硅基籽晶上化学气相沉积金刚石薄膜及其场发射特性

Field Emission Properties of Diamond Film on Silicon Substrate with Seed Crystal by Chemical Capor Deposition

通过控制电泳沉积(EPD)时间,在硅基片上沉积不同密度的金刚石籽晶。再用热丝化学气相沉积(HFCVD)设备,在硅基籽晶上合成多晶金刚石薄膜。薄膜中通常含有非金刚石相碳成分。用扫描电子显微镜(SEM)和Raman光谱对样品的表面形貌和成分进行了表征,测量了样品的场发射特性。比较并分析了样品的表面形貌和非金刚石成分上的差异对金刚石薄膜场发射特性的影响。

Diamond possesses a low or negative electron affinity surface that allows its surface to emit electrons under low electric field, so diamond films have potential applications in the areas such as field emission display. Although a considerable research effort on diamond field emission has been made in the past few years, the influences of crystal texture of diamond films on emission properties are not yet completely understood. In this article, the effect of seed crystal density on the hot film chemical vapor deposition (HFCVD) diamond film's component, crystal texture and field emission property was analyzed. In most cases, the silicon substrate was eroded or rubbed before HFCVD diamond film. In this report, diamond seed crystals were deposited to silicon substrates with different density by controlling the electrophoresis deposition (EPD) time, then synthesized diamond film on the seeded silicon substrates with a HFCVD reactor. The samples were analyzed with scanning electron microscope (SEM) and Raman spectrum, and the field emission properties of those samples were tested. The result shows that the amount of graphite phase with sp2 bond structure at diamond crystal interfaces is a virtual factor for its electron emission ability. A little of the graphite phase is good for the electron transmission in the film, however the amount should not be too much. The high density and small size of the diamond powder on the film surface are helpful to exert the electron emission property. Also the interface resistance of diamond and silicon substrate should be low, ensure the electron inject to diamond film from silicon substrate easily. For the diamond films chemistry vapor deposited on the silicon substrates seeded with diamond powders by EPD process, the area rate of amorphous carbon component and the graphite phase component in the Raman spectrum should be around 1∶031, which corresponds a better field emission property.