Study Of Preparation And Residual Stress Of Diamond Films On Mo Foil

The diamond films on foil substrate with ultra-thin, high flexibility, light weight and high efficiency have attracted attention for many applications. Especially, it meets the needs of low-weight, ultra-thin and high-efficiency for micro devices such as micro electronic devices and biosensors. Hence, the study of diamond film on foil substrate is very important for the low-weight and miniaturization application of CVD diamond films. Mo foil is selected in this study.The residual stress of the films has a very important impact on their performance and service life for thin film. Many articles have reported the residual stress of the CVD diamond films deposited on different bulk substrates, but the formation mechanism of the residual stress has not been studied perfectly and these literatures rarely involved the residual stress of diamond films deposited on foil substrates. So, this work is necessary for meeting the need of application in the field of micro devices.The total residual stress in the film is the sum of thermal stress and intrinsic stress. The former one is determined by the coefficient of thermal expansion (CTE) between the film and substrate. Thus, the deposited temperature, film thickness and substrate thickness have a significant effect on the thermal stress. The cooling-rate changes the loading speed of thermal stress on films. The intrinsic stress is emerged during the growth process, and is related to the micro-structure parameters of film such as thickness, purity and grain size. These structural properties are impacted by deposited temperature, deposited time and the pretreatment of the substrate. In addition, the Mo substrate in different thickness possessed discrepant structure, which causes a discrepant deposition condition of film. Therefore, these deposition conditions all impact the intrinsic stress of film. This work mainly studied the effect of deposited temperature, pretreatment of substrate, cooling-rate, film thickness and substrate film on diamond filmresiudaul stress.In this study, polycrystalline diamond films have been prepared by hot-filament-assisted chemical vapor deposition (HFCVD) on Mo foils. Morphology, growth rate, phase composition and purity of the films were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Raman spectroscopy (Raman). Electron probe micro-analyzer (EPMA) was used to detect the element distribution along depth by performing a point by point line-sweep along the cross-sectional surface. The element distribution of the film surface was studied by Energy Dispersive Spectrometer (EDS). The residual stress of diamond film and substrate were analyzed by Raman and XRD respectively.