Defects and impurities induced structural and electronic changes in pyrite CoS2: first principles studies

2018 ◽  
Vol 20 (17) ◽  
pp. 11649-11655 ◽  
Author(s):  
Shengwen Li ◽  
Yanning Zhang ◽  
Xiaobin Niu

The defects and impurities in CoS2 may cause very localized gap states close to the Fermi level, modifying their electrochemical performances.

2009 ◽  
Vol 1164 ◽  
Author(s):  
Mao-Hua Du ◽  
Hiroyuki Takenaka ◽  
David Joseph Singh

AbstractWe discuss defect engineering strategies in radiation detector materials. The goal is to increase resistivity by defect-induced Fermi level pinning without causing defect-induced reductions in the carrier drifting length. We show calculated properties of various intrinsic defects and impurities in CdTe. We suggest that the defect complex of a hydrogen atom and an isovalent impurity on an anion site may be an excellent candidate in many semiconductors for Fermi level pinning without carrier trapping.


Crystals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 48 ◽  
Author(s):  
Qing Peng ◽  
Nanjun Chen ◽  
Danhong Huang ◽  
Eric Heller ◽  
David Cardimona ◽  
...  

Point defects are inevitable, at least due to thermodynamics, and essential for engineering semiconductors. Herein, we investigate the formation and electronic structures of fifteen different kinds of intrinsic point defects of zinc blende indium arsenide (zb-InAs ) using first-principles calculations. For As-rich environment, substitutional point defects are the primary intrinsic point defects in zb-InAs until the n-type doping region with Fermi level above 0.32 eV is reached, where the dominant intrinsic point defects are changed to In vacancies. For In-rich environment, In tetrahedral interstitial has the lowest formation energy till n-type doped region with Fermi level 0.24 eV where substitutional point defects In A s take over. The dumbbell interstitials prefer < 110 > configurations. For tetrahedral interstitials, In atoms prefer 4-As tetrahedral site for both As-rich and In-rich environments until the Fermi level goes above 0.26 eV in n-type doped region, where In atoms acquire the same formation energy at both tetrahedral sites and the same charge state. This implies a fast diffusion along the t − T − t path among the tetrahedral sites for In atoms. The In vacancies V I n decrease quickly and monotonically with increasing Fermi level and has a q = − 3 e charge state at the same time. The most popular vacancy-type defect is V I n in an As-rich environment, but switches to V A s in an In-rich environment at light p-doped region when Fermi level below 0.2 eV. This study sheds light on the relative stabilities of these intrinsic point defects, their concentrations and possible diffusions, which is expected useful in defect-engineering zb-InAs based semiconductors, as well as the material design for radiation-tolerant electronics.


2020 ◽  
Vol 7 (12) ◽  
pp. 200723
Author(s):  
Hai Duong Pham ◽  
Wu-Pei Su ◽  
Thi Dieu Hien Nguyen ◽  
Ngoc Thanh Thuy Tran ◽  
Ming-Fa Lin

The essential properties of monolayer silicene greatly enriched by boron substitutions are thoroughly explored through first-principles calculations. Delicate analyses are conducted on the highly non-uniform Moire superlattices, atom-dominated band structures, charge density distributions and atom- and orbital-decomposed van Hove singularities. The hybridized 2 p z –3 p z and [2s, 2 p x , 2 p y ]–[3s, 3 p x , 3 p y ] bondings, with orthogonal relations, are obtained from the developed theoretical framework. The red-shifted Fermi level and the modified Dirac cones/ π bands/ σ bands are clearly identified under various concentrations and configurations of boron-guest atoms. Our results demonstrate that the charge transfer leads to the non-uniform chemical environment that creates diverse electronic properties.


2012 ◽  
Vol 116 (46) ◽  
pp. 24445-24448 ◽  
Author(s):  
Seiji Kawasaki ◽  
Kazuto Akagi ◽  
Kan Nakatsuji ◽  
Susumu Yamamoto ◽  
Iwao Matsuda ◽  
...  

Nanoscale ◽  
2020 ◽  
Vol 12 (16) ◽  
pp. 8883-8889 ◽  
Author(s):  
Ronen Dagan ◽  
Yonatan Vaknin ◽  
Yossi Rosenwaks

Gap states and Fermi level pinning play an important role in all semiconductor devices, but even more in transition metal dichalcogenide-based devices due to their high surface to volume ratio and the absence of intralayer dangling bonds.


2014 ◽  
Vol 92 (7/8) ◽  
pp. 619-622
Author(s):  
N. Qamhieh ◽  
S.T. Mahmoud ◽  
A.I. Ayesh

Steady-state photoconductivity measurements in the temperature range 100–300 K on amorphous Ge2Sb2Te5 thin film prepared by dc sputtering are analyzed. The dark conductivity is thermally activated with a single activation energy that allocates the position of the Fermi level approximately in the middle of the energy gap relative to the valance band edge. The temperature dependence of the photoconductivity ensures the presence of a maximum normally observed in chalcogenides with low- and high-temperature slopes, which predict the location of discrete sets of localized states (recombination levels) in the gap. The presence of these defect states close to the valence and conduction band edges leaves the quasi Fermi level shifts in a continuous distribution of gap states at high temperatures, as evidenced from the γ values of the lux–ampere characteristics.


2019 ◽  
Vol 3 (1) ◽  
Author(s):  
Yi-Hsun Chen ◽  
Chih-Yi Cheng ◽  
Shao-Yu Chen ◽  
Jan Sebastian Dominic Rodriguez ◽  
Han-Ting Liao ◽  
...  

AbstractIn two-dimensional (2D)-semiconductor-based field-effect transistors and optoelectronic devices, metal–semiconductor junctions are one of the crucial factors determining device performance. The Fermi-level (FL) pinning effect, which commonly caused by interfacial gap states, severely limits the tunability of junction characteristics, including barrier height and contact resistance. A tunneling contact scheme has been suggested to address the FL pinning issue in metal–2D-semiconductor junctions, whereas the experimental realization is still elusive. Here, we show that an oxidized-monolayer-enabled tunneling barrier can realize a pronounced FL depinning in indium selenide (InSe) transistors, exhibiting a large pinning factor of 0.5 and a highly modulated Schottky barrier height. The FL depinning can be attributed to the suppression of metal- and disorder-induced gap states as a result of the high-quality tunneling contacts. Structural characterizations indicate uniform and atomically thin-surface oxidation layer inherent from nature of van der Waals materials and atomically sharp oxide–2D-semiconductor interfaces. Moreover, by effectively lowering the Schottky barrier height, we achieve an electron mobility of 2160 cm2/Vs and a contact barrier of 65 meV in two-terminal InSe transistors. The realization of strong FL depinning in high-mobility InSe transistors with the oxidized-monolayer presents a viable strategy to exploit layered semiconductors in contact engineering for advanced electronics and optoelectronics.


Nanoscale ◽  
2016 ◽  
Vol 8 (4) ◽  
pp. 2343-2349 ◽  
Author(s):  
Ji Il Choi ◽  
Hyo Seok Kim ◽  
Han Seul Kim ◽  
Ga In Lee ◽  
Jeung Ku Kang ◽  
...  

The formation of fullerene carbon nanobuds (CNBs) on carbon nanotube (CNT) caps is energetically more favorable than that on CNT sidewalls. Generally, CNBs based on CNT ends can induce resonant transmissions near the Fermi level.


2013 ◽  
Vol 477-478 ◽  
pp. 1303-1306
Author(s):  
Qin Xiang Gao

Using the first-principles calculations within the density functional theory (DFT), we have investigated the structure, magnetism and half-metallic stability of Co2FeGa Heusler compound under pressure from 0 to 50GPa. The results revel that the lattice constant is gradually shrank and total magnetic moment in per unit slightly decreased with increasing pressure, respectively. Moreover, with the increase of the pressure, the Fermi level will move towards high-energy orientation. When the pressure reaches at 30GPa the most stable half-metallicity is observed which the Fermi level is located at the middle of the spin-minority gap.


Sign in / Sign up

Export Citation Format

Share Document