Elastic-peak electron spectroscopy (EPES) studies of ZnO single crystals

Electron transport in both ZnO(0 0 0 1)-Zn and ZnO(0 0 0-1)-O bulk single crystals was studied using the elastic-peak electron spectroscopy (EPES) measurements. The inelastic mean free path (IMFP) was evaluated from EPES using both Ni and Au standards in the energy range 200-2000 eV, and compared with IMFPs calculated from the predictive TPP-2 M formula for the measured composition of both single crystal surfaces. In the electron energy range from 1 to 2 keV, the IMFPs were found to be 34% larger for the ZnO(0 0 0 1)-Zn crystal surface than for the ZnO(0 0 0-1)-O crystal surface, and considerably larger than the IMFPs obtained from the TPP-2 M predictive formula. At energies lower than 1 keV, a good agreement between the corresponding IMFPs values was found. However, the electron transport at larger energies seems to be affected by different bulk structure of both crystals.