Method for growing ultra-large-size polycrystalline diamond films

A method for growing ultra-large-size polycrystalline diamond film, comprising the following steps:

• S1:
• cleaning and drying a monocrystalline silicon wafer at room temperature;
• S2:
• subjecting the monocrystalline silicon wafer to a seeding pretreatment process to deposit a diamond nanocrystalline layer across a silicon surface, then transferring the seeded monocrystalline silicon wafer into a microwave plasma chemical vapor deposition (MPCVD) equipment, wherein the MPCVD equipment has a microwave source of 915 MHz or 433 MHz;
• S3:
• evacuating a chamber of the MPCVD equipment, performing hydrogen purging, then performing re-evacuation;
• subsequently, introducing hydrogen gas and regulating a chamber pressure to 5-8 torr to initiate plasma ignition;
• S4:
• increasing microwave power to 70-75 kW with a rate of 4.5-5.5 kW/min, elevating the chamber pressure to 165-180 torr with a rate of 10-30 torr/min, and increasing chamber temperature to 900-950° C. with a rate of 60° C./min;
• S5:
• introducing growth gases with the following flow rates:
• hydrogen (H2) at 5000-6000 sccm, methane (CH4) at 100-150 sccm, oxygen (O2) at 5-8 sccm, nitrogen (N2) at 1-2 sccm, and argon (Ar) at 800-1000 sccm;
• and
• S6:
• upon completion of diamond growth, initiating a cooling process with a temperature decrease rate of 30° C./min until the room temperature is reached, followed by venting the chamber with nitrogen gas, thereby obtaining the ultra-large-size polycrystalline diamond film.