• What's The Hot Filament?
    • Hot filament CVD is one of the initial techniques for preparing diamond films successfully. Compared with other methods, hot filament CVD requires simple equipment, assures the filmforming to be control and generates large area diamond films. The main shortcoming is the low heat efficiency owning to using hot filament as heat soure. The growth rate is 0.3-2μm/h.
    • In the growth process, the distance between the hot filament and the substrate is very crucial. Without any assistant heat soure, it should be less than 10mm. in addition, the film is difficult to be uniformity, and contains non-diamond phase. In order to improve the diamond quality and growth rate, direct voltage is adopted between the hot filament and the substrate to generate plasma for enhancing the filament temperature. The hot filament will distort after several working hours under the high temperature. The longer the W filament or the Ta filament is, the greater distortion generate. Moreover, the higer the carbon concentration is, the greater distortion generates. It leads to the distance change difficult to be controlled. Meanwhile, the surface temperature and the uniformity of DC plasma distribution between the filament and the substrate will also be affected. The following fig is the equipment sketch of a so-called advanced hot filament CVD (AHFCVD). The Ф100mm symmetrical diamond (thick) films can be prepared using this equipment.