Plasma Chemical Vapour Deposition (PCVD) is a technique by which lab growing diamonds can be grown from a hydrocarbon gas mixture. In the CVD process, a thin slice of diamond seed (often an HPHT produced diamond) is placed in a sealed chamber at high temperature and high pressure. The chamber is then filled with a carbon rich gas (usually methane) along with other gases. Then, the gases are ionised into plasma using microwaves, lasers, or other techniques.The Ionisation breaks the molecular bonds in the gases and the pure carbon adheres to the diamond seed and slowly builds up into up into a crystal, atom by atom and layer by layer form.
The method for producing diamond includes positioning diamond in a holder such that a thermal contact is made with a side surface of the diamond adjacent to an edge of a growth surface of the diamond,measuring temperature of the growth surface of the diamond to generate temperature measurements, controlling temperature of the growth surface based upon the temperature measurements and growing single crystal diamond by microwave plasma chemical vapour deposition on the growth surface, wherein the growth rate of the diamond is greater than 1μm per hour. In this whole process temperature plays very important role. We need to measure the temperature of the target diamond rather than the plasma.
Temperature Measurement by Infrared Pyrometers
A non-contact temperature measurement device is positioned to measure the temperature of the diamond across the grown surface of the diamond. The pyrometer is mounted on a glass window of a chamber to read the temperature of target diamond. The challenging part of the application is Plasma emits IR energy at specific wavelengths and we need to measure consistent temperature of the target through the plasma. AST offers Non-contact type IR based Pyrometer which works in selected wavelength where plasma is transparent.
- Temperature Range – 350°C to 1800°C
- Fast response time in millisecond
- Laser sighting
- Connectivity via USB 2.0, Bluetooth V2.0 and RS-232 or RS-485 Serial interface
- Measure the temperature of target through plasma at specific wavelength