Electronic Structure and Electrical Conductivity of Amorphous Si-Ti Alloys Manifesting the Metal-Insulator Transition : Condensed Matter: Electronic Properties, etc.

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The electrical conductivity σ of amorphous Si_<100-x>Ti_x alloys prepared by ion-beam sputtering has been measured over a temperature range between 4.2 and 290 K. The temperature dependence of σ is well expressed by a formula derived by the variable-range hopping theory with an exponent n 〜 0.40 for x ≤ 11.5, whereas, for x ≥ 12.8, it is better expressed by a formula describing the conduction by electrons liberated from weakly localized states through inelastic electron-electron scattering. Thus, the metal-insulator transition takes place at 11.5 < x_c < 12.8 in this system. The electronic structure of these alloys has been studied by measuring XPS and UPS spectra. Furthermore, DV-Xα calculation has been carried out for certain Si-Ti alloy clusters of diamond structure to simulate the electronic structure of the amorphous alloys. The calculated total and partial density of states well reproduces the features of the photoemission spectra. The calculation also provides information on the localization of electronic states in the amorphous alloys.
社団法人日本物理学会の論文
2000-03-15