Comparison of the electronic structures of Zn1−xCoxO and Zn1−xMgxO nanorods using x-ray absorption and scanning photoelectron microscopies

Abstract

X-ray absorption near-edge structure (XANES) and scanning photoelectron microscopy (SPEM) measurements have been performed for Zn1−xCoxO and Zn1−xMgxO to elucidate the effects of the doping of Co and Mg, which have very different electronegativities, on the electronic structures of ZnO nanorods. The intensities of O K-edge near-edge features in the XANES spectra of Zn1−xCoxO and Zn1−xMgxO nanorods are found to be lower than those of ZnO, which suggests that both Co and Mg substitutions of the Zn ions enhance the effective charge on the O ion. The valence-band SPEM measurements show that Mg doping does not increase the density of near-Fermi-level states, which implies that Mg doping will not improve field emission of ZnO nanorods. It is surprising to find that both Co and Mg substitutions of Zn increase the numbers of O 2p dominated valence-band states, despite that Co and Mg have larger and smaller electronegativities than that of Zn.

New Theoretical Insights into the Origin of Highly‐Effective Dispersion of Cu‐Based Catalysts As‐Synthesized Using Mg/Zn Doped Malachite as Precursors

“…Further, the net charges of O for (Cu 6/8 Zn 1/8 Mg 1/8 ) 2 (OH) 2 CO 3 and (Cu 6/8 Mg 2/8 ) 2 (OH) 2 CO 3 are −0.67 e and −0.70 e , respectively which are higher than that for (Cu 6/8 Zn 2/8 ) 2 (OH) 2 CO 3 (‐0.64 e ). This observation agrees well with the previous findings that the effective charges of O atoms increases when Mg substitutes Zn in the Mg/ZnO system. The reason for this is likely derived from the lower electronegativity values of Mg (1.31) than that of Zn (1.65).…”

Getting to the Core of the Problem: Origin of the Luminescence from (Mg,Zn)O Heterostructured Nanowires

“…Results at the Mg K edge are shown in Figure c for type I and in Figure f for type II structures. The XFY curve in Figure c is similar to the recently reported X-ray absorption spectra of Mg-doped wurtzite ZnO nanowires, while the yield of the 367 nm, band-edge excitons shows dips at the positions of the peaks in the XRF spectrum. These dips arise because there is more Mg in the shell region than in the core, so impinging X-rays are preferentially adsorbed in the shell.…”

Tuning the Potentials of “Extra” Electrons in Colloidal n-Type ZnO Nanocrystals via Mg2+ Substitution

“…Interest in Zn 1– x Mg x O frequently stems from its potential applications in optoelectronic devices, for example as a barrier layer in ZnO-based heterostructures, − in UV sensors, and in ZnO-based lasing devices . Zn 1– x Mg x O thin films have been prepared by a variety of techniques including pulsed laser deposition (PLD), low-temperature chemical vapor deposition, molecular beam epitaxy, radio frequency magnetron sputtering, and sol–gel deposition . Colloidal Zn 1– x Mg x O nanocrystals have been synthesized by high-temperature, air-free methods. , Mg 2+ and Zn 2+ have similar tetrahedral ionic radii (0.57 and 0.60 Å), contributing to the relatively high solid solubility of Mg 2+ in wurtzite ZnO.…”