Abstract
The thermally stimulated exoelectron emission (TSEE) from the oxidized surface of nickel, the cleavage plane of NiO single crystal and the pressed disk of nickel oxide powder was investigated using a gas-flow G.M. counter. These specimens showed the same TSEE behaviour and gave the glow curves having glow peaks at 400 and 520 K. The intensity of 520 K peak was nearly constant independent of the atmospheric pressure at which specimens were oxidized or heat-treated prior to the TSEE mesurement, while the intensity of 400 K peak varied with the atmospheric pressure and was proportional to the 6th root of the pressure. This fact implies that the 400 K peak intensity is in direct proportion to the concentration of nickel ion vacancy in NiO. It was revealed that the exoelectron source giving the 400 K peak was closely related to the nickel ion vacancy. This correlation was also shown in the variation in the peak intensity with the heat-treatment temperature range up to about 850 K. The peak intensity, however, decreased as the specimen was heated above 850 K, in spite of the high vacancy concentration. It was surmised that other factors became predominant in the case of high vacancy concentration.
