Characterization of H-Plasma Treated ZnO Crystals by Positron Annihilation and Atomic Force Microscopy

Abstract

Nominally undoped, hydrothermally grown ZnO single crystals have been investigated before and after exposure to remote H-plasma. Defect characterization has been made by two complementary techniques of positron annihilation: positron lifetime spectroscopy and coincidence Doppler broadening. The high-momentum parts of the annihilation photon momentum distribution have been calculated from first principles in order to assist in defect identification. The positron annihilation results are supplemented by Atomic Force Microscopy for characterization of the crystal surface. It was found that virgin ZnO crystal contains Zn-vacancies associated with hydrogen. H-plasma treatment causes a significant reduction in concentration of these complexes. Physical mechanism of this effect is discussed in the paper.

H/He interaction with vacancy-type defects in α-Al2O3 single crystals studied by positron annihilation

“…Correspondingly, the reduction of s 1 could be caused by thermally-activated mutual annihilation of intrinsic point defects. 16 This is a typical phenomenon of materials annealed at high temperature.…”

Design and Construction of a Slow Positron Beam for Solid and Surface Investigations

“…This value agrees well with the expected one of 770 eV, as shown in Fig.15.The results of cDB measurements are commonly presented in so-called ratio plots, where the momentum distribution of the electrons for different positron annihilation sites is referred to a reference sample, mostly to a sample without defects. A typical example for experimental and theoretical ratio curves and their discussion can be found in Ref 21…”