The band-edge excitons observed in few-layer NiPS3

AbstractBand-edge excitons of few-layer nickel phosphorous trisulfide (NiPS3) are characterized via micro-thermal-modulated reflectance (μTR) measurements from 10 to 300 K. Prominent μTR features of the A exciton series and B are simultaneously detected near the band edge of NiPS3. The A exciton series contains two sharp A1 and A2 levels and one threshold-energy-related transition (direct gap, E∞), which are simultaneously detected at the lower energy side of NiPS3. In addition, one broadened B feature is present at the higher energy side of few-layer NiPS3. The A series excitons may correlate with majorly d-to-d transition in the Rydberg series with threshold energy of E∞ ≅ 1.511 eV at 10 K. The binding energy of A1 is about 36 meV, and the transition energy is A1 ≅ 1.366 eV at 300 K. The transition energy of B measured by μTR is about 1.894 eV at 10 K. The excitonic series A may directly transit from the top of valence band to the conduction band of NiPS3, while the B feature might originate from the spin-split-off valence band to the conduction band edge. The direct optical gap of NiPS3 is ~1.402 eV at 300 K, which is confirmed by μTR and transmittance experiments.

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

RSC Advances ◽

10.1039/c8ra10592h ◽

2019 ◽

Vol 9 (20) ◽

pp. 11377-11384 ◽

Cited By ~ 6

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).

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

Scientific Reports ◽

10.1038/s41598-020-77999-8 ◽

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.

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Structural, optical and electronic properties of Ni1−xCoxO in the complete composition range

RSC Advances ◽

10.1039/d0ra09128f ◽

2020 ◽

Vol 10 (71) ◽

pp. 43497-43507

Author(s):

Kiran Baraik ◽

Ashok Bhakar ◽

V. Srihari ◽

Indranil Bhaumik ◽

C. Mukherjee ◽

...

Keyword(s):

Electronic Properties ◽

Conduction Band ◽

Solid Solutions ◽

Composition Range ◽

Band Edge ◽

Conduction Band Edge ◽

Optical Gap ◽

Optical And Electronic Properties

The optical gap of Ni1−xCoxO solid solutions neither varies linearly with Co composition nor shows any bowing in the complete composition range. The nature of this variation of the gap is governed by the position of conduction band edge.

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First principles study of electronic structures of dopants in Mg2Si

MRS Proceedings ◽

10.1557/opl.2011.1239 ◽

2011 ◽

Vol 1329 ◽

Cited By ~ 2

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.

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The Distribution of Occupied Deep Levels in a-Si:H Determined from CPM Spectra

MRS Proceedings ◽

10.1557/proc-219-611 ◽

1991 ◽

Vol 219 ◽

Cited By ~ 8

Author(s):

Nobuhiro Hata ◽

Sigurd Wagner

Keyword(s):

Valence Band ◽

Conduction Band ◽

Peak Height ◽

Peak Position ◽

Deep Levels ◽

Band Edge ◽

Conduction Band Edge ◽

Defect States ◽

Model Calculations ◽

Annealed State

ABSTRACTWe report the determination of the distribution of occupied defect states in hydrogenated amorphous silicon from the deconvolution of constant photocurrent measurement (CPM) spectra, and the modelling of the distribution with the defect pool.The CPM spectra were taken on undoped a-Si:H samples either in their as-grown state, in the annealed state, after quenching from high temperature, or after light-soaking. The spectra were deconvoluted to account for transitions from deep levels and from valence band tail states to a conduction band assumed to have a sharp edge. As-grown or annealed-state samples show a peak at 1.0 eV (0.2 eV FWHM) below the conduction band edge. Assuming a mobility gap of 1.9 eV, this peak lies 0.9 eV above the valence band edge. We ascribe this peak to the Do/+ transition. CPM spectra of light-soaked and thermally quenched samples show shifts in the peak position and increases in die peak height in accordance with the defect pool model. The model calculations agree with the CPM results, so that the applicability of CPM spectral analysis to obtaining detailed values of defect pool parameters is demonstrated.

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

Modern Physics Letters B ◽

10.1142/s0217984919500581 ◽

2019 ◽

Vol 33 (06) ◽

pp. 1950058 ◽

Cited By ~ 3

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.

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Characterization of conduction band edge discontinuity for InAlAs/GaAsSb using InP/GaAsSb heterojunction bipolar transistors

physica status solidi (a) ◽

10.1002/pssa.201127699 ◽

2012 ◽

Vol 209 (8) ◽

pp. 1579-1582

Author(s):

C. W. Ng ◽

H. Wang

Keyword(s):

Conduction Band ◽

Heterojunction Bipolar Transistors ◽

Bipolar Transistors ◽

Band Edge ◽

Conduction Band Edge

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Conduction Band Edge Energy Profile Probed by Hall Offset Voltage in InGaZnO Thin Films

Micromachines ◽

10.3390/mi11090822 ◽

2020 ◽

Vol 11 (9) ◽

pp. 822

Author(s):

Hyo-Jun Joo ◽

Dae-Hwan Kim ◽

Hyun-Seok Cha ◽

Sang-Hun Song

Keyword(s):

Magnetic Field ◽

Electron Density ◽

Conduction Band ◽

Electron System ◽

Band Edge ◽

Conduction Band Edge ◽

Offset Voltage ◽

Three Samples ◽

Dimensional Electron System ◽

Longitudinal Distance

We measured and analyzed the Hall offset voltages in InGaZnO thin-film transistors. The Hall offset voltages were found to decrease monotonously as the electron densities increased. We attributed the magnitude of the offset voltage to the misalignment in the longitudinal distance between the probing points and the electron density to Fermi energy of the two-dimensional electron system, which was verified by the coincidence of the Hall voltage with the perpendicular magnetic field in the tilted magnetic field. From these results, we deduced the combined conduction band edge energy profiles from the Hall offset voltages with the electron density variations for three samples with different threshold voltages. The extracted combined conduction band edge varied by a few tens of meV over a longitudinal distance of a few tenths of µm. This result is in good agreement with the value obtained from the analysis of percolation conduction.

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