Low Temperature Synthesis of Carbide Thin Films by Pulsed Laser Deposition (Pld)
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LOW TEMPERATURE SYNTHESIS OF CARBIDE THIN FILMS BY PULSED LASER DEPOSITION (PLD) M.S. Donley, J.S. Zabinski, and W.J. Sessler, Wright Laboratory, Materials Directorate, WL/MLBT, WPAFB, OH; V.J. Dyhouse, Research Institute, University of Dayton, Dayton, OH; S.D. Walck, SYSTRAN Corp., Linden Ave, Dayton,OH: N.T. McDevitt, RAMSPEC Research, 4399 E. Mohave Dr., Dayton, OH. ABSTRACT Thin films of titanium carbide (TiC) and boron carbide (B4 C) were grown by Films excimer pulsed laser deposition (PLD) at room temperature (RT) and 300'C. were deposited using the output of an excimer laser operating with KrF gas (X = 248 Film chemistry, morphology, nm, 15 ns pulse duration) to ablate hot-pressed targets. Stoichiometric, crystalline TiC films were grown and crystallinity were investigated. The on 440C stainless steel and NaCl substrates at room temperature and at 300°C. films grown on NaCI were nanocrystallinc, cubic TiC, with a grain size ranging Boron carbide films were grown on silicon (100) between 2 and 10 nm in diameter. 0 Film chemistry and stoichiometry substrates at room temperature and at 300 C. duplicated that of the B4 C target, which contained B4C and a mixed C-B-O-N binder SEM analysis indicated that the morphology of the films was uniform, nonphase. The films exhibited good adhesion and wear resistance, porous, and fine-grained. based on friction and wear data collected with a ball-on-disc tribometer. INTRODUCTION Carbide coatings are used in a number of tribological applications for increasing Titanium carbide (TiC) is a transition metal the wear life of contacting components. carbide; boron carbide (B4 C) belongs to a group of ultra-hard, semi-covalently bonded ceramic materials which includes SiC, Si 3 N4 , cubic BN, and diamond. These materials are constructed of a rigid framework of close, tightly bonded atoms, which is responsible for their refractory nature, high melting point, and very high Conventional thin film deposition of many carbide materials requires hardness [1-3]. substrate temperatures in the range of 500 to 1,000'C [1, 4-6], which can reverse the microstructural effects of a heat treatment and/or introduce high levels of stress at the film-substrate interface in materials with substantially different coefficients of thermal expansion. The purpose of this research was to identify the conditions required for growing dense, non-porous, adherent carbide films at low substrate temperatures using PLD. Here, an excimer laser operating with KrF gas (X = 248 nm, 5.06 eV per photon) was used to grow thin films of titanium carbide (TiC) and boron carbide (B4 C) at room The surface chemistry, morphology, crystal temperature (RT) and at 300"C. structure, and tribological properties of films were investigated. EXPERIMENTAL Film Deposition and XPS Analysis System The experimental apparatus used for PLD of tribological materials has been Films were deposited in a stainless steel vacuum chamber described earlier [7-9]. 7 with a base pressure of 9x10- Pa; during film growth, the system pressure rose to 5 6x
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