Detailed structural analysis of Ce doped Si thin films

Abstract

A diluted magnetic semiconductor, Si : Ce thin film was prepared by vacuum evaporation using electron beam guns. As-deposited thin film was n-type conduction due to its amorphous nature. It shows a normal semiconductor like ρ– T behavior with a diamagnetic property. By annealing at 973 K , the conduction type change to p-type and the resistivity remarkably decreases by three orders of magnitude below 30 K . Change in the magnetic susceptibility against the measurement temperature at the low magnetic field (750 Oe) exhibits spin glass like behavior showing cusp around 40 K . We also confirm an extremely large magneto-resistance below the spin glass temperature. To understand the relationship between the magnetic behavior and the micro-structure, detailed structural analyses were performed. Although no precipitation was confirmed by electron transmission diffraction (TED) analysis, widely dispersed black regions with the diameter of around 10 nm were clearly observed. TED and TEM reveal that the crystal structure of the black region is identical to that of Si with stacking faults and twins. This paper describes that the anomalous magneto-transport behavior of annealed Si : 0.5 at% Ce is strongly related to micro-structure.