Comparison of Trapping States at SiO2/Si Interfaces on si(100), (110), and (111) Prepared by Plasma-Assisted Oxidation and Oxide Deposition, and by Exposure to Atomic H Prior to Oxidation and Deposition

ABSTRACTS1O2 layers, ∼ 15 nm thick, were formed on Si (100), (110), and (111) surfaces by a low-temperature, 200–300°C, plasma-assisted oxidation/deposition process sequence. The distribution of the trap density at the S1O2/Si interface, and in the Si band-gap, Dit, was deduced from capacitance-voltage, C-V, measurements. The values of Dit at midgap varied with crystal orientation in a similar way as in thermally grown oxides. In addition, the low-temperature oxides displayed a characteristic and intrinsic dangling bond state, the so-called Pb center, at ∼0.3 eV above the Si valence-band edge. Samples exposed to atomic H prior to the oxidation and deposition steps, showed an increase in Dit due to a roughening of the Si surfaces, which produced additional broad bands of defect states, at ∼0.5 and ∼0.7 eV above the Si valence-band edge.

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

MRS Proceedings ◽

10.1557/proc-192-279 ◽

1990 ◽

Vol 192 ◽

Cited By ~ 1

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.

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Calculation of Band Offsets of Mg(OH)2-Based Heterostructures

Electronic Materials ◽

10.3390/electronicmat2030019 ◽

2021 ◽

Vol 2 (3) ◽

pp. 274-283

Author(s):

Masaya Ichimura

Keyword(s):

Solar Cells ◽

Valence Band ◽

Dye Sensitized Solar Cells ◽

Band Alignment ◽

First Principles Calculation ◽

Band Edge ◽

Level Energy ◽

Type I ◽

Valence Band Edge ◽

Generalized Gradient

The band alignment of Mg(OH)2-based heterostructures is investigated based on first-principles calculation. (111)-MgO/(0001)-Mg(OH)2 and (0001)-wurtzite ZnO/(0001)-Mg(OH)2 heterostructures are considered. The O 2s level energy is obtained for each O atom in the heterostructure supercell, and the band edge energies are evaluated following the procedure of the core-level spectroscopy. The calculation is based on the generalized gradient approximation with the on-site Coulomb interaction parameter U considered for Zn. For MgO/Mg(OH)2, the band alignment is of type II, and the valence band edge of MgO is higher by 1.6 eV than that of Mg(OH)2. For ZnO/Mg(OH)2, the band alignment is of type I, and the valence band edge of ZnO is higher by 0.5 eV than that of Mg(OH)2. Assuming the transitivity rule, it is expected that Mg(OH)2 can be used for certain types of heterostructure solar cells and dye-sensitized solar cells to improve the performance.

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Spin polarization of holes on the valence-band edge of a semiconductor quantum well

Semiconductor Science and Technology ◽

10.1088/0268-1242/13/8/004 ◽

1998 ◽

Vol 13 (8) ◽

pp. 852-857 ◽

Cited By ~ 6

Author(s):

M Z Maialle

Keyword(s):

Quantum Well ◽

Valence Band ◽

Spin Polarization ◽

Band Edge ◽

Valence Band Edge ◽

Semiconductor Quantum Well

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Determination of the valence band edge of Fe oxide nanoparticles dispersed in aqueous solution through resonant photoelectron spectroscopy from a liquid microjet

Nanoscale Advances ◽

10.1039/d1na00275a ◽

2021 ◽

Author(s):

Giorgia Olivieri ◽

Gregor Kladnik ◽

Dean Cvetko ◽

Matthew A. Brown

Keyword(s):

Aqueous Solution ◽

Electronic Structure ◽

Valence Band ◽

Photoelectron Spectroscopy ◽

Band Edge ◽

Photoemission Spectroscopy ◽

Oxide Nanoparticles ◽

Valence Band Edge ◽

Resonant Photoemission

The electronic structure of hydrated nanoparticles can be unveiled by coupling a liquid microjet with a resonant photoemission spectroscopy.

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Defects in SiC for Quantum Computing

MRS Advances ◽

10.1557/adv.2019.301 ◽

2019 ◽

Vol 4 (40) ◽

pp. 2217-2222

Author(s):

Renu Choudhary ◽

Rana Biswas ◽

Bicai Pan ◽

Durga Paudyal

Keyword(s):

Band Gap ◽

Valence Band ◽

Density Functional ◽

Single Photon ◽

Band Edge ◽

Valence Band Edge ◽

Dangling Bonds ◽

Defect Levels ◽

Formation Energies ◽

Qubit Operation

AbstractMany novel materials are being actively considered for quantum information science and for realizing high-performance qubit operation at room temperature. It is known that deep defects in wide-band gap semiconductors can have spin states and long coherence times suitable for qubit operation. We theoretically investigate from ab-initio density functional theory (DFT) that the defect states in the hexagonal silicon carbide (4H-SiC) are potential qubit materials. The DFT supercell calculations were performed with the local-orbital and pseudopotential methods including hybrid exchange-correlation functionals. Di-vacancies in SiC supercells yielded defect levels in the gap consisting of closely spaced doublet just above the valence band edge, and higher levels in the band gap. The divacancy with a spin state of 1 is charge neutral. The divacancy is characterized by C-dangling bonds and a Si-dangling bonds. Jahn-teller distortions and formation energies as a function of the Fermi level and single photon interactions with these defect levels will be discussed. In contrast, the anti-site defects where C, Si are interchanged have high formation energies of 5.4 eV and have just a single shallow defect level close to the valence band edge, with no spin. We will compare results including the defect levels from both the electronic structure approaches.

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Conduction and valence band edge properties of hexagonal InN characterized by optical measurements

physica status solidi (c) ◽

10.1002/pssc.200565386 ◽

2006 ◽

Vol 3 (6) ◽

pp. 1850-1853 ◽

Cited By ~ 18

Author(s):

Y. Ishitani ◽

W. Terashima ◽

S. B. Che ◽

A. Yoshikawa

Keyword(s):

Valence Band ◽

Optical Measurements ◽

Band Edge ◽

Valence Band Edge

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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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