scholarly journals Strong Photoluminescence Enhancement from Bilayer Molybdenum Disulfide via the Combination of UV Irradiation and Superacid Molecular Treatment

2021 ◽  
Vol 11 (8) ◽  
pp. 3530
Author(s):  
Yuki Yamada ◽  
Takeshi Yoshimura ◽  
Atsushi Ashida ◽  
Norifumi Fujimura ◽  
Daisuke Kiriya
Keyword(s):  
Band Gap ◽  
Uv Irradiation ◽  
High Performance ◽  
Transition Metal Dichalcogenides ◽  
Direct Band Gap ◽  
Metal Dichalcogenides ◽  
Direct Band ◽  
Pl Intensity ◽  
Optical Applications ◽  
Indirect Band Gap

A direct band gap nature in semiconducting materials makes them useful for optical devices due to the strong absorption of photons and their luminescence properties. Monolayer transition metal dichalcogenides (TMDCs) have received significant attention as direct band gap semiconductors and a platform for optical applications and physics. However, bilayer or thicker layered samples exhibit an indirect band gap. Here, we propose a method that converts the indirect band gap nature of bilayer MoS2, one of the representative TMDCs, to a direct band gap nature and enhances the photoluminescence (PL) intensity of bilayer MoS2 dramatically. The procedure combines UV irradiation with superacid molecular treatment on bilayer MoS2. UV irradiation induces the conversion of the PL property with an indirect band gap to a direct band gap situation in bilayer MoS2 when the interaction between the top and bottom layers is weakened by a sort of misalignment between them. Furthermore, the additional post-superacid treatment dramatically enhances the PL intensity of bilayer MoS2 by a factor of 700×. However, this procedure is not effective for a conventional bilayer sample, which shows no PL enhancement. From these results, the separated top layer would show a strong PL from the superacid treatment. The monolayer-like top layer is physically separated from the substrate by the intermediate bottom MoS2 layer, and this situation would be preferable for achieving a strong PL intensity. This finding will be useful for controlling the optoelectronic properties of thick TMDCs and the demonstration of high-performance optoelectronic devices.

scholarly journals Light fostered supercapacitor performance of multi-layered ReS2 grown on conducting substrates

2021 ◽  
Author(s):  
Nitika Arya ◽  
Piyush Kumar Avasthi ◽  
Viswanath Balakrishnan
Keyword(s):  
Energy Storage ◽  
Transition Metal ◽  
Band Gap ◽  
Transition Metal Dichalcogenides ◽  
Direct Band Gap ◽  
Metal Dichalcogenides ◽  
Direct Band ◽  
Supercapacitor Performance ◽  
Energy Storage Applications

Light fostered supercapacitor performance introduces a new realm in the field of smart energy storage applications. Transition metal dichalcogenides (TMDC) with direct band gap are intriguing candidates for developing light...

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 Theoretical investigations of a new two-dimensional semiconducting boron–carbon–nitrogen structure

RSC Advances ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 3424-3428
Author(s):  
Yihua Lu ◽  
Xi Zhu ◽  
Min Wang
Keyword(s):  
Band Gap ◽  
Two Dimensional ◽  
Direct Band Gap ◽  
Theoretical Investigations ◽  
Direct Band ◽  
Optical Applications ◽  
Boron Carbon

A predicted 2D BCN structure has a direct band gap and is a good candidate for electronic and optical applications.

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.

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.

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.

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