Photoemission Studies of Wurtzite Zinc Oxide

Preparation and properties of ZnO and devices

“…The band structure calculated by Rössler using Green's function [Korringa-Kohn-Rostoker (KKR) method] [16] did not agree with experiments [17][18][19][20]. Powell et al [18,19] have carried out UV photoemission measurements on hexagonal ZnO cleaved in vacuum and placed the Zn 3d core level at about 7.5 eV below the valence band maximum, which is 3 eV lower than the value predicted by Rössler [16] band calculation which agreed with X-ray photoemission [21] (8.5 eV) and Ley et al [20] (8.81 eV). Local density approximation (LDA) and tight binding methods were carried out [22][23][24][25] by considering the Zn 3d states as core levels to ease calculations.…”

Investigation of pure and Co2+-doped ZnO quantum dot electronic structures using the density functional theory: choosing the right functional

“…The experimentally measured low-temperature bandgap of bulk ZnO is about 3.4 eV [37,38]. Theoretical studies of bulk ZnO yield a broad range of estimated bandgap energies, however, ranging from less than 1.30 eV by LDA and pure generalized gradient density functionals [39]- [42] to 3.2-3.7 eV by self-interaction-corrected LDA [39,42] and hybrid functionals [40,43].…”

Work Function of a Room‐Temperature, Stable Electride [Ca24Al28O64]4+(e–)4

“…[7] The free oxygen ions are situated in two of the twelve cages in the stoichiometric C12A7, and the extra-framework oxygen ions can be replaced with electrons by several different reduction treatments. [5,8,9] Exclusive replacement results in the formation of [Ca 24 Al 28 O 64 ] 4+ (e -) 4 (C12A7:e -), a new type of electride [10,11] in which electrons are located in the crystallographic cages and act as anions. [5,8,9] The empty cage in C12A7 has electronic states typical of a "particle-in-a-box", and the 3D connection of these states forms an additional electronic band in the fundamental bandgap called the "cage conduction band" (CCB) (Fig.…”

“…These properties mainly originate from its unique crystal structure, which is shown in Figure 1a. The unit cell, which contains two molecules of C12A7, is [Ca 24 Al 28 O 64 ] 4+ (O 2-) 2 . The first term of the chemical formula represents a positively charged lattice framework containing twelve cages, each with a radius of ca.…”

“…8 eV below E VAC , as reported for most oxide compounds in which O 2p levels primarily contribute to the VBM. [23][24][25] We also evaluated f WF by UPS measurements. Figure 3a shows He I UPS spectra for samples A and B at different V BIAS .…”