Electronic Structure and Catalytic Study of Solid Solution of GaN in ZnO

Abstract

Solid solutions of GaN in ZnO (Zn 1-z Ga z )(O 1-x N x ) (x and z e 0.15) have been prepared by simple solution combustion method. Except for minor changes in the lattice contraction, no significant change in the Wurtzite structure was observed. Raman and secondary ion mass spectrometry results show the direct Zn-N and Ga-N bonds in (Zn 1-z Ga z )(O 1-x N x ). Visible light absorption and XPS results demonstrate that N 2p states of nitride occupy the states above the O 2p valence band, and hence a change in optical band gap reduction occurs to ∼2.5 eV from 3.37 eV for ZnO. Significant nitrogen fixation catalytic activity through NH 3 formation has been observed at ambient pressure on virgin (Zn 1-z Ga z )(O 1-x N x ) material, indicating its potential as a catalyst.

Synthesis and characterization of (Ga1−xZnx)(N1−xOx) nanocrystals with a wide range of compositions

“…Little compositional mixing is necessary to achieve visible absorption, which is observed at both ends of the composition range, in agreement with previous observations in bulk (Ga 1Àx Zn x )(N 1Àx O x ), 14,25,27,30,36,37 although the appearance of the spectra is qualitatively different at the two ends of the range. By examining the temperature-dependence of nitridation of ZnGa 2 O 4 under NH 3 , we found that, at the relatively low synthesis temperature of 650 C, inclusion of ZnO in the starting material is necessary to obtain wurtzite (Ga 1Àx Zn x )(N 1Àx O x ).…”

“…44 The products at each end (0.06 and 0.98) have E g values of 2.9 and 2.6 eV, respectively. 25 Remarkably, the visible absorption is still relatively strong even when x ¼ 0.98, i.e., almost pure ZnO (Fig. 14,25,27,30,36,37 At the low-x end of the composition range, the diffuse reectance spectra have similar shapes, with the effect of the composition being simply the red shiing of the spectrum (Fig.…”

“…5c, the value of E g for (Ga 1Àx Zn x )(N 1Àx O x ) shis to lower energy range with increasing x value from x ¼ 0.06 to x ¼ 0.87. 14,25,27,30,36,37 At the low-x end of the composition range, the diffuse reectance spectra have similar shapes, with the effect of the composition being simply the red shiing of the spectrum (Fig. An E g value of 2.25 eV is of interest for solar fuel generation because a semiconductor with this band gap has a maximum achievable solar-to-H 2 conversion efficiency of 12%.…”

“…[13][14][15][16][17][18][19][20][21][22][23] The rst reported synthesis of (Ga 1Àx Zn x )(N 1Àx O x ) involves nitridation of a mixture of bulk Ga 2 O 3 and bulk ZnO at temperatures of 850 C and above. [25][26][27] Because nanoscale particles can have improved crystallinity and shorter diffusion distances for photoexcited carriers transported to the surface, 28,29 efforts have also been undertaken to synthesize nanoscale (Ga 1Àx Zn x )(N 1Àx O x ). 24 The fraction of ZnO (x) that can be achieved in this synthetic route is limited by the spinel intermediate and high volatility of zinc at the high nitridation temperature.…”

Band gap reduction and dielectric function of Ga1−xZnxN1−xOx and In1−xZnxN1−xOx alloys

“…However, recent researches have shown that incorporating one material into the other could significantly reduce the band gap. Maeda et al 3 reported that randomly incorporating ZnO into GaN host (with 22% ZnO) reduces the optical band gap to 2.60 eV, and randomly incorporating GaN into ZnO host (with 15% GaN) reduces the optical band gap to 2.50 eV 4. Huda et al 5 also have shown that this band gaps reduction is not symmetric, that is, incorporating GaN in ZnO host (with 1.85% GaN) reduces the band gap much more than that of incorporating ZnO in GaN host (with 1.85% ZnO) based on theoretical calculation.…”