ZnO: Material, Physics and Applications

Abstract

ZnO is presently experiencing a research boom with more than 2000 ZnO-related publications in 2005. This phenomenon is triggered, for example, by hope to use ZnO as a material for blue/UV optoelectronics as an alternative to GaN, as a cheap, transparent, conducting oxide, as a material for electronic circuits that are transparent in the visible or for semiconductor spintronics. Currently, however, the main problem is to achieve high, reproducible and stable p-doping. Herein, we critically review aspects of the material growth, fundamental properties of ZnO and ZnO-based nanostructures and doping as well as present and future applications with emphasis on the electronic and optical properties including stimulated emission.

Atomic-Level Structural and Electronic Properties of Hybrid Inorganic–Organic ZnO:Hydroquinone Superlattices Fabricated by ALD/MLD

“…The PBE0/TZVP band gap of 3.55 eV also compares well with the experimental 0 K estimate of 3.44 eV. 46 Concerning previous computational studies on ZnO, PBE0 band gaps of 3.32 and 3.2 eV have been predicted using full-potential linearized augmented-planewave (FLAPW) and projector-augmented-wave (PAW) basis sets, respectively. [47][48][49][50] The band structure of bulk ZnO calculated at the PBE0/TZVP level of theory is shown in Figure 5a and a comparison to the band structures calculated with the SVP and TZVPP level basis sets is shown in Supporting information.…”

Defects induced luminescence and tuning of bandgap energy narrowing in ZnO nanoparticles doped with Li ions

“…8 At room temperature, ZnO typically exhibits one sharp emission photoluminescence (PL) peak in the ultra-violet region due to the recombination of free exciton (FX), and possibly one or more peaks in the visible spectral range which are attributed to defect luminescence at different energy states. 5,9,10 In addition to experimental studies of the defect emissions, theoretical studies of different defects 5,11,12 and their formation energies 5,13,14 have been determined. However, the origins of different defect emissions are still not fully understood, and different controversial hypotheses have been proposed to explain the different defect luminescence (violet, blue, green, yellow, and orange-red) 10 at various energy levels.…”

“…The specific identification and nature of defects for luminescence in the visible region is difficult and challenging because of various types of defects are possibly exist in the ZnO nanostructures. 9,12 Lithium (Li) related defects in ZnO typically lie in the bandgap such as substitutional Li (Li Zn ) and Zn vacancy (V Zn ) both acts as shallow acceptors while interstitial Li (Li i ) behaves as donor defects and different other complex defects, e.g., Li Zn -Li i and V o -Li i are possible at different energy levels within the bandgap. 21,27 From many fundamental optical properties of impuritydoped ZnO, particularly the variations in bandgap energy, which is about the crucial importance in fabricating devices, is still in need of detailed description.…”

Localized versus delocalized states: Photoluminescence from electrochemically synthesized ZnO nanowires

“…[1][2][3] In general, the nanowires can be characterized as ZnO single crystals with a large aspect ratio, i.e., their length in c-axis direction is significantly exceeding all other lateral dimensions, with the latter ones being in the 10 to some hundred nanometer range. This implies that nanowires have a significantly increased surfaceto-volume ratio when compared to standard bulk crystals, resulting in considerably strong surface effects 4 in nanowirebased optoelectronic devices.…”