Exploring of New Properties of Non-Epitaxial Metallic Superlattices and Development of High Conductivity Superlattice Films

点击翻译按钮获取中文摘要

1.Metallic superlattice films of Ag-Bi, Ag-Au, Yb-Sb and Bi-Sb systems were grown in order to investigate electrical properties and explore new features. In a possible stage of work, non-epitaxial film growth was done. By X-ray diffraction, superlattice structure was confirmed. For Ag-Bi and Ag-Au films, resistivity <rho> was proportional to 1/ <lambda> where <lambda> was the layer period.2.Yb-Sb superlattice system was investigated due to an expectation of getting some new electrical property. By setting the layer number ratio 1:1, the period of thickness <lambda> was varied from 10 to 1000 <ang> and the resistivities were measured as the function of temperature. The films of <lambda> <>!-> 100 <ang> , metallic behavior was obtained, while the films of <lambda> <100 <ang> ,semiconductive negative temperature dependence was found. The log <rho> vs. 1/T was not strait, but log <rho> vs. 1/( <T^(1/4)> gave a good fit of straight line which fact meant the system behaved as the Anderson lo … More calized state. Thus the Yb-Sb superlattice system has been found to show metal・non-metal transition very sharply at the period of <lambda> <:!=> 100 <ang> .3.Bi-Sb superlattice system was investigated rather in detail. The bulk Bi-Sb system is known as a whole range solid solution, nevertheless, 4 to 40 atom.% Sb alloy shows semiconducting nature. How is the behavior for the metallic superlattice films? The alloying concentration of Sb was substituted by the layer number ratio of Sb to the total perioic layer number. On the specimens of about ten kinds of Sb layer ratios, resistivity, Hall coefficient and magnetoresistance were measured as functions of temperature from 300K to 77K. Furthermore, the resistivity was measured as the function of temperature and negative temperature gradients were obtained for 0 to 48 Sb ratio, which gave apparent energy gap values. By analysing these data, such conclusion has been obtained that 4 to 48 Sb ratio of this superlattice system shows semiconductive nature and the maximum energy gap is 13 meV. It may be reasonable because the estimated de Broglie wave lengths of the carriers are 650 <ang> for Bi and 170 <゜!A> for Sb which are generally longer than the periodic length. Less