Transition metal chalcogenide nucleation density regulation and control method and system

Abstract

The invention relates to a transition metal chalcogenide nucleation density regulation and control method which comprises the following steps: placing powdered sulfur in an initial temperature zone of an argon environment, heating the initial temperature zone, placing transition metal in a nucleation temperature zone of the argon environment, and heating the nucleation temperature zone; wherein argon continuously flows to the nucleation temperature zone from the initial temperature zone; after the initial temperature area is heated to the initial temperature, the nucleation temperature area is heated to the nucleation temperature; wherein the initial temperature is lower than the nucleation temperature; when the temperature of the nucleation temperature zone reaches the nucleation temperature, a certain flow of oxygen is continuously introduced into the initial temperature zone for a certain time and continuously flows to the nucleation temperature zone, and the nucleation temperature zone is naturally cooled to the room temperature after a certain time; and increasing the flow rate of the introduced oxygen to reduce the nucleation density of the transition metal chalcogenide. By adopting the method for regulating and controlling the nucleation density of the transition metal chalcogenide, the nucleation density of the transition metal chalcogenide can be regulated and controlled under the condition of ensuring the nucleation quality of the transition metal chalcogenide.

Description

Technical Field

[0001] The present invention relates to the field of single crystal growth, and particularly to a method for regulating the nucleation density of transition metal chalcogenides. Background Art

[0002] Transition metal chalcogenide thin films have unique physical properties such as electrical, optical, mechanical, and magnetic properties. They are the basic units of semiconductor devices and have unique advantages in the preparation of logic, storage, radio frequency, and optoelectronic devices. Since it is difficult to control the nucleation density of single-nucleus growth of transition metal chalcogenides, traditional transition metal chalcogenides generally adopt the method of multi-nucleus growth, and form transition metal chalcogenide thin films through multi-domain splicing. However, the operation of multi-domain splicing will cause many grain boundaries in the thin film, thereby affecting the material properties.

[0003] For example, the patent document with the application number "US20220243335A1" discloses a method for forming a bilayer MoS thin film by directly double-layer nucleation using the atomic steps on the surface of sapphire for existing transition metal chalcogenides. 2 Specifically, sulfur powder (S), metallic molybdenum (Mo), and a sapphire substrate are respectively placed in the first, second, and third temperature zones of a heating chamber. Among them, the sapphire is the C plane with a misorientation angle of 1°, and annealing treatment is carried out in air. The pressure inside the heating chamber is pumped to below 10 Pa, and 100 standard milliliters per minute (sccm) of Ar is introduced. The Mo, S, and sapphire substrate are respectively heated to 180°C, 850°C, and 1080°C. When the temperatures of all substrates reach their respective set values, the substrates are induced to react by 10 sccm of oxygen. After the oxygen reacts for 10 minutes, it is turned off. When the substrate temperature is cooled to 300°C in an Ar and S atmosphere, the S heating device is turned off and cooled to room temperature, thereby obtaining a MoS thin film. 2 Thin film.

[0004] However, the existing nucleation methods for transition metal chalcogenides can only change the nucleation morphology of single-nucleus growth and cannot control the nucleation density. This leads to serious stacking of the nucleation parts, mutual influence, poor growth effect, inability to obtain large-size single-nucleus crystal domains, and some are too loose, wasting material space. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a method for regulating the nucleation density of transition metal chalcogenides, which precisely regulates the nucleation density during the growth of transition metal chalcogenides by adjusting the gas flow rate of oxygen.

[0006] A method for regulating the nucleation density of transition metal chalcogenides includes:

[0007] Place sulfur powder in the starting temperature zone of an argon environment and heat the starting temperature zone while placing a transition metal in the nucleation temperature zone of the argon environment and heating the nucleation temperature zone; wherein, the argon continuously flows from the starting temperature zone to the nucleation temperature zone.

[0008] After the starting temperature zone is heated to the starting temperature, then heat the nucleation temperature zone to the nucleation temperature; wherein, the starting temperature is less than the nucleation temperature.

[0009] When the temperature of the nucleation temperature zone reaches the nucleation temperature, introduce oxygen with a certain flow rate into the starting temperature zone for a certain period of time and continuously flow to the nucleation temperature zone, and after a certain period of time, let the nucleation temperature zone cool down to room temperature naturally.

[0010] Increase the flow rate of the introduced oxygen to reduce the nucleation density of the transition metal chalcogenide.

[0011] Furthermore, the starting temperature is 120 - 160 °C, and the nucleation temperature is 800 - 850 °C.

[0012] Furthermore, heat the starting temperature zone to the starting temperature within 15 minutes and heat the nucleation temperature zone to the nucleation temperature within 40 minutes.

[0013] Furthermore, introduce argon into the heating chamber continuously at a flow rate of 30 - 35 sccm.

[0014] Furthermore, the transition metal is molybdenum or tungsten.

[0015] Furthermore, reduce the action time of introducing oxygen according to the total amount of sulfur powder and transition metal to improve the nucleation quality of the transition metal chalcogenide.

[0016] The present invention also provides a system for regulating the nucleation density of a transition metal chalcogenide, including a heating chamber and an air pump. The heating chamber includes a starting temperature zone and a nucleation temperature zone, wherein sulfur powder is arranged in the starting temperature zone and a transition metal is arranged in the nucleation temperature zone; the air pump continuously inputs argon into the starting temperature zone of the heating chamber, and heats the nucleation temperature zone while heating the starting temperature zone of the heating chamber; after the starting temperature zone is heated to the starting temperature, then heat the nucleation temperature zone to the nucleation temperature, and the starting temperature of the starting temperature zone is less than the nucleation temperature of the nucleation temperature zone; when the temperature of the nucleation temperature zone reaches the nucleation temperature, introduce oxygen with a certain flow rate into the starting temperature zone for a certain period of time and continuously flow to the nucleation temperature zone, and after a certain period of time, close the heating chamber and let the nucleation temperature zone cool down to room temperature naturally; increase the flow rate of the introduced oxygen to reduce the nucleation density of the transition metal chalcogenide.

[0017] Furthermore, it further includes a first receiving unit and a second receiving unit. The first receiving unit is arranged in the starting temperature zone of the heating chamber to receive sulfur powder; the second receiving unit is arranged in the nucleation temperature zone of the heating chamber to receive the transition metal.

[0018] Further, a growth substrate is provided on the surface of the second receiving unit, and the growth substrate is sapphire.

[0019] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of a system for regulating the nucleation density of transition metal chalcogenides according to the present invention.

[0021] Figure 2 It is an optical image of molybdenum disulfide nucleation obtained when oxygen is continuously introduced at a flow rate of 0.1 sccm in the method for regulating the nucleation density of transition metal chalcogenides according to the present invention.

[0022] Figure 3 It is an optical image of molybdenum disulfide nucleation obtained when oxygen is continuously introduced at a flow rate of 1 sccm in the method for regulating the nucleation density of transition metal chalcogenides according to the present invention.

[0023] Figure 4 It is an optical image of molybdenum disulfide nucleation obtained when oxygen is continuously introduced at a flow rate of 3 sccm in the method for regulating the nucleation density of transition metal chalcogenides according to the present invention.

[0024] Figure 5 It is an optical image of molybdenum disulfide nucleation obtained when oxygen is continuously introduced at a flow rate of 6 sccm in the method for regulating the nucleation density of transition metal chalcogenides according to the present invention.

[0025] Figure 6 It is a curve graph showing the relationship between the nucleation density of molybdenum disulfide and the flow rate of oxygen introduced in the method for regulating the nucleation density of transition metal chalcogenides according to the present invention.

[0026] Figure 7 It is a Raman spectrum of the nucleated molybdenum disulfide in the method for regulating the nucleation density of transition metal chalcogenides according to the present invention.

[0027] Figure 8 It is an optical image of tungsten disulfide nucleation obtained when oxygen is continuously introduced at a flow rate of 0.1 sccm in the method for regulating the nucleation density of transition metal chalcogenides according to the present invention.

[0028] Figure 9 It is an optical image of tungsten disulfide nucleation obtained when oxygen is continuously introduced at a flow rate of 1 sccm in the method for regulating the nucleation density of transition metal chalcogenides according to the present invention.

[0029] Figure 10 It is an optical image of tungsten disulfide nucleation obtained when oxygen is continuously introduced at a flow rate of 3 sccm in the method for regulating the nucleation density of transition metal chalcogenides according to the present invention.

[0030] Figure 11 This is the nucleation optical image of tungsten disulfide obtained when oxygen is continuously introduced at a flow rate of 6 sccm in the method for regulating the nucleation density of transition metal chalcogenides of the present invention.

[0031] Figure 12 This is the Raman spectrum of nucleated tungsten disulfide in the method for regulating the nucleation density of transition metal chalcogenides of the present invention.

[0032] Figure 13 This is the nucleation optical image of molybdenum disulfide obtained when oxygen is introduced for 30 minutes in the method for regulating the nucleation density of transition metal chalcogenides of the present invention.

[0033] Figure 14 This is the nucleation optical image of molybdenum disulfide obtained when oxygen is introduced for 5 minutes in the method for regulating the nucleation density of transition metal chalcogenides of the present invention. Detailed implementation manners

[0034] The applicant carefully analyzed the existing methods for nucleating transition metal chalcogenides and found that the reason for their large nucleation density is that sulfur powder is completely vaporized into sulfur vapor at 850 °C, and the flowing sulfur vapor deposits on the sapphire substrate to form a molybdenum disulfide film after contacting molybdenum metal. Each molybdenum atom in contact with the sulfur vapor starts to grow at the sapphire substrate, resulting in a very large nucleation density of molybdenum disulfide. Therefore, the applicant considered reducing the contact between the metal source and the sulfur source, so the heating temperature of the sulfur powder was reduced to lower its evaporation rate, and the sulfur source was reduced from floating with the gas to contact and react with the metal source to obtain transition metal chalcogenides. In addition, the applicant learned that oxygen will erode transition metal chalcogenides at high temperatures, so the flow rate of oxygen introduced was controlled to regulate the nucleation density of transition metal chalcogenides.

[0035] Please refer to Figure 1 , the system for regulating the nucleation density of transition metal chalcogenides of the present invention includes a heating chamber 1, an air pump (not shown in the figure), a first receiving unit 2 and a second receiving unit 3.

[0036] The heating chamber 1 is a three-zone CVD, including a hollow cylinder, which is divided into a starting zone, a transition zone and a nucleation zone with independently adjustable temperatures along the side direction of the cylinder, and an air inlet and an air outlet are respectively provided on the bottom surfaces at both ends.

[0037] The air pump introduces argon and oxygen into the heating chamber 1 through the air inlet of the heating chamber 1 as needed, and extracts the internal gas of the heating chamber 1 through the air outlet of the heating chamber 1 to form a vacuum environment.

[0038] The first receiving unit 2 is arranged in the starting temperature zone of the heating chamber 1 for receiving sulfur powder. The temperature of the starting temperature zone is relatively low, and the material requirement for the first receiving unit 2 is not high. It only needs to be able to receive sulfur powder and conduct heat to the sulfur powder normally.

[0039] The second receiving unit 3 is arranged in the nucleation temperature zone of the heating chamber 1 for receiving transition metals. Since the temperature of the nucleation temperature zone is relatively high, the second receiving unit 3 is made of a quartz plate. The quartz plate has a high melting point, can withstand high temperatures, and has strong thermal conductivity, which can provide a good heat transfer effect for the contact surface of the transition metal. A growth substrate is provided on the surface of the second receiving unit 3 to promote the reaction between the transition metal and sulfur powder to form nucleation of chalcogenide, and the growth substrate is made of sapphire.

[0040] The working process of the regulation system for the nucleation density of transition metal chalcogenide of the present invention is specifically described as follows:

[0041] Place the first receiving unit 2 in the starting temperature zone of the heating chamber 1, and place the second receiving unit 3 in the nucleation temperature zone of the heating chamber 1;

[0042] Place sulfur powder on the surface of the first receiving unit 2, and place transition metal on the surface of the second receiving unit 3; among them, the transition metal can be transition metals such as molybdenum and tungsten;

[0043] Use an air pump to evacuate the inside of the heating chamber 1 to a negative pressure from the air inlet or outlet of the heating chamber 1;

[0044] Continuously introduce argon into the heating chamber 1 through the air inlet at a flow rate of 30 - 35 sccm;

[0045] Control the starting temperature zone of the heating chamber 1 to start heating, heat the sulfur powder to 120 - 160 °C as the starting temperature within 15 minutes, and then control the starting temperature zone of the heating chamber 1 to continuously maintain the temperature at the starting temperature. According to the formula LogP = 14.7 - 0.0062238T - 5405.1 / T, where T is the absolute temperature in units of K; P is the saturated vapor pressure in units of mmHg. Substitute T = 160 + 273.15 = 433.15K into the formula to obtain the saturated vapor pressure of P = 10^(-0.473) mmHg ≈ 0.336 mmHg. When converted to units of Pa, the saturated vapor pressure is about 44.8 Pa. Under a low pressure of less than 10 Pa inside the heating chamber 1, liquid sulfur will continuously evaporate sulfur vapor, and the sulfur vapor will flow to the nucleation temperature zone together with argon. The flowing sulfur vapor makes the inside of the heating chamber 1 far from reaching the saturated vapor pressure, and the pressure is always maintained at a low pressure of 10 Pa.

[0046] At the same time, control the nucleation temperature zone of the heating chamber 1 to start heating, and raise the temperature of the second receiving unit 3 to 800 - 850 °C as the nucleation temperature within 40 minutes;

[0047] Oxygen is continuously introduced into the heating chamber 1 through the air inlet at a certain flow rate for 30 minutes, and the nucleation temperature zone of the heating chamber 1 is controlled to be kept at the nucleation temperature for 30 minutes to carry out the growth process of transition metal chalcogenides;

[0048] The heating of the nucleation temperature zone of the heating chamber 1 is controlled to stop, and the heating chamber 1 is allowed to cool naturally to room temperature;

[0049] Repeat the above operations, but change the flow rate of oxygen introduced each time to regulate the density of single nucleus growth.

[0050] In order to visually verify the effect of the method for regulating the nucleation density of the transition metal chalcogenides of the present invention, the applicant observes the nucleation optical image of the transition metal chalcogenides by using a microscope to analyze the nucleation density of the transition metal chalcogenides, and uses a spectrometer to detect the Raman spectrum of the transition metal chalcogenides to test the nucleation quality of the transition metal chalcogenides.

[0051] Combined with Figures 2 to 6 , Figure 2 shows the nucleation optical image of molybdenum disulfide obtained when oxygen is continuously introduced into the heating chamber 1 at a flow rate of 0.1 sccm; Figure 3 shows the nucleation optical image of molybdenum disulfide obtained when oxygen is continuously introduced into the heating chamber 1 at a flow rate of 1 sccm; Figure 4 shows the nucleation optical image of molybdenum disulfide obtained when oxygen is continuously introduced into the heating chamber 1 at a flow rate of 3 sccm; Figure 5 shows the nucleation optical image of molybdenum disulfide obtained when oxygen is continuously introduced into the heating chamber 1 at a flow rate of 6 sccm; Figure 6 shows the relationship curve between the nucleation density of molybdenum disulfide and the flow rate of oxygen introduced. It can be seen that as the flow rate of oxygen introduced increases, the nucleation density of molybdenum disulfide gradually decreases, thereby realizing the control of the nucleation density of molybdenum disulfide by controlling the oxygen flow rate.

[0052] Please refer to Figure 7 , Figure 7 shows the Raman spectrum of molybdenum disulfide. It can be seen that the main wave peak is obvious and the noise is less, and the nucleation quality of molybdenum disulfide is good, which proves that the method of controlling the nucleation density of molybdenum disulfide by controlling the oxygen flow rate is not achieved at the expense of the nucleation quality. The moderately increased oxygen flow rate reduces the nucleation density during the growth process of transition metal chalcogenides, and a larger space can be obtained between crystal domains, providing conditions for the growth of larger crystal domains.

[0053] Combined with Figures 8 to 12 , Figure 8 shows the nucleation optical image of tungsten disulfide obtained when oxygen is continuously introduced into the heating chamber 1 at a flow rate of 0.1 sccm; Figure 9Shows the optical image of tungsten disulfide nucleation obtained when oxygen is continuously introduced into the heating chamber 1 at a flow rate of 1 sccm; Figure 10 Shows the optical image of tungsten disulfide nucleation obtained when oxygen is continuously introduced into the heating chamber 1 at a flow rate of 3 sccm; Figure 11 Shows the optical image of tungsten disulfide nucleation obtained when oxygen is continuously introduced into the heating chamber 1 at a flow rate of 6 sccm; Figure 12 Shows the Raman spectrum of tungsten disulfide. It can be seen that after replacing molybdenum in the transition metal with tungsten, the grown transition metal chalcogenide becomes tungsten disulfide. At this time, as the flow rate of introduced oxygen increases, the nucleation density of tungsten disulfide also gradually decreases. That is, the method for regulating the nucleation density of the transition metal chalcogenide of the present invention is not limited to being only applicable to the growth process of molybdenum disulfide, but can be applied to the nucleation process of the reaction of various transition metals with sulfur powder.

[0054] During the process of observing the nucleation of the transition metal chalcogenide, the applicant considered that oxygen would erode the transition metal chalcogenide, so the introduction time of oxygen was changed. Combining Figure 13 and Figure 14 , Figure 13 Shows the optical image of molybdenum disulfide nucleation obtained under the condition of introducing oxygen for 30 minutes, Figure 14 Shows the optical image of molybdenum disulfide nucleation obtained under the condition of introducing oxygen for 5 minutes. It can be seen that when the introduction time of oxygen is shortened, the average distance between adjacent molybdenum disulfides does not decrease, but the size of a single molybdenum disulfide significantly increases, thereby ensuring the nucleation quality of molybdenum disulfide.

[0055] The method for regulating the nucleation density of the transition metal chalcogenide of the present invention uses oxygen to regulate the growth of the transition metal chalcogenide, so that the nucleation density is reduced, and a single crystal domain will grow to a larger size, reducing the amount of grain boundaries per unit area, making various optoelectronic properties such as the electron mobility of the transition metal chalcogenide thin film more excellent.

[0056] The above-described embodiments only represent the optimal implementation modes of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and the present invention also intends to include these changes and modifications.

Claims

1. A method for controlling the nucleation density of transition metal chalcogenides, characterized in that: include: The sulfur powder is placed in the starting temperature zone of the argon environment and the starting temperature zone is heated, while the transition metal is placed in the nucleation temperature zone of the argon environment and the nucleation temperature zone is heated; wherein the argon gas continuously flows from the starting temperature zone to the nucleation temperature zone; After the starting temperature zone is heated to the starting temperature, the nucleation temperature zone is heated to the nucleation temperature; wherein the starting temperature is lower than the nucleation temperature; When the temperature of the nucleation temperature zone reaches the nucleation temperature, a certain flow of oxygen is introduced into the starting temperature zone for a certain period of time, and the oxygen continues to flow into the nucleation temperature zone. After a certain period of time, the nucleation temperature zone is naturally cooled to room temperature. The flow rate of oxygen was increased to reduce the nucleation density of transition metal chalcogenides.

2. The method for controlling the nucleation density of transition metal chalcogenides according to claim 1, characterized in that: The starting temperature is 120-160°C, and the nucleation temperature is 800-850°C.

3. The method for controlling the nucleation density of transition metal chalcogenides according to claim 2, characterized in that: The initiation temperature zone was heated to the initiation temperature within 15 minutes, and the nucleation temperature zone was heated to the nucleation temperature within 40 minutes.

4. The method for controlling the nucleation density of transition metal chalcogenides according to claim 3, characterized in that: Argon gas was continuously introduced into the heating chamber at a flow rate of 30-35 sccm.

5. The method for controlling the nucleation density of transition metal chalcogenides according to claim 4, characterized in that: The transition metal is molybdenum or tungsten.

6. The method for controlling the nucleation density of transition metal chalcogenides according to claim 1, characterized in that: The time of introducing oxygen can be reduced according to the total amount of sulfur powder and transition metal to improve the nucleation quality of transition metal chalcogenide.

7. A transition metal chalcogenide nucleation density control system, characterized in that: The invention comprises a heating chamber and an air pump, wherein the heating chamber comprises a starting temperature zone and a nucleation temperature zone, wherein sulfur powder is arranged in the starting temperature zone, and the transition metal is arranged in the nucleation temperature zone; the air pump continuously inputs argon gas into the starting temperature zone of the heating chamber, and heats the nucleation temperature zone while the heating chamber heats the starting temperature zone; after the starting temperature zone is heated to the starting temperature, the nucleation temperature zone is heated to the nucleation temperature, and the starting temperature of the starting temperature zone is lower than the nucleation temperature of the nucleation temperature zone; when the temperature of the nucleation temperature zone reaches the nucleation temperature, a certain flow rate of oxygen is continuously introduced into the starting temperature zone for a certain period of time, and the oxygen is continuously introduced into the nucleation temperature zone, and the heating chamber is closed after a certain period of time, so that the nucleation temperature zone is naturally cooled to room temperature; the flow rate of the introduced oxygen is increased to reduce the nucleation density of the transition metal sulfide compound.

8. The transition metal chalcogenide nucleation density control system according to claim 7, characterized in that: It also includes a first receiving unit and a second receiving unit. The first receiving unit is arranged in the starting temperature zone of the heating chamber to receive sulfur powder; the second receiving unit is arranged in the nucleation temperature zone of the heating chamber to receive transition metal.

9. The transition metal chalcogenide nucleation density control system according to claim 8, characterized in that: A growth substrate is provided on the surface of the second receiving unit, and the growth substrate is sapphire.

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