{"id":38352,"date":"2024-03-26T16:40:36","date_gmt":"2024-03-26T16:40:36","guid":{"rendered":"https:\/\/www.alicat.com\/?post_type=article&p=38352"},"modified":"2026-01-26T20:52:04","modified_gmt":"2026-01-26T20:52:04","slug":"bau-von-cvd-diamantmaschinen","status":"publish","type":"support","link":"https:\/\/www.alicat.com\/de\/support\/building-cvd-diamond-machines\/","title":{"rendered":"Bau von CVD-Diamantmaschinen mit Durchfluss- und Druckregelung"},"content":{"rendered":"\n[et_pb_section fb_built=”1″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_row _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_heading title=”Building CVD diamond machines with flow and pressure regulation” _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]In 2020, the lab-grown diamond market reached 19.3 billion dollars and by 2030 it is projected to reach about 49.9 billion<\/a>. Lab-grown diamonds are safer, more environmentally friendly, and cheaper to produce than are mined diamonds.\n\nThe main methods for lab-grown diamond manufacturing are HPHT and CVD<\/a>. Although HPHT developed prior to CVD, it is less commonly used since it requires more energy to operate due to its extreme temperature and pressure requirements. Moreover, HPHT is sometimes also considered as a secondary procedure to purify CVD diamonds.\n\nThe different types of CVD for diamond manufacturing include filament-assisted thermal CVD, plasma-enhanced CVD, and combustion-flame assisted CVD. Among these, a subtype of plasma-enhanced CVD, microwave plasma CVD, is the most popular and reliable.\n\nTo produce high quality lab-grown diamonds using any CVD method, manufacturers depend on Alicat\u2019s devices to ensure precise gas mixtures of hydrogen, methane, and carrier gases. In the following, we will discuss how Alicat\u2019s devices enhance each CVD process.\n

Filament-assisted thermal CVD<\/h2>\nFilament-assisted thermal CVD allows for the largest lab-grown diamond growth area and a simpler design than other CVD techniques. Drawbacks include a slower diamond growth rate (0.5-8 \u00b5m\/h), and a worse process stability compared to other CVD methods.\n\nIn this configuration, methane (0.5% to 2.0%) and hydrogen gases are released in a vacuum chamber (pressurized at 10-100 Torr) and dissociated by high-melting point (2,000-2,300\u00b0C) metal filaments, typically tungsten, near a heated substrate (700-1,000\u00b0C) which accumulates diamond particles over time.\n

Gas mass flow and pressure control<\/h3>\nAlicat\u2019s custom mass flow controllers<\/a> maintain accurate gas mixing with no poisoning from atmospheric gas. With only a leak rate of 10e-9<\/sup> ATM SCCS of helium and 2 ms response times, Alicat\u2019s devices mitigate improper gas mixing and contamination of the diamond growing chamber.\n\nConnected to the chamber vacuum source, Alicat\u2019s pressure controllers<\/a> handle back pressure to allow for stable and accurate chamber conditions.\n

Combustion-flame assisted CVD<\/h2>\nCombustion-flame assisted CVD<\/a> grows diamonds at atmospheric pressures using an oxygen-acetylene brazing torch and water-cooled substrate. Advantages include design simplicity, good growth rates (30-100 \u00b5m\/h), and low costs.\n\nIn this setup, at sub or atmospheric pressures oxygen and acetylene gases are released into a chamber controlled by a mass flow controller where they are combusted into a 3300 K flame, producing H2<\/sub>, CO, and reactive intermediates. Outside of the main combustion area of the chamber is the feather, a flame free zone abundant in atomic hydrogen and hydrocarbon radicals where the diamond growing substrate is positioned. In the outer zone, there is a secondary combustion region which oxidizes gases to CO2<\/sub> and H2<\/sub>O. The temperature of the substrate is controlled by water flow in and out the system below a copper substrate mount using a pyrometer.\n

Gas and liquid flow control<\/h3>\nAlicat mass flow controllers precisely control the gas flow of both oxygen and acetylene into the diamond growing chamber while, Alicat\u2019s liquid controllers (LC-Series<\/a> and CODA KC-Series<\/a>) control the flow of water to cool the diamond growing substrate.\n