Studies On Growth Mechanism Of Diamond-like-carbon Films Assembled Of C-clusters By MD Simulation

The growth mechanism and synthesis methods of diamond-like-carbon (DLC) films have attracted much attention, due to their unique physical and chemical properties and potential applications. In experiments, DLC films have been synthesized by various methods, such as chemical vapor deposition (CVD) and microwave plasma deposition, etc. It was observed in Pulsed Laser Deposition (PLD) experiments that energetic small carbon molecules are favorable to DLC film growth. Moreover, Ion Beam Assisted Deposition (IBAD) can improve the corresponding film's density, hardness and adhesion to the substrate. The synthesis of DLC films is a complicated process. It is relative to the atomic interaction on both surface and interface and the competition between thermodynamics and collision dynamics of the system. The microscopic process is difficult to observe experimentally. Therefore, it is important to explore the growth mechanism at atomic scale and the appropriate experimental parameters, which favor the growth of DLC films. In this paper, we first investigated the chemisorption of small molecules, C2 and C10, deposition on the diamond (001)-(2. 1) surface by molecular dynamics (MD) simulation. We simulated the full process of the DLC films assembled by C2 and C10 and analyzed the structure properties of the films. Secondly, we mimicked the film growth on silicon (001)-(2. 1) surfaces via Ar assisted deposition. The results were compared with experimental measurements. In our simulation, the semi-empirical many-body Brenner (#2) potential was used to describe the interaction between C-C atoms, and the Tersoff potential was used to describe the interaction between C-Si, and Si-Si atoms. The Ziegler, Biersack and Littmark (ZBL) pair potential, was used to describe the interactions between Ar-C and Ar-Si atoms. Our main results can be summarized as the following:(1) Experimentally, hydrogen-free DLC films were assembled by means of PLD, where energetic small-carbon-clusters were deposited on the substrate. In this paper, the chemisorption of energetic C2 and C10 clusters on diamond (001)-(2xl) surface was investigated by molecular dynamics simulation. The influence of cluster size and the impact energy on the structure character of the deposited clusters is mainly addressed. The impact energy was varied from 10 to 100 eV. The chemisorption of C10 was found to occur only when its incident energy is above a threshold value Eth (5-40 eV). While the C2 cluster was easily to adsorb on the surface even at much lower incident energy (0.01 eV). With increasing the impact energy, the structures of the deposited C2 and C10 are different from the free clusters. We also observed the dimmer-opening reaction caused by C2 deposition, which plays an important role in the process of DLC film growth. The adsorption rate is raised with increasing the incident energy of C2- Finally, the growth of films synthesized by energetic C2 and C10 clusters were simulated. The statistics indicate the C2 cluster has high probability of adsorption and films assembled of C2 present higher SP3 fraction than that of C1-films, especially at higher impact energy and lower substrate temperature. Our results agree well with the experimental observation.(2) The growth of DLC films via ion-beam-assisted deposition (IBAD) is simulated using molecular dynamical simulation. The C2-molecules and Ar ions were selected as deposition and assistance projectiles, respectively. The impact energy of Ar ranged from 10, 30, 50, to 100 eV. We focused our examination on the effects pf the assistance/deposition atomic ratio and the incident energy of Ar ions on the growth dynamics and film structure. We analyzed quantitatively the film structure by calculating the density distribution and the coordinate-number-distribution and atomic mixing at the film/substrate interface. In order to study the mechanism of Ar ion assisted deposition, the cascade volume was defined in the simulation. The recoil energy and migration of carbon atoms within the cascade volume were studied quantitativ...