Preparation of Crystalline Chromium Carbide Thin Films Synthesized by Pulsed Nd:YAG Laser Deposition
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Preparation of Crystalline Chromium Carbide Thin Films Synthesized by Pulsed Nd:YAG Laser Deposition Kazuya DOI, Satoshi HIRAISHI, Hiroharu KAWASAKI, Yoshiaki SUDA, Department of ElectricalEngineering,Sasebo National College of Technology, Okishin 1-1, Sasebo, Nagasaki 857-1193, Japan ABSTRACT
Chromium carbide thin films are synthesized on Si(100) substrates by a pulsed Nd:YAG laser deposition (PLD) method as parameters of methane gas pressure. Glancing-angle X-ray diffraction patterns show that the film prepared by PLD method is a polycrystalline thin film composed of Cr 3C2 and Cr 7C3, even in the base pressure. Diffraction patterns, however, are depended on the methane gas pressure. Grain size of the prepared film increases with increasing methane gas pressure. One of the reasons of these phenomena may be considered to the phase reaction between the ablated species, such as Cr, CrCx and CH 4 gas in the plasma plume. INTRODUCTION Crystalline chromium carbide (Cr 3C2) is one of the most popular carbides used to fabricate wear resistant surface films and in steel industries, because of its excellent physical properties, such as high melting temperature, strength, hardness and corrosion resistance.1-2) However, there have not been many studies regarding this topic. Donley et al. prepared CrCx thin films using a KrF excimer laser deposition method at the Si substrate temperature of room temperature and 300'C. However, both of the films were amorphous,3' and high quality crystalline Cr 3C2 films were not prepared. We also prepared the Cr 3C2 films using a pulsed Nd:YAG laser deposition (PLD) method 4-9), which is a versatile method for deposition of crystalline thin films, such as superconducting, semiconducting, and ferroelectric films. Our previous results suggest that the substrate temperature is one of the most important parameters in the fabrication of crystalline chromium carbide film, and the film prepared at Ts > 500 'C is a polycrystalline thin film composed of Cr 3C2 and Cr7C 3. 10 However, the growth mechanism of the Cr 7C3 component was not well understood. In this paper, we described the fundamental characteristics of the chromium carbide films prepared using the PLD method, and the effects of methane gas pressure on the properties of CrC, thin films. On the basis of them, we discuss about the mechanism of the preparing crystalline Cr 3C2 thin film. EXPERIMENTAL The schematic of the experimental apparatus is shown in Fig. 1. A deposition chamber was made of stainless steel with a diameter of 400 mm and a length of 370 mm. The chamber was evacuated to a base pressure (below 4.0 x 10-4 Pa) using a turbo molecular pump and a rotary pump. The gas pressure was varied from the base pressure to 10 Pa by feeding pure methane (CH 4) gas into the chamber. A pulsed Nd:YAG laser (Lumonics YM600; wavelength of 532 nm, pulse J7.8.1
duration of 6.5 ns, maximum output energy of 340 mJ) was used to Quart; (purity Cr 3C2 irradiate windo Their targets. 99.9%) radiated area was kept at 2.8 mmi. The laser energy density (Ed
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