Defects Studies of ZnO Single Crystals Prepared by Various Techniques

F. Lukáča, J. Čížeka, I. Procházkaa, O. Melikhovaa, W. Anwandb and G. Brauerb aCharles University in Prague, Faculty of Mathematics and Physics, V Holešovičkách 2, 180 00 Praha 8, Czech Republic bInstitut für Strahlenphysik, Forschungszentrum Dresden-Rossendorf, Postfach 510119, D-01314 Dresden, Germany

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The aim of the present work was a comparison of defects in ZnO crystals grown by various techniques available nowadays, namely hydrothermal growth, pressurized melt, Bridgman method growth and vapor phase growth. Positron annihilation spectroscopy was employed as a principal tool for characterization of defects in ZnO crystals grown by above mentioned various techniques. ZnO crystals can be divided into two groups: (i) hydrothermal grown crystals, which exhibit positron lifetime of 179-182 ps and (ii) ZnO crystals grown by the other techniques (pressurized melt, Bridgman method, vapor phase growth) which are characterized by the lower lifetimes falling in the range of 160-173 ps. Comparison of experimental data with ab initio theoretical calculations revealed that HT grown ZnO crystals contains Zn vacancies associated with hydrogen atom in a bond-centered site. On the other hand, ZnO crystals prepared by other techniques contain most probably stacking faults created by stresses induced by temperature gradients in the melt.

DOI: 10.12693/APhysPolA.125.748 PACS numbers: 78.70.Bj, 61.72.J-