Structure and optical properties of diamondlike carbon synthesized by plasma immersion ion processing
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Structure and optical properties of diamondlike carbon synthesized by plasma immersion ion processing Xiao-Ming He, D. H. Lee, and K. C. Walter Los Alamos National Laboratory, Materials Science and Technology Division, Los Alamos, New Mexico 87545
D. Q. Li Los Alamos National Laboratory, Chemical Science and Technology Division, Los Alamos, New Mexico 87545
M. Nastasi Los Alamos National Laboratory, Materials Science and Technology Division, Los Alamos, New Mexico 87545 (Received 15 June 1998; accepted 14 January 1999)
Hard and transparent diamondlike carbon (DLC) films have been prepared on room-temperature substrates by using a C2 H2 –Ar plasma immersion ion processing (PIIP) method. The optical properties of the DLC films with different thicknesses deposited on PMMA (polymethyl methacrylate), silicon wafers, and glass plates were systematically examined. It was found that careful control of substrate bias voltage was needed for favorable growth of DLC films with low atomic hydrogen content, high hardness and wear resistance, and excellent optical properties. The resultant DLC films exhibited a low friction coefficient, high optical gap energy, and very high optical transmittance both in infrared and visible light ranges. The study confirmed that C2 H2 –Ar PIIP with low negative bias voltages and suitable C2 H2yAr gas ratios can produce optically transparent and hard DLC films on optical materials.
I. INTRODUCTION
Diamondlike carbon (DLC) films, structured with both sp 3 and sp 2 hybridized bonds in an amorphous form, are well known for possessing unique properties that are close to diamond. Depending on the deposition method and preparation conditions, DLC films can be prepared with extreme hardness, chemical inertness, optical transparency, high electrical resistivity, and a low coefficient of friction. Such films have been used as wear-resistant layers, transparent optical windows, and electrodes in optics and electronics.1–4 In recent years, one of the advanced preparation methods, plasma immersion ion processing (PIIP), has been successfully applied for the deposition of DLC materials, by which either high voltage pulse5 or low voltage pulse6 are used to induce the energetic ion impingement in plasma to enhance the film formation. The PIIP technique, which combines the advantages of ion beam assisted deposition and plasma source ion implantation, allows independent control of ion energy and plasma density to produce nonline-ofsight depositions.7 These advantages promise that hard and well bonded DLC films can be easily synthesized on complicated-shaped substrates at low temperature with excellent properties.6,8 In our previous work, we have used PIIP to deposit DLC for optical investigations.6 This was a demonstration of the preparation of hard DLC films on soft 2080
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J. Mater. Res., Vol. 14, No. 5, May 1999
Downloaded: 18 Mar 2015
plastic substrates without deterioration of their optical properties. As a continuation of the w
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