Effects of pressure and temperature on sp 3 fraction in diamondlike carbon materials
- PDF / 855,330 Bytes
- 6 Pages / 585 x 783 pts Page_size
- 32 Downloads / 173 Views
nwei Wanga) and Xuhui Feng Department of Mechanical Engineering, The University of Nebraska–Lincoln, Lincoln, Nebraska 68588-0656 (Received 2 May 2007; accepted 22 May 2007)
In this work, formation of diamond coating is studied using large-scale molecular dynamics (MD) simulation. The diamond coating is studied to explore how and to what extent the temperature and pressure affects the deposition structure. To analyze the coating results, the radial distribution function and the fraction of diamond (sp3 bonds) is calculated. It is found that the sp3 fraction in the deposition structure increases with the temperature and pressure. When the pressure becomes large enough (10 GPa), the effect of the pressure on the coating structure is quite small and the sp3 fraction tends to be constant.
I. INTRODUCTION
In recent years, the fabrication and characterization of diamondlike carbon (DLC) materials has attracted significant attention because of their special physical, chemical, and mechanical properties. To date, extensive experimental work in this area has been conducted to fabricate diamondlike thin films. Different techniques have been applied for synthesizing DLC, including the mass-selected ion beams,1 filtered vacuum arc,2 and laser ablation3 techniques. A common feature of these deposition methods is that the DLC films with high sp3 fraction are obtained only by hyperthermal ions. It is important to study the effect of the deposition conditions on structural quality of DLC for much-improved experimental control and optimization. Numerically, molecular dynamics (MD) simulation and the many-body Brenner–Tersoff potential function have been widely used to simulate the growth of diamondlike materials. Wei et al.4 studied the deposition of energetic C2 clusters on silicon and diamond surfaces and found that the mobility of surface atoms is enhanced at elevated energies in an earlier stage of deposition. Du et al.5 investigated the deposition of C20 fullerenes on a diamond surface using the many-body Brenner bondorder potential. The deposited C20 film showed high sta-
a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0344 2770
J. Mater. Res., Vol. 22, No. 10, Oct 2007
bility even when the temperature was raised up to 1500 K. Jäger and Albe6 simulated the ion beam deposition of DLC films using MD simulations and calculated the sp3 fractions. To date, little MD research has been reported about the effects of temperature and pressure on the sp3 fraction in DLC over a wide range of experimental conditions. In this work, MD simulations using the Brenner– Tersoff potential are used to study two methods for fabricating diamondlike materials: deposition and compression. To characterize the sp3 fraction in the simulation results, the variation of the nearest-neighboring distance in diamond and graphite with temperature is first explored. By analyzing the radial distribution function (RDF) and the nearest-neighboring distance among atoms, the sp3 fraction in the material is obtained. Th
Data Loading...
