Effects of Vanadium Atoms on Electronic Band Structure of ZnO
Band edge energies (triangles) and low emission peak energy position (squares) as a function of vanadium content. Solid lines represent fitting results of sub-band model.
Demonstrated anti-crossing interaction, or splitting of the conduction band, between d-electrons localized on Vanadium atoms and delocalized electrons of the entire ZnO crystal. Showed the interaction’s effects on electronic structure & properties of the ZnVO alloy.
Significance and Impact
The newly discovered interaction opens the possibility of using transition metals for modification of electrical & optical properties of semiconductors, and of researching a broad class of alloys with standard compound semiconductors.
- Synthesized Znx-1VxO thin films (x between 0 and 0.08): electrical measurements show electron concentration increases with vanadium content up to x=0.04; then decreases and films are insulating for x>0.06
- Optical characterization reveals that the absorption edge shifts to higher energy with increasing vanadium content, while photoluminescence peak (emission) shifts to lower energy
- This difference in absorption and emission is explained by splitting of the conduction by the anticrossing interaction between localized d-levels of V and extended states of ZnO conduction band
- The interaction results in upward shift of unoccupied conduction band states (E+) and formation of a narrow, fully occupied donor band (E-)