scholarly journals Multiscale Investigation of the Structural, Electrical and Photoluminescence Properties of MoS2 Obtained by MoO3 Sulfurization

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 182
Author(s):  
Salvatore E. Panasci ◽  
Antal Koos ◽  
Emanuela Schilirò ◽  
Salvatore Di Franco ◽  
Giuseppe Greco ◽  
...  
Keyword(s):  
Thickness Distribution ◽  
Compressive Strain ◽  
Optical Emission ◽  
Photoluminescence Properties ◽  
Standing Up ◽  
High Resolution Tem ◽  
Raman Modes ◽  
Spectroscopic Signatures ◽  
P Type ◽  
Moo3 Film

In this paper, we report a multiscale investigation of the compositional, morphological, structural, electrical, and optical emission properties of 2H-MoS2 obtained by sulfurization at 800 °C of very thin MoO3 films (with thickness ranging from ~2.8 nm to ~4.2 nm) on a SiO2/Si substrate. XPS analyses confirmed that the sulfurization was very effective in the reduction of the oxide to MoS2, with only a small percentage of residual MoO3 present in the final film. High-resolution TEM/STEM analyses revealed the formation of few (i.e., 2–3 layers) of MoS2 nearly aligned with the SiO2 surface in the case of the thinnest (~2.8 nm) MoO3 film, whereas multilayers of MoS2 partially standing up with respect to the substrate were observed for the ~4.2 nm one. Such different configurations indicate the prevalence of different mechanisms (i.e., vapour-solid surface reaction or S diffusion within the film) as a function of the thickness. The uniform thickness distribution of the few-layer and multilayer MoS2 was confirmed by Raman mapping. Furthermore, the correlative plot of the characteristic A1g-E2g Raman modes revealed a compressive strain (ε ≈ −0.78 ± 0.18%) and the coexistence of n- and p-type doped areas in the few-layer MoS2 on SiO2, where the p-type doping is probably due to the presence of residual MoO3. Nanoscale resolution current mapping by C-AFM showed local inhomogeneities in the conductivity of the few-layer MoS2, which are well correlated to the lateral changes in the strain detected by Raman. Finally, characteristic spectroscopic signatures of the defects/disorder in MoS2 films produced by sulfurization were identified by a comparative analysis of Raman and photoluminescence (PL) spectra with CVD grown MoS2 flakes.

scholarly journals Strain Effects on the Electronic and Thermoelectric Properties of n(PbTe)-m(Bi2Te3) System Compounds

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4086
Author(s):  
Weiliang Ma ◽  
Marie-Christine Record ◽  
Jing Tian ◽  
Pascal Boulet
Keyword(s):  
Density Functional ◽  
Lattice Thermal Conductivity ◽  
Compressive Strain ◽  
Van Der Waals Interactions ◽  
Functional Theory ◽  
Band Engineering ◽  
Seebeck Coefficients ◽  
The Density Functional Theory ◽  
P Type ◽  
Narrow Band Gap Semiconductors

Owing to their low lattice thermal conductivity, many compounds of the n(PbTe)-m(Bi2Te3) homologous series have been reported in the literature with thermoelectric (TE) properties that still need improvement. For this purpose, in this work, we have implemented the band engineering approach by applying biaxial tensile and compressive strains using the density functional theory (DFT) on various compounds of this series, namely Bi2Te3, PbBi2Te4, PbBi4Te7 and Pb2Bi2Te5. All the fully relaxed Bi2Te3, PbBi2Te4, PbBi4Te7 and Pb2Bi2Te5 compounds are narrow band-gap semiconductors. When applying strains, a semiconductor-to-metal transition occurs for all the compounds. Within the range of open-gap, the electrical conductivity decreases as the compressive strain increases. We also found that compressive strains cause larger Seebeck coefficients than tensile ones, with the maximum Seebeck coefficient being located at −2%, −6%, −3% and 0% strain for p-type Bi2Te3, PbBi2Te4, PbBi4Te7 and Pb2Bi2Te5, respectively. The use of the quantum theory of atoms in molecules (QTAIM) as a complementary tool has shown that the van der Waals interactions located between the structure slabs evolve with strains as well as the topological properties of Bi2Te3 and PbBi2Te4. This study shows that the TE performance of the n(PbTe)-m(Bi2Te3) compounds is modified under strains.

scholarly journals Investigation of spray pyrolyzed cubic structured Cu doped SnS films

2021 ◽  
Author(s):  
Emrah SARICA
Keyword(s):  
Spray Pyrolysis Technique ◽  
Hole Concentration ◽  
Compressive Strain ◽  
Cubic Phase ◽  
Cu Doping ◽  
Glass Substrates ◽  
High Electrical Resistivity ◽  
Hall Effect Measurements ◽  
P Type ◽  
Deposited Films

Abstract In this work undoped and Cu doped SnS film at 4% and 8% were deposited onto glass substrates by spray pyrolysis technique in order to investigate the effect of Cu doping on their physical properties. Surface investigations showed that Cu doping reduced the surface roughness of SnS films from 36.5 nm to 8.8 nm. XRD studies revealed that all films have recently solved large cubic phase of SnS (p-SnS) with a- lattice of 11.53 Å and Cu doping led to reduction in crystallite size from 229 Å to 198 Å. Additionally, all deposited films were found to be under compressive strain. Optical band gaps of SnS:Cu varied in the range of 1.83 eV-1.90 eV. Hall-effect measurements exhibited that all film have p-type conductivity with low hole concentration (~10 11 -10 12 cm -3 ) and high electrical resistivity (~10 4 -10 5 Ωcm).

Electroluminescence and Photoluminescence Properties of Porous Silicon Nanostructures with Optimum Current Density of Photo-Electrochemical Anodisation

2013 ◽  
Vol 667 ◽  
pp. 180-185
Author(s):  
M. Ain Zubaidah ◽  
F.S. Husairi ◽  
S.F.M. Yusop ◽  
Noor Asli Asnida ◽  
Mohamad Rusop ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Volume Ratio ◽  
Boron Doping ◽  
Peak Position ◽  
Silicon Nanostructures ◽  
Etching Time ◽  
Photoluminescence Properties ◽  
Current Densities ◽  
Pl Spectrum ◽  
P Type

P-type silicon wafer ( orientation; boron doping; 0.75 ~ 10 Ω cm-1) was used to prepare samples of porous silicon nanostructures (PSiNs). All samples have been prepared by using photo-electrochemical anodisation. A fixed etching time of 30 minutes and volume ratio of electrolyte, hydrofluoric acid 48% (HF48%) and absolute ethanol (C2H5OH), 1:1 were used for various current densities, J. There were sample A (J=10 mA/cm2), sample B (J=20 mA/cm2), sample C (J=30 mA/cm2), sample D (J=40 mA/cm2) and sample E (J=50 mA/cm2). Photoluminescence (PL) and electroluminescence (EL) spectra were investigated. Maximum peak position of PL spectrum at about ~675 nm, while the maximum EL spectrum at about ~650 nm (which is similar to the PL spectrum).

Optical Emission Study of the Energy Levels of Ga-VACANCY/HYDROGEN Complexes in N and P-TYPE GaAs

1992 ◽  
Vol 262 ◽  
Author(s):  
A. Amore Bonapasta ◽  
B. Bonanni ◽  
M. Capizzi ◽  
L. Cherubini ◽  
V. Emiliani ◽  
...  
Keyword(s):  
Ion Irradiation ◽  
Energy Levels ◽  
Optical Emission ◽  
Shallow Donor ◽  
Equal Treatment ◽  
Present Observation ◽  
Emission Study ◽  
The Individual ◽  
P Type ◽  
Impurities And Defects

ABSTRACTThe formation of Ga-vacancy/hydrogen complexes in GaAs has been detected via photoluminescence measurements. Different degrees of hydrogénation can be achieved by low-energy H- or D-ion irradiation from a Kaufman source. The volume incorporation, for equal treatment, is dependent upon the density of impurities and defects where H can bind. In originally p-type MBE-GaAs, prolonged hydrogen treatments lead to the appearance of three emission structures in the range 1.15–1.34 eV. The results are explained in terms of transitions to different states of charge of gallium vacancies trapping one or more H-atoms, the activity of the individual states being dependent upon the H-dose and the nature of the laser excitation. The model is supported by comparison with the changes in the Ga-vacancy/donor emission band in degenerate n-type samples, as it evolves, from the virgin condition, through hydrogenation. The present observation provides also valid support to the creation, in p-type material, of a semi-shallow donor associated to H trapped along the As-Ga bond, in the immediate neighborhood of the gallium vacancy.

scholarly journals Control of photoluminescence properties of Si nanocrystals by simultaneously doping n- and p-type impurities

2004 ◽  
Vol 85 (7) ◽  
pp. 1158-1160 ◽  
Author(s):  
Minoru Fujii ◽  
Yasuhiro Yamaguchi ◽  
Yuji Takase ◽  
Keiichi Ninomiya ◽  
Shinji Hayashi
Keyword(s):  
Photoluminescence Properties ◽  
Si Nanocrystals ◽  
P Type

Resonant Raman Scattering in MoS2

2015 ◽  
Vol 1726 ◽  
Author(s):  
Katarzyna Gołasa ◽  
Magdalena Grzeszczyk ◽  
Przemysław Leszczyński ◽  
Karol Nogajewski ◽  
Marek Potemski ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Optical Emission ◽  
Sample Thickness ◽  
High Symmetry ◽  
Acoustic Phonons ◽  
Longitudinal Acoustic ◽  
Transverse Acoustic ◽  
Raman Modes ◽  
Resonant Raman ◽  
Resonant Raman Scattering

ABSTRACTResonant Raman scattering in molybdenum disulfide (MoS2) is studied as a function of the sample thickness. Optical emission from 1ML, 2ML, 3ML and bulk MoS2 is investigated both at room and at liquid helium temperature. The experimental results are analysed in terms of the recently proposed attribution of the Raman peaks to multiphonon replica involving transverse acoustic phonons from the vicinity of the high-symmetry M point of the MoS2 Brillouin zone. It is shown that the corresponding processes are quenched in a few monolayer samples much stronger than the modes involving longitudinal acoustic phonons. It is also shown that along with the disappearance of multiphonon replica, the Raman modes, which are in-active in bulk become active in a few-monolayer flakes.

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