FET gas sensor device

Abstract

A field effect transistor, FET, gas sensor device (100) arranged to sense a gas is provided, as well as a method of sensing a gas by a FET gas sensor device. The FET gas sensor device comprises at least one gate (110a, 110b), a source (120), a drain (130), and a semiconductor channel (140). The semiconductor channel and the gate form a FET channel-gate coupling (150) by which an applied gate potential is arranged to control a current flowing through the semiconductor channel. The FET gas sensor device further comprises a space (200) arranged between the gate and the semiconductor channel and configured to receive a gas, whereby the received gas is arranged to affect an electrical property of the FET channel-gate coupling, and wherein the FET gas sensor device is arranged to sense the gas based on the affected electrical property of the FET channel-gate coupling.

Description

Technical Field

[0001] This invention relates to a field-effect transistor (FET) gas sensor device. Background Technology

[0002] Field-effect transistors (FETs) can be used in particular to determine the gas components in a gas mixture. For example, the gate electrode of a FET can respond to the gas components, thereby triggering a change in the control voltage applied to the gate electrode. The resulting change in current flow between the source and drain electrodes can be detected and correlated with the concentration of the gas components.

[0003] This type of FET sensor can be used to detect atoms, molecules, and ions in gases. This sensor for gas analysis is made of... (I) S. Shivaraman, C. Svensson, and L. Lundkvist, "A hydrogen-sensitive MOS field-effect transistor," Appl. Phys. Lett. 26, 55 (1975). In this study, a metal-oxide-semiconductor FET (MOSFET) was used to detect hydrogen.

[0004] However, it should be noted that a common problem with using FETs for gas sensing is that the common architecture or structure of FETs may result in limited sensitivity to the sensed gas.

[0005] Therefore, the object of the present invention is to provide a FET-type sensor that can provide increased sensitivity, response time, accuracy and / or specificity related to gas sensing. Summary of the Invention

[0006] It is of interest to provide alternatives to existing FET-type gas sensors in order to improve the sensitivity, response time, accuracy and / or specificity of these gas sensors.

[0007] This and other objectives are achieved by providing a FET gas sensor device and method having the features of the independent claims. Preferred embodiments are defined in the dependent claims.

[0008] Therefore, according to a first aspect of the invention, a field-effect transistor (FET) gas sensor device arranged to sense a gas is provided. The FET gas sensor device includes at least one gate, a source, a drain, and a semiconductor channel disposed between the source and the drain. The semiconductor channel and the at least one gate form a FET channel-gate coupling, through which an applied gate potential is arranged to control a current flowing through the semiconductor channel. The FET gas sensor further includes at least one space disposed between the at least one gate and the semiconductor channel. The at least one space is configured to receive gas, whereby the gas received in the at least one space is arranged to affect at least one electrical characteristic of the FET channel-gate coupling, and wherein the FET gas sensor device is arranged to sense the gas based on the affected at least one electrical characteristic of the FET channel-gate coupling.

[0009] According to a second aspect of the invention, a method for sensing a gas using a field-effect transistor (FET) gas sensor device is provided. The FET gas sensor device includes at least one gate, a source, a drain, and a semiconductor channel disposed between the source and the drain, wherein the semiconductor channel and the at least one gate form a FET channel-gate coupling, and a gate potential is arranged to control a current flowing through the semiconductor channel via the FET channel-gate coupling. The FET gas sensor further includes at least one space disposed between the at least one gate and the semiconductor channel. The method includes: biasing the source and drain with a first voltage to generate a current flowing through the semiconductor channel. The method further includes: biasing the gate with a second voltage and controlling the current flowing through the semiconductor channel via the FET channel-gate coupling formed by the semiconductor and the at least one gate. The method further includes: receiving gas in the at least one space, whereby the gas received in the at least one space is arranged to affect at least one electrical characteristic of the FET channel-gate coupling. The method further includes: sensing the gas based on the affected at least one electrical characteristic of the FET channel-gate coupling.

[0010] Therefore, the present invention is based on the concept or idea of ​​providing a FET gas sensor device comprising one or more gas receiving spaces located between a gate and a semiconductor channel, such that the space is directly coupled to the FET channel-gate coupling. Through the arrangement of the gas receiving space between the gate and the semiconductor channel, the gas to be sensed can be received or injected between the gate and the semiconductor channel during sensing. The presence of gas in the provided space between the gate and the semiconductor channel enhances the ability of the semiconductor channel of the FET gas sensor device to respond to gas. In other words, the gas received in the space interacts with and / or couples to the FET channel-gate coupling. Therefore, the FET gas sensor device improves the sensitivity, response time, accuracy, and / or specificity of gas sensing.

[0011] The advantage of this invention lies in the fact that the arrangement of the gate and semiconductor channel in the same (common) plane (e.g., on the same side (surface) of the substrate) results in an efficient response of the FET gas sensor device to gas received in the space between the gate and the semiconductor channel. Because the space is directly coupled to the FET channel-gate coupling, the gas sensing capability of this invention is more efficient compared to prior art FET sensors, and particularly to prior art back-gate type FET sensors (where the gate and semiconductor channel are arranged in different planes (e.g., on opposite sides (surfaces) of the substrate)). These types of prior art FET sensors have been observed to have relatively weak capacitive coupling to the semiconductor channel. In stark contrast, the arrangement of the FET gas sensor device of this invention achieves strong coupling to the FET channel-gate coupling. The architecture or structure of the FET gas sensor device of this invention enables direct coupling and / or transduction to the semiconductor channel, which greatly enhances the gas sensitivity of the FET gas sensor device.

[0012] A further advantage of the present invention is that the structure and / or arrangement of the FET gas sensor device has high transconductance, miniaturization and / or low power consumption.

[0013] A field-effect transistor (FET) gas sensor device is provided, arranged to sense a gas. Here, "gas" essentially refers to any gas, particularly hydrogen (H2). The FET gas sensor device includes at least one gate, a source, a drain, and a semiconductor channel disposed between the source and the drain. The potential of the gate is in communication with the channel of semiconductor material, and a voltage bias applied between the source and the drain biases current to flow between the source and the drain. It will be understood that these FET components and their operation are known to those skilled in the art, and therefore any further description thereof is omitted. The semiconductor channel and the at least one gate form a FET channel-gate coupling, through which the applied gate potential is arranged to control the current flowing through the semiconductor channel. Thus, the term "FET channel-gate coupling" can be described as representing the correlation between the current through the channel and the gate potential (voltage) when the electric field in the semiconductor channel is changed by voltage biasing the gate, thereby forming the FET channel-gate coupling. The FET gas sensor device further includes at least one space disposed between the at least one gate and the semiconductor channel. The term "space" here refers to a three-dimensional (3D) (air) gap, space, chamber, region, void, etc., arranged or disposed between the gate and the semiconductor channel. In other words, since the gate and semiconductor are physically separated in a FET gas sensor device, a space is provided between the gate and the semiconductor channel.

[0014] At least one space in a FET gas sensor device is configured to receive gas. Therefore, the FET gas sensor device allows gas to enter the space between the gate and the semiconductor channel. The gas received in this at least one space is arranged to affect at least one electrical characteristic of the FET channel-gate coupling. Therefore, when gas is received (entering) the space between the gate and the semiconductor channel of the FET gas sensor device, the electrical characteristics of the FET channel-gate coupling may be influenced or affected by the presence of gas in the space. The FET gas sensor device is arranged to sense the gas based on the affected at least one electrical characteristic of the FET channel-gate coupling. Therefore, the FET gas sensor device is arranged or configured to sense or detect the gas based on the electrical characteristics of the FET channel-gate coupling, wherein the gas influences or acts on the electrical characteristics of the FET channel-gate coupling.

[0015] According to embodiments of the present invention, at least one of the source and drain, at least one gate, a semiconductor channel, and at least one space can be arranged in the same plane. Therefore, the gate, semiconductor channel, space, and source and / or drain of the FET gas sensor device are arranged in the same (common) plane. The arrangement of the FET gas sensor device components in the same common plane results in a particularly efficient response of the FET gas sensor device to gas received in the space between the gate and the semiconductor channel. This architecture or structure of the FET gas sensor device of the present invention enables direct coupling and / or transduction to the semiconductor channel, which greatly enhances the gas sensitivity of the FET gas sensor device. Therefore, the source, drain, and channel are arranged in a coplanar configuration. Furthermore, at least one gate, at least one gas gap, and channel are arranged in a coplanar configuration. Preferably, at least one of the source or drain, at least one gate, space, and channel are arranged in a coplanar configuration. Preferably, at least one gate, space, channel, source, and gate are arranged in a coplanar configuration. Therefore, at least one gate, space, channel, source, and gate are arranged in a common plane. Preferably, the two gates, two spaces, a channel, a source, and the gate are arranged in a coplanar configuration. Therefore, the two gates, two spaces, a channel, a source, and the gate are arranged in a common plane.

[0016] According to embodiments of the present invention, the FET gas sensor device further includes a substrate, wherein at least one of a source and a drain, at least one gate, a semiconductor channel, and at least one space are arranged in a common plane parallel to the surface of the substrate. The arrangement of the FET gas sensor device components in the same common plane parallel to the surface of the substrate allows for highly efficient fabrication of the device, requiring fewer fabrication steps. This arrangement also provides the possibility of defining the size of the space during the fabrication of the FET gas sensor device, wherein the size of the space is preferably ≤500 nm, which is particularly suitable for gas sensing purposes.

[0017] According to embodiments of the present invention, a FET gas sensor device may further include at least one layer disposed on at least a portion of a semiconductor channel, wherein the at least one layer includes a first layer arranged to interact with a gas received in at least one space. The term "layer" herein refers to a (relatively thin) layer, coating, covering, film, etc. Therefore, a FET gas sensor may include one or more layers, coatings, coverings, and / or films disposed on at least a portion of a semiconductor channel. An advantage of this embodiment is that the layers can improve one or more gas sensing characteristics of the FET gas sensor device.

[0018] The at least one layer may include a first layer arranged to interact with a gas received in at least one space. In other words, the first layer (which may also be represented as a sensing layer) is configured or arranged to interact with a gas received in the space. The first (sensing) layer thus interfaces with the gas received in at least one space between the gate and the semiconductor channel. The gas received in the space can interact with the first layer, and the gas can thereby affect at least one electrical characteristic of the FET channel-gate coupling. In other words, the interaction between the first layer and the gas is coupled to the FET channel-gate coupling, and thereby modulates the potential (voltage) sensed by the semiconductor channel from the gate. The gas received or injected into the space interacts with the first layer and is able to change the electrical characteristics of the FET channel-gate coupling. Thus, the FET gas sensor device is arranged to sense the gas based on the affected electrical characteristics of the FET channel-gate coupling, whereby this effect is enhanced by the first layer. According to an example, the first layer may be configured for enhanced interaction with one or more target compounds in the gas (relative to other components of the gas). It should be noted that the differentiated interactions between the first layer and various specific target compounds can allow for even more specific sensing or detection of the target compounds.

[0019] According to an embodiment of the invention, the at least one layer includes a portion disposed on the gate-facing surface of the semiconductor channel. Disposing the first layer on the gate-facing surface of the channel increases the coupling between the gate, the sensing layer, and the semiconductor channel, thereby providing increased sensitivity. In one embodiment, the side surface of the semiconductor channel faces the gate, and the first layer is disposed on the side surface. Therefore, the first layer is disposed between the gate / space and the semiconductor channel, thereby allowing direct coupling.

[0020] According to an example of the invention, the at least one layer includes a first portion disposed on a surface of the channel facing a gate, and a second portion disposed on a surface of the channel facing a second gate. According to one example, the first layer includes a portion disposed on a surface of the channel that is coplanar with the gate, space, channel, source, and drain.

[0021] According to embodiments of the present invention, the first layer may include at least one metal. Therefore, the first layer may include one or more metals, or even be composed of one or more metals. An advantage of this embodiment is that a metallic first layer can further enhance the gas sensitivity of the FET gas sensor device.

[0022] According to embodiments of the invention, the first layer comprises one of the following: a film of at least one metal; metal nanoparticles (NPs); and nanoparticles of at least one metal selected from the group consisting of platinum (Pt), palladium (Pd), gold (Au), and nickel (Ni). Thus, the first layer may comprise or constitute a (relatively thin) film of one or more metals, or the first layer may comprise metal nanoparticles of platinum (Pt), palladium (Pd), gold (Au), and / or nickel (Ni). "Nanoparticles" refers to particles having a small size of approximately less than 100 nm and preferably less than 20 nm. An advantage of this embodiment is that the metal film or nanoparticles of the first layer are particularly suitable for the gas sensitivity of FET gas sensor devices. The nanoparticles can be designed to have a desired size, which allows for enhanced interaction with specific gaseous substances. A particular advantage of this embodiment is that the nanoparticles of the mentioned metal act as catalysts for molecular hydrogen (H2) to generate a reaction and penetrate the first layer toward the interface between the sensing layer and the semiconductor channel. The nanoparticles may comprise alloy or oxide nanoparticles.

[0023] According to embodiments of the invention, the at least one layer may include a second layer disposed on at least a portion of the first layer, wherein the second layer comprises at least one polymer and is arranged to protect the first layer from moisture. Therefore, the FET gas sensor may include a second layer comprising or composed of one or more polymers, wherein the second layer is at least partially disposed on the first layer to protect the first layer from moisture.

[0024] According to embodiments of the present invention, the at least one layer may include a third layer, wherein the third layer is dielectric and is arranged to passivate the surface of the semiconductor channel. Therefore, the FET gas sensor may include a third dielectric layer configured or arranged to passivate the surface of the semiconductor channel. The term "passivation" here refers to protection, shielding, etc. The third layer (which may also be referred to as a barrier layer) may be configured to protect the semiconductor channel from gas degradation. According to an example, the third (barrier) layer may include or even constitute an oxide. According to an example, the third layer may include an oxide (e.g., silicon dioxide SiO2, hafnium oxide HfO). x Aluminum oxide AlO x At least one of ) and nitride. The third layer may be, for example, an electrical insulator.

[0025] According to embodiments of the present invention, a third layer may be disposed on at least a portion of the semiconductor channel, and a first layer may be disposed on at least a portion of the third layer. Therefore, a third (barrier) layer is disposed on the semiconductor channel, and a first (sensing) layer is disposed on the third (barrier) layer. According to an example, the third layer may include the first layer.

[0026] According to embodiments of the invention, the third layer can have a thickness ranging from 0.5 nm to 10 nm. Therefore, the third layer can be relatively thin. Having a space or distance of, for example, less than 500 nm between the gate and the semiconductor channel ensures the formation of a main conductive channel in the side surface of the semiconductor channel or nanowire, which is separated from the first layer only by the third layer. The relatively thin third layer according to this embodiment allows electron tunneling through it. In the example, electrons can tunnel between the first layer (the metal NP embedded in the first layer) and the semiconductor channel, thus balancing them. Therefore, NPs with potential energy below the Fermi level will be filled with electrons. When exposed to H2 gas, for example, Pd NPs (palladium nanoparticles) can react with H2, even at room temperature. The gas reaction will form a new phase in the NP and generate an interfacial dipole between the NP and SiO2, which will increase the potential energy of the NP. Therefore, some filled NP states will be raised above the Fermi level, and electrons in these states will be decapitated back into the semiconductor channel to generate a current signal. Electron capture / decapture processes create a direct connection between, for example, the Pd NP-H2 reaction and the main conduction channel, thereby enabling highly efficient signal transduction.

[0027] According to an embodiment of the invention, the third layer can have a thickness ranging from 0.5 nm to 5 nm. This embodiment is particularly advantageous regarding the tunneling effect as described above, because the (very) thin third layer causes even more efficient signal transduction.

[0028] According to an embodiment of the invention, the semiconductor channel may extend along axis A, and the FET gas sensor device includes two gates arranged on opposite sides of the semiconductor channel perpendicular to axis A. An advantage of this embodiment is that providing two gates enhances the FET channel-gate coupling, thereby resulting in higher sensitivity to gases received in and / or present in the space between the gate and the semiconductor channel. Therefore, according to this embodiment, the FET gas sensor device is thus provided with a dual-gate architecture, which can further enhance its gas sensitivity compared to a single-gate architecture including a single gate. According to one embodiment of the invention, the two gates, source, drain, channel, and space are arranged in a common plane that is on and parallel to the surface of the substrate.

[0029] According to embodiments of the invention, at least a portion of the semiconductor channel may comprise a nanowire. The term "nanowire" here refers to a semiconductor channel in the form of a fine wire, the cross-sectional diameter of which is preferably less than 100 nm. An advantage of this embodiment is that nanowires having a relatively small cross-section (i.e., a relatively small cross-sectional area of ​​the semiconductor channel) can increase the coupling between the semiconductor channel and a first layer (if provided). In the case where a first layer is provided, according to an example, at least a portion of the first layer may be disposed on the nanowire. Furthermore, the semiconductor channel may be a 1D nanowire (channel) wherein the 1D nanowire has a particularly strong electrical coupling with the first layer.

[0030] According to embodiments of the present invention, the FET gas sensor device may further include a substrate, wherein at least one of a gate, a source, a drain, and a semiconductor channel is disposed on a surface of the substrate. Thus, the gate, source, drain, and / or semiconductor channel are disposed on the same surface (i.e., the same side) of the substrate. The term substrate herein refers to a substrate used for providing mechanical and / or electrical support to components disposed thereon. The substrate may be insulating.

[0031] According to embodiments of the invention, the semiconductor channel can be arranged above the surface of the substrate. Therefore, the semiconductor channel can be suspended, and this arrangement can be referred to as a "floating (semiconductor) channel." An advantage of this embodiment is that the FET gas sensor device achieves even more improved thermal management. For example, with an insulating substrate provided, heat dissipation from the semiconductor channel (e.g., in the form of (1D) nanowires) to the insulating substrate is significantly reduced. Consequently, heat from the Joule effect of the semiconductor channel current accumulates in the semiconductor channel, and the semiconductor channel (and the first layer (if provided)) is heated. This increased temperature can accelerate the response of the FET gas sensor device, and thus improve the sensing sensitivity and / or response time of the FET gas sensor device.

[0032] According to embodiments of the present invention, the FET gas sensor device may further include a measurement unit configured to measure at least one affected electrical characteristic of the FET channel-gate coupling and to sense gas based on the measured affected electrical characteristic of the FET channel-gate coupling. "Measurement unit" herein refers to any unit, device, arrangement, component, etc., arranged or configured to measure the affected electrical characteristic of the FET channel-gate coupling. An advantage of this embodiment is that the measurement unit can efficiently and accurately measure the affected electrical characteristic of the FET channel-gate coupling. Therefore, the FET gas sensor device can sense and / or detect gas even more efficiently and accurately.

[0033] According to embodiments of the invention, the measuring unit can be further configured to determine the concentration of molecular hydrogen (H2) in the gas based on at least one affected electrical characteristic of the FET channel-gate coupling. This embodiment is advantageous in terms of the ability of FET gas sensor devices to sense and / or detect molecular hydrogen (H2).

[0034] According to embodiments of the present invention, the source, drain, and semiconductor channel can be formed from the same semiconductor material layer. Therefore, the source, drain, and semiconductor channel of the FET gas sensor device are formed from the same (common) semiconductor material layer. Forming the source, drain, and channel by patterning a thin film of the same material layer allows for highly efficient device fabrication. Forming these FET gas sensor device components from the same semiconductor material can be performed, for example, via photolithographic patterning followed by dry etching.

[0035] According to an embodiment of the invention, at least one space is ≤500nm. Therefore, the space between at least one gate and the semiconductor channel arranged in the FET gas sensor device is less than or equal to 500nm.

[0036] According to an example of the invention, a FET gas sensor device is configured to passively or actively induce a gas flow through at least one space of the FET gas sensor device. The FET gas sensor device may include any unit, means, etc., for driving a gas flow to and through a gas receiving space. Such passive or active gas flow induction can further improve the sensing sensitivity and / or response time of the FET gas sensor device.

[0037] According to an embodiment of a second aspect of the invention, the method may further include: measuring at least one affected electrical characteristic of the FET channel-gate coupling; and sensing gas based on the measured at least one affected electrical characteristic of the FET channel-gate coupling.

[0038] According to an embodiment of a second aspect of the invention, the method may further include providing a layer on at least a portion of a semiconductor channel, wherein the layer comprises one of the following: a film of at least one metal; metal nanoparticles; and nanoparticles of at least one metal selected from the group consisting of platinum (Pt), palladium (Pd), gold (Au), and nickel (Ni). The method may further include: measuring a current through the semiconductor channel and determining the concentration of molecular hydrogen (H2) in a gas based on the measured current.

[0039] Further objectives, features, and advantages of the invention will become clear upon studying the following detailed disclosure, drawings, and appended claims. Those skilled in the art will recognize that different features of the invention can be combined to create embodiments other than those described below. Attached Figure Description

[0040] This and other aspects of the invention will now be described in more detail with reference to the accompanying drawings, which illustrate one or more embodiments of the invention.

[0041] Figure 1 An example of a FET gas sensor 10 according to the prior art is shown schematically.

[0042] Figure 2a A FET gas sensor device according to an exemplary embodiment of the present invention is illustrated schematically.

[0043] Figures 2b to 2e A cross-section of a FET gas sensor device according to an exemplary embodiment of the present invention is shown schematically.

[0044] Figure 3a A FET gas sensor device according to an exemplary embodiment of the present invention is illustrated schematically.

[0045] Figure 3b A cross-section of a FET gas sensor device according to an exemplary embodiment of the present invention is shown schematically.

[0046] Figure 4a A FET gas sensor device according to an exemplary embodiment of the present invention is illustrated schematically.

[0047] Figure 4b A cross-section of a FET gas sensor device according to an exemplary embodiment of the present invention is shown schematically.

[0048] Figure 5a A FET gas sensor device according to an exemplary embodiment of the present invention is illustrated schematically.

[0049] Figure 5b A cross-section of a FET gas sensor device according to an exemplary embodiment of the present invention is shown schematically.

[0050] Figure 6 A flowchart illustrating a method according to an exemplary embodiment of the present invention is shown schematically.

[0051] Figure 7a and Figure 7b The performance of a FET gas sensor device according to an exemplary embodiment of the present invention is illustrated schematically. Detailed Implementation

[0052] Figure 1A FET gas sensor 10, an example of an existing technology, is schematically shown. Gas sensing is crucial for safety and environmental monitoring. Hydrogen sensing is used as an example, but other gases can also be sensed. Hydrogen is emphasized as a clean fuel because only water is produced when hydrogen is burned. At the same time, hydrogen is a flammable gas with a low explosive limit of 4% by volume in air. Therefore, even relatively low levels of hydrogen leakage can be a serious concern for its safe production and use. Consequently, there is a high demand for sensitive and rapid sensors for detecting gas (hydrogen) leaks, particularly for safety needs in hydrogen energy development.

[0053] FETs, due to their high transconductance, miniaturization, and low power consumption, have been explored as a device platform for hydrogen sensing. For example... Figure 1 The prior art FET gas sensor 10 illustrated includes a source 120, a drain 130, and a semiconductor channel 140 disposed between the source 120 and the drain 130. The source 120, drain 130, and semiconductor channel 140 are disposed on an insulating substrate 145. The insulating substrate 145 is in turn disposed on a gate 110. However, a problem with this FET gas sensor 10 is its low (limited) gas sensitivity and / or detection limit. Therefore, it is of interest to provide alternatives to prior art FET-type gas sensors in order to improve the sensitivity, response time, accuracy, and / or specificity of these gas sensors.

[0054] Figure 2a A FET gas sensor device 100 according to an exemplary embodiment of the present invention is schematically illustrated. The FET gas sensor device 100 (which in...) Figure 1 A FET gas sensor device (which may represent a side-gate FET gas sensor device) is arranged to sense a gas, such as hydrogen (H2). The FET gas sensor device 100 includes at least one gate 110a. Figure 2a In the diagram, only a single gate 110a is shown, but the FET gas sensor device 100 may alternatively include two or more gates. The FET gas sensor device 100 further includes a source 120, a drain 130, and a semiconductor channel 140 disposed between the source 120 and the drain 130. The semiconductor channel 140 extends along axis A, and when the source 120 and drain 130 are disposed at opposite ends of the semiconductor channel 140, the source 120, drain 130, and semiconductor channel 140 form an array of components extending along axis A.

[0055] According to this example of the FET gas sensor device 100, a gate 110a, a source 120, a drain 130, and a semiconductor channel 140 are disposed on an insulating substrate 145. The gate 110a, source 120, drain 130, and semiconductor channel 140 are thus disposed in a common plane. The semiconductor channel 140 and the gate 110a form (schematically indicated) a FET channel-gate coupling 150, through which the potential applied to the gate 110a is arranged to control the current flowing through the semiconductor channel 140. The FET channel-gate coupling 150 thus represents the correlation between the current through the semiconductor channel 140 and the potential (voltage) of the gate 110a, thereby forming the FET channel-gate coupling 150.

[0056] The gate 110a is physically separated from the semiconductor channel 140 in a direction B perpendicular to axis A. The FET gas sensor device 100 thus includes at least one space 200, indicated by a dashed line, arranged between the gate 110a and the semiconductor channel 140. The space 200 here constitutes a three-dimensional (3D) space, chamber, region, gap, etc., arranged or disposed between the gate 110a and the semiconductor channel 140. Therefore, the gate 110a is spaced apart from the semiconductor channel 140, thereby forming a gap between the gate 110a and the semiconductor channel 140, whereby the gap is not occupied by solid material. The gap forms a gas receiving space 200 for receiving the gas to be sensed. The space 200 can be open to the environment to allow communication between the gas and the environment. Therefore, the gas present in the gas receiving space 200 can be replaced by fresh gas from the environment.

[0057] The width w of space 200 can be defined by the arrangement of gate 110a from semiconductor channel 140 (i.e., the distance between gate 110a and semiconductor channel 140 parallel to direction B). The length l of space 200 can be defined by the length of gate 110a and / or semiconductor channel 140 parallel to axis A. The height h of space 200 can be defined by the height of gate 110a and / or semiconductor channel 140 perpendicular to axis A and perpendicular to direction B. Figure 1 An example of a FET gas sensor device 100 has a space 200 disposed between a gate 110a and a semiconductor channel 140 having a parallelepiped shape as indicated by the dashed line.

[0058] Space 200 is configured to receive gas because FET gas sensor device 100 allows gas to enter space 200 between gate 110a and semiconductor channel 140. The gas received in space 200 is arranged to affect at least one electrical characteristic of FET channel-gate coupling 150. FET gas sensor device 100 is arranged to sense the gas based on the affected at least one electrical characteristic of FET channel-gate coupling 150. Therefore, FET gas sensor device 100 is arranged or configured to sense or detect gas based on (according to) the electrical characteristics of FET channel-gate coupling 150, wherein the gas affects or acts on the electrical characteristics of FET channel-gate coupling 150.

[0059] Figure 2b A cross-section along axis A of a FET gas sensor device 100 according to an exemplary embodiment of the present invention is schematically shown. Figure 2b The FET gas sensor device 100 illustrated in the example corresponds to, for example, Figure 2a The FET gas sensor device 100 is illustrated in the figure, and its reference is... Figure 2a And associated text to enhance understanding of the features and / or functions of the FET gas sensor device 100. Figure 2b In this configuration, a semiconductor channel 140 and a gate 110a (disposed on an insulating substrate 145) are arranged at a distance B from each other along a direction perpendicular to axis A. This forms a space 200 between the gate 110a and the semiconductor channel 140. The distance between the semiconductor channel 140 and the gate 110a defines the width w of the space 200, and the height h of the space 200 is defined by the height of the semiconductor channel 140 and / or the gate 110a. The space 200 is configured to receive gas, whereby the gas received in the space 200 is arranged to affect the electrical characteristics of the FET channel-gate coupling 150. The FET gas sensor device 100 is arranged to sense the gas based on the affected electrical characteristics of the FET channel-gate coupling 150.

[0060] like Figure 2bThe illustrated FET gas sensor device 100 includes a first layer (sensing layer) 300 disposed on at least a portion of a semiconductor channel 140. The first layer 300 (also referred to as the sensing layer) is arranged to interact with a gas received in a space 200. The first layer 300 (which may include at least one metal) may further comprise or be composed of a film of metal, or include nanoparticles of a metal selected from the group consisting of platinum (Pt), palladium (Pd), gold (Au), and nickel (Ni). One or more electrical characteristics of the FET channel-gate coupling 150 (e.g., the conductivity of the semiconductor channel 140) are modulated by a gate 110a, and the first layer 300 is directly coupled to the semiconductor channel 140. The FET channel-gate coupling 150 is enhanced because the first layer 300 is located between the semiconductor channel 140 and the gate 110a. According to one example, the presence of gas in the gas receiving space 200 can affect the surface charge density of the first layer 300 and can affect the conductivity characteristics of the semiconductor channel 140. Figure 2b For example, at least a portion of the first layer 300 is disposed between the gate 110a and the semiconductor channel 140. An interaction mechanism may involve adsorption or adsorption of a compound on or within the first layer 300, altering the charge distribution in the layer on the semiconductor channel 140. This change in charge distribution can be converted into a potential signal visible in the semiconductor channel 140. According to an example, the first layer 300 may be configured as a liner to at least partially enclose the space 200. According to an example, at least a portion of the layer 300 is disposed on a side surface of the channel. According to an example, at least a portion of the layer 300 is disposed on the surface of the channel facing the space and the gate. According to another example, the first layer 300 is configured such that it is in gas communication with a gas present in the gas receiving space 200. The minimum distance between the surface of the first layer 300 and the surface of the gate 110a is equal to or less than 500 nm. Figure 2b In the example, the distance is 5nm to 100nm, because this size is particularly suitable for gas sensing purposes.

[0061] Figure 2c A cross-section of a FET gas sensor device 100 according to an exemplary embodiment of the present invention is shown schematically. Figure 2c The FET gas sensor device 100 illustrated in the example corresponds to, for example, Figure 2b The FET gas sensor device 100 is illustrated in the figure, and its reference is... Figure 2b And associated text to enhance understanding of the features and / or functions of the FET gas sensor device 100. With Figure 2b Compared to the FET gas sensor device 100 shown, Figure 2cThe illustrated FET gas sensor device 100 further includes a second layer 310 disposed on at least a portion of the first layer 300. Thus, the first layer 300 is disposed on at least a portion of the semiconductor channel 140, and the second layer 310 is disposed on at least a portion of the first layer 300. The second layer 310 comprises at least one polymer and is arranged to protect the first layer 300 from moisture.

[0062] Figure 2d A cross-section of a FET gas sensor device 100 according to an exemplary embodiment of the present invention is shown schematically. Figure 2b Compared to the FET gas sensor device 100 shown, Figure 2d The illustrated FET gas sensor device 100 further includes a third layer 320 disposed on at least a portion of the semiconductor channel 140. The third layer 320 (also referred to as a barrier layer or passivation layer) of the FET gas sensor device 100 is dielectric and is arranged to passivate the surface of the semiconductor channel 140. The third layer 320 is disposed on at least a portion of the semiconductor channel 140, and a first layer 300 is disposed on at least a portion of the third layer 320. According to one example, gas molecules in space 200 can form a dipole layer at the interface between the first layer 300 and the third layer 320, and can affect the conductivity characteristics of the semiconductor channel 140. According to yet another example, gas introduced into space 200 can interact with traps at the interface between the third (dielectric) layer 320 and the semiconductor channel 140, and can affect the electrical characteristics of the FET channel-gate coupling 150.

[0063] Figure 2e A cross-section of a FET gas sensor device 100 according to an exemplary embodiment of the present invention is schematically shown. The FET gas sensor device 100 includes, on a semiconductor channel 140, components according to... Figure 2b And the first layer 300 of the associated text, according to Figure 2c and the second layer 310 of the associated text, and according to Figure 2d The third layer 320 of the associated text.

[0064] Figure 3a A FET gas sensor device 100 according to an exemplary embodiment of the present invention is illustrated schematically. For example... Figure 3a The FET gas sensor device 100 illustrated in the example corresponds to, for example, Figure 2a The FET gas sensor device 100 is illustrated in the figure, and its reference is... Figure 2a And associated text to enhance understanding of the features and / or functions of the FET gas sensor device 100. Figure 3a In this semiconductor channel 140, at least a portion comprises nanowires. For example... Figure 3aAs illustrated, the entire semiconductor channel 140 constitutes a nanowire, and the nanowire may, for example, comprise silicon (Si). The width of the nanowire parallel to direction B is as follows: Figure 2a The width of the semiconductor channel 140 shown is smaller. Here, at least one space 200 arranged or configured to receive gas is arranged between at least one gate 110a and the semiconductor channel 140 including nanowires.

[0065] Figure 3b A cross-section of a FET gas sensor device according to an exemplary embodiment of the present invention is schematically shown. Figure 3b The FET gas sensor device 100 illustrated in the example corresponds to, for example, Figure 3a The FET gas sensor device 100 is illustrated in the figure, and its reference is... Figure 3a The accompanying text is provided to enhance understanding of the features and / or functionality of the FET gas sensor device 100. A first layer 300 is disposed on at least a portion of the nanowire (semiconductor channel) 140. The first layer 300 comprises metal nanoparticles, as schematically indicated by dots, wherein the metal is selected from the group consisting of platinum (Pt), palladium (Pd), gold (Au), and nickel (Ni).

[0066] The FET gas sensor device 100 further includes a third (barrier) layer 320, wherein the third layer 320 may comprise an oxide. Having a space or distance of less than 500 nm between the gate and the channel ensures the formation of a main conductive channel in the side surface of the channel or nanowire, which is separated from the metal nanoparticles embedded in the first layer only by the third layer. In one example, the oxide of the third layer is SiO2 with a thickness of less than 10 nm. In another example, the oxide of the third layer is SiO2 with a thickness of less than 7 nm. In yet another example, the oxide of the third layer is SiO2 with a thickness of less than 5 nm. In yet another example, the oxide of the third layer is SiO2 with a thickness of less than 2 nm. In yet another example, the oxide of the third layer is SiO2 with a thickness of greater than 0.5 nm. In yet another example, the oxide of the third layer is SiO2 with a thickness of greater than 1 nm. Having a thin third layer allows electrons to tunnel through it. In one example, electrons can tunnel between the metal nanoparticles embedded in the first layer and the semiconductor channel, thus balancing them. Therefore, the NP with a potential energy below the Fermi level will be filled with electrons. When exposed to H2 gas, Pd NPs can react with H2, even at room temperature. The gaseous reaction forms a new phase within the NP and creates an interfacial dipole between the NP and SiO2, which increases the NP's potential energy. Consequently, some filled NP states are raised above the Fermi level, and electrons in these states are decapsulated back into the semiconductor channel, generating a current signal. This electron trapping / decapsulation process creates a direct connection between the Pd NP-H2 reaction and the main conduction channel, enabling highly efficient signal transduction.

[0067] Figure 4a A FET gas sensor device 100 according to an exemplary embodiment of the present invention is schematically illustrated. The semiconductor channel 140 is based on... Figure 3a An example of the FET gas sensor device 100 is illustrated as a (silicon Si) nanowire. The FET gas sensor device 100 includes two gates 110a, 110b disposed on opposite sides of a semiconductor channel 140 perpendicular to axis A. Therefore, each of the gates 110a, 110b is separated from the semiconductor channel 140 along a direction B perpendicular to axis A. Thus, compared with the (single-side gate FET gas sensor device 100 disclosed herein... Figures 2a to 2e , Figure 3a and / or Figure 3b Compared to the FET gas sensor device 100, Figure 4a The FET gas sensor device 100 in the text refers to a dual-gate FET gas sensor device 100. Here, two spaces 200 arranged or configured to receive gas are arranged on both sides of the semiconductor channel 140, located between the two gates 110a, 110b and the semiconductor channel 140.

[0068] Figure 4b A cross-section of a FET gas sensor device 100 according to an exemplary embodiment of the present invention is shown schematically. Figure 4b The FET gas sensor device 100 illustrated in the example corresponds to, for example, Figure 4a The FET gas sensor device 100 is illustrated in the figure, and its reference is... Figure 4a The accompanying text is provided to enhance understanding of the features and / or functionality of the FET gas sensor device 100. A first layer 300 is disposed on at least a portion of the nanowire (semiconductor channel) 140. The first layer 300 comprises nanoparticles of metal, as schematically indicated by dots, wherein the metal is selected from the group consisting of platinum (Pt), palladium (Pd), gold (Au), and nickel (Ni). The FET gas sensor device 100 further comprises a third (barrier) layer 320, wherein the third layer 320 may comprise an oxide.

[0069] Figure 5a A FET gas sensor device 100 according to an exemplary embodiment of the present invention is illustrated schematically. For example... Figure 5a The FET gas sensor device 100 illustrated in the example corresponds to, for example, Figure 4a The FET gas sensor device 100 is illustrated in the figure, and its reference is... Figure 4a And associated text to enhance understanding of the features and / or functions of the FET gas sensor device 100. With Figure 4aIn contrast, a semiconductor channel 140 (in the form of a nanowire) is disposed above the surface of the substrate 145. Thus, the semiconductor channel 140 is suspended by the source 120 and the drain 130.

[0070] Figure 5b A cross-section of a FET gas sensor device 100 according to an exemplary embodiment of the present invention is schematically shown, illustrating the suspension arrangement of a semiconductor channel 140 above the surface of a substrate 145.

[0071] Figure 6 A flowchart of a method 500 for sensing a gas using a FET gas sensor device is shown. The FET gas sensor device includes at least one gate, a source, a drain, and a semiconductor channel disposed between the source and the drain, wherein the semiconductor channel and the at least one gate form a FET channel-gate coupling, through which a gate potential is arranged to control a current flowing through the semiconductor channel. The FET gas sensor further includes at least one space disposed between the at least one gate and the semiconductor channel. Method 500 includes the steps of: biasing the source and drain 510 with a first voltage to generate a current flowing through the semiconductor channel. The method further includes the steps of: biasing the gate 520 with a second voltage and controlling the current flowing through the semiconductor channel via the FET channel-gate coupling formed by the semiconductor and the at least one gate. The method further includes the steps of: receiving gas 530 in the at least one space, whereby the gas received in the at least one space is arranged to affect at least one electrical characteristic of the FET channel-gate coupling. The method further includes the steps of: sensing gas 540 based on the affected at least one electrical characteristic of the FET channel-gate coupling.

[0072] Figure 7a This schematically illustrates, for example, according to Figure 2a , Figure 2b , Figure 3a and / or Figure 3b The performance of the (single)-side gate FET gas sensor device 100 according to an exemplary embodiment of the present invention. Figure 7a The image shows a prior art FET sensor (such as...). Figure 1 a, Figure 1 (as shown in b) and the voltage signal (ΔV) between the FET gas sensor device 100 according to the present invention (as shown in b) and the voltage signal (ΔV) between them. TComparison of (V) versus time (s). Both the prior art FET sensor and the FET gas sensor device 100 are subjected to a conventional airflow. At the location of the first arrow 700, molecular hydrogen (H2) at a concentration of 2000 ppm is introduced. The voltage signal 710 of the prior art FET sensor shows almost no response, while the voltage signal 720 of the FET sensor device 100 according to the invention shows a significant response. At the location of the second arrow 730, air is introduced, and the curve shows the recovery behavior. This process is cycled several times with a repeatable response, demonstrating the significant response of the FET gas sensor device 100 of the invention to the gas, while the prior art FET sensor shows minimal response to the gas.

[0073] Figure 7b The illustration shows, for example, according to Figure 4a , Figure 4b , Figure 5a and / or Figure 5b Compared to the FET gas sensor device 100 according to an exemplary embodiment of the present invention, the dual-gate FET gas sensor device 100 has, for example, according to Figure 2a , Figure 2b , Figure 3a and / or Figure 3b The performance of the single-gate FET gas sensor device 100 according to an exemplary embodiment of the present invention is described. At the position of the first arrow 740, molecular hydrogen (H2) at a concentration of 2000 ppm is introduced. Compared to the voltage signal 760 of the single-gate FET gas sensor device 100, the voltage signal 750 of the double-gate FET gas sensor device 100 shows a more significant response. At the position of the second arrow 770, air is introduced, and the curve shows the recovery behavior. This process is cycled several times with a repeatable response.

[0074] Those skilled in the art will recognize that the invention is by no means limited to the preferred embodiments described above. Rather, many modifications and variations are possible within the scope of the appended claims. For example, one or more of the gates 110a, 110b, semiconductor channel 140, space 200, etc., may have different shapes, sizes, and / or dimensions than those depicted / described.

Claims

1. A field effect transistor, FET, gas sensor device (100) arranged to sense a gas, comprising: at least one gate electrode (110a, 110b), a source electrode (120), a drain electrode (130), a semiconductor channel (140) arranged between the source electrode and the drain electrode, wherein the semiconductor channel and the at least one gate electrode form a FET channel-gate coupling (150) through which an applied gate potential is arranged to control a current flowing through the semiconductor channel, and at least one space (200) arranged between the at least one gate electrode and the semiconductor channel, a substrate (145), wherein the at least one gate electrode, the semiconductor channel, the at least one space, and at least one of the source electrode and the drain electrode are arranged in a same plane parallel to a surface of the substrate, wherein the at least one space is configured to receive a gas, and at least one layer (300, 310, 320) provided on at least a portion of the semiconductor channel, wherein the at least one layer comprises: a first layer (300) comprising metal nanoparticles, wherein the first layer is arranged to interact with a gas received in the at least one space, and a third layer (320), wherein the third layer is dielectric and arranged to passivate a surface of the semiconductor channel, wherein the third layer is provided on at least a portion of the semiconductor channel and the first layer is arranged on at least a portion of the third layer, wherein the at least one layer comprises a portion provided on a surface of the semiconductor channel facing a gate electrode of the at least one gate electrode, whereby a gas received in the at least one space is arranged to influence at least one electrical property of the FET channel-gate coupling, and wherein the FET gas sensor device is arranged to sense a gas based on the influenced at least one electrical property of the FET channel-gate coupling.

2. The FET gas sensor device of claim 1, wherein, The first layer is separated from a main conduction channel generated in a lateral surface of the semiconductor channel by the third layer.

3. The FET gas sensor device of claim 1 or 2, wherein, The first layer comprises nanoparticles of at least one metal selected from the group consisting of platinum, Pt, palladium, Pd, gold, Au, and nickel, Ni.

4. The FET gas sensor device according to any one of the preceding claims, wherein, The at least one layer comprises a second layer (310) arranged on at least a portion of the first layer, wherein the second layer comprises at least one polymer and is arranged to protect the first layer from moisture.

5. The FET gas sensor device according to any one of the preceding claims, wherein, The third layer has a thickness in the range of 0.5 nm to 10 nm.

6. The FET gas sensor device of claim 5, wherein, The third layer has a thickness in the range of 0.5 nm to 5 nm.

7. The FET gas sensor device according to any one of the preceding claims, wherein, The semiconductor channel extends along an axis A, and wherein the FET gas sensor device comprises two gate electrodes (110a, 110b) arranged on opposite sides of the semiconductor channel perpendicular to the axis A.

8. The FET gas sensor device according to any one of the preceding claims, wherein, At least a portion of the semiconductor channel comprises a nanowire.

9. The FET gas sensor device according to any one of the preceding claims, wherein, At least one of the at least one gate electrode, the source electrode, the drain electrode, the semiconductor channel is arranged on a surface of the substrate.

10. The FET gas sensor device of claim 9, wherein, The semiconductor channel is arranged above the surface of the substrate.

11. The FET gas sensor device according to any one of the preceding claims, further comprising a measurement unit configured to: measure the affected at least one electrical property of the FET channel-gate coupling, and sense a gas based on the measured affected at least one electrical property of the FET channel-gate coupling.

12. The FET gas sensor device of claim 11, wherein, The measurement unit is further configured to determine a concentration of molecular hydrogen H2 in the gas based on the affected at least one electrical property of the FET channel-gate coupling.

13. The FET gas sensor device according to any one of the preceding claims, wherein, The source, the drain and the semiconductor channel are formed by the same semiconductor material layer.

14. The FET gas sensor device according to any one of the preceding claims, wherein, The at least one space is < 500 nm.

15. The FET gas sensor device of claim 14, wherein, The at least one space is 5 nm to 100 nm.

16. A method (500) of sensing a gas by a field effect transistor, FET, gas sensor device (100), the field effect transistor, FET, gas sensor device comprising: at least one gate (110a, 110b); a source (120); a drain (130); a semiconductor channel (140) arranged between the source and the drain, wherein the semiconductor channel and the at least one gate form a FET channel-gate coupling (150) by which a gate potential is arranged to control a current through the semiconductor channel; at least one space (200) arranged between the at least one gate and the semiconductor channel; and a substrate (145), wherein at least one of the source and the drain, the at least one gate, the semiconductor channel, and the at least one space are arranged in the same plane parallel to a surface of the substrate, wherein the FET gas sensor device further comprises at least one layer (300, 310, 320) provided on at least a portion of the semiconductor channel, wherein the at least one layer comprises: a first layer (300) comprising metal nanoparticles, wherein the first layer is arranged to interact with a gas received in the at least one space; and a third layer (320), wherein the third layer is dielectric and arranged to passivate a surface of the semiconductor channel, wherein the third layer is provided on at least a portion of the semiconductor channel and the first layer is arranged on at least a portion of the third layer, wherein the at least one layer comprises a portion provided on a surface of the semiconductor channel facing a gate of the at least one gate, the method comprising: biasing (510) the source and the drain with a first voltage to generate a current through the semiconductor channel, biasing (520) the gate with a second voltage and controlling the current through the semiconductor channel via a FET channel-gate coupling formed by the semiconductor and the at least one gate, receiving (530) a gas in the at least one space, whereby the gas received in the at least one space is arranged to affect at least one electrical property of the FET channel-gate coupling, sensing (540) a gas based on the affected at least one electrical property of the FET channel-gate coupling.

17. The method according to claim 16, the method further comprising: measuring the affected at least one electrical property of the FET channel-gate coupling, and sensing a gas based on the measured at least one affected electrical property of the FET channel-gate coupling.

18. The method of claim 16 or 17, further comprising: providing the first layer on at least a portion of the semiconductor channel, wherein the first layer comprises nanoparticles of at least one metal selected from the group consisting of platinum (Pt), palladium (Pd), gold (Au), and nickel (Ni), measuring a current through the semiconductor channel, and determining a concentration of molecular hydrogen (H2) in the gas based on the measured current.

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