CN112505108B - Gas detection system and method - Google Patents
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- CN112505108B CN112505108B CN202011503691.9A CN202011503691A CN112505108B CN 112505108 B CN112505108 B CN 112505108B CN 202011503691 A CN202011503691 A CN 202011503691A CN 112505108 B CN112505108 B CN 112505108B
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
Abstract
A gas detection system includes a field effect transistor and a detection device. The field effect transistor includes a source electrode, a drain electrode, a gas sensing layer, a gate electrode, and a first dielectric material layer. The source and drain electrodes are spaced apart. A gas sensing layer includes a gas sensitive medium, a portion of the gas sensing layer extending between and electrically connected to the source and drain electrodes. A first layer of dielectric material is located between the gas sensing layer and the gate electrode. The detection device comprises a shell, an insulating material layer and an opening. The housing defines a detection channel. At least a portion of a surface of a gas sensing layer of the field effect transistor is exposed in the detection channel for contact with a gas to be detected passing through the detection channel. An opening is formed in the housing to allow the detection passage to communicate with gas outside the detection device through the opening.
Description
Technical Field
The present disclosure relates to gas detection technology, and more particularly, to a gas detection system and method.
Background
The gas sensor means a sensor for detecting whether a specific gas is present in a certain area or continuously measuring the concentration of a gas component. In the safety protection aspects of coal mines, petroleum, chemical industry, municipal administration, medical treatment, transportation, families and the like, the gas sensor is often used for detecting the concentration or the existence of combustible, reburning and toxic gases, or the consumption of oxygen and the like. In the field of production and manufacturing in the power industry and the like, a gas sensor is also commonly used for quantitatively detecting the concentration of each component in gas so as to judge the combustion condition, the emission amount of harmful gas and the like. In the field of atmospheric environment monitoring, it is also very common to adopt gas sensors to determine environmental pollution conditions.
In the related art, some gas sensors based on Field Effect Transistors (FETs) enable qualitative detection of gas. Some FET gas sensors are capable of quantitative detection of gases via pre-calibration experiments. However, there is much room for improvement in directly measuring the concentration of gas molecules and identifying molecular species using gas sensors.
Disclosure of Invention
It would be advantageous to provide a mechanism that alleviates, mitigates or even eliminates one or more of the above-mentioned problems.
According to an aspect of the present disclosure, a gas detection system is provided that includes a field effect transistor and a detection device. The field effect transistor includes a source electrode, a drain electrode, a gas sensing layer, a gate electrode, and a first dielectric material layer. The source and drain electrodes are spaced apart. A gas sensing layer includes a gas sensitive medium, a portion of the gas sensing layer extending between and electrically connected to the source and drain electrodes. A first layer of dielectric material is located between the gas sensing layer and the gate electrode. The detection device comprises a shell, an insulating material layer and an opening. The housing defines a detection channel. At least a portion of a surface of a gas sensing layer of the field effect transistor is exposed in the detection channel for contact with a gas to be detected passing through the detection channel. An opening is formed in the housing to allow the detection passage to communicate with gas outside the detection device through the opening.
According to another aspect of the present disclosure, a gas detection method is provided that utilizes embodiments of some gas detection systems of the present disclosure. The gas detection method comprises contacting at least a portion of a surface of a gas sensing layer of a field effect transistor with a gas to be detected passing through a detection channel; detecting a signal indicative of a response of the gas sensing layer to the gas to be detected; and processing the signals to determine a plurality of parameters of the gas to be detected.
These and other aspects of the disclosure will be apparent from and elucidated with reference to the embodiments described hereinafter.
Drawings
Further details, features and advantages of the disclosure are disclosed in the following description of exemplary embodiments, taken in conjunction with the accompanying drawings, in which:
FIGS. 1A-1C are schematic diagrams of a related art field effect transistor-based gas detection apparatus;
FIG. 2 is a top view of a gas detection system according to an exemplary embodiment of the present disclosure;
FIG. 3 is a schematic cross-sectional view of the gas detection system along line A-A in FIG. 2 according to an exemplary embodiment of the present disclosure;
FIG. 4 is a schematic cross-sectional view of another gas detection system along line A-A in FIG. 2 according to an exemplary embodiment of the present disclosure;
FIG. 5 is a schematic diagram of a structure of a detection channel in the gas detection system of FIG. 2, according to an exemplary embodiment of the present disclosure;
FIG. 6 is a graph of current power density versus frequency for the gas detection system of FIG. 4 according to an exemplary embodiment of the present disclosure;
FIG. 7 is a schematic block diagram of a gas detection system according to an exemplary embodiment of the present disclosure;
fig. 8 is a flow chart of a gas detection method according to an exemplary embodiment of the present disclosure.
Detailed Description
It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure.
Spatially relative terms such as "below …," "below …," "lower," "below …," "above …," "upper," and the like may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that these spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" or "under" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "below …" and "below …" may encompass both an orientation above … and below …. Terms such as "before …" or "before …" and "after …" or "next to" may similarly be used, for example, to indicate the order in which light passes through the elements. The devices may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. In addition, it will also be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items, and the phrase "at least one of a and B" refers to a alone, B alone, or both a and B.
It will be understood that when an element or layer is referred to as being "on," "connected to," "coupled to" or "adjacent to" another element or layer, it can be directly on, connected to, coupled to or adjacent to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly connected to," "directly coupled to," or "directly adjacent to" another element or layer, there are no intervening elements or layers present. However, neither "on … nor" directly on … "should be construed as requiring that one layer completely cover an underlying layer in any event.
Embodiments of the present disclosure are described herein with reference to schematic illustrations (and intermediate structures) of idealized embodiments of the present disclosure. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the present disclosure should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the present disclosure.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and/or the present specification and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As used herein, the term "substrate" may refer to a substrate of a diced wafer, or may refer to a substrate of an unslit wafer. Similarly, the terms chip and die (die) may be used interchangeably unless such interchange causes a conflict. It should be understood that the term "layer" includes films and, unless otherwise specified, should not be construed as indicating a vertical or horizontal thickness.
In the related art Field Effect Transistor (FET) based gas sensors, the principle of operation is to directly expose the gas sensitive medium of the sensor to the gas environment to be detected. When gas molecules are adsorbed or close to the surface of the gas sensitive medium of the sensor, the molecules induce carriers in the gas sensitive medium, or carry out carrier transfer with the medium, or change the electric conductivity of the gas sensitive medium through other proximity actions, and the change is detected in the form of an electric signal.
FIG. 1A is a schematic diagram of a field effect transistor gas sensor based on a fixed gate in the related art. As shown in fig. 1A, a fixed gate-less FET gas sensor 100A includes a layer of insulating material 110, a source 120, a drain 130, a gas to be sensed 140, and a gas sensitive medium 150. The conventional FET gas sensor without fixed gate shown in fig. 1A can only perform qualitative detection because the carrier energy state of the gas sensitive medium 150 is unknown and the electrical signal output by a single molecule is unknown.
FIG. 1B is a schematic diagram of a fixed gate based field effect transistor gas sensor in the related art. Like reference numerals in fig. 1B refer to like elements in fig. 1A and are not described again here. In contrast to fig. 1A, the fixed gate based FET 100B of fig. 1B further includes a gate 160. In order to realize quantitative detection, the conventional FET gas sensor with a fixed gate in fig. 1B needs to perform a series of preliminary experiments to establish a correlation between concentration and an electrical signal, so that only known molecules calibrated by the preliminary experiments can be quantitatively detected, and the detection object is single in type.
In the conventional FET sensor of fig. 1A and 1B, the gas 140 is directly adsorbed to the gas sensitive medium 150, and due to the universality of adsorption, neither sensor can distinguish molecules with the same electric signal contribution but different types, and thus the discrimination is low. In practical applications, complex surface modifications are generally required, so that the sensor can only identify exactly one molecule. However, the limited number of surface aptamers makes quantitative detection feasible only in a limited concentration range.
Fig. 1C is a schematic diagram of a conventional top-gate based field effect transistor gas sensor in the related art. Like reference numerals in fig. 1C denote like elements in fig. 1A and 1B, and are not described again here. In contrast to fig. 1B, the conventional top-gate based FET 100C of fig. 1C further includes a layer of insulating material 170. The gate electrode 160 of which is located above the gas sensitive medium 150 and is separated therefrom by a layer of insulating material 170. In a conventional top-gate FET gas sensor such as that of fig. 1C, the area of the insulating material layer 170 that the gas 140 can contact is reduced by the presence of the gate electrode 160, thereby reducing the effective sensing area.
FIG. 2 is a top view of a gas detection system 200 according to an exemplary embodiment of the present disclosure. As shown in fig. 2, the gas detection system 200 includes a detection device 210. The detection device 210 includes a housing 211 and an opening 212, and the housing 211 defines a detection channel 230. An opening 212 is formed in the housing 211 to allow the detection channel 230 to communicate with a gas 240 to be detected outside the detection device 210. That is, gas 240 to be detected outside of detection device 210 can enter and exit detection channel 230 via opening 212.
At least a portion of the surface of the gas sensing layer 224 in the FET220 is exposed in the detection channel 230 for contact with the gas 240 to be detected entering the detection channel 230 through the opening 212.
According to some embodiments of the present disclosure, a voltage V may be applied between the source electrode 222 and the drain electrode 223 of the FET220dAnd a voltage V is applied between the gate electrode 221 and the source electrode 222gTo cause FET220 to operate at a current I between source electrode 222 and drain electrode 223sdFollowing VgIn the region of linear variation. In operation, the gas detection system 200 may be used to measure gas concentrations and/or identify different kinds of gas molecules, the working principle of which will be described in detail later.
According to some embodiments of the present disclosure, the housing 211 may be an insulating material including, for example, silicon dioxide or the like.
According to some embodiments of the present disclosure, the gate electrode 221, the source electrode 222, and the drain electrode 223 may be a metal material including, for example, gold, copper, or the like; but may also be an oxide including, for example, aluminum oxide, hafnium oxide, yttrium oxide, and the like.
According to some embodiments of the present disclosure, the size of the opening 212 may be configured to enable gas outside the detection device 210 to continuously enter and exit the detection channel 230 through the opening 212. In the example of fig. 2, the detection device 210 is shown with its housing 211 provided with two openings 212 at both ends of the detection channel 230 in the length direction. This allows gas outside the detection device 210 to enter and exit the detection channel 230 via, for example, the left opening 212 and/or enter and exit the detection channel 230 via, for example, the right opening 212.
Although the left and right openings 212 are illustrated in fig. 2 as having substantially the same shape and size, this is merely exemplary and the disclosure is not limited thereto. In other embodiments, the different openings 212 may have respective different shapes and sizes, and the number of openings 212 is not limited to two.
According to some embodiments of the present disclosure, the gas sensing layer 224 may be located between the gate electrode 221 and the detection channel 230, thereby constituting an inverted FET structure. The inverted FET structure has a configuration of the gate electrode 221, the gas sensing layer 224, and the detection channel 230 from top to bottom such that the gas sensing layer 224 is in contact with the gas 240 to be detected in the detection channel 230 without the sensing area occupied by the gate electrode 221.
In summary, some embodiments of the present disclosure adopt an inverted FET configuration, so that the sensing layer is ensured to be flat while using an efficient top gate structure, and the effective sensing area is increased. In addition, the opening of the detection system can enable the gas outside the detection device to enter the detection channel through random diffusion movement, so that the accuracy of subsequent diffusion coefficient calculation is ensured.
FIG. 3 is a schematic cross-sectional view of a gas detection system 200 along line A-A in FIG. 2 according to an exemplary embodiment of the present disclosure. Like reference numerals in fig. 3 refer to like elements in fig. 2 and are not described again. In the embodiment shown in FIG. 3, the gas sensing layer 224 includes only the gas sensitive medium 225. Fig. 3 further illustrates the first layer of dielectric material 226. In some exemplary embodiments, the first layer of dielectric material 226 is positioned between the gate electrode 221 and the gas-sensitive medium 225 such that when the gas 240 to be detected is adsorbed onto the gas-sensitive medium 225, the gas-sensitive medium 225 is electrically isolated from the gate electrode 221 without shorting.
In some exemplary embodiments, the first dielectric material layer 226 may be a dielectric material having a high dielectric constant (e.g., a high K value).
In some exemplary embodiments, the gas sensitive medium 225 may be capable of exhibiting a change in conductivity in response to exposure of the gas sensing layer 224 to the gas 240 to be detected.
In some exemplary embodiments, the gas sensitive medium 225 may be a two-dimensional semiconductor material including semiconductor materials with high on-off ratios such as graphene, silicon nanowires, and molybdenum disulfide.
In some exemplary embodiments, the gas 240 to be detected enters the detection channel 230 via the opening 212 and is proximate to or in contact with the gas sensitive medium 225. The gas 240 to be detected may thereby induce or undergo carrier transfer with the gas-sensitive medium 225, such that the electrical conductivity of the gas-sensitive medium 225 changes. In addition, due to the bias voltage V applied to the drain electrode and the gate electrode of the FET220dAnd VgSource-drain current I for operating FET220 between source electrode 222 and drain electrode 223sdFollowing VgIn the region of linear variation. Namely:
Isd＝gm.Vg
the conductivity g of the gas-sensitive medium 225 can thus be obtainedm：
gm＝Isd/Vg
Thus, the conductivity g of the gas 240 to be detected is caused by its contact with the gas-sensitive medium 225mCan be varied by detecting the inclusion of a source-drain current I between the source electrode 222 and the drain electrode 223sdIs known from the electrical signal of (a).
FIG. 4 is a schematic cross-sectional view of another gas detection system along line A-A in FIG. 2 according to an exemplary embodiment of the present disclosure. Like reference numerals in fig. 4 refer to like elements in fig. 2 and 3 and are not described again. As shown in fig. 4, a second dielectric material layer 227 may be further included. The second layer of dielectric material 227 is located on a surface 225' of the gas sensitive medium 225 facing away from the first layer of dielectric material 226. The gas sensing layer 224' as shown in FIG. 4 may include a gas sensitive medium 225 and a second layer 227 of dielectric material. In some exemplary embodiments, the second layer of dielectric material 227 has a thickness such that adsorption of the gas 240 to be detected to the second layer of dielectric material 227 causes a change in the carrier concentration of the gas sensitive medium 225. Illustratively, when the gas 240 to be detected is adsorbed on the second dielectric material layer 227 due to the electric field of the FET220, a charge can be induced in the gas sensitive medium 225 by electrostatic interaction, thereby changing the conductivity of the gas sensitive medium. Alternatively, the second dielectric material layer 227 may be a material having a high dielectric constant.
In summary, the direct adsorption of gas molecules to the gas sensitive medium 225 may make the cause of the change in the carrier concentration of the gas sensitive medium 225 uncertain, for example, the direct adsorption of molecules may cause the carrier mobility in the gas sensing layer to change, thereby causing the noise to change. By introducing the second dielectric material layer 227, the carrier concentration of the gas to be detected 240 in the gas sensitive medium 225 can be changed through electrostatic interaction without being adsorbed to the gas sensitive medium 225, so that interference factors such as change of carrier migration properties caused by direct adsorption can be eliminated when the gas is quantitatively detected, and the accuracy of the gas quantitative detection result is improved.
In some exemplary embodiments, the detection channel 230 may be a structure as shown in fig. 5. Fig. 5 shows a schematic diagram of the structure of a detection channel 230 according to an embodiment of the present disclosure. As shown in FIG. 5, detection channel 230 has a length 510, a width 520, and a height 530. Where the length 510 and width 520 may be on the order of micrometers and the height 530 may be on the order of nanometers. As used herein, the term "micron-scale"refers to the micrometer scale, that is, several micrometers to several tens of micrometers, and accordingly, the term" nanoscale "refers to the nanometer scale, that is, several nanometers to several tens of nanometers. Illustratively, the length 510 may be 10 microns or less (i.e., the length 510 ≦ 10 × 10)-6Meter), the width 520 may be 5 microns or less (i.e., width 520 ≦ 5 × 10-6Meters) and the height 530 may be 10 nanometers or less (i.e., height 530 ≦ 10 × 10-9Rice).
The detection channel 230 based on the configuration of fig. 5 may have such a length to height ratio that the movement of the gas 240 to be detected therein may be viewed as a one-dimensional random movement along the length 510. Such a detection channel 230 has a distinct detection limit compared to the external environment of the detection device 210, so that the molecular motion characteristics can be revealed, which is beneficial for the identification of the gas molecular species.
In some exemplary embodiments having detection channel 230 of fig. 5, the conductivity of gas-sensitive medium 225 changes as gas 240 to be detected rapidly enters and exits detection channel 230 and continues to adsorb and desorb on second layer 227 of dielectric material. Due to the limitation of the detection channel 230 having the nano-space, the gas 240 to be detected rapidly enters and exits therein to generate noise, so that the source-drain current I detected between the source and drain of the EFT 220sdIs a current with a frequency f. Using this noise generated by the nanospace confinement (rather than the traditional dc current/voltage) as a detection signal, multi-dimensional information can be obtained for gas identification, as will be further described below.
Optionally, at source-drain current IsdAnd the voltage V between the gate and source of the EFT 220gIs a ratio of change Δ Isd/ΔVgAt maximum, the current power density s (f) between the source electrode 222 and the drain electrode 223 is detected, which has a frequency f that is responsive to the velocity at which gas outside the detection arrangement 210 continues to enter and exit the detection channel 230 via the opening 212.
Illustratively, FIG. 6 shows a graph of current power density versus frequency for the gas detection system of FIG. 4 according to an exemplary embodiment of the present disclosure. Wherein S (f) satisfies:
S(f)＝S0/[1+(f/f0)3/2]
wherein S is0Is a value of the current power density s (f) in a low frequency band, and satisfies:
where l is the sensing region length of the gas sensing layer 224', ipThe signal contributed by a single gas 240 to be detected,<N>is the average number of molecules.
Further, the value of the current power density s (f) at the low frequency band represents the reference current contributed by the average molecular number < N > of the gas 240 to be detected, whereby the concentration C of the gas 240 to be detected can be obtained:
C＝<N>/V
where V is the effective sensing area of the gas sensing layer 224'.
Since the gas 240 to be detected rapidly enters and exits the detection channel 230, S (f) decays with frequency in the high frequency band, f0Is a critical frequency which represents the motion characteristics of the gas 240 to be detected and is proportional to the velocity of the gas 240 to be detected, i.e., the effective diffusion coefficient D of the gas 240 to be detectedeff. From diffusion coefficient DeffThe species of the molecules can be distinguished and compared by the effective diffusion coefficient DeffAnd the eigenvalues D allow the molecular adsorption equilibrium constant to be calculated.
In summary, due to the adoption of the detection channel structure with the nanometer height and the micrometer length and width, the detection channel has an extremely large length-height ratio, so that the movement of the gas molecules in the detection channel can be regarded as one-dimensional random movement. The source-drain current has a frequency responsive to the velocity of the gas molecules into and out of the detection channel due to the rapid ingress and egress of the gas molecules into and out of the detection channel. By detecting the power density of the source-drain current and calculating, the concentration of the gas can be detected without an early calibration experiment and surface modification of a gas detection system. And a plurality of parameters including diffusion coefficient, adsorption equilibrium constant and the like of gas can be obtained through the critical frequency of the source-drain current power density, so that the identification capability of molecular species is improved, and the use scene of the same detection system is widened.
Fig. 7 is a schematic block diagram illustrating a gas detection system 700 according to an exemplary embodiment of the present disclosure. As shown in fig. 7, gas detection system 700 includes gas detection system embodiment 710. Gas detection system embodiment 710 may be a gas detection system embodiment as shown in fig. 2, 3, and 4 or described in the present disclosure.
The gas detection system 700 also includes a detector 720. Detector 720 may be connected to the source and drain electrodes of the FETs in gas detection system embodiment 710 to detect signals indicative of the response of the gas sensing layer to the gas to be detected. Illustratively, the detector 720 may be a ratio Δ I of a change in current between the source and drain of the FET to a change in voltage between the gate and source of the FETsd/ΔVgAt the maximum, the current power density s (f) between the source and drain of the foregoing EFT is detected as a signal.
In some demonstrative embodiments, signal processor 730 may be in communication with detector 720, such as in a wireless or wired manner, via an electrical or optical connection, to receive signals from detector 720. The signal processor 730 may be a programmable device or a device that performs specified computational or logic functions. For example, the signal processor 730 may be a microprocessor, a Central Processing Unit (CPU), various dedicated computing chips, a Digital Signal Processor (DSP), or the like. In some embodiments, the signal processor 730 may be any type of computer or internet computer, which may include, but is not limited to, one or more of a smartphone, a tablet computer, a personal computer, a mainframe computer, or any combination thereof.
In summary, gas detection system 700 can be operated at Δ I via detector 720sd/ΔVgThe current power density s (f) is detected at the maximum of the ratio to minimize the effect of some noise generated by the device itself, thereby increasing the accuracy of detection. In addition, gas detection system 700 determines a plurality of parameters of the gas to be detected via signal processor 730, which increases the ability of the system to identify different gases.
Fig. 8 is a flow chart of a gas detection method 800 according to an exemplary embodiment of the present disclosure. The gas detection method 800 as shown in fig. 8 utilizes an exemplary embodiment of a gas detection system of the present disclosure, such as the gas detection system shown in fig. 2, 3, 4 or described in the present disclosure. Gas detection method 800 includes steps 810, 820, and 830. At step 810, at least a portion of a surface of a gas sensing layer of a field effect transistor of a gas detection system is brought into contact with a gas to be detected passing through a detection channel. At step 820, a signal indicative of a response of the gas sensing layer to the detection gas is detected. At step 830, the signals are processed to determine a plurality of parameters of the gas to be detected.
In some embodiments of the present disclosure, step 820 may detect the current power density between the source and drain as the signal where the ratio of the change in current between the source and drain of the FET to the change in voltage between the gate and source of the FET is largest.
In summary, according to the gas detection method disclosed by the embodiment of the present disclosure, by using the gas detection system disclosed above, the concentration of the gas can be detected without the need of an early calibration experiment and surface modification, and meanwhile, a plurality of parameters of the gas to be detected are obtained, so that the ability of identifying different gas molecules is improved.
While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative and exemplary and not restrictive; the present disclosure is not limited to the disclosed embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps not listed, the indefinite article "a" or "an" does not exclude a plurality, and the term "a plurality" means two or more. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
Aspect 1a gas detection system, comprising:
a field effect transistor, the field effect transistor comprising:
a source electrode for generating a source voltage,
a drain electrode spaced apart from the source electrode,
a gas sensing layer comprising a gas sensitive medium, wherein at least a portion of the gas sensing layer extends between and is electrically connected to the source and drain electrodes,
a gate electrode, and
a first layer of dielectric material between the gas sensing layer and the gate electrode; and
a detection device, the detection device comprising:
a housing defining a detection channel, wherein at least a portion of a surface of the gas sensing layer of the field effect transistor is exposed in the detection channel for contact with a gas to be detected passing through the detection channel, and
an opening formed on the housing such that the detection channel communicates with a gas outside the detection device through the opening.
Aspect 2. the gas detection system of aspect 1, wherein the detection channel has a height on the order of nanometers and a length and a width on the order of micrometers.
Aspect 3. the gas detection system of aspect 1, wherein the gas sensing layer is located between the gate and the detection channel.
Aspect 4 the gas detection system of aspect 3, wherein the gas sensing layer further comprises a second layer of dielectric material on a surface of the gas sensitive medium facing away from the first layer of dielectric material and having a thickness such that adsorption of the gas to be detected to the second layer of dielectric material causes a change in carrier concentration of the gas sensitive medium.
Aspect 5. the gas detection system of aspect 3, wherein the opening is sized to enable gas outside the detection device to continuously enter and exit the detection channel through the opening.
Aspect 6 the gas detection system of aspect 5, further comprising a detector electrically connected to the source electrode and the drain electrode to detect a signal indicative of a response of the gas sensing layer to the gas to be detected.
Aspect 7. the gas detection system of aspect 6,
wherein the detector is configured to detect a current power density between the source and the drain as the signal at a point where a ratio of a change in current between the source and the drain of the field effect transistor to a change in voltage between the gate and the source of the field effect transistor is maximum,
wherein the current power density has a frequency responsive to a velocity of gas outside the detection device continuously entering and exiting the detection channel via the opening.
Aspect 8 the gas detection system of aspect 7, further comprising a signal processor configured to determine a plurality of parameters of the gas to be detected based on the signal from the detector.
Aspect 9. the gas detection system of aspect 8, wherein the plurality of parameters of the gas to be detected includes at least one selected from the group consisting of: the concentration, diffusion coefficient and adsorption equilibrium constant of the gas to be detected.
Aspect 10 the gas detection system of aspect 1, wherein the gas sensitive medium is capable of exhibiting a change in conductivity in response to exposure of the gas sensing layer to the gas to be detected.
Aspect 11 the gas detection system of any of aspects 1-10, wherein the gas sensitive medium comprises a two-dimensional semiconductor material.
Aspect 12 the gas detection system of aspect 11, wherein the two-dimensional semiconductor material comprises at least one selected from the group consisting of: graphene, silicon nanowires and molybdenum disulfide.
Aspect 13 a gas detection method, comprising:
contacting at least a portion of a surface of a gas sensing layer of the field effect transistor with a gas to be detected passing through the detection channel using the gas detection system of any one of aspects 1 to 12;
detecting a signal indicative of a response of the gas sensing layer to the gas to be detected; and
processing the signals to determine a plurality of parameters of the gas to be detected.
Aspect 14 the method of aspect 13, wherein detecting the signal indicative of the response of the gas sensing layer to the gas to be detected comprises:
detecting a current power density between the source and the drain as the signal where a ratio of a change in current between the source and the drain of the field effect transistor to a change in voltage between the gate and the source of the field effect transistor is largest.
Claims (13)
1. A gas detection system, comprising:
a field effect transistor, the field effect transistor comprising:
a source electrode for generating a source voltage,
a drain electrode spaced apart from the source electrode,
a gas sensing layer comprising a gas sensitive medium, wherein at least a portion of the gas sensing layer extends between and is electrically connected to the source electrode and the drain electrode,
a gate electrode, and
a first layer of dielectric material between the gas sensing layer and the gate electrode; and
a detection device, the detection device comprising:
a housing defining a detection channel, wherein at least a portion of a surface of the gas sensing layer of the field effect transistor is exposed in the detection channel for contact with a gas to be detected passing through the detection channel, wherein the detection channel has a height on the order of nanometers, a length and a width on the order of micrometers, and an aspect ratio such that movement of the gas to be detected in the detection channel can be viewed as one-dimensional random movement along the length, and
an opening formed on the housing such that the detection passage communicates with a gas outside the detection device through the opening,
wherein a current power density of a current noise between the source electrode and the drain electrode generated under the limitation of the detection channel having the aspect ratio is taken as a detection signal, the current power density having a frequency responsive to a velocity at which the gas to be detected enters and exits the detection channel via the opening.
2. The gas detection system of claim 1, wherein the gas sensing layer is located between the gate electrode and the detection channel.
3. The gas detection system of claim 2, wherein the gas sensing layer further comprises a second layer of dielectric material on a surface of the gas sensitive medium facing away from the first layer of dielectric material and having a thickness such that adsorption of the gas to be detected to the second layer of dielectric material causes a change in carrier concentration of the gas sensitive medium.
4. The gas detection system of claim 2, wherein the opening is sized such that gas outside the detection device can continuously enter and exit the detection channel through the opening.
5. The gas detection system of claim 4, further comprising a detector electrically connected to the source electrode and the drain electrode to detect the detection signal.
6. The gas detection system of claim 5,
wherein the detector is configured to detect the current power density where a ratio of a change in current between the source electrode and the drain electrode of the field effect transistor to a change in voltage between the gate electrode and the source electrode of the field effect transistor is largest.
7. The gas detection system of claim 6, further comprising a signal processor configured to determine a plurality of parameters of the gas to be detected based on the detection signal from the detector.
8. The gas detection system of claim 7, wherein the plurality of parameters of the gas to be detected include at least one selected from the group consisting of: the concentration, diffusion coefficient and adsorption equilibrium constant of the gas to be detected.
9. The gas detection system of claim 1, wherein the gas sensitive medium is capable of exhibiting a change in conductivity in response to exposure of the gas sensing layer to the gas to be detected.
10. The gas detection system of any one of claims 1 to 9, wherein the gas sensitive medium comprises a two-dimensional semiconductor material.
11. The gas detection system of claim 10, wherein the two-dimensional semiconductor material comprises at least one selected from the group consisting of: graphene, silicon nanowires and molybdenum disulfide.
12. A gas detection method, comprising:
contacting at least a portion of a surface of a gas sensing layer of the field effect transistor with a gas to be detected passing through the detection channel using the gas detection system of any one of claims 1 to 11;
detecting the detection signal; and
processing the detection signal to determine a plurality of parameters of the gas to be detected.
13. The method of claim 12, wherein the detecting the detection signal comprises:
detecting the current power density where a ratio of a change in current between the source electrode and the drain electrode of the field effect transistor to a change in voltage between the gate electrode and the source electrode of the field effect transistor is maximum.
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