Optical and Electronic Energy Band Properties of Nb-Doped β-Ga2O3 Crystals

Systemic investigations are performed to comprehend the structural, optical, and electrical characteristics of four niobium (Nb) doped β-Ga2O3 crystals (β-Ga2O3:Nb) grown by the optical floating zone (OFZ) method. All of the β-Ga2O3:Nb crystals revealed monoclinic phases and good crystalline qualities. While the different Nb doped (i.e., 0.0001 mol%, 0.01 mol%, 0.1 mol% and 0.5 mol%) samples exhibited slightly changed bandgap energies Eg (≡ 4.72 eV, 4.73 eV, 4.81 eV, 4.68 eV)—the luminescence features indicated distinctive defect levels—affecting the electronic energy structure significantly. By increasing the Nb doping level from 0.0001 mol% to 0.1 mol%, the Fermi level (EF) moves closer to the bottom of the conduction band. For the sample with Nb doping 0.5 mol%—no further improvement is noticed in the electronic properties. Finally, the energy band diagrams of four samples are given.

Trends of elemental adsorption on graphene

Adding impurities or doping through adsorption is an effective way to tailor the properties of graphene-based materials. The capability of making predictions with regard to the trends of elemental adsorption on graphene is crucial to a better understanding of the more complex adsorption cases. It also provides useful guidelines for fabricating 2D graphene materials with novel properties. In this review, we show trends of elemental adsorption on graphene with elements of the periodic table, based on previous studies and supplemented with our recent calculations. We also discuss the effects of atomic ratios on some properties of this element-adsorbed graphene system. Trends of properties studied include binding energy, most stable site, adatom height, migration energy, Fermi energy shift, graphene distortion, magnetization, charge transfer, and electronic energy band gap at Fermi energy. Certainly, there is ample scope to investigate the electronic structures of elemental adsorption on graphene based on period and group of the periodic table, and atomic ratio.