热阴极DC-PCVD方法制备的金刚石厚膜的生长特性和内应力

The growth behavior and internal stress of diamond thick films synthesized by hot-cathode DC-PCVD

采用热阴极DC PCVD(DirectCurrentPlasmaChemicalVaporDeposition)方法制备出大尺寸高质量的金刚石厚膜,研究了金刚石厚膜的生长特性和内应力状态。由热阴极DC PCVD方法制备的金刚石厚膜大多数为〈110〉取向,表面显露面主要是(100)面和(111)面,厚膜的表面被较多的孪晶所覆盖,部分(111)面退化为3个相互垂直的(110)面,孪晶使厚膜表面结晶特性复杂化,金刚石厚膜的晶粒沿生长方向呈现柱状生长。金刚石厚膜的生长速率随甲烷流量和工作气压的增加而增加,但随生长速率的提高金刚石膜的品质明显下降。金刚石厚膜的内应力以压应力为主,随着甲烷浓度的增加压应力增加,随着工作气压的增加压应力减小,到某个气压之后变为张应力。

Large size diamond thick films with high quality were synthesized by hot-cathode DC-PCVD, and the growth behavior and internal stress of diamond thick films were studied. Under the experimental condition investigated, most of the diamond thick films were found to have a <110> orientation, with main visible faces of ( 100) and ( I I I). Penetration twins were found to be widespread. The surface microphologies are more complex, and the crystalline grains of the thick films are grown in columns along the growth orientation. The growth rate was greatly influenced by methane concentration and gas pressure. The growth rate increases with increasing methane concentration, but quality is degraded with increasing growth rate. Initially the growth rate increased rapidly with increasing gas pressure, and then decreased. Substrate temperature greatly influenced quality, with high quality diamond films being grown at substrate temperatures ranging from 950 degreesC to 1050 degreesC. For freestanding thick films, the thermal stress was mostly released after breaking them away from the substrate. Thus, the total stress of freestanding films is mainly an internal stress. Under the present experimental conditions, the internal stress is mainly a compressive stress, which increase with increasing methane concentration, and changes to a tensile-stress with increasing gas pressure.