In2Se3 nanowire and preparation method and application thereof

Abstract

The invention provides an In2Se3 nanowire as well as a preparation method and application thereof. The preparation method of the In2Se3 nanowire comprises the following steps: conveying gas-phase Se to a substrate containing a catalyst by a second carrier gas, enabling the gas-phase Se to be in contact with In2O3, introducing a first carrier gas to reduce the In2O3, and depositing and growing on the substrate to obtain the In2Se3 nanowire. The preparation method disclosed by the invention is simple and efficient, the uniformity, the diameter and the length of the nanowire can be regulated and controlled, and the prepared In2Se3 nanowire overcomes the disadvantage that the In2Se3 nanowire is short and sparse in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and particularly relates to an In2Se3 nanowire and a preparation method and application thereof. Background Art

[0002] In2Se3 is a layered III-VI group semiconductor material with various crystal forms (such as α, β, β′, γ, etc.), and exhibits unique optoelectronic, gas-sensing, ferroelectric and piezoelectric properties. Its two-dimensional layered structure is combined by van der Waals forces, making it easy to be exfoliated into nanowires or nanosheets, and showing application potential in the following fields: (1) Optoelectronic devices: The wide bandgap (~1.3 eV) and high carrier mobility of In2Se3 are suitable for optoelectronic detectors, solar cells, etc.; (2) Non-volatile memories: Its ferroelectric phase transition characteristics (such as the transition between the α phase and the β phase) can be used for low-power phase change memories (PCMs); (3) Flexible electronics: The high mechanical flexibility and surface sensitivity characteristics of the nanowires make them ideal materials for flexible sensors and wearable devices.

[0003] Currently, the synthesis methods of In2Se3 nanowires mainly include chemical vapor deposition (CVD), solvothermal method and template method. The raw materials synthesized by the CVD method mainly include the synthesis using indium powder and selenium powder, In2Se3 source powder synthesis, and the synthesis using InCl3 and selenium powder. However, these methods still have the following problems: (1) Process complexity and cost: 1) The CVD method requires high temperature (500 - 800 °C) and precise gas flow control, with high equipment cost and difficult to scale up production; 2) The nanowires synthesized by the solvothermal method have poor crystallinity and uneven size distribution; 3) Safety and efficiency: The traditional vacuum sealed tube method or high-pressure synthesis method is prone to the risk of tube explosion due to the violent exothermic reaction of elemental indium (In) and selenium (Se), and the high volatility of selenium leads to uneven composition; 4) The atmospheric pressure synthesis method reduces the risk through two-step reactions, but the feeding amount is limited and the production efficiency is low; (2) Insufficient control of structure and performance: 1) Existing methods are difficult to precisely control the crystal orientation of the nanowires (such as growing along the

[0001] or [11-20] directions) and phase transition behavior, restricting their application in quantum devices; (3) The existing growth methods limit the growth length of In2Se3 nanowires.

[0004] The length of nanowires has important practical significance in specific scientific and technological applications. Taking silicon nanowires as an example, their length and diameter have a significant impact on their physical and chemical properties. In particular, ultra-long silicon nanowires show great application potential in the field of flexible wearable sensors. These sensors can quickly and accurately detect various physiological parameters in medical monitoring, such as human joint activities, because ultra-long silicon nanowires have unique mechanical, optical, and electrical properties. In addition, the applications of long nanowires are not limited to sensor technology. Their large specific surface area and high sensitivity to changes in the external environment also make them have broad application prospects in the field of biochemical sensors. These characteristics enable nanowire-based sensors to show advantages in terms of response speed, accuracy, selectivity, and service life.

[0005] Due to its unique physical and chemical properties, In2Se3 nanowires have broad prospects in the fields of optoelectronics, memory, and flexible devices. However, existing synthesis methods have significant bottlenecks in terms of efficiency, safety, and performance regulation. Summary of the Invention

[0006] The purpose of the present invention is to overcome the disadvantages in the prior art and provide an In2Se3 nanowire, its preparation method, and its application. The In2Se3 nanowire of the present invention overcomes the disadvantages of short and sparse In2Se3 nanowires in the prior art.

[0007] The first aspect of the present invention provides a preparation method of In2Se3 nanowires, including the following steps:

[0008] Transport gaseous Se to a substrate containing a catalyst with a second carrier gas and contact it with In2O3, then reduce In2O3 under the action of introducing a first carrier gas, and then deposit and grow In2Se3 nanowires on the substrate.

[0009] The present invention prepares In2Se3 nanowires using the VLS growth mechanism based on chemical vapor deposition technology. The specific chemical reaction equation is as follows:

[0010] In2O3 + 3Se + H2 → In2Se3 + H2O↑

[0011] The preparation method of the present invention is simple and efficient, and can regulate the uniformity, diameter, and length of the nanowires. The prepared In2Se3 nanowires have a unique structure and ultra-long length, showing excellent mechanical, optical, and electrical properties, and can be widely applied in sensor technology, and show advantages in terms of response speed, accuracy, selectivity, and service life.

[0012] In some embodiments, the first carrier gas is hydrogen and the second carrier gas is nitrogen.

[0013] In some embodiments, the flow rate of the second carrier gas is 107 - 127 sccm; for example, it is 107 sccm, 112 sccm, 117 sccm, 120 sccm, 125 sccm, 126 sccm, 127 sccm, or any value therebetween. In some embodiments, the flow rate of the second carrier gas is 120 - 126 sccm. In some embodiments, the flow rate of the second carrier gas is 124 - 126 sccm.

[0014] In some embodiments, the flow rate of the first carrier gas is 0.2 - 20 sccm, for example, it is 0.2 ccm, 1 ccm, 1.5 ccm, 2 sccm, 2.5 ccm, 3 ccm, 5 sccm, 6 sccm, 7 sccm, 8 sccm, 9 sccm, 10 sccm, 15 sccm, 17 sccm, 20 sccm, or any value therebetween. In some embodiments, the flow rate of the first carrier gas is 1 - 7 sccm. In some embodiments, the flow rate of the first carrier gas is 1 - 3 sccm. In some embodiments, the flow rate of the first carrier gas is 2 sccm.

[0015] Since the flow rate of the carrier gas can change the growth density and length of the nanowires, thereby affecting the optoelectronic properties of the nanowires, thus, within the above range, the first carrier gas flow rate can obtain nanowires with excellent optoelectronic properties.

[0016] In some embodiments, the catalyst is gold particles.

[0017] In some embodiments, the thickness of the catalyst is 0.5 nm - 40 nm, for example, it is 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 20 nm, 40 nm, or any value therebetween. The thickness of the catalyst affects the sparsity of the nanowires, and within the above range, the obtained nanowires have a higher density.

[0018] In some embodiments, the catalyst is loaded on the substrate by sputtering.

[0019] In some embodiments, the sputtering time is 5 s - 4 min, for example, it is 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 1 min, 2 min, 3 min, 4 min, or any value therebetween.

[0020] In some embodiments, the sputtering rate is 5 - 20 nm / min, for example, it is 5 nm / min, 10 nm / min, 15 nm / min, 20 nm / min, or any value therebetween.

[0021] In some embodiments, the substrate includes a silicon oxide wafer and / or mica.

[0022] In some embodiments, in order to further regulate the uniformity of the nanowire diameter, the substrate containing the catalyst is also annealed.

[0023] In some embodiments, the annealing time is 10 - 60 min, such as 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, or any value therebetween.

[0024] In some embodiments, the annealing time is 20 - 40 min.

[0025] In some embodiments, the heating rate of the annealing is 0.1 - 100 °C / s, such as 0.1 °C / s, 1 °C / s, 5 °C / s, 10 °C / s, 15 °C / s, 20 °C / s, 50 °C / s, 80 °C / s, 100 °C / s, or any value therebetween.

[0026] In some embodiments, the annealing temperature is 200 °C - 720 °C, such as 200 °C, 250 °C, 300 °C, 350 °C, 400 °C, 500 °C, 600 °C, 720 °C, or any value therebetween.

[0027] In some embodiments, the mass ratio of the gaseous Se to In2O3 is 1:(0.4 - 0.5), such as 1:0.4, 1:0.42, 1:0.44, 1:0.46, 1:0.48, 1:0.5, or any value therebetween.

[0028] In some embodiments, the temperature of the deposition growth is 550 - 750 °C; such as 550 °C, 600 °C, 620 °C, 640 °C, 660 °C, 680 °C, 700 °C, 720 °C, 750 °C, or any value therebetween. In some embodiments, the temperature of the deposition growth is 650 - 750 °C. In some embodiments, the temperature of the deposition growth is 700 - 750 °C. The temperature of the deposition growth directly affects the diameter of the nanowires. When the temperature decreases, the solubility of In in Au decreases, so the amount of In element precipitated from the alloy droplets per unit time becomes less, and there are fewer binding sites for the subsequent Se atoms, thus resulting in a smaller diameter. And, according to the definition of viscosity in fluid mechanics, when the temperature increases, the molecular motion intensifies, the viscosity rises, and the probability of intermolecular collisions increases, and there will be a greater probability of nucleation to form nanowires. Therefore, within the above range of the deposition growth temperature, In2Se3 nanowires with a suitable diameter can be generated.

[0029] In some embodiments, the deposition growth time is 30 min - 6 h, such as 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, or any value therebetween. In some embodiments, the deposition growth time is 1 - 5 h. In some embodiments, the deposition growth time is 3 - 5 h. The deposition growth time affects the length and diameter of the nanowires. Within the above growth times, In2Se3 nanowires can be obtained. Appropriately extending the deposition growth time can increase the length of the nanowires.

[0030] In some embodiments, the heating temperature for the reduction of In2O3 is 550 - 750 °C; such as 550 °C, 620 °C, 640 °C, 660 °C, 680 °C, 700 °C, 720 °C, 750 °C, or any value therebetween. In some embodiments, the heating temperature for the reduction of In2O3 is 650 - 750 °C. In some embodiments, the heating temperature for the reduction of In2O3 is 700 - 750 °C. Different temperatures result in different diameters, lengths, and yields of the nanowires. If the temperature is too low, the diameter, length, and yield of the nanowires will all decrease.

[0031] In some embodiments, the heating rate is 26.5 - 35 °C / min, such as 26.5 °C / min, 30 °C / min, 31 °C / min, 32 °C / min, 33 °C / min, 34 °C / min, 35 °C / min, or any value therebetween.

[0032] In some embodiments, the method for preparing gaseous Se includes heating Se powder to sublimation.

[0033] In some embodiments, the heating temperature of Se powder is 300 - 350 °C; such as 300 °C, 310 °C, 330 °C, 350 °C, or any value therebetween.

[0034] In some embodiments, the heating rate of Se powder is 14 - 18 °C / min, such as 14 °C / min, 15 °C / min, 16 °C / min, 17 °C / min, 18 °C / min, or any value therebetween.

[0035] In some embodiments, the apparatus used in the preparation method is a two-temperature tube furnace.

[0036] In some embodiments, the preparation method includes:

[0037] (1) Flushing the two-temperature tube furnace with a second carrier gas and a first carrier gas in sequence;

[0038] (2) Heat Se powder to the gas phase in the low-temperature zone of a two-temperature tube furnace, bring In2O3 into contact with the catalyst-containing substrate in the high-temperature zone of the two-temperature tube furnace, and keep it at the high-temperature zone temperature.

[0039] (3) Use the second carrier gas to transport the gaseous Se to the high-temperature zone to contact with In2O3, use the first carrier gas to reduce In2O3, and deposit and grow on the substrate.

[0040] In some embodiments, the time for each gas washing is 1 - 5 min; for example, it is 1 min, 2 min, 3 min, 4 min, 5 min or any value between them.

[0041] In some embodiments, in step (1), during the gas washing process, the flow rate of the second carrier gas is 1200 - 1300 sccm; for example, it is 1200 sccm, 1250 sccm, 1300 sccm or any value between them.

[0042] In some embodiments, in step (1), during the gas washing process, the flow rate of the first carrier gas is 30 - 50 sccm; for example, it is 30 sccm, 35 sccm, 40 sccm, 45 sccm, 50 sccm or any value between them.

[0043] In some embodiments, the temperature of the low-temperature zone is 300 - 350 °C; for example, it is 300 °C, 310 °C, 330 °C, 350 °C or any value between them.

[0044] In some embodiments, the heating rate of the low-temperature zone is 14 - 18 °C / min; for example, it is 14 °C / min, 15 °C / min, 16 °C / min, 17 °C / min, 18 °C / min or any value between them.

[0045] In some embodiments, the temperature of the high-temperature zone is 550 - 750 °C; for example, it is 550 °C, 600 °C, 620 °C, 640 °C, 660 °C, 680 °C, 700 °C, 720 °C, 750 °C or any value between them. In some embodiments, the temperature of the high-temperature zone is 650 - 750 °C. In some embodiments, the temperature of the high-temperature zone is 700 - 750 °C.

[0046] In some embodiments, the heating rate of the high-temperature zone is 26.5 - 35 °C / min; for example, it is 26.5 °C / min, 30 °C / min, 31 °C / min, 32 °C / min, 33 °C / min, 34 °C / min, 35 °C / min or any value between them.

[0047] In some embodiments, to obtain nanowires with appropriate length and diameter, the heat preservation time is 30 min - 6 h, preferably 1 - 5 h, more preferably 3 - 5 h.

[0048] In some embodiments, in step (3), the flow rate of the second carrier gas is 107 - 127 sccm; for example, it is 107 sccm, 112 sccm, 117 sccm, 120 sccm, 125 sccm, 126 sccm, 127 sccm or any value between them. In some embodiments, the flow rate of the second carrier gas is 120 - 126 sccm. In some embodiments, the flow rate of the second carrier gas is 124 - 126 sccm.

[0049] In some embodiments, in step (3), the flow rate of the first carrier gas is 0.2 - 20 sccm, for example, it is 0.2 ccm, 1 ccm, 1.5 ccm, 2.5 ccm, 3 ccm, 2 sccm, 5 sccm, 6 sccm, 7 sccm, 8 sccm, 9 sccm, 10 sccm, 15 sccm, 17 sccm, 20 sccm or any value between them. In some embodiments, the flow rate of the first carrier gas is 1 - 7 sccm. In some embodiments, the flow rate of the first carrier gas is 1 - 3 sccm. In some embodiments, the flow rate of the first carrier gas is 2 sccm.

[0050] In some embodiments, the preparation method further includes a post - treatment step.

[0051] In some embodiments, the post - treatment step includes: placing the substrate containing the In2Se3 nanowires in deionized water or alcohol and performing ultrasonic treatment.

[0052] In some embodiments, the preparation method includes the following steps:

[0053] Step 1: Spraying the catalyst on the polished surface of the cleaned substrate for 5 s - 4 min;

[0054] Step 2: Placing In2O3 powder and Se powder on the quartz boat respectively. Among them, the In2O3 powder is placed at three positions in the quartz boat, with each position about 1 cm apart. Place the catalyst - containing surface of the substrate in step 1 on top of the quartz boat containing In2O3 powder. After placement, put them into the low - temperature zone and high - temperature zone of the double - temperature tube furnace respectively;

[0055] Step 3: Washing the double - temperature tube furnace in step 2. First, wash it with nitrogen (N2) for 3 min, and then wash it with hydrogen (H2) for 3 min;

[0056] Step 4: Set the furnace temperature for the double-temperature tube furnace in Steps 2 and 3. The temperature of the low-temperature zone is set to 300 - 350 °C, with a heating rate of 14 - 18 °C / min. The temperature of the high-temperature zone is set to 550 °C - 750 °C, with a heating rate of 26.5 °C / min - 35 °C / min. The holding time is set to 30 min - 6 h, and then it is naturally cooled;

[0057] Step 5: When the temperature of the low-temperature zone of the double-temperature tube furnace in Step 4 is 0 °C - 350 °C and the temperature of the high-temperature zone is 0 °C - 750 °C, adjust the nitrogen flow rate to 107 sccm - 127 sccm;

[0058] Step 6: During the holding process of the double-temperature tube furnace in Steps 4 and 5, adjust the flow rates of N2 and H2 to 107 sccm - 127 sccm and 0.2 - 20 sccm respectively. Here, hydrogen is used as a reducing agent to start growing nanowires;

[0059] Step 7: After the holding in Step 6 ends, when the temperature of the high-temperature zone drops to 550 °C - 690 °C, turn off H2, and N2 continues to be 107 - 127 sccm, and start natural cooling.

[0060] Step 8: Put the substrate with the product obtained in Step 7 into deionized water or alcohol and ultrasonicate it slightly to obtain In2Se3 nanowires.

[0061] The second aspect of the present invention provides In2Se3 nanowires prepared by the preparation method described in the first aspect. The length of the In2Se3 nanowires is 20 nm - 10 mm, and the diameter of the In2Se3 nanowires is 20 nm - 2 μm.

[0062] The In2Se3 nanowires of the present invention have a unique structure and an extremely long length, showing excellent mechanical, optical, and electrical properties. They can be widely applied to sensor technology and exhibit advantages in terms of response speed, accuracy, selectivity, and service life.

[0063] In some embodiments, the length of the In2Se3 nanowires can be 20 nm, 100 nm, 10 μm, 100 μm, 500 μm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or any value between them.

[0064] In some embodiments, the length of the In2Se3 nanowires is 1 - 10 mm.

[0065] In some embodiments, the length of the In2Se3 nanowires is 1 - 7 mm.

[0066] In some embodiments, the diameter of the In2Se3 nanowires can be 20 nm, 50 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 500 nm, 700 nm, 900 nm, 1 μm, 1.5 μm, 2 μm, or any value therebetween.

[0067] The diameter of the In2Se3 nanowires has a substantial impact on the optoelectronic properties. In the range of 20 nm - 2 μm in diameter, the In2Se3 nanowires have better optoelectronic properties.

[0068] In some embodiments, the In2Se3 nanowires have an α crystal form and / or a β crystal form.

[0069] The In2Se3 nanowires having an α crystal form means that the In2Se3 nanowires include a tetrahedral structure stacked layer by layer, and each tetrahedral structure includes 3 rhombic structures, as Figure 2 shown.

[0070] The In2Se3 nanowires having a β crystal form are as Figure 8 shown.

[0071] The third aspect of the present invention provides an application of the In2Se3 nanowires prepared by the preparation method described in the first aspect or the In2Se3 nanowires described in the second aspect in the fields of optoelectronic devices, memories, and flexible devices.

[0072] In some embodiments, the present invention provides an application of the In2Se3 nanowires prepared by the preparation method described in the first aspect or the In2Se3 nanowires described in the second aspect in semiconductor transistor devices.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] The preparation method of the present invention is simple and efficient, and can regulate the uniformity, diameter, and length of the nanowires. The In2Se3 nanowires prepared by the preparation method of the present invention have a unique structure and an ultra-long length, and exhibit excellent mechanical properties, optical properties, and electrical properties, and can be widely applied to sensor technology, and show advantages in response speed, accuracy, selectivity, and service life. Description of the Drawings

[0075] Figure 1 is a flowchart for the preparation of In2Se3 nanowires in an embodiment of the present invention;

[0076] Figure 2 is an SEM image of the In2Se3 nanowires prepared in Example 1 of the present invention;

[0077] Figure 3 Picture of the In2Se3 nanowires prepared in Example 1 of the present invention;

[0078] Figure 4 Mapping diagram of a single In2Se3 nanowire prepared in Example 1 of the present invention;

[0079] Figure 5 Raman spectrum diagram of the In2Se3 nanowires prepared in Example 1 of the present invention; among them, (a) is the Raman spectrum diagram of α-In2Se3, and (b) is the Raman spectrum diagram of β-In2Se3;

[0080] Figure 6 XPS energy spectrum diagram of the In2Se3 nanowires prepared in Example 1 of the present invention;

[0081] Figure 7 Morphology diagram and TEM diagram of the In2Se3 nanowires prepared in Example 1 of the present invention; among them, (a) is the morphology diagram of α-In2Se3 nanowires, (b) is the TEM diagram of α-In2Se3 nanowires, (c) is the morphology diagram of β-In2Se3 nanowires, and (d) is the TEM diagram of β-In2Se3 nanowires;

[0082] Figure 8 SEM diagram of the In2Se3 nanowires prepared in Example 2 of the present invention;

[0083] Figure 9 SEM diagram of the In2Se3 nanowires prepared in Example 3 of the present invention;

[0084] Figure 10 Energy spectrum diagram of the In2Se3 nanowires prepared in Example 3 of the present invention;

[0085] Figure 11 SEM diagram of the In2Se3 nanowires prepared in Example 4 of the present invention;

[0086] Figure 12 SEM diagram of the In2Se3 nanowires prepared in Example 5 of the present invention;

[0087] Figure 13 SEM diagram of the In2Se3 nanowires prepared in Example 6 of the present invention;

[0088] Figure 14 SEM diagram of the In2Se3 nanowires prepared in Example 7 of the present invention;

[0089] Figure 15 SEM diagram of the In2Se3 nanowires prepared in Example 8 of the present invention;

[0090] Figure 16 SEM image of the In2Se3 nanowires prepared in Example 9 of the present invention;

[0091] Figure 17 SEM image of the In2Se3 nanowires prepared in Example 10 of the present invention;

[0092] Figure 18 SEM image of the In2Se3 nanowires prepared in Example 11 of the present invention;

[0093] Figure 19 SEM image of the In2Se3 nanowires prepared in Example 12 of the present invention;

[0094] Figure 20 SEM image of the In2Se3 nanowires prepared in Example 13 of the present invention;

[0095] Figure 21 SEM image of the In2Se3 nanowires prepared in Example 14 of the present invention;

[0096] Figure 22 SEM image of the In2Se3 nanowires prepared in Example 15 of the present invention;

[0097] Figure 23 Device diagram of a single In2Se3 nanowire prepared in Example 1 of the present invention;

[0098] Figure 24 I-V curve diagram of the photocurrent and dark current of the In2Se3 nanowires prepared in Example 1 of the present invention;

[0099] Figure 25 Multiple photoelectric detection response diagram (left) and single response diagram (right) of the In2Se3 nanowires prepared in Example 1 of the present invention under 405 nm laser;

[0100] Figure 26 Multiple photoelectric test diagrams (left) and single photoelectric test diagrams (right) of the In2Se3 nanowires prepared in Example 1 of the present invention under 532 nm laser;

[0101] Figure 27 Multiple photoelectric test diagrams (left) and single photoelectric test diagrams (right) of the In2Se3 nanowires prepared in Example 1 of the present invention under 650 nm laser;

[0102] Figure 28 Multiple photoelectric test diagrams (left) and single photoelectric test diagrams (right) of the In2Se3 nanowires prepared in Example 1 of the present invention under 808 nm laser. Detailed implementation manners

[0103] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings. The specific embodiments described herein are only used to explain the present invention and do not constitute any limitation to the present invention.

[0104] In the ranges disclosed herein, the endpoints and any values are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0105] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the raw materials, instruments and equipment used in the following embodiments can all be obtained through market purchase or can be obtained by existing methods; the reagent dosages are all the dosages of reagents in conventional experimental operations unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0106] The sputtering rate of the catalyst in the embodiment of the present invention is 10 nm / min.

[0107] Example 1

[0108] As Figure 1 shown, this embodiment includes the following steps:

[0109] Step 1: Spray the catalyst (i.e., gold particles) on the polished surface of the cleaned silicon oxide wafer for 5 s (the thickness of the catalyst reaches 0.8 nm) to obtain a gold-sprayed silicon wafer as the growth substrate;

[0110] Step 2: Place 40 mg of selenium powder on a quartz boat. Place 20 mg of indium oxide powder on another quartz boat, and the indium oxide powder is placed at three points with a distance of about 1 cm. Place the gold-sprayed silicon wafer obtained in Step 1 with the gold-sprayed polished surface facing the indium oxide powder. After placement, place the quartz boat containing selenium powder in the low-temperature zone of the tube furnace as the selenium source, and place the quartz boat containing indium oxide powder in the high-temperature zone of the tube furnace as the indium source.

[0111] Step 3: Wash with N2 and H2 for 3 min respectively. At this time, the N2 flow rate is 1213 sccm and the H2 flow rate is 40.8 sccm. After the washing is completed, adjust the N2 flow rate to 120 sccm and turn off H2.

[0112] Step 4: Heating and heat preservation process

[0113] Set the temperature of the low - temperature zone of the tube furnace to 300 °C, the heating rate to 14 °C / min, the temperature of the high - temperature zone to 720 °C, the heating rate to 35 °C / min, and the holding time to 4 h, then cool it naturally; among them, the N2 flow rate is always maintained at 120 sccm;

[0114] During the holding process in the high - temperature zone, turn on H2, adjust the flow rate to 7 sccm, and start depositing and growing nanowires in the high - temperature zone;

[0115] Step Five: After the holding is completed, wait for it to cool to 690 °C, turn off H2, and the N2 flow rate remains 120 sccm, then start natural cooling.

[0116] Step Six: Put the sputtered - gold silicon wafer with the product obtained in Step Five into alcohol and ultrasonicate it slightly to obtain nanowires with an average diameter of about 20 nm - 2 μm and the longest length that can reach 7 mm.

[0117] Figure 2 This is the SEM image of the nanowires in this example. It can be seen that the nanowires have two morphologies, including a tetrahedral structure stacked layer by layer. Each tetrahedral structure includes 3 rhombic morphologies and a smooth - surface morphology.

[0118] Figure 3 This is a picture of the nanowires in this example taken by a mobile phone. Nanowires with a length of 1 - 7 mm can be seen with the naked eye.

[0119] Figure 4 This is the elemental surface - distribution picture of a single nanowire in this example. It can be seen that there is an enrichment of In element and Se element.

[0120] Figure 5 (a) This is the Raman spectrum of the nanowires grown in this example. It can be seen that there are two oscillation peaks. The peak positions are located at 104 cm -1 and 201 cm -1 respectively, belonging to the A1(LO + TO) vibration mode and the A1(LO) vibration mode, which are the vibration modes of α - In2Se3 and are consistent with those reported in the relevant literature. Figure 5 (b) This is a nanowire with a smooth surface morphology. It can be seen from the figure that there are 3 oscillation peaks. The characteristic peaks at 109 cm -1 and 77 cm -1 are the main vibration modes of β - In2Se3. The peak at 204 cm -1 is assigned to the stretching vibration of the In - Se bond and the A1(LO + TO) vibration mode. Therefore, through the Figure 5 Raman spectrum, it can be known that nanowires with α and β two crystal forms are synthesized in this example.

[0121] Figure 6This is the XPS energy spectrum diagram of this embodiment. As can be seen from the figure, for the electron binding energies of In and Se elements, the orbital energy of In in 3d 2 / 3 is 452.25 eV, and in 3d 2 / 5 the orbital energy is 444.72 eV. The orbital energy of Se in 3d 2 / 3 is 54.93 eV, and in 3d 2 / 5 the orbital energy is 53.96 eV.

[0122] Figure 7 This is the morphology diagram and TEM diagram of the nanowires obtained in this embodiment. Among them, (a) is the morphology diagram of α-In2Se3 nanowires, (b) is the TEM diagram of α-In2Se3 nanowires, (c) is the morphology diagram of β-In2Se3 nanowires, and (d) is the high-resolution TEM diagram of β-In2Se3 nanowires. As can be seen from the figure, the growth directions of α-In2Se3 nanowires and β-In2Se3 nanowires are

[001] and

[110] respectively.

[0123] Example 2

[0124] As Figure 1 shown, this embodiment includes the following steps:

[0125] Step 1: Spray the polished surface of the cleaned silicon oxide wafer with a catalyst (i.e., gold particles) for 30 s (the thickness of the catalyst is 5 nm) to obtain a gold-sprayed silicon wafer as the growth substrate;

[0126] Step 2: Place 40 mg of selenium powder on a quartz boat. Place 20 mg of indium oxide powder on another quartz boat, and place the indium oxide powder at three points with a distance of about 1 cm. Place the gold-sprayed polished surface of the gold-sprayed silicon wafer obtained in Step 1 facing the indium oxide powder. After placement, place the quartz boat containing selenium powder in the low-temperature zone of the tube furnace as the selenium source, and place the quartz boat containing indium oxide powder in the high-temperature zone of the tube furnace as the indium source.

[0127] Step 3: Purge with N2 and H2 for 3 min respectively. At this time, the N2 flow rate is 1213 sccm and the H2 flow rate is 40.8 sccm. After purging, adjust the N2 flow rate to 120 sccm and turn off H2.

[0128] Step 4: Heating and holding process

[0129] Set the temperature of the low-temperature zone of the tube furnace to 300 °C, the heating rate to 14 °C / min, the temperature of the high-temperature zone to °C, the heating rate to 35 °C / min, and the holding time to 90 min, and then cool naturally;

[0130] Among them, the nitrogen flow rate is maintained at 120 sccm;

[0131] During the heat preservation process in the high-temperature zone, open H2, adjust the flow rate to 7 sccm, and start depositing and growing nanowires in the high-temperature zone;

[0132] Step Five: After the heat preservation ends, wait for it to cool down to 690 °C, close H2, keep the N2 flow rate at 120 sccm, and start natural cooling.

[0133] Step Six: Put the sputtered gold silicon wafer with the product obtained in Step Five into alcohol and ultrasonicate it slightly to obtain nanowires with an average diameter of about 20 nm - 350 nm and a length in the millimeter range. Figure 8 This is the SEM image of this example.

[0134] Example 3

[0135] As Figure 1 shown, this example includes the following steps:

[0136] Step One: Spray the polished surface of the cleaned silicon oxide wafer with a catalyst (i.e., gold particles) for 30 s (the thickness of the catalyst is 5 nm) to obtain a sputtered gold silicon wafer as the growth substrate;

[0137] Step Two: Place 40 mg of selenium powder on a quartz boat. Place 20 mg of indium oxide powder on another quartz boat, and place the indium oxide powder at three points with a distance of about 1 cm. Place the sputtered gold silicon wafer obtained in Step One with the sputtered gold polished surface facing the indium oxide powder. After placement, place the quartz boat containing selenium powder in the low-temperature zone of the tube furnace as the selenium source, and place the quartz boat containing indium oxide powder in the high-temperature zone of the tube furnace as the indium source.

[0138] Step Three: Purge with N2 and H2 for 3 min respectively. At this time, the N2 flow rate is 1213 sccm and the H2 flow rate is 40.8 sccm. After purging, adjust the N2 flow rate to 125 sccm and close H2.

[0139] Step Four: Heating and heat preservation process

[0140] Set the temperature of the low-temperature zone of the tube furnace to 300 °C, the heating rate to 14 °C / min, the temperature of the high-temperature zone to 720 °C, the heating rate to 35 °C / min, the heat preservation time to 90 min, and then cool naturally;

[0141] Among them, the nitrogen flow rate is kept at 125 sccm;

[0142] During the heat preservation process in the high-temperature zone, open H2, adjust the flow rate to 2 sccm, and start growing nanowires in the high-temperature zone;

[0143] Step Five: After the heat preservation ends, wait for it to cool down to 690 °C, close H2, keep the N2 flow rate at 125 sccm, and start natural cooling.

[0144] Step 6: The sputtered gold silicon wafer with the product obtained in Step 5 is placed in alcohol and slightly ultrasonicated to obtain nanowires with an average diameter of about 20 nm - 2 μm and a maximum length of up to 2 mm. Figure 9 This is the SEM image of this example, which is Figure 9 It can be seen that it is denser in-plane and in the upwind direction (the carrier gas inlet end) compared with other examples. The energy spectrum is as Figure 10 shown. It can be seen that the sample is composed of In element and Se element and conforms to the atomic stoichiometric ratio of 2:3, and the synthesized product is In2Se3 nanowires.

[0145] Example 4

[0146] The difference from Example 2 is only that the temperature in the high-temperature zone in Step 4 is 650 °C. The SEM image of the obtained nanowires is as Figure 11 shown.

[0147] Example 5

[0148] The difference from Example 2 is only that the temperature in the high-temperature zone in Step 4 is 600 °C. The SEM image of the obtained nanowires is as Figure 12 shown.

[0149] Example 6

[0150] The difference from Example 2 is only that the temperature in the high-temperature zone in Step 4 is 550 °C. The SEM image of the obtained nanowires is as Figure 13 shown.

[0151] It can be seen from Examples 2, 4, 5, and 6 that the growth temperature of the nanowires is directly proportional to the average diameter of the nanowires, but inversely proportional to the density and length.

[0152] Example 7

[0153] The difference from Example 2 is only that after Step 1, the growth substrate is heated to 720 °C at a rate of 0.1 °C / s and annealed for 30 min. The SEM image of the obtained nanowires is as Figure 14 shown, and it can be seen that the diameter of the nanowires is more uniform.

[0154] Example 8

[0155] The difference from Example 7 is only that in Step 6, during the heat preservation process, the flow rates of N2 and H2 are adjusted to 125 sccm and 2 sccm respectively. The SEM image of the obtained nanowires is as Figure 15 shown. Compared with Example 3, the diameter of the nanowires is more uniform.

[0156] Example 9

[0157] The difference from Example 3 is only that in Step Six during the heat preservation process, the flow rates of N2 and H2 are adjusted to 107 sccm and 20 ccm respectively, and the SEM image of the obtained nanowires is as Figure 16 shown.

[0158] Example 10

[0159] The difference from Example 3 is only that in Step Six during the heat preservation process, the flow rates of N2 and H2 are adjusted to 112 sccm and 15 sccm respectively, and the SEM image of the obtained nanowires is as Figure 17 shown.

[0160] Example 11

[0161] The difference from Example 3 is only that in Step Six during the heat preservation process, the flow rates of N2 and H2 are adjusted to 117 sccm and 10 sccm respectively, and the SEM image of the obtained nanowires is as Figure 18 shown.

[0162] Example 12

[0163] The difference from Example 3 is only that in Step Six during the heat preservation process, the flow rates of N2 and H2 are adjusted to 126.8 sccm and 0.2 sccm respectively, and the SEM image of the obtained nanowires is as Figure 19 shown.

[0164] It can be seen from Examples 2 - 3, 9 - 12 that the influence of the carrier gas flow rate on the length of the nanowires is as follows: the carrier gas volume will affect the density and length of the nanowires. It can be obtained from the above examples that under the same conditions, when the H2 flow rate is 2 sccm, the density and length are the largest.

[0165] Example 13

[0166] The difference from Example 2 is only that in Step Four, the heat preservation time is 30 min, and the SEM image of the obtained nanowires is as Figure 20 shown.

[0167] Example 14

[0168] The difference from Example 2 is only that in Step Four, the heat preservation time is 45 min, and the SEM image of the obtained nanowires is as Figure 21 shown.

[0169] Example 15

[0170] The difference from Example 2 is only that in Step Four, the heat preservation time is 60 min, and the SEM image of the obtained nanowires is as Figure 22 shown.

[0171] It can be seen from Examples 2 and 13 - 15 that the influence of the heat preservation time on the length of the nanowires: the heat preservation duration is positively correlated with the length of the nanowires.

[0172] The results of the above - mentioned examples are recorded in Table 1.

[0173] Table 1

[0174]

[0175]

[0176] In summary, the heat preservation time, heat preservation temperature, and carrier gas flow rate have a substantial impact on the diameter and length of the nanowires. Further, annealing the substrate can effectively control the uniformity of the nanowires.

[0177] Further, compared with the nanowires directly prepared from In2Se3 in the prior art, the length of the In2Se3 nanowires in the prior art is only in the micrometer order of magnitude, while the length of the nanowires of the present invention is in the millimeter order of magnitude, which is more than 100 times that of the prior art and is more promising in the preparation of flexible electronic devices.

[0178] Test Example 1

[0179] As Figure 23 shown, optoelectronic devices were fabricated using the nanowires obtained in Example 1. Photoresponse tests were carried out under a laser with a wavelength of 405 nm at a light power density of 10.62 mW / cm 2 , and a bias voltage of 10 V. Figure 24 is the I - V curve of the photocurrent and dark current of the nanowires. It can be obtained that the impedance of the nanowires is in the order of 10 9 Ω. Figure 25 are the multiple detection results (left) and single - time photoresponse test results (right) under a 405 - nm laser respectively, and the photoresponsivity is 125.368 A / W.

[0180] Test Example 2

[0181] The difference between this test example and Test Example 1 is that a laser with a wavelength of 532 nm and a power density of 8.20 mW / cm 2 was used. Figure 26 are the multiple optoelectronic detection results (left) and single - detection results (right) respectively. It was tested that the photoresponsivity is 15.33 A / W.

[0182] Test Example 3

[0183] The difference between this test example and Test Example 1 is that a laser with a wavelength of 650 nm and a power density of 67.53 mW / cm 2 was used. Figure 27They are the results of multiple optoelectronic tests (left) and single detection results (right) respectively. Through testing, it is known that its optical responsivity is 9.8 A / W.

[0184] Test Example 4

[0185] The difference between this test example and Test Example 1 is that a laser with a wavelength of 808 nm and a power density of 35.07 mW / cm 2 , Figure 28 They are the results of multiple optoelectronic tests (left) and single detection results (right) respectively. Through testing, it is known that its optical responsivity is 5.61 A / W.

[0186] From the above test examples, it can be seen that the In2Se3 nanowires synthesized by using this method have a very sensitive detection ability for light of different wavelengths.

[0187] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing In2Se3 nanowires, comprising the following steps: Transport gaseous Se to a substrate containing a catalyst using a second carrier gas and contact it with In2O3, then introduce a first carrier gas to reduce In2O3, and then deposit and grow In2Se3 nanowires on the substrate.

2. The preparation method according to claim 1, characterized in that The first carrier gas is hydrogen, and the second carrier gas is nitrogen. Preferably, the flow rate of the second carrier gas is 107 - 127 sccm, preferably 120 - 126 sccm, more preferably 124 - 126 sccm. And / or, the flow rate of the first carrier gas is 0.2 - 20 sccm, preferably 1 - 7 sccm, more preferably 1 - 3 sccm.

3. The preparation method according to claim 1 or 2, characterized in that, The catalyst is gold particles. Preferably, the thickness of the catalyst is 0.5 nm - 40 nm. Preferably, the catalyst is loaded on the substrate by sputtering. Preferably, the sputtering time is 5 s - 4 min. Preferably, the sputtering rate is 5 - 20 nm / min. And / or, the substrate includes a silicon oxide wafer and / or mica. Preferably, the substrate containing the catalyst is also annealed. Preferably, the annealing time is 10 - 60 min, more preferably 20 - 40 min. Preferably, the heating rate of annealing is 0.1 - 100 °C / s. Preferably, the annealing temperature is 200 °C - 720 °C.

4. The preparation method according to any one of claims 1-3, characterized in that, The mass ratio of gaseous Se to In2O3 is 1:(0.4 - 0.5); and / or, the deposition and growth temperature is 550 - 750 °C, preferably 650 - 750 °C, more preferably 700 - 750 °C; and / or, the deposition and growth time is 30 min - 6 h, preferably 1 - 5 h, more preferably 3 - 5 h.

5. The preparation method according to any one of claims 1 - 4, wherein Preferably, the heating temperature for In2O3 reduction is 550 - 750 °C, preferably 650 - 750 °C, more preferably 700 - 750 °C. Preferably, the heating rate is 26.5 - 35 °C / min.

6. The preparation method according to any one of claims 1-4, characterized in that, The preparation method of gaseous Se includes: heating Se powder to sublimation. Preferably, the heating temperature of Se powder is 300 - 350 °C. Preferably, the heating rate of Se powder is 14 - 18 °C / min.

7. The preparation method according to any one of claims 1-6, characterized in that, The device used in the preparation method is a two - temperature tube furnace.

8. The preparation method according to claim 7, wherein The preparation method includes: (1) Wash the two - temperature tube furnace successively with the second carrier gas and the first carrier gas; preferably, the time for each gas washing is 1 - 5 min. (2) Heat Se powder to the gaseous state in the low - temperature zone of the two - temperature tube furnace, contact In2O3 with the substrate containing the catalyst in the high - temperature zone of the two - temperature tube furnace, and keep it at the high - temperature zone temperature. (3) Use the second carrier gas to transport gaseous Se to the high - temperature zone to contact In2O3, then introduce the first carrier gas to reduce In2O3, and deposit and grow on the substrate.

9. In2Se3 nanowires prepared by the preparation method according to any one of claims 1-8, wherein the length of the In2Se3 nanowires is 20 nm - 10 mm, preferably 1 - 10 mm; the diameter of the In2Se3 nanowires is 20 nm - 2 μm; Preferably, the In2Se3 nanowires have an α crystal form and / or a β crystal form.

10. Application of the In2Se3 nanowires prepared by the preparation method according to any one of claims 1-8 or the In2Se3 nanowires according to claim 9 in the fields of optoelectronic devices, memories and flexible devices; Preferably, application of the In2Se3 nanowires prepared by the preparation method according to any one of claims 1-8 or the In2Se3 nanowires according to claim 9 in semiconductor transistor devices.

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