Tuyển tập các báo cáo nghiên cứu khoa học ngành toán học được đăng trên tạp chí toán học quốc tế đề tài: Synthesis of highly transparent ultrananocrystalline diamond films from a lowpressure, low-temperature focused microwave plasma jet | Liao et al. Nanoscale Research Letters 2012 7 82 http content 7 1 82 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Synthesis of highly transparent ultrananocrystalline diamond films from a low-pressure low-temperature focused microwave plasma jet Wen-Hsiang Liao1 2 Da-Hua Wei1 2 and Chii-Ruey Lin1 2 Abstract This paper describes a new low-temperature process underlying the synthesis of highly transparent ultrananocrystalline diamond UNCD films by low-pressure and unheated microwave plasma jet-enhanced chemical vapor deposition with Ar-1 CH4-10 H2 gas chemistry. The unique low-pressure low-temperature LPLT plasma jet-enhanced growth even with added H2 and unheated substrates yields UNCD films similar to those prepared by plasma-enhanced growth without addition of H2 and heating procedure. This is due to the focused plasma jet which effectively compensated for the sluggish kinetics associated with LPLT growth. The effects of pressure on UNCD film synthesis from the microwave plasma jet were systematically investigated. The results indicated that the substrate temperature grain size surface roughness and sp3 carbon content in the films decreased with decreasing pressure. The reason is due to the great reduction of Ha emission to lower the etching of sp2 carbon phase resulting from the increase of mean free path with decreasing pressure. We have demonstrated that the transition from nanocrystalline 80 nm to ultrananocrystalline 3 to 5 nm diamond films grown via microwave Ar-1 CH4-10 H2 plasma jets could be controlled by changing the pressure from 100 to 30 Torr. The 250-nm-thick UNCD film was synthesized on glass substrates glass transition temperature Tg 557 C using the unique LPLT 30 Torr 460 C microwave plasma jet which produced UNCD films with a high sp3 carbon content and offered high optical transmittance approximately 86 at 700 nm . Keywords ultrananocrystalline diamond films focused microwave plasma
