Atomic-Level Stress Calculation and Investigation of Thin Film Deposition Process Using Molecular Dynamics Simulation

• Main Authors: Zheng-Han Hong, 洪正翰
• Other Authors: Te-Hua Fang
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/79657869301147525643

博士 === 雲林科技大學 === 工程科技研究所博士班 === 96 === Molecular dynamics is employed to investigate the film growth at different deposition conditions of incident energy, substrate temperature, incident angle, and deposition rate. The Morse two-body potential and the Second-Moment Approximation of the Tight-Binding (TB-SMA) many-body potential are employed for Fe, Co, Al or Cu onto Cu(001) substrate. For epitaxy, mixing, and sputtering modes, the results indicate that when the TB-SMA potential is used under 5 atom/ps deposition rate, the epitaxy mode of film growth is observed as the incident energy is lower than 3 eV, the film mixing mode clearly occurs from 3 to 5 eV, and the sputtering phenomenon is significant after 10 eV. When the Morse potential is used, the epitaxy mode is observed below 5 eV, the film mixing mode occurs around 5~50 eV, and the sputtering process may be clear only after 50 eV. To discuss the morphology of the eptiaxy mode, an excessive incident angle does not improve surface roughness because it is associated with limited surface diffusion. Furthermore, increasing the incident energy from 0.5 to 5 eV improves the surface roughness by improving the energetic atom mobility. However, increasing the substrate temperature may be more effective in smoothening the surface than increasing the incident energy when the latter does not exceed 5 eV. Hence, to improve the surface roughness, the substrate temperature should be increased in Volmer-Weber mode. As for the atomic-level stress, the average normal stress along thickness direction and the average mean biaxial stress are considered. Both the average stresses at the substrate layer are compressive stresses, because the substrate suffered from the deposition of incident atoms and the substrate atoms are also compressed due to periodic boundary conditions along the x and y directions. For the mixing system, the first peak of the radial distribution function becomes low and wide for as the substrate temperature is increasing from 300 to 1000 K. Hence, the mixing mode becomes clear as the substrate temperature is increased.