Composition influence on positron annihilation parameters in ZnO-based nanocrystal semiconductor powders

L. C. DAMONTE; M.A.HERNÁNDEZ-FENOLLOSA; V.DONDERIS; B.MARÍ

Physica Status Solidi c

Wiley Interscience

Año: 2007 vol. 4 p. 3899 - 3902

Intrinsic and induced point defects in ZnO lead to the generation of bounded states with important effects on the material properties. Magnesium substitution on the cation site may lead to an increase in the direct bandgap of this semiconductor. In consequence, a complete knowledge of point defect structure is needed to understand its optical and electronic behaviour. Mechanical milling is an effective, useful and simple processing technique to produce the synthesis of alloy phases including nanocrystalline materials. Under milling, the powders are subjected to severe plastic deformation giving rise to particle and grain refinement, creating, simultaneously, different kinds of defects. Zn1-xMgxO powders at various compositions were obtained by mechanical milling from the binary oxides. In the present work we analyze the influence of the different cation contents on positron lifetime parameters.  The results indicate that positron and positronium trapping occur. The evolution of annihilation parameters with milling time and composition were analyzed and related with the kind of mechanical and substitutional induced defect involved. A comparation with PALS results in ZnO single crystals is also presented.