Modification of diamond surfaces by plasma process and its application to cold cathode

研究了等离子体对金刚石表面的改性及其在冷阴极上的应用。获得了以下结果。[1]经O_2等离子体处理的掺磷多晶金刚石薄膜的电子发射电场强度增大，而经H_2等离子体处理的掺磷多晶金刚石薄膜的电子发射电场强度减小。然而，用O_2等离子体处理金刚石膜的背面时，同样的H_2等离子体处理不能恢复金刚石膜的场发射特性。结果表明，这是由于存在致密的晶界。[2]测量了P掺杂和未掺杂金刚石薄膜的场发射特性随温度的变化。对于P掺杂金刚石膜，电子发射的开启电压随着温度的升高而降低。另一方面，对于未掺杂的金刚石膜，随着温度的升高，导通电压没有变化。场发射特性的这一行为很好地解释了内部电子发射的基础上的电子场发射模型结合电离施主浓度的温度依赖性。[3]用不同功函数的金属在氧等离子体处理的掺磷同质外延金刚石薄膜表面形成阴极。结果表明，场发射特性与阴极金属的功函数有关。

Studies on modification of diamond surfaces by plasma process and its application to cold cathode are carried out. The following results are obtained.[1] The electric field strength commencing electron emission increases for phosphorus (P)-doped polycrystalline diamond films, the surface of which is treated with O_2 plasma, while the electric field strength is decreased by H_2 plasma treatment. In the case when the rear face of diamond films is treated with O_2 plasma, however, the field emission characteristic is not recovered by the same H_2 plasma treatment. It is revealed that this is due to existence of dense grain boundaries.[2] Temperature dependence of field emission characteristics is measured for P-doped and undoped polycrystalline diamond films. The turn-on voltage of the electron emission is reduced with increasing temperature for the P-doped diamond film. On the other hand, no variation in the turn-on voltage occurs with increasing temperature for the undoped diamond film. This behavior of the field emission characteristic is well explained by the internal electron emission based on the thermionic field emission model combined with the temperature dependence of the ionized donor concentration.[3] Cathode electrodes are formed using metals with different work function on the surface of P-doped homoepitaxial diamond dilms treated with O_2 plasma. It is shown that the field emission characteristic depends on the work function of the cathode metals.