L. Makhova

Valence band offset at interfaces between CuI and indium sulfides

The energy differences between In 3d5/2, In 4d5/2, and S 2p3/2 core levels are almost the same in β-In2S3, CuIn5S8, AgIn5S8, CuInS2, In6S7, and InS semiconductors. The system of these core levels provides a reference energy that can be used to put the valence band edges of these materials on a common energy scale. The experimental study shows that this common energy scale remains valid within ±0.2 eV for prediction of valence band discontinuities at heterointerfaces between these (and potentially other) indium sulfides and CuI. CuI/CuIn5S8 heterojunction showed no valence band offset and it may be interesting for applications as a diode.

Small valence band offset in (010) InS∕CuI heterojunction diodes

Heterojunctions between the (010) facet of an orthorhombic InS single crystal and evaporated CuI show a remarkably small valence band offset of 0.15eV (cliff). This minor band offset allows rather good injection conditions for holes. In accordance to this result, the current-voltage characteristics of the device are rectifying and show a large forward voltage.

X-ray photoconductivity due to trap-sensitive relaxation of hot carriers

We observed the temperature-dependent modulation of the electrical conductivity in ZnO thin films under periodic illumination by soft x rays. At specific temperatures, small variations of the excitation energy near the x-ray absorption edges resulted in large element-specific variations of the conductivity modulation. The emission rate of electrons at traps E1/E2 and E3/E4 in ZnO at these specific temperatures roughly equals the excitation frequency. We conclude that relaxation of electrons, excited from localized core levels into the conduction band, predominantly happens into trap states with the same localization. The experimental results were explained using symmetry selection rules and local transition probabilities.