scholarly journals Transparent All-Oxide Hybrid NiO:N/TiO2 Heterostructure for Optoelectronic Applications

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 988
Author(s):  
Chrysa Aivalioti ◽  
Alexandros Papadakis ◽  
Emmanouil Manidakis ◽  
Maria Kayambaki ◽  
Maria Androulidaki ◽  
...  
Keyword(s):  
Band Gap ◽  
Single Phase ◽  
Structural Disorder ◽  
Energy Band Gap ◽  
Nitrogen Doped ◽  
Nio Thin Film ◽  
Direct Band ◽  
Output Characteristics ◽  
Indirect Band Gap ◽  
P Type

Nickel oxide (NiO) is a p-type oxide and nitrogen is one of the dopants used for modifying its properties. Until now, nitrogen-doped NiO has shown inferior optical and electrical properties than those of pure NiO. In this work, we present nitrogen-doped NiO (NiO:N) thin films with enhanced properties compared to those of the undoped NiO thin film. The NiO:N films were grown at room temperature by sputtering using a plasma containing 50% Ar and 50% (O2 + N2) gases. The undoped NiO film was oxygen-rich, single-phase cubic NiO, having a transmittance of less than 20%. Upon doping with nitrogen, the films became more transparent (around 65%), had a wide direct band gap (up to 3.67 eV) and showed clear evidence of indirect band gap, 2.50–2.72 eV, depending on %(O2-N2) in plasma. The changes in the properties of the films such as structural disorder, energy band gap, Urbach states and resistivity were correlated with the incorporation of nitrogen in their structure. The optimum NiO:N film was used to form a diode with spin-coated, mesoporous on top of a compact, TiO2 film. The hybrid NiO:N/TiO2 heterojunction was transparent showing good output characteristics, as deduced using both I-V and Cheung’s methods, which were further improved upon thermal treatment. Transparent NiO:N films can be realized for all-oxide flexible optoelectronic devices.

Electronic State and Piezoresistivity Analysis of Zinc Oxide Nanowires for Force Sensing Devices

2015 ◽  
Vol 644 ◽  
pp. 16-21 ◽  
Author(s):  
Koichi Nakamura
Keyword(s):  
Band Gap ◽  
Compressive Strain ◽  
Force Sensing ◽  
Wall Structure ◽  
Direct Band Gap ◽  
Direct Band ◽  
The Difference ◽  
Piezoresistance Coefficient ◽  
Indirect Band Gap ◽  
P Type

The piezoresistivity for force sensing in wurtzite-ZnO nanowires with [0001] orientation has been simulated on the basis of the first-principles calculations of model structures. According to the difference in wall structure, our devised nanowire models can be divided into three groups by their conductivities; no band-gap conducting models, direct band-gap semiconducting models, and indirect band-gap semiconducting models. The strain responses to carrier conductivity of n-or p-doped semiconducting wurtzite-ZnO[0001] nanowire models were calculated using band carrier densities and their corresponding effective masses derived from the one-dimensional band diagram by our original procedure for a small amount of carrier occupation. The conductivities of p-type direct band-gap models change drastically due to longitudinal uniaxial strain in the simulation: the longitudinal piezoresistance coefficient is 120 × 10–11 Pa–1 for p-type (ZnO)24 nanowire model with 1% compressive strain at room temperature.

Optical Studies of Poly (N-Carbazole) (PVK) Blending with Polyvinylpyrrolidone (PVP) Using Tauc/Davis-Mott Model

2013 ◽  
Vol 652-654 ◽  
pp. 527-531 ◽  
Author(s):  
A.N. Alias ◽  
T.I. Tunku Kudin ◽  
Z.M. Zabidi ◽  
M.K. Harun ◽  
Ab Malik Marwan Ali ◽  
...  
Keyword(s):  
Band Gap ◽  
Urbach Energy ◽  
Quartz Substrate ◽  
Optical Studies ◽  
Direct Band Gap ◽  
Mott Model ◽  
Blended Polymer ◽  
Electronic Parameters ◽  
Direct Band ◽  
Indirect Band Gap

The optical absorption spectra of blended poly (N-carbazole) (PVK) with polyvinylpyrrolidone (PVP) in various compositions are investigated. A doctor blade technique was used to coat the blended polymer on a quartz substrate. The electronic parameters such as absorption edge (Ee), allowed direct band gap (Ed), allowed indirect band gap (Ei), Urbach edge (Eu) and steepness parameter (γ) were calculated using Tauc/Davis-Mott Model. The results reveal that the Ee, Ed and Ei increase with increasing of PVP ratio. There also have variation changing in Urbach energy and steepness parameter.

scholarly journals Biaxial strain modulated the electronic structure of hydrogenated 2D tetragonal silicene

RSC Advances ◽  
2019 ◽  
Vol 9 (72) ◽  
pp. 42245-42251
Author(s):  
Haoran Tu ◽  
Jing Zhang ◽  
Zexuan Guo ◽  
Chunyan Xu
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Biaxial Strain ◽  
Direct Band Gap ◽  
Direct Band ◽  
Indirect Band Gap

Hydrogenation can open the band gap of 2D tetragonal silicene, α-SiH is semiconductors with a direct band gap of 2.436 eV whereas β-SiH is indirect band gap of 2.286 eV. The band gap of α-SiH, β-SiH and γ-SiH can be modulated via biaxial strain.

scholarly journals Optoelectronics applications of electrodeposited p- and n-type Al2Se3 thin films

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
A. A. Faremi ◽  
S. S. Oluyamo ◽  
O. Olubosede ◽  
I. O. Olusola ◽  
M. A. Adekoya ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Band Gap ◽  
Energy Band ◽  
Selenium Dioxide ◽  
Photoelectrochemical Cells ◽  
Energy Band Gap ◽  
Cathodic Deposition ◽  
Conductivity Type ◽  
P Type

Abstract In this paper, energy band gaps and electrical conductivity based on aluminum selenide (Al2Se3) thin films are synthesized electrochemically using cathodic deposition technique, with graphite and carbon as cathode and anode, respectively. Synthesis is done at 353 K from an aqueous solution of analytical grade selenium dioxide (SeO2), and aluminum chloride (AlCl2·7H2O). Junctions-based Al2Se3 thin films from a controlled medium of pH 2.0 are deposited on fluorine-doped tin oxide (FTO) substrate using potential voltages varying from 1,000 mV to 1,400 mV and 3 minutes −15 minutes respectively. The films were characterized for optical properties and electrical conductivity using UV-vis and photoelectrochemical cells (PEC) spectroscopy. The PEC reveals a transition in the conduction of the films from p-type to n-type as the potential voltage varies. The energy band gap reduces from 3.2 eV to 2.9 eV with an increase in voltage and 3.3 eV to 2.7 eV with increase in time. These variations indicate successful fabrication of junction-based Al2Se3 thin films with noticeable transition in the conductivity type and energy band gap of the materials. Consequently, the fabricated Al2Se3 can find useful applications in optoelectronic devices.

LASER-INDUCED MULTIPHOTON PHOTOCONDUCTIVITY IN DIRECT AND INDIRECT BAND GAP CRYSTALS USING Z-SCAN TECHNIQUE

2009 ◽  
Vol 23 (23) ◽  
pp. 2783-2789 ◽  
Author(s):  
ARUN GAUR ◽  
D. K. SHARMA ◽  
K. S. SINGH ◽  
NAGESHWAR SINGH
Keyword(s):  
Absorption Coefficient ◽  
Band Gap ◽  
Laser Pulses ◽  
Beam Waist ◽  
Photon Absorption ◽  
Nanosecond Laser ◽  
Direct Band Gap ◽  
Direct Band ◽  
Nanosecond Laser Pulses ◽  
Indirect Band Gap

Nanosecond laser pulses have employed the photoconductive Z-scan technique. Photoconductivity traces measured by moving the sample across the laser beam waist were used for measuring two and three-photon absorption processes. The value of the three-photon absorption coefficient β3=9.6×10-10 cm 3/ GW 2 in the case of direct, and 8.96×10-12 cm 3/ GW 2 and 5.0×10-12 cm 3/ GW 2 in the case of indirect band gap crystals have been estimated from a comparison of traces measured by exciting the sample with the first and second harmonics of Nd : YAG laser. The low value of β3 in the case of indirect band gap crystals compared to direct band gap crystals is attributed to phonon-assisted transitions.

Electronic Properties of Calcium and Zirconium Co-Doped BaTiO3

2020 ◽  
Vol 1010 ◽  
pp. 308-313
Author(s):  
Akeem Adekunle Adewale ◽  
Abdullah Chik ◽  
Ruhiyuddin Mohd Zaki
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Density Of States ◽  
Energy Band ◽  
Density Functional ◽  
Partial Density ◽  
Total Density ◽  
Energy Band Gap ◽  
Wide Energy ◽  
Direct Band

Barium titanate (BaTiO3) is a perovskite based oxides with many potential application in electronic devices. From experimental report BaTiO3 has wide energy band gap of about 3.4 eV which by doped with Ca and Zr at A- and B- sites respectively can enhance their piezoelectric properties. Using first principles method within the density functional theory (DFT) as implement in Quantum Espresso (QE) with the plane wave pseudo potential function, the influence of the Ca and Zr doping in BaTiO3 are studied via electronic properties: band structure, total density of states (TDOS) and partial density of states (PDOS). The energy band gap calculated was underestimation which is similar to other DFT work. Two direct band gap where observed in Ba0.875Ca0.125Ti0.875Zr0.125O3 sample at Γ- Γ (2.31 eV) and X- X (2.35 eV) symmetry point.

SHIFT OF BAND GAP FROM DIRECT TO INDIRECT AND OPTICAL RESPONSE OF LiF UNDER PRESSURE

2013 ◽  
Vol 27 (09) ◽  
pp. 1350061 ◽  
Author(s):  
A. SAJID ◽  
G. MURTAZA ◽  
A. H. RESHAK
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Lithium Fluoride ◽  
Pressure Range ◽  
Pressure Effect ◽  
Indirect Transition ◽  
Direct Band Gap ◽  
Direct Band ◽  
Indirect Band Gap

We hereby are reporting the transition pressure at which lithium fluoride ( LiF ) compound transforms from direct band gap to indirect band gap insulator on the basis of FP-LAPW calculations. The fundamental band gap of LiF compound suffers direct to indirect transition at a pressure of 70 GPa. The study of the pressure effect on the optical properties e.g. dielectric function, reflectivity, refractive index and optical conductivity of LiF in the pressure between 0–100 GPa, shows that this pressure range is very critical for LiF compound as there are significant changes in the optical properties of this compound.

Photo-Deposition of Ag Metal Particles on Ni-Doped TiO2 for Photocatalytic Application

2017 ◽  
Vol 42 (3) ◽  
pp. 244-250 ◽  
Author(s):  
Mohammad Reza Elahifard ◽  
Reza Vatan Meidanshahi
Keyword(s):  
Photocatalytic Activity ◽  
Band Gap ◽  
Metal Particles ◽  
Electron Hole ◽  
Photocatalytic Application ◽  
Negative Effect ◽  
Direct Band ◽  
Indirect Band Gap ◽  
Co Precipitation ◽  
Acid Blue

Ni-doped TiO2 and Ag-deposited@Ni-doped TiO2 photocatalysts were prepared using the co-precipitation technique and characterised using X-ray powder diffraction, scanning electron microscopy and Brunauer–Emmett-Teller analysis. Our results confirmed the presence of Ni atoms in the TiO2 bulk structure and Ag° metal particles deposited on the surface. The Ni impurity generates defect midgap states in the TiO2 band structure, providing visible light (VL) absorption, which are responsible for photocatalytic activity under VL conditions. Against this advantage, Ni changes the indirect band gap of pure anatase to the direct band gap which may dramatically suppress the photocatalytic activity of Ni-doped TiO2. Moreover, Ni may provide a centre of electron–hole (e–h) recombination which enhances the negative effect of Ni impurity on TiO2 photo-efficiency. These drawbacks were overcome by deposition of Ag° on the Ni-doped TiO2 which sinks the photo-excited electrons, quenching e–h recombination. This improvement yields three times more photo-efficiency in the decolourisation of Acid Blue 92. Although Ag@Ni-doped anatase shows a higher adsorption constant ( Kads) than Ag@Ni-doped rutile, both catalysts surprisingly present the same rate constant ( k).

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