MPCVD法合成硼掺杂金刚石薄膜的次级发射性能

Secondary electron emission properties from boron doped diamond films

为解决电子倍增器、场发射阴极和粒子/光子探测器现有阴极材料次级发射系数低且发射不稳定的问题,对微波等离子体化学气相沉积(Microwave Plasma Chemical Vapor Deposition,MPCVD)法结合H等离子体表面处理工艺制备的不同B2H6/CH4浓度的硼掺杂金刚石薄膜的次级发射能力进行了研究。样品表面扫描电子显微镜和拉曼光谱分析结果显示,硼掺杂金刚石膜表面形貌与未掺杂的金刚石膜相似,样品表面均为高纯度的金刚石相。将置于空气中数日且未经任何表面处理的硼掺杂金刚石样品进行次级电子发射性能测试,结果显示一次电子入射能量为1keV时,得到高达18.3的二次电子发射系数。试验证实这种具有高二次电子发射系数的硼掺杂金刚石膜,暴露空气中由于表面氧化会破坏其表面的负电子亲和势,而真空中加热会使表面重新恢复负电子亲和势,这种负电子亲和势的完整保留,提高了该材料次级发射的稳定性,在器件中具有重要的应用前景。

The cathode materials used in electron multiplier, field emission cathode and particle/ photon detector have the problem of low secondary electron emission yield and unstable emission. To solve this problem,different boron concentration diamond films by microwave plasma chemical vapor deposition were prepared.The surface of B-doped diamond film was treated by Hydrogen plasma.The secondary electron emission （SEE）from B-doped diamond films was investigated.The scanning electron microscopy （SEM） and the Raman spectrum analysis were used to examine the properties of the B-doped diamond film.The maximum SEE yield up to 18.3 at 1 keV primary beam energy was found under the condition that the samples were left in air for weeks and subject to no treatment prior to the measurement.Oxidation treatment destroys negative electron affinity （NEA）whereas heating up in vacuum substantially brings back NEA.B-doped diamond film is expected to be used in electron multiplier,field emission cathode and particle/photon detector.