CN109668942B - Two-dimensional metal/oxide heterojunction, preparation method thereof and sensor - Google Patents
Two-dimensional metal/oxide heterojunction, preparation method thereof and sensor Download PDFInfo
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- 229910052723 transition metal Inorganic materials 0.000 claims abstract description 50
- -1 transition metal chalcogenide compound Chemical class 0.000 claims abstract description 50
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- 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
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Abstract
The invention relates to a two-dimensional metal/oxide heterojunction, which comprises a two-dimensional transition metal oxide layer and a metallic two-dimensional transition metal chalcogenide compound layer, wherein the two-dimensional transition metal oxide layer and the metallic two-dimensional transition metal chalcogenide compound layer form a heterojunction in the same two-dimensional material plane. The preparation method of the two-dimensional metal/oxide heterojunction adopts laser to locally heat the metallic two-dimensional transition metal chalcogenide layer, so that one part of the metallic two-dimensional transition metal chalcogenide layer is converted into the two-dimensional transition metal oxide layer. The invention also relates to a sensor using the two-dimensional metal/oxide heterojunction.
Description
Technical Field
The invention relates to the technical field of nanometer, in particular to a two-dimensional metal/oxide heterojunction, a preparation method thereof and a sensor adopting the heterojunction.
Background
The metallic two-dimensional transition metal chalcogenide nano material has good conductivity and has wide application potential in two-dimensional electronic devices. The metallic two-dimensional transition metal chalcogenide nanomaterial is usually niobium disulfide (NbS)2) Tantalum disulfide (TaS)2) Vanadium disulfide (VS)2) Niobium diselenide (NbSe)2) Tantalum diselenide (TaSe)2) Vanadium diselenide (VSe)2) And the like.
In the prior art, the controllability of heterojunction prepared by growing on the surface of a metallic two-dimensional transition metal chalcogenide is poor, and the specific position and shape are difficult to realize. The heterojunction built by the transfer method can only be prepared in a stacked mode, and the contact interface is poor. Further, conventional oxide sensors and two-dimensional material sensors are subject to high operating temperature and low sensitivity.
Disclosure of Invention
In view of the above, the present invention provides a metal/oxide heterojunction in the same two-dimensional material plane, a method for preparing the same, and a sensor using the same.
A two-dimensional metal/oxide heterojunction comprising a two-dimensional transition metal oxide layer and a metallic two-dimensional transition metal chalcogenide layer, wherein the two-dimensional transition metal oxide layer and metallic two-dimensional transition metal chalcogenide layer form a heterojunction within the same two-dimensional material plane.
A sensor comprising a two-dimensional metal/oxide heterojunction, and first and second spaced apart metal electrodes, wherein the two-dimensional metal/oxide heterojunction comprises: the two-dimensional transition metal chalcogenide material comprises a two-dimensional transition metal oxide layer, a first metallic two-dimensional transition metal chalcogenide compound layer and a second metallic two-dimensional transition metal chalcogenide compound layer, wherein the first metallic two-dimensional transition metal chalcogenide compound layer and the second metallic two-dimensional transition metal chalcogenide compound layer are respectively positioned at two sides of the two-dimensional transition metal oxide layer and are positioned in the same two-dimensional material plane; the first metal electrode is electrically connected to the first metallic two-dimensional transition metal chalcogenide layer, and the second metal electrode is electrically connected to the second metallic two-dimensional transition metal chalcogenide layer.
A method of making a two-dimensional metal/oxide heterojunction, the method comprising the steps of: providing a metallic two-dimensional transition metal chalcogenide layer; and locally heating the metallic two-dimensional transition metal chalcogenide layer with laser in an oxygen-containing atmosphere so that a portion of the metallic two-dimensional transition metal chalcogenide layer is converted into a two-dimensional transition metal oxide layer.
Compared with the prior art, the preparation method of the metal/oxide heterojunction in the same two-dimensional material plane is simple, and when the heterojunction is used as a sensor, the heterojunction has higher sensitivity by using a sensing material which is completely exposed, a good contact interface and a novel sensing mechanism.
Drawings
Fig. 1 is a flow chart of a method for preparing a two-dimensional metal/oxide heterojunction according to an embodiment of the present invention.
Fig. 2 is a schematic top view of a two-dimensional metal/oxide heterojunction according to an embodiment of the present invention.
Fig. 3 is a schematic top view of another two-dimensional metal/oxide heterojunction according to an embodiment of the present invention.
Fig. 4 is a schematic top view of another two-dimensional metal/oxide heterojunction according to an embodiment of the present invention.
Fig. 5 is a schematic structural diagram of a sensor using a two-dimensional metal/oxide heterojunction according to an embodiment of the present invention.
Fig. 6 is an optical photograph of a linear channel of a sensor according to an embodiment of the present invention.
FIG. 7 is an optical photograph of a serpentine channel of a sensor provided by an embodiment of the present invention.
Fig. 8 is an Atomic Force Microscope (AFM) of a sensor having a linear channel according to an embodiment of the present invention.
FIG. 9 shows an NbS sensor with a linear channel according to an embodiment of the present invention2Electron diffraction photograph (SAED) of (a).
FIG. 10 shows Nb for a sensor with a linear channel according to an embodiment of the present invention2O5High Resolution Transmission Electron Microscopy (HRTEM).
Fig. 11 is a Fast Fourier Transform (FFT) of region 1 of fig. 10.
Fig. 12 is a fast fourier transform of region 2 of fig. 10.
Fig. 13 is a schematic diagram illustrating an operation principle of a sensor according to an embodiment of the present invention.
Fig. 14 is a current-voltage curve diagram of a sensor provided by an embodiment of the invention in an electrical test under a high vacuum environment.
Fig. 15 is a current-voltage curve diagram of a sensor provided by an embodiment of the invention under different humidity environments.
FIG. 16 shows an Nb of a sensor according to an embodiment of the present invention2O5An infrared spectrum of (1).
Fig. 17 is a graph of current versus humidity for a sensor provided by an embodiment of the present invention.
Fig. 18 is a current-time graph of response speed of a sensor provided by an embodiment of the present invention.
FIG. 19 is a current-time plot of the stability of a sensor provided by an embodiment of the present invention.
Fig. 20 is a graph of current versus temperature for a sensor provided by an embodiment of the present invention.
Fig. 21 is a graph of resistance versus temperature and resistance versus time for a sensor provided by an embodiment of the present invention.
FIG. 22 is a graph comparing positive temperature coefficient versus temperature for different temperature sensing materials.
FIG. 23 is a reversible current-voltage graph of a sensor according to an embodiment of the present invention.
Fig. 24 shows the results of the sensitivity test of the sensor provided in the embodiment of the present invention to ammonia gas concentration.
Fig. 25 shows the response time and recovery time test results of the sensor provided in the embodiment of the present invention.
FIG. 26 is a graph showing the sensitivity and response time of an ammonia gas sensor according to an embodiment of the present invention compared with those of ammonia gas sensors made of other materials.
Fig. 27 shows results of a gas selectivity test of a sensor according to an embodiment of the present invention.
FIG. 28 is a diagram of Au-Nb with conventional gold electrode contact2O5Schematic structural diagram of the Au sensor.
FIG. 29 shows Au-Nb of conventional gold electrode contact2O5-current-voltage curves of Au sensors compared to sensors provided by the present invention.
Fig. 30 is an optical photograph of a flexible sensor provided by an embodiment of the present invention.
Fig. 31 is a graph illustrating humidity and temperature sensing tests of a flexible sensor according to an embodiment of the present invention.
FIG. 32 is a graph of an ammonia gas sensing test of a flexible sensor according to an embodiment of the present invention.
Fig. 33 shows a current-radius of curvature test result of a flexible sensor according to an embodiment of the present invention.
FIG. 34 shows the results of a current-bend radius test of a flexible sensor according to an embodiment of the invention.
Description of the main elements
Detailed Description
The invention will be described in further detail with reference to the following drawings and specific embodiments.
For the convenience of understanding, the present invention first introduces a method for preparing a two-dimensional metal/oxide heterojunction provided in the embodiments of the present invention. The embodiment of the invention only uses NbS2/Nb2O5The heterojunction is illustrated as an example.
Referring to fig. 1, a method for preparing a two-dimensional metal/oxide heterojunction 101 according to an embodiment of the present invention includes the following steps:
step S10, providing a metallic two-dimensional transition metal chalcogenide layer 102; and
step S20, locally heating the metallic two-dimensional transition metal chalcogenide layer 102 with the laser 20 in an oxygen-containing atmosphere, so that a portion of the metallic two-dimensional transition metal chalcogenide layer 102 is converted into a two-dimensional transition metal oxide layer 103.
In the step S10, the thickness, shape, and preparation method of the metallic two-dimensional transition metal chalcogenide layer 102 are not limited and may be selected as needed. The thickness of the metallic two-dimensional transition metal chalcogenide layer 102 may be 5 nanometers to 100 nanometers. The metallic two-dimensional transition metal chalcogenide layer 102 may be a single layer of two-dimensional transition metal chalcogenide, or may include a plurality of two-dimensional transition metal chalcogenides stacked one on another. In this embodiment, the metallic two-dimensional transition metal chalcogenide layer 102 is NbS grown on the surface of the silicon substrate 100 by Chemical Vapor Deposition (CVD)2And (3) a layer. The NbS2The layer has a thickness of 30 nanometers, a lateral dimension of 15 microns to 30 microns, and a triangular shape. The NbS2The layers comprise 40-50 single layers of NbS arranged one on top of the other2。
In the step S20, any part of the metallic two-dimensional transition metal chalcogenide layer 102 may be locally scanned with the laser 20, and the shape and size of the part scanned with the laser 20 are not limited as long as the entire metallic two-dimensional transition metal chalcogenide layer is not scannedThe compound layer 102 may be used. The oxygen-containing atmosphere is air. The power of the laser 20 may be 10mW to 50 mW. The scanning speed of the laser 20 may be between 0.1 microns/sec and 1 micron/sec. In this example, the NbS was locally scanned in air at a scanning speed of 0.5 μm/sec using a laser having a power of 30mW and a wavelength of 532 nm2Middle part of layer, making the NbS2Thermal oxidation of the middle part of the layer to Nb2O5Layer, while both sides are still NbS2And (3) a layer. The NbS2The layer is metallic, the Nb2O5The layer is an insulator.
Referring to fig. 2, the two-dimensional metal/oxide heterojunction 101 is a metal-insulator-metal heterojunction NbS in the same two-dimensional material plane2-Nb2O5-NbS2. The two-dimensional metal/oxide heterojunction 101 includes a two-dimensional transition metal oxide layer 103 and metallic two-dimensional transition metal chalcogenide layers 102 respectively located on both sides of the two-dimensional transition metal oxide layer 103. It is understood that the two-dimensional metal/oxide heterojunction 101 may also comprise only one metallic two-dimensional transition metal chalcogenide layer 102 and one two-dimensional transition metal oxide layer 103, as shown in fig. 3; or includes a plurality of metallic two-dimensional transition metal chalcogenide layers 102 and a plurality of two-dimensional transition metal oxide layers 103 alternately disposed as shown in fig. 4. The metallic two-dimensional transition metal chalcogenide layer 102 and the two-dimensional transition metal oxide layer 103 may be disposed side by side as shown in fig. 2 or may be disposed circumferentially as shown in fig. 3.
It can be understood that, since the present invention employs the laser local thermal oxidation method to prepare the two-dimensional metal/oxide heterojunction 101, it is possible to obtain a heterojunction in the same two-dimensional material plane, and the method can precisely control the shape and size of the two-dimensional transition metal oxide layer 103. The sensor using the two-dimensional metal/oxide heterojunction 101 is characterized in that Nb is included in the two-dimensional metal/oxide heterojunction 1012O5The two opposing surfaces are fully exposed and have a large gas contact surface. It will be appreciated that the NbS of the present invention2-Nb2O5-NbS2Heterojunctions can also be used to make other electronic devices.
Referring to fig. 5, an embodiment of the present invention provides a sensor 10 including: a two-dimensional metal/oxide heterojunction 101, and a first electrode 104 and a second electrode 105. Specifically, the two-dimensional metal/oxide heterojunction 101 is NbS2-Nb2O5-NbS2A heterojunction.
The first electrode 104 is disposed on a surface of one metallic two-dimensional transition metal chalcogenide layer 102 and electrically connected to the metallic two-dimensional transition metal chalcogenide layer 102, and the second electrode 105 is disposed on a surface of the other metallic two-dimensional transition metal chalcogenide layer 102 and electrically connected to the metallic two-dimensional transition metal chalcogenide layer 102. The sensor 10 may further include a substrate 100, and the two-dimensional metal/oxide heterojunction 101 is disposed on a surface of the substrate 100. The substrate 100 may be a growth substrate, such as a silicon wafer, on which the metallic two-dimensional transition metal chalcogenide layer 102 is grown; the first electrode 104 and the second electrode 105 may also be fabricated on other substrates, for example, by first transferring the two-dimensional metal/oxide heterojunction 101 to a flexible polymer substrate surface. The first electrode 104 and the second electrode 105 are metal electrodes. In this embodiment, the first electrode 104 and the second electrode 105 are gold films, and the NbS is2-Nb2O5-NbS2The heterojunction is arranged on the surface of the silicon substrate.
The two-dimensional transition metal oxide layer 103 forms a channel of the sensor 10. The embodiment of the present invention separately prepares the sensor 10 with a linear channel (linear) and the sensor 10 with a serpentine channel (serpentine). As can be seen with reference to FIGS. 6-7, NbS2-Nb2O5The interfacial contact is good.
Fig. 8 is an Atomic Force Microscope (AFM) of a sensor having a linear channel according to an embodiment of the present invention. Referring to FIG. 8, it can be seen that Nb2O5Nb with channel width of about 1 μm and formed by thermal oxidation2O5Thickness ratio of layer NbS2The thickness of the layer is reduced by about 2 nm to 3 nm.
FIG. 9 shows a sensor with a linear channel according to an embodiment of the present inventionNbS of device2Electron diffraction photograph (SAED) of (a). FIG. 10 shows Nb for a sensor with a linear channel according to an embodiment of the present invention2O5High Resolution Transmission Electron Microscopy (HRTEM). Fig. 11 is a Fast Fourier Transform (FFT) of region 1 of fig. 10. Fig. 12 is a fast fourier transform of region 2 of fig. 10. From FIGS. 9-12, it can be seen that NbS2Is a 3R crystal phase, and Nb2O5T-Nb being orthorhombic2O5。
Said using NbS2-Nb2O5-NbS2The heterojunction sensor 10 can be used as a humidity sensor, a temperature sensor, and a gas sensor. Next, the present invention first explains the operation principle of the sensor 10. The working principle of the sensor 10 is based on the external factors, such as water vapor or ammonia, vs. Nb2O5Regulating and controlling the surface hydrogen ion conductance.
Referring to FIG. 13, specifically, Nb2O5Is an insulator, and has surface adsorbing water molecules in air to form a conductive path with carrier H+. Total channel conductance G-N q mu, where N is H+Number q is H+The unit charge amount, μ, is the H + mobility. When power is applied, NbS2/Nb2O5The interface can generate electrochemical reaction to provide and consume H+Reaction 2H at the positive electrode2O→O2+4H++4e-The negative electrode reacts with 2H++2e→H2. Further, a reducing gas NH3Can participate in the electrochemical reaction of the positive electrode of the sensor 10 electrode, in particular 2NH3·H2O-6e-→N2+2H2O+6H+。
Fig. 14 is a current-voltage graph of the sensor 10 electrically tested in a high vacuum environment. As can be seen in FIG. 14, the sensor 10 is non-conductive and appears as an insulator Nb2O5Is the charge-discharge curve of the capacitor of the dielectric layer. Fig. 15 is a graph of current versus voltage for the sensor 10 tested in various humidity environments. As can be seen from fig. 15, the sensor 10 is conductive, and the current of the sensor 10 increases with the ambient humidityAnd is increased. FIG. 16 shows Nb of the sensor 102O5An infrared spectrum of (1). As can be seen in FIG. 16, there is a water molecule vibration peak in the sensor 10, demonstrating Nb2O5The surface is adsorbed by water molecules.
Next, the present invention further tests and analyzes the operational performance of the sensor 10.
As humidity sensor
The working principle is as follows: nb at constant temperature under different air humidity2O5The surface of the layer absorbs different amounts of water and carries H+The number is different, resulting in device conductance variations.
Test condition 1: the temperature of the test environment is constant at 25 ℃, the test voltage of the sensor 10 is constant at 0.8V, and the relative humidity of the test environment is gradually changed from 30% to 90%. Fig. 17 is a graph of current versus humidity for the sensor 10. As can be seen from fig. 17, the current of the sensor 10 can vary by 3 orders of magnitude with changes in humidity, i.e., the sensor 10 is highly sensitive to humidity.
Test condition 2: the temperature of the test environment is constant at 25 ℃, the test voltage of the sensor 10 is constant at 0.8V, and the relative humidity of the test environment is rapidly switched from 50% to 100% and then rapidly switched to 50%. Fig. 18 is a current-time graph of the response speed of the sensor 10. As can be seen in fig. 18, the response time of the sensor 10 is 10 seconds when the test environment relative humidity is rapidly switched from 50% to 100%, and the response time of the sensor 10 is 58 seconds when the test environment relative humidity is rapidly switched from 100% to 50%. That is, the response speed of the sensor 10 at the time of humidity rise is faster than that at the time of humidity fall. This is because Nb2O5The surface of the layer adsorbs water vapor faster than it desorbs water vapor. Nb if the test environment temperature rises2O5The layer will desorb water vapor faster, and the response speed will also be faster when the humidity drops.
Test condition 3: the temperature of the test environment is constant at 25 ℃, the test voltage of the sensor 10 is constant at 0.8V, and the sensor 10 continuously works for 1 hour in the test environment with the relative humidity of 50%, 70%, 90% and 100% respectively. Fig. 19 is a current-time plot of the stability of the sensor 10. As can be seen from fig. 19, the sensor 10 has stable performance in continuous 1-hour testing under different humidity environments.
(II) as a temperature sensor
The working principle is as follows: nb at different temperatures under constant absolute humidity2O5The surface of the layer absorbs different amounts of water and carries H+The number is different, resulting in device conductance variations. Specifically, as the temperature increases, Nb2O5Water molecules adsorbed on the surface of the layer are desorbed, and carriers H+Reduced number of Nb2O5The layer resistance increases; when the temperature is lowered, Nb2O5Water molecules adsorbed on the surface of the layer are increased, and current carriers H+Increased number of, Nb2O5The layer resistance decreases. That is, Nb2O5The layer exhibits a positive temperature coefficient of resistance PTCR (temperature rise, resistance rise). The temperature measurement mechanism is different from that of the existing temperature sensor.
Test condition 1: the absolute humidity of the fixed test environment is unchanged, the water vapor partial pressure is 1.5kPa, the test voltage of the sensor 10 is constant and is 0.8V, and the temperature of the test environment is increased from 25 ℃ to 55 ℃. Fig. 20 is a graph of current versus temperature for the sensor 10. As can be seen from fig. 20, the current of the sensor 10 can vary by 2-3 orders of magnitude with temperature, i.e. the sensor 10 is highly sensitive to temperature.
Test condition 2: the absolute humidity of a fixed test environment is unchanged, the water vapor partial pressure is 1.5kPa, the test voltage of the sensor 10 is constant and is 0.8V, the sensor 10 works for 550 seconds in the test environment with the temperature of 25 ℃, and the resistance of the sensor 10 is tested.
Test condition 3: the absolute humidity of a fixed test environment is unchanged, the water vapor partial pressure is 1.5kPa, the test voltage of the sensor 10 is constant and is 0.8V, the temperature of the test environment is continuously increased from 25 ℃ to 75 ℃, and the resistance of the sensor 10 is tested.
Fig. 21 is a graph of resistance versus temperature and resistance versus time for the sensor 10. As can be seen from fig. 21, in the continuous temperature rise test of the sensor 10, the device resistance increases with the temperature, the positive temperature coefficient of resistance can reach 20%/deg.c, and the current stability of the sensor 10 is good at 25 deg.c.
FIG. 22 is a graph comparing positive temperature coefficient versus temperature for different temperature sensing materials. As can be seen from FIG. 22, the positive temperature coefficient of the temperature sensor 10 is comparable to that of BaTiO currently commercialized3The positive temperature coefficient of the ceramic thermistor is equivalent, and the working temperature is lower than BaTiO3A ceramic. BaTiO 23The operating temperature of the ceramic is typically above 100 c and the temperature sensor 10 can operate between 25 c and 75 c.
Test conditions 4: the absolute humidity of a fixed test environment is unchanged, the water vapor partial pressure is 1.5kPa, the test voltage of the sensor 10 is constant and is 0.8V, and the test temperature is increased from 25 ℃ to 55 ℃ and then is decreased to 25 ℃. FIG. 23 is a reversible current-voltage graph of the sensor 10. As can be seen from fig. 23, the sensor 10 shows good reversibility, in which the current decreases with increasing temperature when the temperature increases from 25 ℃ to 55 ℃, and the current returns to the original value when the temperature decreases from 55 ℃ to 25 ℃.
(III) as ammonia (NH)3) Sensor with a sensor element
The working principle is as follows: in a constant temperature and humidity environment, reducing gas NH32NH capable of participating in a positive electrochemical reaction of the electrodes of the sensor 103·H2O-6e-→N2+2H2O+6H+Eventually, the carrier H is increased+Number, thereby affecting channel conductance. The ammonia gas sensor can work at room temperature, and the working principle of the ammonia gas sensor is different from that of the existing ammonia gas sensor.
Test condition 1: the temperature of the test environment is fixed at 25 ℃, the relative humidity is fixed at 50%, and the test voltage of the sensor 10 is constant at 0.8V. FIG. 24 shows the results of measuring the sensitivity of the sensor 10 to ammonia gas concentration, wherein the sensitivity is measured by current change I/I0And the resistance change amount Δ R/R. As can be seen from FIG. 24, the sensor 10 has a sensitivity to ammonia gas at a concentration of 1000ppmSensitivity I/I0The sensitivity deltar/R for ammonia at a concentration of 50ppm can reach 80%, i.e. the sensor 10 has a high sensitivity for ammonia concentrations. Fig. 25 shows the response time and recovery time test results of the sensor 10. As can be seen from fig. 25, the response time of the sensor 10 is 40 seconds and the recovery time is 110 seconds. Fig. 26 is a graph comparing the sensitivity and response time of the ammonia gas sensor 10 of the present invention with those of a conventional room temperature ammonia gas sensor based on a two-dimensional material. As can be seen from fig. 26, the sensitivity and response time of the ammonia sensor 10 of the present invention are significantly better than most existing room temperature ammonia sensors based on two-dimensional materials.
The superior performance of the ammonia gas sensor 10 of the present invention is attributed to its novel sensing mechanism: the ammonia gas participates in the electrode reaction, thereby realizing the regulation and control of the surface hydrogen ion conductance. The ammonia gas sensor of the invention can work at room temperature and can be in a nanometer size. However, the current commercialized ammonia gas sensors based on oxides are all charge doping mechanisms, which not only have low sensitivity but also need a working temperature higher than 200 ℃. The existing two-dimensional material sensor is also a charge doping mechanism and has lower sensitivity. The commercialized electrochemical sensor adopts a three-electrode complex structure, is generally a millimeter-scale device, and cannot realize a micron-scale device.
Test condition 2: the temperature of the test environment is fixed at 25 ℃, the relative humidity is fixed at 50%, and the test voltage of the sensor 10 is constant at 0.8V. The sensitivity of the sensor 10 to ammonia gas, hydrogen chloride gas, ethanol gas, acetone gas, ether gas, and cyclohexane gas was tested, respectively. Fig. 27 shows the results of the gas selectivity test of the sensor 10. As can be seen from fig. 27, the sensor 10 showed a clear response to only ammonia gas, showing excellent selectivity.
FIG. 28 is a diagram of Au-Nb with conventional gold electrode contact2O5Schematic structural diagram of the Au sensor. Au-Nb of traditional gold electrode contact2O5Au-based sensor and NbS-based sensor provided by invention2-Nb2O5-NbS2The structure of the sensor 10 of the heterojunction is substantially the same, except that the gold electrode is disposed directly on Nb2O5On both sides ofBut the same channel length and width. FIG. 29 shows Au-Nb of conventional gold electrode contact2O5Au-based sensor and NbS-based sensor provided by invention2-Nb2O5-NbS2Current-voltage curves of the heterojunction sensor 10 are plotted in comparison. As can be seen in FIG. 29, the present invention provides NbS-based devices2-Nb2O5-NbS2Heterojunction sensor 10 Au-Nb with electrode contact over conventional gold2O5The Au sensor has higher working current and lower working voltage. This is because the interface contact resistance of a high-quality metal/oxide heterojunction resulting from one-step laser processing is small. When NbS2-Nb2O5-NbS2When the length of the channel of the device is as low as 1 micron, the working voltage can be further reduced to 0.5V-0.8V, and when the width of the channel is increased by adopting a snake-shaped electrode design, the working current can reach 100 nA.
In another embodiment, the present invention produces a flexible sensor using a PET film as substrate 100. Fig. 30 is an optical photograph of a flexible sensor. FIG. 31 is a graph of humidity and temperature sensing tests for a flexible sensor. FIG. 32 is a graph of an ammonia gas sensing test for a flexible sensor. As can be seen from fig. 31-32, the performance of the flexible sensor is comparable to that of the sensor on a rigid silicon substrate. FIG. 33 is a current-radius of curvature test result for a flexible sensor. FIG. 34 is a graph of the current-bend radius test results for a flexible sensor. As can be seen from fig. 33-34, the minimum test curvature radius of the flexible sensor is 3 mm, and the bending times with the curvature radius of 10 mm is 200 times, and only slight changes of the current occur, which indicates that the flexible sensor has good mechanical properties.
In addition, other modifications within the spirit of the invention may occur to those skilled in the art, and such modifications within the spirit of the invention are intended to be included within the scope of the invention as claimed.
Claims (8)
1. A two-dimensional metal/oxide heterojunction comprising a two-dimensional transition metal oxide layer and a metallic two-dimensional transition metal chalcogenide layer, wherein said two-dimensional transition metal oxide layerAnd a metallic two-dimensional transition metal chalcogenide layer in the same two-dimensional material plane to form a heterojunction, wherein the two-dimensional transition metal oxide layer is Nb2O5A layer of said metallic two-dimensional transition metal chalcogenide layer being NbS2And (3) a layer.
2. A two-dimensional metal/oxide heterojunction as claimed in claim 1 wherein said two-dimensional metal/oxide heterojunction is NbS2-Nb2O5-NbS2A heterojunction.
3. A two-dimensional metal/oxide heterojunction as claimed in claim 1 wherein said Nb2O5The thickness of the layer is less than the NbS2The thickness of the layer.
4. A sensor comprising a two-dimensional metal/oxide heterojunction, and first and second spaced apart metal electrodes, wherein the two-dimensional metal/oxide heterojunction comprises: the two-dimensional transition metal chalcogenide material comprises a two-dimensional transition metal oxide layer, a first metallic two-dimensional transition metal chalcogenide compound layer and a second metallic two-dimensional transition metal chalcogenide compound layer, wherein the first metallic two-dimensional transition metal chalcogenide compound layer and the second metallic two-dimensional transition metal chalcogenide compound layer are respectively positioned at two sides of the two-dimensional transition metal oxide layer and are positioned in the same two-dimensional material plane; the first metal electrode is electrically connected to the first metallic two-dimensional transition metal chalcogenide layer, and the second metal electrode is electrically connected to the second metallic two-dimensional transition metal chalcogenide layer; the two-dimensional transition metal oxide layer is Nb2O5A layer, the first and second metallic two-dimensional transition metal chalcogenide layers being NbS2And (3) a layer.
5. A method of making a two-dimensional metal/oxide heterojunction, the method comprising the steps of:
providing NbS2A layer; and
locally heating the NbS with a laser in an oxygen-containing atmosphere2Layer, after laser local heating, saidNbS2Partial layer transformation to Nb2O5Layer of said Nb2O5Layer and the NbS2The layers form a heterojunction within the same two-dimensional material plane.
6. The method of claim 5, wherein the NbS is a two-dimensional metal/oxide heterojunction2The layer is grown on the substrate surface by chemical vapor deposition.
7. The method of claim 5, wherein the laser has a power of 10mW to 50mW and a scanning speed of 0.1 μm/sec to 1 μm/sec.
8. The method of claim 5, wherein the oxygen-containing atmosphere is air.
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