Experimental Studies on the Electronic Structure of Pb_1-xEu_xTe

Abstract

P - and n -type Pb 1- x Eu x Te (0≤ x ≤0.25) single-crystal films were prepared on BaF 2 (111) substrates using the hot-wall epitaxy technique. The lattice constant increases nonlinearly with the composition ratio x , and the energy gap increases rapidly up to x =0.07, while its rate of increase decelerates for x >0.07. X-ray photoelectron spectroscopy measurements revealed that the localized Eu 4 f level centers around 1.2-1.5 eV below the valence band maximum. It is seen from the transport measurements that all of the n-type films are metallic but for the p -type films a metal-to-insulator transition takes place at x =0.07. Using these results, the electronic structure of Pb 1- x Eu x Te is proposed in which the Eu 4 f localized electron plays an important role in the electronic properties for intermediate composition ratio ( x >0.07).