!!! The curious jumping point of stress

1. 1 2 Ⅲ.Experimental Deposition parameters Schematic diagram of present system Working gas: Ar + C6H6 Base pressure : 2.0 10-6Torr Deposition Pressure : 0.2~610-4Torr Ion gun power: 100-150 V; 0.48A Sputter gun power: 600V; 0.10~0.16A Bias Voltage : -200V Substrate : P-type Si (100) wafer Thickness: 350±50nm Total flow rate: 12sccm Structure and properties of nanocomposite WC-C films deposited by a hybrid process of ion-beam deposition and DC magnetron sputtering 2004 Ai-Ying Wanga, Tae-Young Kima, Se-Jun Parka, Kwang-Ryeol Leea*(krlee@kist.re.kr)，Jun-Hee Hahnb aFuture Technology Research Division, Korea Institute of Science and Technology, Seoul, 130-650, South Korea bKorea Research Institute of Standards and Science, Daejon 305-600, South Korea Ⅰ. Abstract The nanocomposite WC-C films were prepared on silicon (100) wafer by a hybrid deposition system composed of an end-hall type ion gun of hydrocarbon and a DC magnetron sputter source of W. W concentration in the film was controlled by changing the Ar fraction of the Ar / C6H6 supplying gas. Residual stress and hardness were investigated as a function of W concentration. Micro-Raman spectroscopy and GIXRD were employed to characterize the microstructure of the deposited films at various W concentrations. It was shown that the films consisted of nano-sized WC1-x particles embedded in the hydrocarbon matrix resulting in a nanocomposite thin film in the wide range of W concentration. A significant reduction of stress, without the deterioration of mechanical properties, was observed at W concen. of 4.2 at.%. The clues for this curious phenomena were discussed in terms of the atomic bond structure and the formation of the WC1-x particles. • Ⅳ.Results and discussion b) Residual compressive stress. a) RBS and GIXRD. !!! The curious jumping point of stress stress Ⅱ. Motivation of this work Significant progress in the understanding of DLC films growth processes has been achieved in the last three decades. Nevertheless, high residual compressive stress (up to 12GPa) and poor adhesion are still the main barrier to their widely industrial applications. Recently, it is reported that Me-DLC films have shown considerable improvement of physical properties than those of pure DLC films. Taking into account the reduction of residual stress being always at a sacrifice of mechanical properties, however, more elaborate studies on Me-DLC films are necessarily required. Using a novel hybrid deposition system, in this present work, we reported the structure and physical properties of nanocomposite WC-C films as a function of W concentration in the films by a comprehensive set of experiments. W concen. was almost proportional to Ar fraction. The evaluated WC1-x particle size D < 20nm. Why ??? Why ??? Knock-on implantation Thermal spikes c) Mechanical properties. Since the W atomic radius is larger than that of C, as W atoms have sufficient energy and then were embedded into the subsurface, causing the local distortion of atomic bonds,  stress . C. A. Davis, Thin Solid films, 226(1993) 30; H. Windischmann, J. Appl.Phys. 62(1987)1800 Based on this model, for low C6H6 flux:  J    However, further  W concen., the WC1-x phases begun to form in the matrix, which in turn  stress. d) Raman spectra and G-Peak positions. e) Electrical resistivity. : 4.1 cm-1/GPa The changes of G-peak at this point proposed that the essential changes of atomic bond structure in some way. The formation of WC1-x significantly decreased the resistivity. Ⅴ.Conclusions The nanocomposite WC-C films were successfully prepared by the hybrid deposition system combining ion beam with DC magnetron sputtering of tungsten. Without the significant deterioration of mechanical properties, the lowest residual stress was observed at W concen. of 4.2 at.%, named by stress jumping point. It is deduced that the carbon implantation mechanism might dominate the growth behavior as the W concen. was less than 4.2 at.%. However, above the stress jumping point( >W 4.2 at.%),  W concen., separate embedded W atoms  stress; futher increasing W concen., the WC1-x phases begun to form in the carbon matrix  stress.  Raman spectra proposed that the larger amount of W incorporation (> W 4.2 at.%) might not affect the atomic bond structure of carbon within 12.6 at.% W; but in the range of 2.9~4.2 at.% W, both the W incorporation and the decrease of C6H6 flux played a great role in the significant reduction of stress.  The gradual decrease of resistivity demonstrated that the conductive W atoms were embedded into the carbon matrix and the subsequent formation of WC1-x phases.  In order to get more physical insight into the curious phenomena( stress jumping) in this work, more elaborate studies on structure are in process.