Investigation of the electronic structure of amorphous SnO film using x-ray absorption spectroscopy

摘要

The electronic structure of an amorphous SnO (a-SnO) thin film was examined by using spectroscopic methods including tender and soft x-ray absorption spectroscopies (XAS) and spectroscopic ellipsometry (SE). XAS at the Sn L-1-, L-3-, and O K-edges revealed that in a-SnO, the Sn 5p(x/y) orbital states, which comprise the conduction band minimum (CBM), are broadened significantly compared to the case of crystalline SnO, whereas the hybridized Sn 5sp(z)-O 2p states above the CBM are persistent. A lowering of the 5p(x/y) states at the CBM by -0.4 eV and a reduction of the indirect bandgap were also observed. These orbital-dependent evolutions upon amorphization were caused by weakened interlayer couplings in the disordered quasi-2-dimensional semiconductor. However, the functionality of a-SnO as a p-type semiconductor would not be degraded significantly because the isotropic Sn 5s orbital states dominate in the valence band states.