In situ analysis of optoelectronic properties of dislocations in ZnO in TEM observations

Abstract

Extended defects acting as non‐radiative recombination center or those acting as radiative one were, respectively, studied by transmission electron microscopy under the illumination of a monochromatic light or cathodoluminescence spectroscopy combined with light illumination. By means of this method, defect levels associated with dislocations in ZnO, which were introduced at elevated temperatures above 923 K, were determined. It was proposed that (i) a screw dislocation, presumably acting as non‐radiative recombination center, glides under the illumination of a light with photon energy above 2.48–2.61 eV, due to an electron–hole recombination at a defect level of 2.48–2.61 eV depth, and (ii) a mixed dislocation acts as radiative recombination center with a defect level of 3.1 eV depth.

In-Situ Analysis of Optoelectronic Properties of Semiconductor Nanostructures and Defects in Transmission Electron Microscopes

“…The inset in (a) shows a TEM image of dislocations in the deformed specimen. (Ohno et al, 2008b) In-situ TEM observation with 80 keV electrons reveals that (Ohno et al, 2009b), screw and edge dislocations glide forming mixed dislocation segments when electrons are irradiated at temperature of 120 K, as well as at room temperature (Fig. 3).…”

“…Those properties are similar to wurtzite GaN (Maeda et al, 1999). In order to determine the optoelectronic properties of each individual dislocation, the recombination-enhanced glide is determined in detail by TEM observation under the illumination of a light, in the energy range of 2.25-2.92 eV, at temperature of 120K (Ohno et al, 2009b). A screw dislocation glides when a light with photon energy around 2.5 eV is illuminated (Fig.…”

“…Transmission electron microscopy under light illumination has been used to study in-situ photo-induced structural variations such as the dislocation motion related to photo-plasticity (Suzuki et al, 1984) and degradations in photoemitters (Ohno, 2005b, 2010a, Ohno et al, 2009b; the glide of dislocations under light illumination is observabed in-situ. Photocatalytic reactions in catalysts are also observable in-situ, and a photo-induced decomposition , structural transformation (Yoshida et al, 2006), and nucleation of nanostructures (Yoshida et al, 2007) are observed in a photocatalytic system.…”

“…Such a structural variation is induced via a photo-induced electronic excitation, and depends on the photon energy, intensity and polarization of the illuminating light. A defect level related to the photoexcitation can be estimated with a proper photon energy, since the degree of the structural variation is the maximum when the photon energy is close to the energy difference between the defect level and an another level (Ohno, 2005b, Ohno et al, 2009b, Ohno, 2010a. Semiconductors under light illumination can emit photoluminescence (PL) light, similar to CL, so as to release some of the photon energy absorbed from the illuminating light.…”

“…The emission band peaking at 3.1 eV, due to a defect level of 0.3 eV depth associated with dislocations (Ohno et al, 2008b), is determined by CL spectroscopy (Ohno et al, 2009b). Since a CL light emitted from a dislocation is rather weak, CL lights are obtained from an area in which a number of dislocations exist (the total length of the dislocation lines of about 2x10 3 nm).…”