulation and control module, the temperature range of the sample to be tested can be tested at minus 180-300 ℃ by the liquid nitrogen bottle and the heating plate, almost all the use temperature range of the polymer material is covered, and the use condition of the polymer material can be really represented; and the trap parameters of the polymer material at a specific temperature can be accurately characterized, and the method can be widely applied to the testing and researching processes of the polymer material in a special use environment.
In one implementation of the present application, the device further comprises an electrode structure unit; the electrode structure unit comprises an annular metal front electrode and a metal flat plate rear electrode; the annular metal front electrode is used for contacting with a front electrode of a sample to be detected so as to introduce direct-current voltage; the metal plate back electrode is used for contacting with the back electrode of the sample to be measured so as to collect current signals.
In one implementation manner of the present application, the apparatus further includes: the light energy meter is used for testing the energy of the excitation light source; the air chamber is closed, adopts a stainless steel metal cavity and is used for providing a vacuum environment for a sample to be detected and shielding noise; a plurality of preset flanges are arranged on the stainless steel metal cavity.
The characterization device provided by the embodiment of the application places the sample to be tested in a closed cavity, realizes characterization under a high vacuum atmosphere, avoids interference of charges generated by air ionization caused by an excitation light source on a test result, and can simulate vacuum operation conditions of polymer materials due to the fact that certain polymer materials are used under the vacuum environment.
In one implementation of the present application, the excitation light introduction module mainly includes a wavelength tunable laser, a beam expander, a beam splitter, a fiber laser input end, an optical fiber, and a fiber laser output end; the fiber laser output end leads in an excitation light source through a preset flange on the stainless steel cavity; the direct-current voltage leading-in module mainly comprises a direct-current high-voltage source, a protection resistor, a grading ring and a lead; the current signal derivation module mainly comprises an electrometer.
In one implementation mode of the application, the output wavelength range of the wavelength tunable laser is 210-2600 nm, the lowest output energy is 1.4mJ, and the luminous flux density is 1024cm-2s-1The magnitude, the precision is +/-0.25 nm, and the pulse width is 2-5 ns.
In the characterization device provided by the embodiment of the application, the excitation light source is realized by adopting a wavelength tunable laser based on an optical parametric oscillator, the output wavelength range of the laser is 210-2600 nm, and the lowest output energy is 1.4 mJ. Therefore, compared with the traditional xenon lamp and monochromator as an excitation light source, the laser adopted by the characterization device in the embodiment of the application has the advantages of good monochromaticity, wide wavelength range, full excitation and the like. Moreover, the PSD method characterization device based on the laser has the advantages of wide measurable energy level range (0.48-5.9 eV), high precision, large signal-to-noise ratio and the like.
In one implementation manner of the application, the temperature regulation and control module is used for regulating and controlling the temperature of a sample to be detected to-180-300 ℃.
On the other hand, the embodiment of the present application further provides a PSD-based polymer material trap parameter characterization method, which is implemented by using the PSD-based polymer material trap parameter characterization device, and the method includes: determining the test temperature of a sample to be tested and the vacuum degree of the closed air chamber; when the test temperature and the vacuum degree reach a first preset threshold value, a direct-current high-voltage power supply is switched on to introduce direct-current voltage into a sample to be tested; disconnecting the direct-current high-voltage power supply and connecting the electrometer to remove free charges on the surface of the sample to be measured; when the current value displayed by the electrometer reaches a second preset threshold value, switching on the wavelength tunable laser and the light energy meter, and carrying out light scanning on the sample to be detected through the excitation light source based on preset scanning parameters; the preset scanning parameters mainly comprise at least one of the following items: scanning wavelength range, scanning step length and scanning time; and determining the trap parameter of the polymer material at the test temperature according to the current value displayed by the electrometer, the light energy value displayed by the light energy meter and the preset scanning parameter.
The method for characterizing the trap parameters of the polymer material based on the PSD method has the advantages of high test precision, short test period, no damage to a sample to be tested and the like of the PSD method; meanwhile, in the process of testing a sample to be tested when the preset temperature is reached, the influence of the actual use temperature of the polymer material on the trap energy level is comprehensively considered, the accurate characterization of the trap parameter of the polymer material at the specific temperature is realized, and the method has typical engineering actual guidance significance.
In one implementation of the present application, the method further comprises: determining a test sample, and cutting the test sample; electroplating a front electrode and a rear electrode on the cut test sample to obtain a sample to be tested; and placing the sample to be tested on the electrode structure unit so that the rear electrode of the sample to be tested is in contact with the metal flat plate rear electrode of the electrode structure unit, and simultaneously compacting the annular metal front electrode of the electrode structure unit.
In an implementation manner of the present application, determining a trap parameter of a polymer material at a test temperature according to a current value displayed by an electrometer, light energy data displayed by a light energy meter, and a preset scanning parameter specifically includes: determining the scanning wavelength of the excitation light source, and determining a current value and an optical energy value corresponding to the scanning wavelength; determining the relation between the scanning wavelength of the excitation light source and the trap energy level depth through E ═ h × c/lambda; wherein E represents the trap level depth; h is the Planck constant; c is the speed of light; λ represents a wavelength of the excitation light source; determining a corresponding relation between the trap energy level depth and the trap energy level density based on an energy normalization algorithm; and determining the trap parameters of the polymer material at the test temperature through the corresponding relation.
In one implementation of the present application, the scanning wavelength range is 2600-210 nm; the scanning step length is 2 nm; the scanning time was 2 s.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
fig. 1 is a schematic overall structure diagram of a PSD-based polymer material trap parameter characterization device according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a polarization and electrode structure unit of a sample to be tested according to an embodiment of the present disclosure;
fig. 3 is a timing diagram of a process for characterizing trap parameters of a polymer material based on a PSD method according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In recent years, researches show that the polymer material inevitably introduces impurities such as additives and intrinsic defects of the material in the production and manufacturing process, and local states with energy levels in forbidden bands are formed in the polymer material, so that defect points allowing carriers to stay appear in the material, and conditions are provided for the accumulation of space charges. The action of space charge in polymer such as trap, trap and migration can induce local electric field concentration, thereby leading to the aging of polymer material and even breakdown (volume penetration and surface flashover), and seriously threatening the safety of polymer insulation material. The existence of traps in the polymer directly influences the actions of space charge trapping, detrapping, migration and the like. Therefore, the accurate characterization of trap parameters in the polymer has important guiding values for material selection, new material development and material insulation performance evaluation.
The existing method for measuring trap parameters in the polymer insulating material mainly comprises an isothermal surface potential attenuation method (ISPD), a thermal stimulation current method (TSC), a light stimulation discharge method (PSD) and the like. The TSC method is one of basic methods for researching macroscopic rules and microscopic properties of electrets. The measuring system is simple and convenient to operate, and is widely applied to the research of charge traps of dielectrics and even the research of charge storage and attenuation processes in semiconductors and photoconductors. However, the heating process not only thermally excites the charges in the traps, but also thermally erodes the traps themselves, causing changes in the traps and the central environment, which inevitably results in changes in trap parameters. Furthermore, the trap levels characterized using this method are all below 1.5eV, subject to the lower melting point of the polymer, which is clearly contrary to the excellent insulating properties of the polymer. The PSD method characterizes trap parameters by means of optical excitation. Compared with the TSD method, the sample can be always kept at a low temperature value which is set arbitrarily in the PSD experiment process, so that the trap information of the sample can be accurately acquired on the premise of keeping the original physical characteristics of the material structure or the trap structure. Secondly, the PSD method can accurately detect deep traps up to 6eV in depth since the method is not affected by the low melting point of the polymer.
However, the existing PSD methods have been characterized only at room temperature. However, in practical application, the polymer material is affected by the temperature of the application environment, and the thermal relaxation causes the formation or release of kinks on the polymer molecular chains and the molecular motion of the main chain and the side groups, thereby affecting the change of the trap parameters of the polymer, and the change of the trap parameters can obviously change the electrical properties of the polymer material. For example, the temperature difference between spacecrafts running to the light-facing side and the backlight side is great, and the electrical properties of polymer insulating materials show great difference.
Therefore, only studying the trap parameters of the polymer material in the room temperature environment does not truly reflect the actual use condition of the polymer material. Therefore, the PSD method capable of accurately representing the trap parameters of the polymer material at the specific temperature has important theoretical significance and engineering value.
The embodiment of the application provides a device and a method for representing trap parameters of a polymer material based on a PSD (phase-sensitive Detector) method, which utilize a wavelength tunable laser as an excitation light source and realize the representation of the trap parameters of the polymer material by combining a temperature control unit so as to solve the technical problem that the trap parameters of the polymer material at a specific temperature cannot be accurately represented in the prior art.
The technical solutions proposed in the embodiments of the present application are described in detail below with reference to the accompanying drawings.
Fig. 1 is a schematic view of an overall structure of a PSD-based polymer material trap parameter characterization device according to an embodiment of the present application. As shown in fig. 1, the trap parameter characterization device includes an excitation light introducing module composed of a wavelength tunable laser 1, a beam expander 2, a spectroscope 3, a fiber laser input end 5, an optical fiber 6, and a fiber laser output end 7, and an excitation light source for introducing trapped charges that excite a sample to be measured 13.
In one embodiment of the present application, the wavelength tunable laser 1 is a NT423B laser from EKSPLA, with an output wavelength range of 210-2600 nm, a minimum output energy of 1.4mJ, and a light flux density of 1024cm-2s-1The magnitude is 2-5 ns in pulse width.
As shown in fig. 1, the characterization device further includes a dc voltage introducing module composed of a dc high voltage source 8, a protection resistor 10, a grading ring 9, and a connection wire 11, and configured to introduce a dc voltage applied to a front electrode of a sample 13 to be measured; the device also comprises a current signal derivation module formed by an electrometer 19 and used for collecting a current signal formed by the trapped charges under the excitation light source in an external circuit.
In one embodiment of the present application, electrometer 19 is a Keithley model 6517A electrometer.
As shown in fig. 1, the trap parameter characterization device further includes a temperature control unit for controlling the temperature of the sample 13 to be measured. Specifically, the temperature regulation and control unit comprises a heating plate 15, a heating controller 20, a red copper cold head 16, a liquid nitrogen bottle 21, a liquid nitrogen transmission pipe 22 and a circulating pump 23; through the structure, the temperature of the sample 13 to be detected in the embodiment of the application can be regulated to-180-300 ℃.
Further, the trap parameter characterization device provided by the embodiment of the present application further includes an optical energy meter 4, which is used for testing the energy of the excitation light source at each output wavelength. The device also comprises a closed air chamber 17 which is used for providing a vacuum environment for the sample to be detected and shielding noise. The airtight air chamber 17 in the embodiment of the application is realized by adopting a stainless steel metal cavity, and the vacuum degree of the airtight air chamber can reach 10-6And (6) PA. As shown in fig. 1, the cavity has a spherical structure, and a plurality of preset flanges are arranged on the cavity for guiding in and out modules or units.
In one embodiment of the present application, the optical energy meter 4 is a model 1918C optical energy meter manufactured by NEWPORT corporation.
Further, the characterization device provided by the embodiment of the present application further includes a vacuum regulation and control unit 24, which is used for providing a vacuum environment for the sample 13 to be tested. The device mainly comprises a mechanical pump, a molecular pump and an ion pump for vacuumizing, and the pumping state of the device is controlled by an electric gate valve 25.
Further, the characterization device provided by the embodiment of the present application further includes an electrode structure unit, and the electrode structure unit includes an annular metal front electrode 12, a metal flat plate rear electrode 14; when the characterization device is used for characterizing trap parameters, a sample 13 to be tested is placed on the electrode structure unit, a rear electrode of the sample 13 to be tested is in contact with a metal flat plate rear electrode 14, and a front electrode of the sample 13 to be tested is in contact with a front electrode 12 of the sample 13 to be tested in an annular shape, so that direct current voltage is introduced or a current signal generated by excitation is led out. The specific structure of the electrode structural unit is shown in fig. 2.
Fig. 2 is a schematic diagram of a polarization and electrode structure unit of a sample to be tested according to an embodiment of the present disclosure. As shown in FIG. 2, when the sample 13 to be measured is subjected to trap parameter measurement, the sample is installed on the electrode structure unit, the front electrode 13-1 thereof is in contact with the annular metal front electrode 12 of the electrode structure unit, and the rear electrode 13-2 thereof is in contact with the metal flat plate rear electrode 14 of the electrode structure power supply. So that during the polarization of the sample 13 to be measured, a direct voltage is applied via the front electrode 12 of the electrode structure unit and a current signal formed by an external circuit is applied via the rear electrode 14 of the electrode structure unit.
Based on the same inventive concept, the embodiment of the present application further provides a method for characterizing parameters of a polymer material trap based on a PSD method, where the method is implemented by using the device for characterizing parameters of a polymer material trap based on a PSD method provided in the above embodiment, and a specific test and characterization process sequence is shown in fig. 3.
Fig. 3 is a timing diagram of a process for characterizing trap parameters of a polymer material based on a PSD method according to an embodiment of the present application. As shown in fig. 3, the PSD-based polymer material trap parameter characterization method provided in this embodiment of the present application includes 5 processes a to E, which respectively correspond to different implementation steps in the trap parameter characterization method, and specifically includes the following steps:
In one embodiment of the present application, before placing the sample to be tested 13 on the electrode structure unit, the method further comprises: a test sample is determined and cut into a wafer corresponding to the size of the electrode. Then, after wiping with alcohol, a translucent front electrode 13-1 and a conductive rear electrode 13-2 are plated on both sides of the test sample to obtain a sample 13 to be tested.
In one embodiment of the present application, the transparent front electrode 13-1 of the sample 13 to be measured is a gold or aluminum electrode with a diameter of 2-6 cm and a thickness of 20-60 nm.
Further, the sample 13 to be measured is placed in a vacuum oven at a specific temperature, and after a preset time, the residual charge carried on the sample 13 to be measured is removed. It is taken out and placed on an electrode structure unit.
In one embodiment of the present application, the temperature of the vacuum oven is set to 50 to 120 ℃ and the predetermined time is set to 5 to 24 hours, which corresponds to the process a in fig. 3.
In the process A shown in FIG. 3, the working state of the DC high voltage source, the working state of the laser, the working state of the electrometer and the scanning current signal ISAll the high-voltage DC source, the laser and the electrometer are in a low-level state, namely that the high-voltage DC source, the laser and the electrometer do not work in the process, and the scanning current I does not exist in the processS. In addition, the temperature T of the sample to be measured is subjected to a heating process from room temperature, and the temperature is increased until the temperature reaches a preset temperature value, and then a process B is carried out.
To this end, the sample to be tested 13 is ready to be completed, the installation process thereof in the characterization device is completed, and the setting process of the test temperature and the vacuum degree is completed.
And 2, after the temperature of the sample 13 to be detected and the vacuum degree of the closed air chamber 17 reach preset values and are stable, switching on the switch 8-1 to the direct-current high-voltage source 8-3, and simultaneously grounding the switch 19-1 to the ground 19-2 to realize the charge injection process of the sample 13 to be detected.
As shown in FIG. 2, a DC high voltage power supply 8-3 is connected with the annular metal front electrode 12 through a switch 8-1, and an electrometer 19-3 is connected with the metal flat plate rear electrode 14 through a switch 19-1. When the switch 8-1 is connected with the direct-current high-voltage source 8-3 and the switch 19-1 is grounded 19-2, the direct-current voltage in the direct-current high-voltage source 8-3 is led into the front electrode of the sample 13 to be measured, namely, the charges are injected into the sample 13 to be measured by a contact direct-current charging method.
In one embodiment of the present application, the intensity of the charging electric field is 30 to 50kV/mm, and the charging time is 30 to 90 min.
This step corresponds to the B procedure in fig. 3. As shown in fig. 3, at this time, the temperature T of the sample to be measured reaches the preset temperature value and remains stable withoutThen changing; in addition, the working state of the direct current high voltage source is changed into a high level state, which indicates that the direct current high voltage source is in the working state, and charge injection is carried out on the sample to be measured. While the working state of the electrometer, laser, etc. is still in the low level state, i.e. not working. And the scanning current I does not exist in the processS。
Step 3, after the charge injection in the step 2 lasts for a preset time, disconnecting the switch 8-1 from the direct current high voltage source 8-3 and disconnecting the switch 19-1 from the ground 19-2; meanwhile, the switch 8-1 is grounded 8-2, and the switch 19-1 is connected with the electrometer 19-3 to remove free charges on the surface of the sample 13 to be measured, and meanwhile, a current signal formed in an external circuit is collected through the electrometer 19-3, and the current value of the current signal is observed.
In one embodiment of the present application, the free charge on the surface of the sample 13 to be tested is considered to be completely dissipated after the current signal collected by the electrometer is lower than 1 pA.
To this end, the polarization process of the sample to be measured 13 is completed, and this step corresponds to the C process in fig. 3.
In the C process shown in fig. 3, the operating state of the high-voltage dc power supply and the operating state of the laser are low, which indicates that the laser is not expected to operate by the high-voltage dc power supply and only the electrometer is in the operating state in this process. In addition, a scanning current signal ISIn the process, the current signal I is in the process of attenuationSAnd entering a D process when the attenuation reaches a certain value.
And 4, when the scanning current is attenuated to a preset value, turning on the laser and the light energy meter, and carrying out light scanning on the sample to be detected according to preset scanning parameters. At the same time, the working state of the electrometer is maintained, enabling it to record the current signal in the external circuit.
In one embodiment of the application, the preset scan parameters include any one or more of: scanning wavelength range, scanning time, scanning step length. In addition, the scanning wavelength range in the embodiment of the application is 2600-210 nm, the scanning compensation is 2nm, and the scanning time is 2 s.
By means of an excitation light source as described aboveOptical scanning process for exciting charges in sample to be measured to generate scanning current ISSo as to measure the trap parameter of the sample to be measured subsequently.
This step corresponds to the D procedure in fig. 3. As shown in fig. 3, when the characterization process of the trap parameters of the polymer material proceeds to step D, the operation states of the laser and the electrometer are all in a high state, that is, the electrometer and the laser are in an operation state. And as can be seen from fig. 3, the scanning wavelength of the laser is gradually decreased from 2600nm to 210nm, and in the working process of the laser, the external circuit of the sample to be measured generates a scanning current signal IS。
And 5, determining trap parameters of the polymer material at a preset temperature according to the current value displayed by the electrometer, the light energy value displayed by the light energy meter and preset scanning parameters.
In one embodiment of the present application, a trap parameter calculation method includes: determining the scanning wavelength of the excitation light source, and determining the corresponding current value and light energy value under the scanning wavelength; determining the relation between the scanning wavelength of the excitation light source and the trap energy level depth through the following formula;
E＝h*c/λ
wherein E represents the trap level depth; h is the Planck constant; c is the speed of light; λ represents a wavelength of the excitation light source;
further, determining a corresponding relation between the trap energy level depth and the trap energy level density based on an energy normalization algorithm; and drawing a variation curve according to the corresponding relation, wherein the abscissa of the variation curve represents trap energy and depth, and the ordinate represents trap energy level density.
The trap parameters of the polymeric material at the predetermined test temperature are then analyzed by plotting the variation curves.
And finishing the characterization process of the trap parameters of the polymer material at a specific temperature.
The method for representing the trap of the polymer material based on the PSD method provided by the embodiment of the application not only has all advantages of the existing PSD technology, but also provides accurate representation of the trap parameter of the polymer material at a specific temperature through the temperature control system, and has typical engineering practical guidance significance. Compared with the existing characterization process of the polymer trap parameters, the characterization process of the trap parameters provided in the embodiment of the application has the following excellent effects:
(1) compared with the existing TSC (thyristor switched capacitor) and other thermal stimulation methods, the PSD-based polymer material trap parameter characterization method has the advantages of high test precision, short test period, no damage to a tested sample, wide measurable energy level range, good test repeatability, simple device and the like;
(2) the excitation light source in the embodiment of the application is realized by adopting a wavelength tunable laser based on an optical parametric oscillator, the wavelength range of the laser is 2600-210 nm, the precision is +/-0.25 nm, and the lowest energy is more than 1.4 mJ. Therefore, compared with the traditional xenon lamp and monochromator excitation light source, the xenon lamp and monochromator excitation light source has the advantages of good monochromaticity, wide wavelength range, full excitation and the like. The PSD method based on the laser has the advantages of wide measurable energy level range (0.48-5.9 eV), high precision, large signal-to-noise ratio and the like;
(3) according to the characterization device provided by the embodiment of the application, the test sample is placed in the closed air chamber, so that the characterization under a high-vacuum atmosphere is realized, and on one hand, the interference of the electric charge generated by the ionization of air by laser on the test result is avoided; on the other hand, because some polymer materials are used in a vacuum environment, the scheme provided in the embodiment of the application can simulate the vacuum operation condition of the polymer materials, so that the characterization result is closer to the practical application;
(4) the influence of the actual use temperature of the polymer on the trap energy level is considered, so that the specific test temperature of the sample is realized by adopting a heating wire heating and liquid nitrogen bottle cooling mode through the characterization device provided by the embodiment of the application, the test process of the temperature range of-180-300 ℃ is realized, and almost all use temperature ranges of the polymer material are covered.
The embodiments in the present application are described in a progressive manner, and the same and similar parts among the embodiments can be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, as for the apparatus embodiment, since it is substantially similar to the method embodiment, the description is relatively simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (10)
1. A PSD method-based polymer material trap parameter characterization device is characterized by comprising the following components:
the excitation light guide-in module is used for guiding in an excitation light source; the excitation light source is used for exciting the trapped charge of the sample to be detected;
the direct-current voltage leading-in module is used for leading direct-current voltage into the front electrode of the sample to be detected;
the temperature regulation and control module is used for regulating and controlling the temperature of the sample to be detected;
the current signal derivation module is used for collecting a current signal formed by detrapping charges of the sample to be detected;
the temperature regulation and control module mainly comprises a heating plate, a heating controller, a red copper cold head, a liquid nitrogen bottle, a liquid nitrogen transmission pipe and a circulating pump.
2. The PSD method-based polymer material trap parameter characterization device according to claim 1, further comprising an electrode structure unit;
the electrode structure unit comprises an annular metal front electrode and a metal flat plate rear electrode;
the annular metal front electrode is used for being in contact with a front electrode of the sample to be detected so as to introduce the direct-current voltage; the metal flat plate rear electrode is used for contacting with the rear electrode of the sample to be detected so as to collect the current signal.
3. The PSD-based polymer material trap parameter characterization device of claim 1, further comprising:
a light energy meter for testing the energy of the excitation light source;
the closed air chamber adopts a stainless steel metal cavity and is used for providing a vacuum environment for the sample to be detected and shielding external interference;
and a plurality of preset flanges are arranged on the stainless steel metal cavity.
4. The PSD method-based polymer material trap parameter characterization device of claim 3,
the excitation light introduction module mainly comprises a wavelength tunable laser, a beam expander, a spectroscope, an optical fiber laser input end, an optical fiber and an optical fiber laser output end; the fiber laser output end is led in an excitation light source through a preset flange on the stainless steel cavity;
the direct-current voltage leading-in module mainly comprises a direct-current high-voltage source, a protection resistor, an equalizing ring and a lead;
the current signal derivation module mainly comprises an electrometer.
5. The PSD-based polymer material trap parameter characterization device according to claim 4, wherein the wavelength tunable laser has an output wavelength range of 210-2600 nm, a minimum output energy of 1.4mJ, and a light flux density of 1024cm-2s-1The magnitude is 2-5 ns in pulse width.
6. The PSD-based polymer material trap parameter characterization device according to claim 1, wherein the temperature control module is used for controlling the temperature of the sample to be tested to-180-300 ℃.
7. The method for characterizing the trap parameters of the polymer material based on the PSD method is realized by the device for characterizing the trap parameters of the polymer material based on the PSD method according to any one of claims 1 to 6, and comprises the following steps:
determining the test temperature of a sample to be tested and the vacuum degree of the closed air chamber;
when the test temperature and the vacuum degree reach a first preset threshold value, a direct-current high-voltage power supply is switched on to introduce direct-current voltage into the sample to be tested;
disconnecting the direct-current high-voltage power supply and connecting an electrometer to remove free charges on the surface of the sample to be measured;
when the current value displayed by the electrometer reaches a second preset threshold value, switching on the wavelength tunable laser and the light energy meter;
based on preset scanning parameters, performing optical scanning on the sample to be detected through an excitation light source; wherein the preset scanning parameters include at least one of: scanning wavelength range, scanning step length and scanning time;
and determining the trap parameter of the polymer material at the test temperature according to the current value displayed by the electrometer, the light energy value displayed by the light energy meter and the preset scanning parameter.
8. The PSD-based method for characterizing trap parameters of a polymer material according to claim 7, further comprising:
determining a test sample, and cutting the test sample;
electroplating a front electrode and a rear electrode on the cut test sample to obtain a sample to be tested;
and placing the sample to be detected on the electrode structure unit so as to enable the rear electrode of the sample to be detected to be in contact with the metal flat plate rear electrode of the electrode structure unit, and simultaneously compacting the annular metal front electrode of the electrode structure unit.
9. The PSD-based method for characterizing trap parameters of a polymer material according to claim 7, wherein determining trap parameters of a polymer material at the test temperature according to the current value displayed by the electrometer, the light energy data displayed by the light energy meter, and the preset scan parameter specifically comprises:
determining the scanning wavelength of the excitation light source, and determining a current value and an optical energy value corresponding to the scanning wavelength;
by passing
Determining the relation between the scanning wavelength of the excitation light source and the trap energy level depth; wherein E represents the trap level depth; h is the Planck constant; c is the speed of light; λ represents a wavelength of the excitation light source;
determining a corresponding relation between the trap energy level depth and the trap energy level density based on an energy normalization algorithm;
and determining the trap parameters of the polymer material at the test temperature through the corresponding relation.
10. The PSD-based method for characterizing trap parameters of a polymer material according to claim 7, wherein the scanning wavelength range is 2600-210 nm; the scanning step length is 2 nm; the scan time is 2 s.
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