Electronic Structure of Defects in SnTe

2013 ◽  
Vol 701 ◽  
pp. 125-130
Author(s):  
Salameh Ahmad
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Valence Band ◽  
Fundamental Difference ◽  
Density Of State ◽  
Defect States ◽  
Deep Defect ◽  
Conduction Bands ◽  
Resonant States ◽  
Structure Calculations

Myab initioelectronic structure calculations inRSn2n-1Te2n, n=16, R = a vacancy, Cd, and In show that when Sn atom is substituted by R, the Density of State (DOS) of the valence and conduction bands get strongly perturbed. There are significant changes near the band gap region. Sn vacancy causes very little change near the bottom of the conduction band DOS whereas there is an increase in the DOS near the top of the valence band. Results for In impurity shows that, unlike PbTe, the deep defect states in SnTe are resonant states near the top of the valence band. In PbTe these deep defect states lie in the band-gap region (act asn-type). This fundamental difference in the position of the deep defect states in SnTe and PbTe explains the experimental anomalies seen in the case of In impurities (act asn-type in PbTe andp-type in SnTe).

scholarly journals Ab initioStudies of Electronic Structure of Defects in PbTe

2005 ◽  
Vol 864 ◽  
Author(s):  
Salameh Ahmad ◽  
Daniel Bilc ◽  
S.D. Mahanti ◽  
M.G. Kanatzidis
Keyword(s):  
Electronic Structure ◽  
Valence Band ◽  
Conduction Band ◽  
Density Of States ◽  
Resonance State ◽  
Interesting Case ◽  
The Other ◽  
Defect States ◽  
Strong Resonance ◽  
Structure Calculations

AbstractAb initioelectronics structure calculations have been carried out in a series of RPb2n-1Te2n, n=16, compounds to understand the nature of “defect” states introduced by R where R = vacancy, monovalent Na, K, Rb, Cs, Ag atoms and divalent Cd atoms. We find that the density of states (DOS) near the top of the valence band and the bottom of the conduction band get significantly modified. The Na atom seems to perturb this region least (ideal acceptor in PbTe) and the other monovalent atoms enhance the DOS near the top of the valence band. Cd is an interesting case, since it introduces a strong resonance state near the bottom of the conduction band.

Ab initiostudies of electronic structure of defects on the Te sites in PbTe

2005 ◽  
Vol 886 ◽  
Author(s):  
Salameh Ahmad ◽  
S. D. Mahanti ◽  
M. G. Kanatzidis
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Ternary Systems ◽  
Electronic Structure Calculations ◽  
Valence Band Maximum ◽  
Defect States ◽  
Electronic Density ◽  
Substitutional Defect ◽  
New States ◽  
Structure Calculations

ABSTRACTAb initioelectronic structure calculations have been carried out to understand the nature of anionic defect states in PbTe. We find that Te vacancies strongly perturb the electronic density of states (DOS) near the band gap region. New states of predominantly Pb p character appear in the band gap. Iodine is an ideal substitutional defect and a donor. Sulpher and Selenium do not affect the states near the conduction band minimum but suppress the DOS near the valence band maximum. These results have important implications on the thermoelectric properties of PbTe and PbTexM1−x(M=S, Se) ternary systems.

Electronic structure of Cd, In, Sn substitutional Defects in GaSe

2007 ◽  
Vol 994 ◽  
Author(s):  
Zsolt Rak ◽  
Subhendra D Mahanti ◽  
Krishna C Mandal ◽  
Nils C Fernelius
Keyword(s):  
Electronic Structure ◽  
Effective Mass ◽  
Valence Band ◽  
Density Functional ◽  
Particle Density ◽  
Defect States ◽  
Mass Model ◽  
Single Particle Density ◽  
Resonant States ◽  
Substitutional Defects

AbstractAb initio electronic structure calculations within density functional theory have been carried out in pure GaSe and GaSe doped with substitutional impurities (Cd, In and Sn) at the Ga site in order to understand the nature of the defect states and how they depend on the nominal valence of these three impurities. We find that Cd impurity introduces a defect state located between 0.1 – 0.18 eV above the valence band, in good agreement with photoluminescence peaks seen at 0.13 eV and 0.18 eV. Using both experimental and theoretical effective mass parameters we show that effective mass model fails to describe these acceptor states. Sn changes the single particle density of states (DOS) near the bottom of the conduction band, and gives rise to resonant states deep in the valence band. In, on the other hand, behaves like Ga, it does not make noticeable change in the DOS of the host GaSe crystal.

Electronic Structure and Magnetic Properties of Iron Doped TiO2 (Rutile): XPS Measurements and CPA Calculations

2014 ◽  
Vol 215 ◽  
pp. 28-34 ◽  
Author(s):  
Michael A. Korotin ◽  
Nikolay A. Skorikov ◽  
Ernst Z. Kurmaev ◽  
Dmitry A. Zatsepin ◽  
Seif O. Cholakh
Keyword(s):  
Magnetic Properties ◽  
Electronic Structure ◽  
Band Gap ◽  
Valence Band ◽  
Coherent Potential Approximation ◽  
Photoelectron Spectra ◽  
Cation Substitution ◽  
Spectral Features ◽  
Potential Approximation ◽  
X Ray

X-ray photoelectron spectra of TiO2:Fe are measured. Electronic structure and magnetic properties of rutile doped by iron are calculated in frames of the coherent potential approximation. The main experimental spectral features of TiO2:Fe such as heterovalent cation substitution (Fe3+→Ti4+), decreasing of the band gap value and appearance of additional features at the bottom and top of X-ray photoelectron spectra of valence band in comparison with those for undoped TiO2 are described.

Electronic structure modification in two-dimensional pentagonal PdS2 by external strain

2021 ◽  
Author(s):  
Mridu Sharma ◽  
Ranber Singh
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Valence Band ◽  
Electronic Structures ◽  
Two Dimensional ◽  
Structure Modification ◽  
Indirect Band Gap ◽  
D Orbitals ◽  
External Strain

We investigated the electronic structure modifications in two-dimensional (2D) pentagonal PdS<sub>2</sub> materials by external strains. In the absence of external strain the 2D pentagonal PdS<sub>2</sub> materials are indirect band gap semiconductors. The band gap decreases with an increase in the number of stacking PdS<sub>2</sub> monolayers. The external uniaxial and biaxial strains significantly modify the contributions of p-orbitals of S atoms and d-orbitals of Pd atoms to the conduction and valence band edges. It consequently modify the electronic structures of 2D pentagonal PdS<sub>2</sub> materials. This strain tunability of electronic structures of 2D pentagonal PdS<sub>2</sub> materials may be useful for their electro-mechanical applications.

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.

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