Selective growth of nanodiamond films in microwave plasma

Abstract

A patterned nanodiamond film is grown using microwave plasma-enhanced chemical vapor deposition. A selective growth method compatible with traditional silicon processing is described. A diamond pattern of high quality and moderate resolution is achieved. The process utilized is simple to generate patterns without etching diamond. A rectifying junction is demonstrated using a p-type nanodiamond and p-type silicon heterojunction with rectifying ratio of two orders of magnitude. This simple patterning technique could be applied in the fabrication of diamond electronic and mechanical devices and biological sensors. The plasma emission spectra indicate the presence of both CH and C 2 species, which are responsible for diamond growth. IntroductionAmong many methods employed for diamond film growth, chemical vapor deposition (CVD) using microwave (MW) plasma is quite popular due to several reasons. The well-confined plasma does not touch the reaction chamber walls and can be produced directly on the substrate. Hence, contamination in the grown films can be minimized unlike in hot filamentbased CVD. Indirect substrate heating is also achieved by the MW. Diamond films and coatings have found wide ranging applications in sensors [1], protective coatings [2], optical windows [3], and electronic and electrochemical devices [4]. Many such applications require patterning of diamond thin films. However, the unusual chemical inertness and hardness makes patterning of diamond quite difficult. Reactive ion etching is a common method for diamond patterning [5-8] that involves a reactive gas like SF 6 and a highly selective masking material such as gold. This process suffers from the problems of over etching and micro mask effect [9,10]. In this paper, we describe a novel method for selective growth of a nanodiamond film in a MW, which is compatible with conventional Si processing. A rectifying isotype junction is demonstrated using a p-type nanodiamond (p-NCD)/p-type silicon (p-Si) heterojunction diode with rectifying ratio of two orders of magnitude. Diamond patterns are achieved without dry etching.