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。结果如下所示O_2等离子体处理后，磷掺杂多晶金刚石膜的电子发射起始电场强度增加，而H_2等离子体处理后，电场强度降低。而在金刚石膜的后表面进行O_2等离子体处理时，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，这是由于致密晶界的存在测量了p掺杂和未掺杂多晶金刚石薄膜场发射特性的温度依赖性。掺杂p的金刚石薄膜的电子发射导通电压随温度的升高而降低。另一方面，未掺杂金刚石薄膜的导通电压不随温度的升高而变化。基于热离子场发射模型的内部电子发射，结合电离供体浓度的温度依赖性，很好地解释了这种场发射特性的行为用不同功函数的金属在O_2等离子体处理的p掺杂同外延金刚石薄膜表面形成阴极电极。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.