The effect of silicon doping on the residual stress of CVD diamond films is examined using both X-ray diffraction (XRD) analysis and Raman spectroscopy measurements. The examined Si-doped diamond films are deposited on WC-Co substrates in a home-made bias-enhanced HFCVD apparatus. Ethyl silicate (Si(OC2H5)4) is dissolved in acetone to obtain various Si/C mole ratio ranging from 0.1% to 1.4% in the reaction gas. Characterizations with SEM and XRD indicate increasing silicon concentration may result in grain size decreasing and diamond [110] texture becoming dominant. The residual stress values of as-deposited Si-doped diamond films are evaluated by both sin2ψ method, which measures the (220) diamond Bragg diffraction peaks using XRD, with ψ-values ranging from 0° to 45°, and Raman spectroscopy, which detects the diamond Raman peak shift from the natural diamond line at 1332 cm-1. The residual stress evolution on the silicon doping level estimated from the above two methods presents rather good agreements, exhibiting that all deposited Si-doped diamond films present compressive stress and the sample with Si/C mole ratio of 0.1% possesses the largest residual stress of ~1.75 GPa (Raman) or ~2.3 GPa (XRD). As the silicon doping level is up further, the residual stress reduces to a relative stable value around 1.3 GPa.
采用热化学气相沉积法(Thermal Chemical Vapor Deposition,TCVD)和机械剥离法分别制备了单层和少层石墨烯并转移至MPCVD制备的多晶金刚石基体表面,利用原子力显微镜研究了大气环境下石墨烯在金刚石基体上的纳米摩擦和磨损性能.研究结果表明:单层和少层石墨烯在金刚石基体上具有良好的减摩作用,摩擦系数分别为0.03和0.014.然而,由于石墨烯和金刚石表面之间的物理吸附作用较弱,其摩擦力会略高于SiO2/Si基体表面石墨烯的摩擦力.随扫描速度升高,金刚石表面的单层与少层石墨烯的摩擦力的变化可以分为自然对数正比上升,基本保持不变以及黏性阻尼增加三个阶段.在磨损试验中,TCVD法制备和转移石墨烯的过程中产生的缺陷和污染物降低了单层石墨烯的耐磨性能,而机械剥离的少层石墨烯因为无缺陷的石墨烯晶体结构在金刚石基体上展现了优异的耐磨特性.本研究可为以金刚石为基体的石墨烯固体润滑剂使用提供理论基础.
