Effect of hydrogenated amorphous carbon films on nucleation of diamond particles by hot-filament chemical vapor depositi
- PDF / 790,723 Bytes
- 5 Pages / 576 x 792 pts Page_size
- 35 Downloads / 233 Views
To enhance a nucleation rate of diamond particles, hydrogenated amorphous carbon (a-C: H) intermediate layers have been formed by radio frequency plasma chemical vapor deposition (CVD) on silicon substrates prior to diamond deposition by hot filament CVD, and the effect of a-C: H intermediate layers on the nucleation and growth rate of diamond particles is studied by varying the thickness of a-C: H films. It is found that diamond particles are well synthesized on thin a-C: H intermediate layers and the nucleation density and growth rate are decreased with increasing the thickness of a-C: H films. Atomic force microscope observations show that a-C: H intermediate layers with rough surface are more effective than the smooth surface for diamond synthesis. Raman spectroscopy shows that the bonding state of carbon atoms in a-C: H films does not change by varying the thickness of a-C: H films. It is proposed that diamond nucleation is affected by the surface morphology rather than the bonding state of carbon atoms in a-C: H films.
I. INTRODUCTION During the past two decades, a wide variety of methods have been employed to synthesize diamond films. To obtain high nucleation density of diamond particles, substrates are usually abraded with diamond powders or other types of abrasive medium. It has been reported that the diamond nucleation density on a mirrorpolished silicon substrate is generally 104 cm" 2 , but nucleation density is increased up to 107 cm" 2 by abrading silicon substrates by means of hot filament or microwave chemical vapor deposition (CVD).1-2 Recently, the present authors have developed a nucleation method of diamond particles on unscratched silicon substrates by applying carbon fibers.3 It is well known that diamond particles are nucleated on various materials and different kinds of intermediate layers are formed between substrates and diamonds.4"6 We reported that hydrogenated amorphous carbon (a-C:H) layers are formed naturally between diamond particles and silicon substrates by the hot filament chemical vapor deposition (HFCVD) method.7 The a-C: H intermediate layer is similar in properties to diamond films and is effective in enhancing diamond nucleation.8 The effect of amorphous carbon films on scratched silicon substrates was studied by Barnes and Wu.9 According to their work, the silicon substrate was scratched with 0.5 fim diamond pastes and cleaned in acetone, and then the amorphous carbon films were deposited on the scratched substrate by microwave plasma enhanced CVD. This pretreatment of silicon resulted in diamond nucleation at densities averaging J. Mater. Res., Vol. 10, No. 2, Feb 1995 http://journals.cambridge.org
Downloaded: 18 Mar 2015
around 3 X 1010 cm 2 . However, it is not clear what factor, e.g., thickness, component, or morphology of a-C: H films, affects an enhancement of the nucleation density of diamond particles. In the present paper, we try to elucidate the effective factor for enhancement of diamond nucleation. For this purpose, diamond particles are synthesized on abrad
Data Loading...
