An energy band engineering design to enlarge the band gap of KTiOPO4 (KTP)-type sulfates via aliovalent substitution

2019 ◽  
Vol 7 (26) ◽  
pp. 8131-8138 ◽  
Author(s):  
Fei Yang ◽  
Lijuan Huang ◽  
Xiaoyu Zhao ◽  
Ling Huang ◽  
Daojiang Gao ◽  
...  
Keyword(s):  
Band Gap ◽  
Engineering Design ◽  
Energy Band ◽  
Band Gaps ◽  
Band Engineering ◽  
Aliovalent Substitution

The two fluoride sulfates RbSnFSO4 and RbSbF2SO4 derived from the famous commercial crystal KTiOPO4via aliovalent substitution exhibited remarkably enlarged band gaps.

scholarly journals Tunable SnO2 Nanoribbon by Electric Fields and Hydrogen Passivation

2017 ◽  
Vol 2017 ◽  
pp. 1-12
Author(s):  
Xin-Lian Chen ◽  
Bao-Jun Huang ◽  
Chang-Wen Zhang ◽  
Ping Li ◽  
Pei-Ji Wang
Keyword(s):  
Band Gap ◽  
Electric Fields ◽  
Stark Effect ◽  
Tin Dioxide ◽  
Band Gaps ◽  
Hydrogen Passivation ◽  
Band Engineering ◽  
Metal Semiconductor Metal ◽  
Projector Augmented Wave ◽  
Electronic Field

Under external transverse electronic fields and hydrogen passivation, the electronic structure and band gap of tin dioxide nanoribbons (SnO2NRs) with both zigzag and armchair shaped edges are studied by using the first-principles projector augmented wave (PAW) potential with the density function theory (DFT) framework. The results showed that the electronic structures of zigzag and armchair edge SnO2NRs exhibit an indirect semiconducting nature and the band gaps demonstrate a remarkable reduction with the increase of external transverse electronic field intensity, which demonstrate a giant Stark effect. The value of the critical electric field for bare Z-SnO2NRs is smaller than A-SnO2NRs. In addition, the different hydrogen passivation nanoribbons (Z-SnO2NRs-2H and A-SnO2NRs-OH) show different band gaps and a slightly weaker Stark effect. The band gap of A-SnO2NRs-OH obviously is enhanced while the Z-SnO2NRs-2H reduce. Interestingly, the Z-SnO2NRs-OH presented the convert of metal-semiconductor-metal under external transverse electronic fields. In the end, the electronic transport properties of the different edges SnO2NRs are studied. These findings provide useful ways in nanomaterial design and band engineering for spintronics.

Template effects in Cu(i)–Bi(iii) iodide double perovskites: a study of crystal structure, film orientation, band gap and photocurrent response

2020 ◽  
Vol 8 (15) ◽  
pp. 7288-7296 ◽  
Author(s):  
Le-Yu Bi ◽  
Tian-Li Hu ◽  
Mu-Qing Li ◽  
Bo-Kai Ling ◽  
Mohamed Saber Lassoued ◽  
...  
Keyword(s):  
Thin Film ◽  
Crystal Structure ◽  
Band Gap ◽  
Energy Band ◽  
Band Gaps ◽  
Double Perovskites ◽  
Photocurrent Response ◽  
Bismuth Iodide ◽  
Structural Dimensions

Structural dimensions, energy band gaps and thin film orientations are revealed to be amine-dependent in seven newly prepared cuprous–bismuth iodide double perovskites.

The energy band structure of Si and Ge nanolayers

2016 ◽  
Vol 30 (34) ◽  
pp. 1650402 ◽  
Author(s):  
Xueke Wu ◽  
Weiqi Huang ◽  
Zhongmei Huang ◽  
Chaojie Qin ◽  
Yanlin Tang
Keyword(s):  
Band Gap ◽  
Energy Band ◽  
Density Functional ◽  
Band Gaps ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Quantum Confinement Effects ◽  
Calculation Results ◽  
Direct Band ◽  
Band Gap Structure

First-principles calculation based on density functional theory (DFT) with the generalized gradient approximation (GGA) were carried out to investigate the energy band gap structure of Si and Ge nanofilms. Calculation results show that the band gaps of Si(111) and Ge(110) nanofilms are indirect structures and independent of film thickness, the band gaps of Si(110) and Ge(100) nanofilms could be transfered into the direct structure for nanofilm thickness of less than a certain value, and the band gaps of Si(100) and Ge(111) nanofilms are the direct structures in the present model thickness range (about 7 nm). Moreover, the changes of the band gaps on the Si and Ge nanofilms follow the quantum confinement effects. It will be a good way to obtain direct band gap emission in Si and Ge materials, and to develop Si and Ge laser on Si chip.

Effect of Pressure on the energy band gaps of InxGa1-xN and InxAl1-xN

2002 ◽  
Vol 743 ◽  
Author(s):  
Z. Dridi ◽  
B. Bouhafs ◽  
P. Ruterana
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Energy Band ◽  
Alloy Composition ◽  
Band Gaps ◽  
Fundamental Band ◽  
Pressure Coefficients ◽  
Effect Of Pressure ◽  
Strong Deviation ◽  
First Principles Method

ABSTRACTUsing a first-principles method, we study the effect of pressure on the band gap energies of wurtzite InxGa1-xN, and InxAl1-xN. The fundamental band gap energies are direct and increase rapidly with pressure. The pressure coefficients vary in the range of 19.8–24.8 meV/GPa for InxGa1-xN, and 16.7–20.7 meV/GPa for InxAl1-xN; they depend on alloy composition with a strong deviation from linearity. The band gap bowing of the InGaN increases continuously with pressure while those of InAlN strongly decreases at p=14 GPa.

Preparation, Structural, Electrochemical and Photocatalytic Studies of Cadmium Sulfide Quantum Dots

2021 ◽  
Vol 66 ◽  
pp. 103-111
Author(s):  
Peter A. Ajibade ◽  
Lebogang L.R. Mphahlele
Keyword(s):  
Quantum Dots ◽  
Cadmium Sulfide ◽  
Band Gap ◽  
Energy Band ◽  
Cadmium Sulphide ◽  
Band Gap Energy ◽  
Band Gaps ◽  
Photocatalytic Decomposition ◽  
Cds Quantum Dots ◽  
Optical Absorption Band

We report the preparation, structural, electrochemical and photocatalytic studies of monodispersed cadmium sulphide quantum dots from didecylaminyl dithiocarbamate and 4-chloro-3-(trifluoromethyl) anilinyl dithiocarbamate cadmium(II) complexes. Powder X-ray diffraction pattern confirms hexagonal crystalline phases for the as-preapred CdS quantum dots irrespective of the precursor used with particle size of 3.39-5.51 nm. Optical absorption band edges of 515 nm were observed for the cadmium sulfide quantum dots with energy band gaps estimated from the Tauc plots of 1.97 eV for OLM-CdS1 prepared from Cd(II) didecylaminyl dithiocarbamate and 1.92 eV for OLM-CdS2 prepared from Cd(II) 4-chloro-3-(trifluoromethyl) anilinyl dithiocarbamate. These energy band gaps are blue shifted with respect to the bulk cadmium sulphide. The calculated electrochemical band gap of 2.34 V and 3.30 V are higher than band gap energy. The as-prepared CdS quantum dots were used as photocatalysts for the photocatalytic decomposition of methylene blue (MB) with efficiency of 61 % and 55 %.

scholarly journals Density Functional Theory (DFT) Study on α,α-Bis(2-benzothiophen-1-yl)-4H-cyclopenta[2,1-b,3;4-b′]dithiophene Derivatives for Optoelectronic Devices

2019 ◽  
Vol 8 (2) ◽  
pp. 126-139
Author(s):  
Banjo Semire ◽  
◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Energy Band ◽  
Density Functional ◽  
Molecular Structures ◽  
Band Gaps ◽  
Photovoltaic Devices ◽  
Energy Band Gap ◽  
Functional Theory ◽  
Molecular Hyperpolarizability

Bis(2-benzothiophen-1-yl)-4H-cyclopenta[2,1-b,3;4-b′]dithiophene derivatives comprised of three series; bis(2-thienyl)-4H-cyclopenta[2,1-b,3;4-b]dithiopene (BTDT), diphenyl4Hcyclopenta[2,1-b,3;4-b]dithiophene (DPDT) and bis(2-benzothiophen-1-yl)-4Hcyclopenta[2,1-b,3;4-b]dithiophene (BBDT) have been studied using Density Functional Theory (B3LYP/6-31G**). In each series, molecules with C=S bridge exhibited the lowest band gap; for instance in BBDT series, the energy band gap could be arranged as 2.29, 2.23 and 1.66 eV for CH2, C=O and C=S bridge respectively. The low band gaps calculated for BBDT-C=S (1.66 eV) and BTDT-C=S (1.82 eV) could facilitate photo-excited electron transfer as one the criteria for a molecule to be used in photovoltaic devices. Also, the results showed that longest UV-vis absorption wavelength was observed for molecules with C=S bridge, i.e. 1013.66, 874.75 and 1097.66 nm for BTDT, DPDT and BBDT respectively. The polarizability (α0) valves calculated for the molecules follow as -CH2 < C=O < C=S bridge in each series, indicating that the higher the polarizability (α0) valve the longer the λmax nm and the lower the energy band gap. The magnitude of the molecular hyperpolarizability β0 showed that molecular structures with -C=O bridge could be best NLO material in each series.

scholarly journals No Resistive Normal Electrons in Beginning Superconducting States

Mathematics ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1512
Author(s):  
Changho Seo ◽  
Seongsoo Cho ◽  
Je Huan Koo
Keyword(s):  
Band Gap ◽  
Energy Band ◽  
Energy Band Gap

We investigate why normal electrons in superconductors have no resistance. Under the same conditions, the band gap is reduced to zero as well, but normal electrons at superconducting states are condensed into this virtual energy band gap.

scholarly journals The Band-Gap Studies of Short-Period CdO/MgO Superlattices

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Ewa Przeździecka ◽  
P. Strąk ◽  
A. Wierzbicka ◽  
A. Adhikari ◽  
A. Lysak ◽  
...  
Keyword(s):  
Band Gap ◽  
Layer Thickness ◽  
Energy Gap ◽  
Band Gaps ◽  
Short Period ◽  
Wide Range ◽  
Salt Structure ◽  
Short Period Superlattices ◽  
Direct Band ◽  
Sublayer Thickness

AbstractTrends in the behavior of band gaps in short-period superlattices (SLs) composed of CdO and MgO layers were analyzed experimentally and theoretically for several thicknesses of CdO sublayers. The optical properties of the SLs were investigated by means of transmittance measurements at room temperature in the wavelength range 200–700 nm. The direct band gap of {CdO/MgO} SLs were tuned from 2.6 to 6 eV by varying the thickness of CdO from 1 to 12 monolayers while maintaining the same MgO layer thickness of 4 monolayers. Obtained values of direct and indirect band gaps are higher than those theoretically calculated by an ab initio method, but follow the same trend. X-ray measurements confirmed the presence of a rock salt structure in the SLs. Two oriented structures (111 and 100) grown on c- and r-oriented sapphire substrates were obtained. The measured lattice parameters increase with CdO layer thickness, and the experimental data are in agreement with the calculated results. This new kind of SL structure may be suitable for use in visible, UV and deep UV optoelectronics, especially because the energy gap can be precisely controlled over a wide range by modulating the sublayer thickness in the superlattices.

Sign in / Sign up

Export Citation Format

Share Document