Deposition of thick and thin nanocrystalline diamond films by microwave plasma enhanced chemical vapor deposition

Thick (around 3 μm) and thin (48-310 nm) nanocrystalline diamond (NCD) films have been produced from Ar-rich CH4/Ar/H2 (1/89/10 %) and H2-rich CH4/H2 (1/99 %) microwave plasmas, respectively. The thick NCD films were obtained with and without an initial buffer layer (BL). The BL is easily obtained under typical microcrystalline diamond growth conditions (CH4/H2 mixtures). The effect of the deposition temperature (TD, 630-900°C) was investigated on the morphology, the surface roughness and the bonding characteristics of the films grown with and without BL. The thin NCD films were grown on Si substrates treated by two different methods, i.e. ultrasonic agitation in a suspension of diamond powders of 40-60 μm or combinatorial approach in a suspension of mixed diamond powders of 250 nm and 40-60 μm. The present experimental results show that the buffer layer procedure allows a good preservation of the surface of treated Si substrate and the combinatorial approach promotes effectively the seeding of the Si surface.

本研究分别通过富氩CH₄/Ar/H₂（体积比1/89/10）和富氢CH₄/H₂（体积比1/99）微波等离子体体系，制备得到厚度约3μm的厚膜纳米晶金刚石（NCD）薄膜，以及厚度为48~310nm的薄膜纳米晶金刚石（NCD）薄膜。厚膜纳米晶金刚石样品分别采用初始缓冲层（BL）和无缓冲层两种工艺制备。缓冲层可通过典型微晶金刚石生长工艺（CH₄/H₂混合气体体系）便捷获得。本研究探究了沉积温度（TD，630~900℃）对有无缓冲层制备的薄膜的形貌、表面粗糙度及键合特性的影响。薄膜纳米晶金刚石样品生长于经两种不同预处理的硅（Si）衬底之上：一种是将衬底置于40~60μm金刚石粉末悬浮液中进行超声搅拌处理，另一种是采用组合式预处理工艺，将衬底置于250nm与40~60μm混合金刚石粉末的悬浮液中处理。本实验结果表明：缓冲层工艺可有效保留经预处理的硅衬底表面形貌，而组合式预处理工艺则可显著提升硅衬底表面的晶种附着效果。