ICMCTF2006 Session H5-2: The Atomistics of Thin Film Growth: Computational and Experimental Studies
Monday, May 1, 2006 1:30 PM in Terrace Pavilion
H5-2-1 STM and LEED Studies of SiN@sub x@ Growth on TiN(001) and TiN(111): Toward Understanding Interface Structure in Superhard Nanocomposites
J. Bareño (University of Illinois at Urbana-Champaign); A. Flink (Linköping University, Sweden); V. Petrova, J.E. Greene (University of Illinois at Urbana-Champaign); L. Hultman (Linköping University, Sweden); I. Petrov (University of Illinois at Urbana-Champaign)
The synthesis (PVD and CVD) and bulk properties of the M@sub n@N-SiN@sub x@ (M = transition metal) family of nanocrystalline superhard composites have been extensively studied over the past three decades. Among this large group of nanocomposites, TiN-SiN@sub x@ has received special attention as a model system due to its exceptionally high Vicker's hardness (from 50 to 100 GPa, depending upon the presence of TiSi@sub 2@ phases). The commonly accepted model for the phase structure of TiN-SiN@sub x@ is that it consists of a set of nanometer-sized TiN crystallites surrounded by an amorphous SiN@sub x@ tissue-phase.@paragraph@In an attempt to gain better understanding of the origin of TiN-SiN@sub x@ superhardness, we use in-situ STM and LEED to investigate the atomic-scale structure of the SiN@sub x@/TiN interface, of which very little is known. Samples were prepared in a multi-chamber UHV (base pressure < 10@super -10@ Torr) system by reactive magnetron sputtering of epitaxial TiN layers onto single-crystal TiN(001) or TiN(111) substrates at temperatures between 700 and 900@super o@C followed by formation of SiN@sub x@ overlayers at temperatures ranging from 600 to 800@super o@C.@paragraph@We show both topographic (STM) and diffraction (LEED) evidence that (a) SiN@sub x@ overlayers on TiN are crystalline with reconstructions including 2x2, 3x3, and 1x5, depending upon SiN@sub x@ coverage, surface orientation, and annealing temperature; and (b) TiN grows epitaxially on top of the SiN@sub x@ layers. Specifically, our results show that for SiN@sub x@ coverages near 1 ML, where maximum TiN-SiN@sub x@ hardness is achieved, the SiN@sub x@ layer is "not amorphous" as deposited.
H5-2-2 Entropy Evolution During the Growth of Concomitant Nitrided Layers Produced by a Post-Discharge Process
J. Oseguera (ITESM-CEM, Mexico); F. Castillo (ITESM, Mexico); A. Gomez (UFRO Chile); A. Fraguela (BUAP, Mexico)
The present work proposes an interpretation of the growth kinetics of nitride concomitant layers during microwave post-discharge nitriding in terms of the production of entropy. Using a mathematical model for layer growth based on the inverse problem of identification of nitrogen diffusion coefficients and the associated problem of direct moving boundary with conditions of Stefan type, the entropy production of the process was analyzed.