用于二次电子发射阴极的纳米金刚石膜

Nano diamond films used as cathode for secondary electron emission

为获得导电性和二次电子发射性能均好的金刚石阴极材料,分别以CH4/Ar/H2、CH4/N2及CH4/N2/H2混合气体作为反应气源,用微波等离子化学气相沉积(MWPCVD)法制备出不同组成结构特点的纳米金刚石薄膜。XRD和Raman检测表明3种气源条件下得到的膜材均为金刚石多晶膜,但用CH4/N2反应源沉积的膜材中非金刚石相成分明显更多;AFM分析证实所有膜层的平均晶粒尺寸均在100nm以下,属纳米晶金刚石膜。用自行设计的二次电子发射系数测量装置对比检测所得膜层的二次电子发射特性,结果表明各金刚石膜均在初级入射电子能量达约1keV时,有最高的二次发射系数(δmax);并且以CH4/Ar/H2反应源制备的金刚石相纯度最高的膜材的δmax最大,达到17左右,是适用于二次电子发射阴极的潜在材料。

Aimed to obtain ideal diamond cathode materials with good electric conductivity and secondary electron emitting performance,nano diamond films were respectively prepared with CH4/Ar/H2, CH4/N2 and CH4/N2/ H2 using microwave plasma chemical vapor deposition technology, which possessed different characteristics of composition and structure. XRD and Raman spectroscopy characterization showed the as-prepared all were polycrystalline diamond films, while those grown with CH4/N2 contained more non-diamond continents. AFM analysis proved every obtained film has mean grain sizes below one hundred nanometer. By secondary electron emitting performance examination with special setup designed by ourselves, the results demonstrated that under the condition for the primary incident electrons with energy of l keV,the nano diamond films have maximum emitting coefficient of secondary electrons（δmax）,and within these films, the one deposited with CH4/N2/H2 and at the same time possessing the highest phase purity holds the biggest δmax Of 17,SO it will be a promising material for cathode of secondary electron emission.