1. Ш.Results and discussion Ш. Results and discussion a) W Composition b) Stress and Mechanical Properties c) TEM-microstructures ШІІІ C Si substrate Ar W W incorporated carbon nanocomposite films prepared by hybrid ion beam deposition Ai-Ying Wang a, * (aywang@kist.re.kr), Hyo-Shin Ahn a, Kwang-Ryeol Lee a, Jae-Pyoung Ahn b a Future Technology Research Division, Korea Institute of Science and Technology, Seoul, 130-650, South Korea b Nano-Materials Research Center, KIST, South Korea І. Introduction Significant progress in understanding the growth behavior and atomic bond structure of diamond-like carbon (DLC) film has been achieved in the last three decades. Nevertheless, high residual stress and poor adhesion are still the main barriers to its applications. In the present work, we employed a hybrid deposition method to prepare W incorporated DLC films in a wide range of W concentration from 2.4 to 12.5 at.%. We observed a stress jumping behavior as the W concentration increased from 2.4 to 5.0 at.%. Beyond 5.0 at.%, gradual decrease in the residual stress was observed as in the previous work. High resolution TEM analysis showed that the stress jumping was closely related to the change in the W incorporation behavior from atomic scale incorporation into the amorphous carbon matrix at low W concentration to formation of a nanosized  -W 2 C phase at higher W concentration. Ab initio calculation of the excess energy by atomic bond distortion suggested that the stress reduction with atomic scale W incorporation was due to the reduction of the directionality of W-C bonds. П. Experimental  Working gas: Ar + C 6 H 6 (total: 12sccm)  Base pressure : 2.0  10 -6 Torr  Substrate bias : - 200 V  Power density of target: 4.2~7.3 W/cm 2  Deposition Pressure : 0.6 ~ 1  10 -4 Torr  Thickness: 350±50nm  Substrate: P-type Si(100), 500  m, 100  m W n+ H +, C m+ 21±3 GPa 170±15 GPa !! Stress jumping occurred with increasing W concentration. The mechanical properties also showed the same dependence, although the variation is not as significant as that of the stress. (e) 4 nm  -W 2 C (102)  -W 2 C (101) 4 nm (c)  -W 2 C (101) 4 nm (b) (a) 4 nm (d)  -W 2 C (102)  -W 2 C (101) І П Ш Region І : nanosized W embedded in carbon matrix. Region П : Segregation of tungsten started. Region Ш : crystalline carbides phase presented (a) 3.0, (b) 4.2, (c) 5.1, (d) 8.7, (e) 12.5 at.% d) GIXRD-phase identification. e) Raman and EELS- atomic bond structure f) Ab Initio Calculation – energy increase due to bond distortion g) Stress Jumping and Atomic Bond Structure І П Characteristic of amorphous structure. Weak crystallinity of carbides. Ш High crysallinity and fraction of carbides. No change was observed in the carbon network with the W incorporation. The less significant change in the mechanical properties can be understood in terms of the unvaried amorphous carbon network. ШІІІ  Region І : W essentially acts as a relaxation site of nearby carbon network, resulting in a significant stress reduction as W is incorporated.  Region Π : Segregation of W as a preliminary form of carbide seems to enhance the distortion of nearby carbon network.  Region Ш : Formation of the large crystalline W 2 C phase relieves the distortion of the bonds. C-W bonds has more flexibility to accommodate the distortion of the surrounding carbon network comparing with the rigid C-C bonds. Ⅳ.Conclusions Ⅳ. Conclusions  W-C:H nanocomposite films prepared by hybrid ion beam deposition.  The significant stress reduction by W incorporation.  The stress is reduced by 50% at 4.2 at.% W, while hardness is only reduced by 20%.  W essentially acts as a relaxation site of surrounding carbon network via forming more flexible C-W bond, which proposed a generic origin of the stress reduction with W incorporation.  Evolution of crystalline carbides plays a subsidiary role on the stress reduction in case of higher W concentration.  W concentration is varied by the Ar fraction in gas mixture. Defined by stress jumping