Structural characterization of H plasma‐doped ZnO single crystals by positron annihilation spectroscopies

Abstract

Nominally undoped, hydrothermally grown ZnO single crystals have been investigated before and after exposure to remote H plasma. Structural characterizations have been made by various positron annihilation spectroscopies (continuous and pulsed slow positron beams, conventional lifetime). The content of bound hydrogen (H‐b) before and after the remote H plasma treatment at the polished side of the crystals was determined at depths of 100 and 600 nm, respectively, using nuclear reaction analysis. At a depth of 100 nm, H‐b increased from (11.8 ± 2.5) to (48.7 ± 7.6) × 1019 cm−3 after remote H plasma treatment, whereas at 600 nm no change in H‐b was observed.

Effect of high temperature annealing on defects and optical properties of ZnO single crystals

“…However, this lifetime is longer than that in ZnO grown by other methods 19–21, and is higher than the theoretically calculated value between 144 and 177 ps 20–23. Moreover, this value is also higher than the bulk lifetime in ZnO obtained by application of two‐state trapping model 24. The reason for this difference is still not clear.…”

“…This is a little shorter than the value of 52 nm reported by Uedono in a high quality ZnO grown by chemical vapor transportation (EP‐ZnO) 26. This means that the annealed SPC‐ZnO may contain some positron trapping or scattering centers, but obviously the concentration is not so high, which excluded the possibility of saturation trapping by vacancies 23, 24. In case of saturation trapping of positrons, the diffusion length will be greatly reduced to a few nm.…”

Structural characterization of H plasma‐doped ZnO single crystals by Hall measurements and photoluminescence studies

“…Interestingly, Al impurities have not been found in samples #1 and #5 (see Ref. 2, Table 1 of Ref. 2) because their concentration is perhaps below the detection limit of ICP‐MS.…”

“…Typical chemical compositions and H content before and after the remote H plasma treatment are given in Ref. 2.…”

“…Part I of this investigation describes results obtained by PAS [slow positron implantation spectroscopy (SPIS), pulsed low energy positron spectroscopy (PLEPS), positron lifetime spectroscopy (LT), and coincidence Doppler broadening spectroscopy (CDB)] measurements and their discussion in Ref. 2. Also, the H content before and after remote H plasma treatment has been determined using NRA, and changes in the polished surface of the crystals have been monitored by atomic force microscopy (AFM).…”