Growth of (100) oriented diamond thin films on ball structure diamond-like particles
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Bahram Roughani and Swaminatha Sundaram Department of Physics, University of South Florida, Tampa, Florida 33620 (Received 16 August 1991; accepted 13 March 1992)
The morphology of typical CVD diamond thin films has been shown to be controlled by the concentration of methane during deposition. For example, for CH4 concentrations c < 0.4% the (111) faces dominate, while at 0.4% < c < 1.2% (100) faces dominate. Here we showed that the (100) oriented diamond films can be grown on top of the microcrystalline ball-like particles under suitable conditions. These (100) oriented diamond films are grown under the condition of 1.5% methane in hydrogen, substrate temperature of 680 °C-750 °C, and pressure of 30-80 Torr. The bombardment of the diamond thin films by ions in the plasma is believed to be an important factor for the formation of (100) oriented films on top of the ball-like particles. SEM, Raman, and x-ray techniques were used to characterize the deposited (100) oriented diamond thin films.
For practical applications in optics and electronics, large area single crystal synthesized diamond thin films on Si or other suitable substrates are very desirable. However, due to the lattice mismatch and random nucleation, usually only polycrystalline diamond films were deposited on Si substrates in the past.1 These polycrystalline diamond films are formed by intergrowth of disjointed diamond crystallites and usually have very rough surfaces. Depending on the deposition conditions,1 the morphology of these diamond films can be either crystalline which is usually dominated by (111) or (100) faces, or microcrystalline which generally consists of ball-like particles. These (111) or (100) faces are usually randomly oriented. Here we present results which indicate that (100) oriented diamond film can be grown on top of the microcrystalline ball-like particles under suitable conditions. These (100) oriented diamond films can join together and form a semicontinuous (100) oriented diamond surface. The morphologies of low-pressure plasma assisted CVD diamond films have been discussed recently by several authors.2"7 Badzian2'3 reported that in the filament assisted CVD system at temperatures of 900 °C or lower, (111) faces dominated. At 1000 °C or higher, (100) faces dominated the morphology. Kobashi and colleagues4"6 showed that with a microwave CVD system at substrate temperature of 800 °C and methane concentrations of 0.4% or less, (111) faces dominated. At methane concentrations of 0.4% to 1.2% the (100) faces became the dominant faces, and at methane concentrations of 1.4% or higher, only microcrystallites formed. Wild et al.7 observed a preferential alignment 1606 http://journals.cambridge.org
J. Mater. Res., Vol. 7, No. 7, Jul 1992 Downloaded: 13 Mar 2015
of (110) planes perpendicular to the growth direction in their CVD system, which was a combination of hot filament and microwave plasma techniques. Haubner and Lux,8 on the other hand, indicated that in their microwave CVD system the (100) faces dominated at 0.3% methane co
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