Current Status of Diamond Thin Films

Abstract

Artifact (man made) diamond films are currently being made by several different types of plasma-assisted processes, hot filament processes, and even by conventional acetylene welding torches. Carbonaceous feed gases include methane, acetylene, carbon monoxide, various alcohols, and more recently, the effluent of city sewer plants. Most of these processes rely on atomic hydrogen to prevent the carbon atoms of the diamond surface from forming unwanted pi bonds and subsequent graphitic inclusions. While hydrogen has been thought to be essential to the growth of diamond, it is more recently thought to be the greatest impediment to the formation of contiguous, smooth, single crystalline diamond films. This unwanted aspect of hydrogen accrues from the inabilities of the growth processes to absolutely insure that ALL hydrogen terminations are subsequently replaced by carbon. Atomic layer epitaxy (ALE) may provide a solution as may chemical terminators other than hydrogen. While the use of lattice-matched substrates may be useful in seeding a continuous thin diamond film, carbide formation problems, the ability to withstand high temperature growth conditions, and thermal expansion coefficients are factors that must be considered when choosing the proper substrate.