ＦＩＭによるＧａ‐ＷおよびＧａ‐Ｍｏ界面の研究 Ｉ Ｇａ層の構造と電界放射電流

Abstract

Evaporation fields of Ga covering a W or a Mo tip surface were measured by finding the variation in the field emission current due to the field evaporation of the Ga layer. The observed current variation suggests the existence of two Ga layers; the overlayer and the interface layer in which Ga atoms are in direct contact with the substrate atoms and arranged in the pseudomorph or the superstructure. The evaporation field of the overlayer is almost independent of the substrate and the crystal plane, and is significantly lower than that of the interface layer, indicating that the binding energy of the overlayer is much smaller than that of the interface layer. An interesting finding is that the evaporation fields of the pseudomorph and the superstructure on W are nearly equal to those on Mo, respectively, in spite of the large difference in the evaporation fields of W and Mo. The measurement of the work functions of the Ga layers and the substrate revealed that the Ga pseudomorph maximizes the work function.