Laser Assisted Deposition of Carbon Nitride Coatings
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ABSTRACT We have investigated the growth of carbon nitride (CNx) coatings on various substrates using laser assisted methods such as pulsed laser deposition (PLD) and laser chemical vapor deposition (LCVD). It has been shown that the both techniques produce good quality thin films of CNx. In PLD, a laser beam (X= 248 nm) has been used to ablate the pyrolytic graphite target in nitrogen atmosphere, where as CO 2 laser was used to irradiate carbon-nitrogen containing mixtures such as C 2H2/N20/NH3 in LCVD method. A comparative analysis will be presented in terms of structural properties of CNx films prepared by both techniques.
1. INTRODUCTION Liu and Cohen's theoretical work of 1989 indicated that the properties of P-C 3N4 might be similar or superior to diamond [1] and many research groups reported their progress in this area [2-6]. Most published results confirmed the formation of amorphous carbon nitride with incorporation, in some cases, of nano-sized crystals [3-6]. Various techniques have been used to synthesize crystalline C3N4 films. The production methods include shock compression of nitrogen-containing organic materials, pyrolysis of organic compounds with high nitrogen content under high temperatures and pressures, and several PVD methods, such as r.f. sputtering of a graphite target in a nitrogen ambient and ion beam methods [7-12]. In most of the experiment the overall composition of the films was not stoichiometric, suggesting that these phases are obtained in small crystallites embedded in an amorphous CNx film (x = 0.2 - 0.7). In this paper, we report our study on the formation of carbon nitride films by pulsed laser deposition (PLD) and laser chemical vapor deposition (LCVD) methods. It has been reported the formation of CNx/TiN coatings using dual-cathode magnetron sputtering [13]. TiN provides a lattice-matched structural template to seed the growth of carbon nitride crystallites. We have earlier shown that the laser ablation technique is the best method to deposit high-quality TiN films on semiconductor substrates [14-15]. In this investigation, the PLD method has been used to grow CN, films on Si(100) substrates with TiN underlayer. There are very few published studies on CNx films deposition by laser-induced chemical vapor deposition (LCVD) methods, may be due the fact that most of the other mentioned techniques are characterized by high-energy implantation of nitrogen into the films. In the previous work [16], it was demonstrated the possibility of LCVD method to produce CNx thin films, by using different carbon/nitrogen containing gas precursors and substrates. It was shown that, depending on the experimental conditions, x could vary between 0.13 and 0.45. The main focus of this investigation is to study the effects of gas phase-composition on the formation of CNx films by LCVD method.
387 Mat. Res. Soc. Symp. Proc. Vol. 555 © 1999 Materials Research Society
2. EXPERIMENTAL 2.1 PLD Processed CN, Films: The deposition of the films was carried out using the PLD method and the detailed descr
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