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.

Electronic properties and band offsets in InP(1−x−y)BixNy

2019 ◽  
Vol 33 (06) ◽  
pp. 1950058 ◽  
Author(s):  
Kailin Wang ◽  
Dan Liang ◽  
Yang Li ◽  
Shumin Wang ◽  
Ming Lei ◽  
...  
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Hamiltonian Matrix ◽  
Band Offset ◽  
Electronic Band ◽  
Strong Control ◽  
Band Anticrossing

Electronic band structures of [Formula: see text] have been theoretically studied by using Conduction Band Anticrossing (CBAC) model and Valence Band Anticrossing model (VBAC) in conjugation with [Formula: see text] method. This mathematical model’s manifestation is a 16 band Hamiltonian matrix. Our results reveal that the addition of Bi and N to InP causes substantial reduction of band gap, and the conduction band offset is greater than valence band offset. It can provide better electronic confinement and improve the temperature-insensitive characteristics for optoelectronic devices. Material compositions and band gap under various strain conditions have also been added in our calculation. By adjusting the concentration of Bi and N, we obtained a strong control of conduction band edge and valence band edge, which increases the flexibility of design InPBiN/InP structures.

scholarly journals Photocatalytic properties of a new Z-scheme system BaTiO3/In2S3 with a core–shell structure

RSC Advances ◽  
2019 ◽  
Vol 9 (20) ◽  
pp. 11377-11384 ◽  
Author(s):  
Kaili Wei ◽  
Baolai Wang ◽  
Jiamin Hu ◽  
Fuming Chen ◽  
Qing Hao ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Valence Band ◽  
Conduction Band ◽  
Shell Structure ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Core Shell ◽  
Valence Band Edge ◽  
Core Shell Structure ◽  
Positive Valence

It's highly desired to design an effective Z-scheme photocatalyst with excellent charge transfer and separation, a more negative conduction band edge (ECB) than O2/·O2− (−0.33 eV) and a more positive valence band edge (EVB) than ·OH/OH− (+2.27 eV).

The Density of States in a-Si:C:H Revealed by Electrophotography

1993 ◽  
Vol 297 ◽  
Author(s):  
R.A.C.M.M. Van Swaaij ◽  
W.P.M. Willems ◽  
J. Bezemer ◽  
M.B. Von Der Linden ◽  
W.F. Van Der Weg
Keyword(s):  
Conduction Band ◽  
Density Of States ◽  
Carbon Concentration ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Temperature Dependent ◽  
Energy Position ◽  
A Value ◽  
Dark Decay ◽  
Bulk Space

Electrophotographic dark decay measurements have been used to determine the surface density of states (SDOS) of a-Si:C:H. Injection of trapped charge from these deep states into the conduction band governs the dark discharge of a photoconductor, provided bulk generation and bulk space charge are negligible. It is found that the SDOS profiles peak around 0.60 eV below the conduction band for materials with different carbon concentration. This observation implies that the energy position of these states is fixed with respect to the conduction band edge, even though the optical band gap of these materials increases with increasing carbon concentration. The nature of these states may be ascribed to D− states, whose density is strongly enhanced by filling D° states when the material is charged negatively. Furthermore, we observed that the SDOS around 0.60 eV below the conduction band edge is approximately the same for materials with up to 8 at.% carbon. From temperature dependent measurements a value of 2·108 s−1 was obtained for the attempt-to-escape frequency.

Characterization of Localized Density of States in Intrinsic a-Si and poly-Si Films by Transient Voltage Spectroscopy

1995 ◽  
Vol 377 ◽  
Author(s):  
G. Kawachi ◽  
M. Ishii ◽  
T. Tanaka ◽  
N. Konishi
Keyword(s):  
Conduction Band ◽  
Density Of States ◽  
Band Edge ◽  
Conduction Band Edge ◽  
High Impedance ◽  
Pool Model ◽  
Transient Voltage ◽  
Mis Diode ◽  
Si Films

ABSTRACTThe localized density of states (LDOS) at interfaces between intrinsic silicon and silicon nitride (Si3N4 films are studied using transient voltage spectroscopy (TVS). In the TVS technique, the transient of the voltage across a MIS-diode after a trap filling voltage pulse is measured using a high-impedance voltage probe. This allows us to make a precise measurement of the LDOS at undoped Si/insulator interfaces. The LDOS in a-Si:H/Si3N4systems has a broad peak around the energy of 0.9 eV below the conduction-band edge. A modification of the LDOS at a-Si:H/Si3N4 interfaces by bias-annealing is clearly observed using this technique. The results are consistent with the defect pool model. The LDOS in laser annealed poly-Si/Si3N4 systems has a peak centered 0.6eV below the conduction-band edge, which seems to be the Si dangling bond states in the poly-Si films.

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.

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.

scholarly journals Theoretical investigation on $$\hbox {BeN}_{{2}}$$ monolayer for an efficient bifunctional water splitting catalyst

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
M. R. Ashwin Kishore ◽  
R. Varunaa ◽  
Amirhossein Bayani ◽  
Karin Larsson
Keyword(s):  
Water Splitting ◽  
Valence Band ◽  
Conduction Band ◽  
Theoretical Investigation ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Substantial Impact ◽  
Solar Hydrogen Production

AbstractThe search for an active, stable, and abundant semiconductor-based bifunctional catalysts for solar hydrogen production will make a substantial impact on the sustainable development of the society that does not rely on fossil reserves. The photocatalytic water splitting mechanism on a $$\hbox {BeN}_{{2}}$$ BeN 2 monolayer has here been investigated by using state-of-the-art density functional theory calculations. For all possible reaction intermediates, the calculated changes in Gibbs free energy showed that the oxygen evolution reaction will occur at, and above, the potential of 2.06 V (against the NHE) as all elementary steps are exergonic. In the case of the hydrogen evolution reaction, a potential of 0.52 V, or above, was required to make the reaction take place spontaneously. Interestingly, the calculated valence band edge and conduction band edge positions for a $$\hbox {BeN}_{{2}}$$ BeN 2 monolayer are located at the potential of 2.60 V and 0.56 V, respectively. This indicates that the photo-generated holes in the valence band can oxidize water to oxygen, and the photo-generated electrons in the conduction band can spontaneously reduce water to hydrogen. Hence, the results from the present theoretical investigation show that the $$\hbox {BeN}_{{2}}$$ BeN 2 monolayer is an efficient bifunctional water-splitting catalyst, without the need for any co-catalyst.

Electronic States in the Gap of a-Si from Bond Angle Variations

1990 ◽  
Vol 192 ◽  
Author(s):  
B. N. Davidson ◽  
G. Lucovsky
Keyword(s):  
Valence Band ◽  
Density Of States ◽  
Bond Angle ◽  
Bethe Lattice ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Valence Band Edge ◽  
Defect States ◽  
Discrete State ◽  
Bond Angles

ABSTRACTWe investigate the formation of defect states in the gap of a-Si arising from deviations from the ideal tetrahedral bond angles. The local density of states for Si atoms in disordered environments is calculated using tight-binding parameters for the cluster-Bethe lattice method. The Hamiltonian for a-Si with bond angle distortions is taken as an average over many configurations associated with a random choice of bond angles, weighted by Gaussian distributions with standard deviations between 2°.and 10°. Bond angle deviations in this range generate a density of defect states at the valence band edge that: 1) increases as the average bond angle deviation increases; and 2) is significantly larger than the density of band tail states generated at the conduction band edge. We obtain a shift of the absorption edge from the joint density of states (DOS) as a function of bond angle deviations. In addition, a calculation of the DOS for a distorted tetrahedral cluster embedded in an idealized Bethe lattice yields a threshold bond angle distortion of ±20° for the appearance of a discrete state in the gap near the valence band edge.

The Electronic and Structural Properties of 3C-SiC: A First-Principles Study

2014 ◽  
Vol 971-973 ◽  
pp. 208-212 ◽  
Author(s):  
Ying Gao ◽  
Fu Chun Zhang ◽  
Wei Hu Zhang
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
First Principles ◽  
Density Functional ◽  
Energy Splitting ◽  
Functional Theory ◽  
Structure Density ◽  
Indirect Band Gap ◽  
Electronic And Structural Properties

We investigate geometric structure, electronic structure and ground properties of 3C-SiC as obtained form first-principles calculations based on density functional theory with the LDA, GGA, B3LYP and HSE06 method. After comparative analysis of the total energy, band structure, density of states and the bulk modulus, we found that 3C-SiC was an indirect band gap semiconductor, the top of valence band was located at Γ point, and the bottom of conduction band was located at X point. The indirect band gap of 3C-SiC calculated by LDA, GGA, B3LYP and HSE06 was 1.34 eV, 1.44 eV, 2.88 eV and 2.26 eV, respectively. Especially for B3LYP and HSE06 methods which clearly calculated the energy splitting and the energy dispersion of both the top of valence band and the bottom of conduction band was in well agreement with the experimental data. These results will provide theoretical basis for the design and application of SiC materials.

First-Principles Calculations on the Electronic Structure of ZnO Nanowires

2012 ◽  
Vol 198-199 ◽  
pp. 23-27
Author(s):  
Nan Zhang ◽  
Hong Sheng Zhao ◽  
Dong Yang ◽  
Wen Jie Yan
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
First Principles ◽  
Density Functional ◽  
Valence Band Maximum ◽  
Zno Nanowires ◽  
Cross Sectional ◽  
Quantum Size

Based upon the density functional theory (DFT) in this paper, the first-principles approach is used to study the electronic structure of different cross-sectional diameters of ZnO [0001] nanowires of wurtzite structure. The results show that ZnO [0001] nanowires have a wide direct band gap. Located in the G-point of the Brillouin zone the conduction band minimum and valence band maximum are relatively smooth. The conduction band is mainly composed of Zn 4s and Zn 4p states, and the valence band is composed of Zn 3d and O 2p states. The effective mass of conduction band electrons and valence band holes are large while their mobility is very low which show that conductive ability of pure defect-free [0001] ZnO nanowires is weak. Along with the increase of the cross-sectional diameters, the band gap gradually decreases that indicates quantum size effects are obvious in the nano size range.

Sign in / Sign up

Export Citation Format

Share Document