关键词: 金刚石膜;无裂纹;晶体结构;直流等离子体喷射

Abstract: Crack patterns in self-standing diamond film were observed as network-shape pattern, river-shape and circle-shape pattern, depending on growth temperature. Fracture mechanism was firstly studied by atomic force microscope (AFM) on the fractured section. Both intergranular fracture and transgranular fracture were found by this technique. Transgranular fracture was easy to observe in network-shape pattern, and intergranular fracture was found in circle-shape pattern. The river-shape pattern seemed to result from the combination of inter- and trans-granular fracture. X-ray diffraction (XRD) test was done on all of growth side, nucleation side and fractured section of the film body. Corresponding to XRD results, transgranular fracture took place in the film with (111)-crystalline surface being dominant in all of the three detected surfaces. Intergranular fracture occurred in the film with (220)-crystalline surface being dominant in all of the three detected surfaces. Raman test showed that the intrinsic stress was in the range of several tens MPa to several hundreds MPa. Micro-Raman test on fractured section indicated that there was the distribution of stress in the film body. Also by micro-Raman, testing along the crack path indicated that crystalline structure with few defects was benefit for blocking the propagation of crack. A mechanical model was set up to analyze the effect of dominant surface on fracture strength. Based on the experimental results and mechanical analysis, crack-free self-standing diamond films with 2mm in thickness and 120mm in diameter were successfully grown by controlling the crystalline structure of the films.