Electronic Structure and Surface Properties of SrBi2Ta2O9 and Related Oxides

1997 ◽  
Vol 493 ◽  
Author(s):  
J Robertson ◽  
C W Chen
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Conduction Band ◽  
Tight Binding ◽  
Schottky Barriers ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Edge States ◽  
Tight Binding Method ◽  
S States

ABSTRACTThe electronic structure of SrBi2Ta2O9 and related oxides such as SrBi2Nb2O9, Bi2WO6 and Bi3Ti4O12 have been calculated by the tight-binding method. In each case, the band gap is about 4.1 eV and the band edge states occur on the Bi-O layers and consist of mixed O p/Bi s states at the top of the valence band and Bi p states at the bottom of the conduction band. The main difference between the compounds is that Nb 5d and Ti 4d states in the Nb and Ti compounds lie lower than the Ta 6d states in the conduction band. The surface pinning levels are found to pin Schottky barriers 0.8 eV below the conduction band edge.

Using cluster studies to approach the electronic structure of bulk water: Reassessing the vacuum level, conduction band edge, and band gap of water

1997 ◽  
Vol 107 (16) ◽  
pp. 6023-6031 ◽  
Author(s):  
James V. Coe ◽  
Alan D. Earhart ◽  
Michael H. Cohen ◽  
Gerald J. Hoffman ◽  
Harry W. Sarkas ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Conduction Band ◽  
Bulk Water ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Vacuum Level

scholarly journals Phase transition-induced band edge engineering of BiVO4 to split pure water under visible light

2015 ◽  
Vol 112 (45) ◽  
pp. 13774-13778 ◽  
Author(s):  
Won Jun Jo ◽  
Hyun Joon Kang ◽  
Ki-Jeong Kong ◽  
Yun Seog Lee ◽  
Hunmin Park ◽  
...  
Keyword(s):  
Phase Transition ◽  
Visible Light ◽  
Band Gap ◽  
Conduction Band ◽  
Density Functional ◽  
Density Functional Theory Calculation ◽  
Pure Water ◽  
Volume Growth ◽  
Band Edge ◽  
Conduction Band Edge

Through phase transition-induced band edge engineering by dual doping with In and Mo, a new greenish BiVO4 (Bi1-XInXV1-XMoXO4) is developed that has a larger band gap energy than the usual yellow scheelite monoclinic BiVO4 as well as a higher (more negative) conduction band than H+/H2 potential [0 VRHE (reversible hydrogen electrode) at pH 7]. Hence, it can extract H2 from pure water by visible light-driven overall water splitting without using any sacrificial reagents. The density functional theory calculation indicates that In3+/Mo6+ dual doping triggers partial phase transformation from pure monoclinic BiVO4 to a mixture of monoclinic BiVO4 and tetragonal BiVO4, which sequentially leads to unit cell volume growth, compressive lattice strain increase, conduction band edge uplift, and band gap widening.

scholarly journals Al Doped ZnO Thermoelectrics Determined from Electronic Structure

2020 ◽  
Author(s):  
Rundong Wan ◽  
Quanwei Jiang ◽  
Zhengfu Zhang ◽  
Sharon Kao-Walter ◽  
Ying Lei ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Sample Preparation ◽  
Conduction Band ◽  
Carrier Mobility ◽  
Transport Theory ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Boltzmann Transport ◽  
Boltzmann Transport Theory ◽  
Doped Zno

Abstract For the aluminium doped wurtzite ZnO, comparing the Boltzmann transport theory calculated results and existing experiments, we acquire a few properties that are inaccessible otherwise. We find that the doping makes the samples metallic as the shifted Fermi levels are above the conduction band edge. We further find that the contradictory conclusions from two experiments with similar formula can be attributed to the quite disparate carrier concentrations and carrier mobility and the carrier mobility strong relates to the sample preparation.

Electronic Structure of the Layered Ferroelectric Perovskite SrBi2Ta2O9

1996 ◽  
Vol 433 ◽  
Author(s):  
J Robertson ◽  
C W Chen ◽  
W L Warren
Keyword(s):  
Conduction Band ◽  
Tight Binding ◽  
Valence Band Maximum ◽  
Fatigue Properties ◽  
Layered Perovskite ◽  
Band Maximum ◽  
Tight Binding Method ◽  
Electronic Response ◽  
S States ◽  
Ferroelectric Perovskite

AbstractThe band structure of the Bi layered perovskite SrBi2Ta2O9 (SBT) has been calculated by the tight binding method. We find both the valence and conduction band edges to consist of states primarily derived from the Bi-O layer rather than the perovskite Sr-Ta-O blocks. The valence band maximum arises from 0 p and some Bi s states, while the conduction band minimum consists of Bi p states, with a band gap of 5.1 eV. It is argued that the Bi-O layers largely control the electronic response of SBT while the ferroelectric response originates from the perovskite Sr-Ta-O block. Bi and Ta centered traps are calculated to be shallow, which may account in part for the excellent fatigue properties of SBT.

First principles study of electronic structures of dopants in Mg2Si

2011 ◽  
Vol 1329 ◽  
Author(s):  
K. Xiong ◽  
S. Sobhani ◽  
R. P. Gupta ◽  
W. Wang ◽  
B. E. Gnade ◽  
...  
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
Density Of States ◽  
First Principles ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Hybrid Functional ◽  
Thermoelectric Efficiency ◽  
The Impact

ABSTRACTWe investigate the impact of various dopants (Na, Ag, Cd, Zn, Al, Ga, In, Tl, Ge, and Sn) on the electronic structure of Mg2Si by first principles calculations using a hybrid functional that does not need a band gap correction. We find that for Na and Ge in Mg2Si, the impurity-induced states do not affect the density of states at both edges of the valence band and the conduction band. Ag- and Sn affect slightly the density of states at the valence band edge, while Cd and Zn affect slightly the density of state at the conduction band edge. Al and In could modify significantly the density of states at the conduction band edge. Ga introduces states just at the bottom of the conduction band. Tl introduces states in the band gap. This study provides useful information on optimizing the thermoelectric efficiency of Mg2Si.

PART II: CONDUCTION BAND-EDGE STATES ASSOCIATED WITH REMOVAL OF d-STATE DEGENERACIES BY THE STATIC JAHN-TELLER EFFECT

2006 ◽  
Vol 16 (01) ◽  
pp. 263-300
Author(s):  
GERALD LUCOVSKY
Keyword(s):  
Conduction Band ◽  
Complete Removal ◽  
Teller Effect ◽  
Oxide Semiconductor ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Edge States ◽  
Nano Crystalline ◽  
Jahn Teller ◽  
Jahn Teller Effect

X-ray absorption spectroscopy (XAS) is used to study band edge electronic structure of high-k transition metal (TM) and trivalent lanthanide rare earth (RE) oxide dielectrics. The lowest conduction band d*-states in nano-crystalline TiO 2, ZrO 2 and HfO 2 are correlated with features in the O K 1 edge, and transitions from occupied Ti 2p, Zr 3p and Hf 4p states to empty Ti 3d-, Zr 4d-, and Hf 5d-states, respectively. Optical band gaps, E opt , and conduction band offset energy with respect to Si , E B , scale monotonically with d-state energies of the TM/RE atoms. The multiplicity of d-state features in the Ti L 2,3 spectrum of TiO 2, and the O K 1 derivative spectra for ZrO 2 and HfO 2 indicate a complete removal of d-state degeneracies resulting from a static Jahn-Teller effect. Similar degeneracy removals are shown for complex nano-crystalline TM/RE oxides such as Zr and Hf titanates, and La , Gd and Dy scandates. XAS and band edge spectra indicate an additional band edge defect state assigned Jahn-Teller distortions at internal grain boundaries. These defect states are electronically active act as bulk traps in metal oxide semiconductor (MOS) devices, contributing to asymmetries in tunneling and Frenkel-Poole transport with important consequences for performance and reliability in advanced Si devices.

Sign in / Sign up

Export Citation Format

Share Document