Possible Applications In Optoelectronic Devices Research Articles

A study of 2D GeI2/InTe van der Waals hetero bilayer as a photocatalyst material

The computational study of the van der Waals hetero (vdW) bilayer GeI2/InTe has been carried out in present study. The isolated monolayer GeI2 and InTe have been studied first and the results were compared to the previous studies. The possible stackings are considered after the vdW interaction correction is applied in the structure relaxation. The vdW hetero bilayer stability has been checked from the phonon dispersion and ab initio Molecular Dynamics calculations. The charge transfer from InTe to GeI2 monolayer. Type-II indirect band gap (1.98, 2.01 eV) is verified by the projected band structure and band alignment calculations. The vdW hetero bilayer is a superior photocatalyst for the pH value up to pH = 0 to 11. The optical properties are calculated from the complex dielectric constant. The absorption coefficient shows the enhance absorption of light in the visible and ultraviolet regions. The vdW hetero bilayer has shown low reflectivity (37%) and a high refractive index (2.80) in the visible region. The enhanced optical properties have shown its possible applications in optoelectronic devices.

Ab-initio study about the electronic structure, optical, and transport properties of novel AIn2O4 (A = Ca, Sr, and Na) materials

Here, using first-principles calculations within the framework of density functional theory, we reported results relating to the structural stability, electronic, optical, and thermoelectric properties of AIn2O4 (A = Ca, Sr, and Na) spinel oxides. Among the three materials CaIn2O4, and NaIn2O4 have a direct bandgap semiconductor nature, whereas the SrIn2O4 shows an indirect bandgap semiconductor nature. These materials’ broad energy bandgaps reveal that the bonds present are strongly covalent in nature. The results of the band structures are also strongly supported by the calculated density of states for the three materials, which also validates their semiconducting nature. Our calculated density of states plots shows an overall similarity trend, indicating that the top of the valence bands in the CaIn2O4 materials originate primarily from the p-states and for SrIn2O4, and NaIn2O4 are due to the s-states of the oxygen anions. Additionally, the linear optical constants like the complex dielectric function, the refractive index, the electron energy loss function, the absorption coefficient, and the reflectivity spectra of these novel spinel oxides are computed and examined in detail for their possible applications in optoelectronic devices. The thermoelectric transport parameters were also calculated, and the findings obtained are presented in depth, indicating that these materials are suitable for thermoelectric device applications. Essentially, the present effort must assist the progress of discrete and integrated semiconductor device applications.

A Facile Microwave-Assisted Nanoflower-to-Nanosphere Morphology Tuning of CuSe1–xTe1+x for Optoelectronic and Dielectric Applications

Transition metal chalcogenides have gained significant attention for their optoelectronic and electrical applications in various fields due to their elemental composition-dependent tunable properties. Here, a facile microwave-assisted approach was used to synthesize different CuSe1–xTe1+x-based nanomaterials. By varying the Se and Te concentrations, the morphology of CuSe1–xTe1+x was tuned from nanosheet-based flowers to nanospheres. With the increase in the value of the Te-to-Se content ratio, the material shows the transition from mixed nanosheets/nanospheres to pure nanospheres, where the average sheet thickness and sphere diameter are ∼25 and 80 nm, respectively. The as-synthesized material shows high crystallinity with mixed phases of hexagonal Cu2Te and CuSe. The chemical bonding of the material exhibits shifts of the spectra toward lower binding energies with the decrease in the Se-to-Te ratio. The material exhibits a change in the absorption edge with a blue shift of the optical bandgap for the increase of the Te content. The increment in the absorption makes them eligible for solar cell application. The photoluminescence spectra of different CuSeTe samples show broad emission in the 550–950 nm range with a peak at ∼700 nm. Such optical properties enable CuSeTe materials for possible applications in optoelectronic devices. The dielectric measurement of the sample exhibits an increase in the dielectric constant and loss with temperature, whereas a decrease in both the values is apparent for increase in the frequency. The dielectric study of the material reveals its potential application for energy storage. The photo-response study demonstrated that the material can be employed for photodetector application.

Optical and electrochemical properties of pure and Ti-doped CdO nanoparticles for device applications

Cadmium oxide (CdO) is one among the transparent conducting oxides which is famous for its various applications in optoelectronics, gas sensors, and electrochemical sensors, etc. The present work therefore reports the synthesis and structural, optical, and electrochemical properties of pure CdO and Ti doped CdO nanoparticles which were synthesized using simple sol–gel method. The structural analysis of the prepared samples was done by using x-ray diffraction (XRD) technique. The XRD peaks revealed the existence of crystalline structure of the samples. The average crystallite sizes of the samples were calculated by considering the intense peaks observed in the XRD spectrum and they were found to be 59.45 nm and 55.25 nm for pure CdO and Ti doped CdO nanoparticles respectively. The absorption and transmission spectra of synthesized nanoparticles were recorded in the UV–VIS-NIR region. Using the absorption and transmission spectra, the optical band gap of pure CdO and Ti doped CdO were estimated as 2.14 eV and 2.99 eV respectively, using Tauc plot method. The Urbach energies were calculated, and they were found to be 1059 meV and 679 meV for the pure and Ti doped CdO nanoparticles. The optical conductivity, real and imaginary part of dielectric constant, dielectric loss tangent were also investigated using UV–VIS-NIR spectral data for the possible application in opto-electronic devices. The electrochemical performance of the samples was investigated using cyclic voltammetry (CV) technique. The specific capacitance and diffusion coefficients were calculated using the recorded cyclic voltammogram. The results of CV data showed that the maximum specific capacitance was occurred to be 390F/g at the rate 25 mV/s and 219F/g at the rate 50 mV/s for the pure and Ti-doped CdO nanomaterials respectively. The outcome of the present study provided an useful information for the possibilities of these materials in the device applications.

Phase-separated indenofluorene arrays stabilized by hydrogen and halogen bonds on Au(111)

Indenofluorene, which consists of a 6-5-6-5-6 fused-ring structure, is a semiconducting molecule with possible applications in optoelectronic devices. Bulk crystal structures, molecular front orbitals, and on-surface polymerized indenofluorene have recently been studied, but self-assembled structures on the surface have not yet been reported. Here, we report the array structure of 2,8-dibromoindeno[1,2-b]fluorene-6,12-dione on Au(111) studied using scanning tunneling microscopy. We proposed an alternating-tread stair structure as the molecular model for the monolayer molecular islands, which show strong shape anisotropy. The model can be explained by four O⋅⋅⋅H hydrogen bonds and one Br⋅⋅⋅Br halogen bond per molecule, as supported by density functional theory calculations. Although they prefer intermixed heteroprochiral structures in bulk layers, our study shows that these molecules can form phase-separated homoprochiral structures on the surface, leading to potential applications in molecular chiral separation.

Control of Electron Transfer Processes in Multidimensional Arylamine-Based Mixed-Valence Compounds by Molecular Backbone Design.

Four trigonal topology compounds with three diarylamines redox centers and dibenzofulvene as core bridge have been synthesized. Their radical cations exhibit appealing intramolecular electron transfer pathways between three redox centers, depending on their position on the core bridge. By changing such positions (on either 2,7- or 3,6-), and the length of the bridge, the control of the intramolecular electron transfer pathways was achieved through the electron self-exchange route. These processes were investigated by absorption spectroscopy, electron paramagnetic resonance spectroscopy, and (time-dependent) density functional theory calculations. Hole mobility measurements were carried out as well, to correlate the intramolecular electron transfer with the hole-transporting ability for possible applications in optoelectronic devices.

Exploration of New Double Peroviskites Cs2YInX6 (X = Cl, Br, I) for Opto-Electronic and Sustainable Energy Applications

We used theoretical and computational methods to explore the double perovskites Cs2YInX6 (X = Cl, Br, I) by having the scope and goal of finding their physical aspects and characteristic. To properly explain different phenomenological features of density functional theory (DFT), the ab-initio computational model based on the approximation of full-potential augmented plane wave plus local orbitals (FP-LAPW + lo) technique was implemented. The calculated ground state properties with GGA-PBEsol agree well with the available other theoretical data. Mechanical properties, another very important aspect of these double perovskites, are found by using shear modulus, Young’s modulus, and Poisson’s ratio. Further, we obtained bandgaps by investigating electronic properties with and without spin–orbit coupling (SOC). In order to calculate and compare the bandgaps with experimental results, we used SOC in connection with mBJ potential to investigate the direct bandgaps of Cs2YInCl6 (Eg = 0.45 eV), Cs2YInBr6 (Eg = 0.65 eV) and Cs2YInI6 (Eg = 0.82 eV) respectively. Furthermore, optical properties are investigated in terms of calculations like complex dielectric constants (ε(ω)), refractive index (n(ω)), reflectivity (R(ω)) and absorption co-efficient (α(ω)) to find their possible applications in optoelectronic devices. In view of this background, BoltzTraP code will also be used to explore these double perovskites in respect of their thermoelectric applications.

Estimation of Phosphorus Concentration in Silicon Thin Film on Glass Using ToF-SIMS

Evaluating the impurity concentrations in semiconductor thin films using time of flight secondary ion mass spectrometry (ToF-SIMS) is an effective technique. The mass interference between isotopes and matrix element in data interpretation makes the process complex. In this study, we have investigated the doping concentration of phosphorus in, phosphorus doped silicon thin film on glass using ToF-SIMS in the dynamic mode of operation. To overcome the mass interference between phosphorus and silicon isotopes, the quantitative analysis of counts to concentration conversion was done following two routes, standard relative sensitivity factor (RSF) and SIMetric software estimation. Phosphorus doped silicon thin film of 180 nm was grown on glass substrate using hot wire chemical vapor deposition technique for possible applications in optoelectronic devices. Using ToF-SIMS, the phosphorus-31 isotopes were detected in the range of 101~104 counts. The silicon isotopes matrix element was measured from p-type silicon wafer from a separate measurement to avoid mass interference. For the both procedures, the phosphorus concentration versus depth profiles were plotted which agree with a percent difference of about 3% at 100 nm depth. The concentration of phosphorus in silicon was determined in the range of 1019~1021 atoms/cm3. The technique will be useful for estimating distributions of various dopants in the silicon thin film grown on glass using ToF-SIMS overcoming the mass interference between isotopes.

Electronically Weak Coupled Bilayer MoS2 at Various Twist Angles via Folding

Constructing a bilayer system with defined twist angles is an effective way to engineer the physical properties of two-dimensional (2D) materials, opening up a new research area of twistronics. How to achieve high-quality bilayer 2D materials in a controlled and mass production way is of primary importance to this emerging area. In this work, we present a strategy for the large-scale fabrication of twisted bilayer molybdenum disulfide (MoS2) through photolithography patterning and folding of single-crystal monolayer MoS2. Atomic resolution transmission electron spectroscopy directly confirms that the as-achieved folded bilayer MoS2 is of high quality with targeted twist angles. Various twist angles result in tuning Raman mode frequencies and direct optical transition energies. Due to the weak interlayer coupling between the twisted layers, folded bilayers exhibit an extremely high photoluminescence with doubled intensity as compared to the unfolded monolayer, indicating a possible application in optoelectronic devices. Our work provides a new strategy to tailor the properties of MoS2, which will be beneficial to twistable electronics.

Boron Detection Technique in Silicon Thin Film Using Dynamic Time of Flight Secondary Ion Mass Spectrometry

The impurity concentration is a crucial parameter for semiconductor thin films. Evaluating the impurity distribution in silicon thin film is another challenge. In this study, we have investigated the doping concentration of boron in silicon thin film using time of flight secondary ion mass spectrometry in dynamic mode of operation. Boron doped silicon film was grown on i) p-type silicon wafer and ii) borosilicate glass using hot wire chemical vapor deposition technique for possible applications in optoelectronic devices. Using well-tuned SIMS measurement recipe, we have detected the boron counts 101~104 along with the silicon matrix element. The secondary ion beam sputtering area, sputtering duration and mass analyser analysing duration were used as key variables for the tuning of the recipe. The quantitative analysis of counts to concentration conversion was done following standard relative sensitivity factor. The concentration of boron in silicon was determined 1017~1021 atoms/㎤. The technique will be useful for evaluating distributions of various dopants (arsenic, phosphorous, bismuth etc.) in silicon thin film efficiently.

Synthesis, spectroscopic, crystal structure, thermal and optical studies of a novel proton transfer complex: 2-Methyl-8-hydroxyquinoliniumpicrate

A novel proton transfer complex, 2-methyl-8-hydroxyquinoliniumpicrate (MHQP), has been synthesized in methanol solvent using 2-methyl-8-hydroxyquinoline (MHQ) as proton acceptor and picric acid (PA) as proton donor in 1:1 M ratio, and its single crystal growth, thermal, spectroscopic, optical properties along with atomic packing of crystal have been studied. The DSC and TGA infer the thermal behavior of complex and FT-IR and proton NMR spectroscopic studies infer the charge-transfer interaction via transfer of proton. The powder XRD indicates novelty of the complex and single crystal analysis of MHQP crystal confirms the ionic interaction along with H-bonding interactions between MHQ and PA. The association constant and molar extinction coefficients were studied based on higher absorption band in UV–vis. absorption spectrum of the complex. The significant optical transmittance spectrum of grown MHQP crystal is indicative for its possible applications in opto-electronic devices.

Electronic structure, optical and thermoelectric properties of CaMgSi1−xCx (x = 0, 0.5): an ab-initio study

In this study, the CaMgSi and its subsequent doping by carbon atoms has been systematically studied using the first-principles calculations. Ground state properties focusing particularly on the structural, optical and transport coefficients of these alloys are discussed. Semi-metallic character is prominent from the observed band profiles when GGA scheme is utilized. The enhancement of thermoelectric properties with a speculation from the electronic structure is observed when doped with carbon. Also, the thermoelectric properties are envisaged within the specific transport constraints in order to figure out the dimensionless figure of merit (zT). The Seebeck, electrical and thermal conductivity coefficients are calculated and thereby utilized to find out the extremum of zT for both these alloys. The maximum zT for CaMgSi is found to be 0.4 at 400 K and for CaMgSiC, its value increases to 0.8 at 800 K. Thus, the later compound can be developed as a high temperature thermoelectric material. The optical considerations of such alloys are predicted from the calculated values of optical conductivity, reflectivity and electron energy loss within the range of 30.00 eV of incident photons. Likewise, the active region of these alloys for possible application in optoelectronic devices is ultraviolet region because the ultraviolet frequencies are strongly absorbed by these compounds.

Excitonic effects in third-harmonic generation: The case of carbon nanotubes and nanoribbons

Linear and nonlinear optical properties of low-dimensional nanostructures have attracted great interest from the scientific community as tools to probe the strong confinement of electrons and for possible applications in optoelectronic devices. In particular it has been shown that the linear optical response of carbon nanotubes [F. Wang et al., Science 308, 838 (2005)] and graphene nanoribbons [Nat. Commun. 5 4253 (2014)] is dominated by bounded electron-hole pairs, excitons. The role of excitons in linear response has been widely studied, but still, little is known about their effect on nonlinear susceptibilities. Using a recently developed methodology [Phys. Rev. B 88, 235113 (2013)] based on well-established ab initio many-body perturbation theory approaches, we find that quasiparticle shifts and excitonic effects significantly modify the third-harmonic generation in carbon nanotubes and graphene nanoribbons. For both systems the net effect of many-body effects is to reduce the intensity of the main peak in the independent-particle spectrum and redistribute the spectral weight among several excitonic resonances.

Evaluation of optical and electronic properties of silicon nano-agglomerates embedded in SRO: applying density functional theory.

In systems in atomic scale and nanoscale such as clusters or agglomerates constituted by particles from a few to less than 100 atoms, quantum confinement effects are very important. Their optical and electronic properties are often dependent on the size of the systems and the way in which the atoms in these clusters are bonded. Generally, these nanostructures display optical and electronic properties significantly different to those found in corresponding bulk materials. Silicon agglomerates embedded in silicon rich oxide (SRO) films have optical properties, which have been reported to be directly dependent on silicon nanocrystal size. Furthermore, the room temperature photoluminescence (PL) of SRO has repeatedly generated a huge interest due to its possible applications in optoelectronic devices. However, a plausible emission mechanism has not been widely accepted in the scientific community. In this work, we present a short review about the experimental results on silicon nanoclusters in SRO considering different techniques of growth. We focus mainly on their size, Raman spectra, and photoluminescence spectra. With this as background, we employed the density functional theory with a functional B3LYP and a basis set 6-31G* to calculate the optical and electronic properties of clusters of silicon (constituted by 15 to 20 silicon atoms). With the theoretical calculation of the structural and optical properties of silicon clusters, it is possible to evaluate the contribution of silicon agglomerates in the luminescent emission mechanism, experimentally found in thin SRO films.

Photovoltaic application of the V, Cr and Mn-doped cadmium thioindate

The CdIn2S4 spinel semiconductor is a potential photovoltaic material due to its energy band gap and absorption properties. These optoelectronic properties can be potentiality improved by the insertion of intermediate states into the energy bandgap. We explore this possibility using M=Cr, V and Mn as an impurity. We analyze with first-principles almost all substitutions of the host atoms by M at the octahedral and tetrahedral sites in the normal and inverse spinel structures. In almost all cases, the impurities introduce deeper bands into the host energy bandgap. Depending on the site substitution, these bands are full, empty or partially-full. It increases the number of possible inter-band transitions and the possible applications in optoelectronic devices. The contribution of the impurity states to these bands and the substitutional energies indicate that these impurities are energetically favorable for some sites in the host spinel. The absorption coefficients in the independent-particle approximation show that these deeper bands open additional photon absorption channels. It could therefore increase the solar-light absorption with respect to the host.

Optical properties and structural characteristics of zinc oxidecerium oxide doped polyvinyl alcohol films

Abstract Influence of zinc oxide cerium oxide (ZnO Ce 2 O 3 ) nanoparticles on the structural characteristics and optical properties of polyvinyl alcohol (PVA) films have been investigated. The fabricated PVA/ZnO Ce 2 O 3 nanocomposite films have been characterized by UV–visible spectroscopy, photoluminescence spectroscopy, X-ray diffraction (XRD) analysis, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The UV–vis analysis reveals the interaction of ZnO Ce 2 O 3 nanoparticles through hydroxyl groups of PVA. Photoluminescence spectra shows intense emission peaks due to the presence of ZnO Ce 2 O 3 nanoparticles. Microwave irradiation analysis shows the effect of nanoparticles on the degradation profile of PVA. The band gap energy measured based on UV–vis analysis shows enhanced conductivity of PVA films. XRD analysis shows the effect of annealing temperature on the XRD patterns of PVA. DSC analysis shows reduction in percentage of crystallinity with an increase in annealing temperatures and nanoparticles concentration. Thermal analysis by TGA shows enhanced thermal stability for the nanocomposites as compared to the PVA matrix. The data generated from these investigations will support the PVA nanocomposites for possible applications in opto-electronic devices.

<i>Ab Initio</i> Molecular Orbital Calculation for Optical and Electronic Properties Evaluation of Small and Medium Size Silicon Nano-Clusters Found in Silicon Rich Oxide Films

In systems in atomic and nano scales such as clusters or agglomerates constituted of particles from a few to less than one hundred of atoms, quantum confinement effects are very important. Their optical and electronic properties are often dependent on the size of the systems and the way in which the atoms in these clusters are bonded. Generally, these nano-structures display optical and electronic properties significantly different of those found in corresponding bulk materials. Silicon agglomerates found in Silicon Rich Oxide (SRO) films have optical properties, which have reported as depended directly on nano-crystal size. Furthermore, the room temperature photoluminescence (PL) of Silicon Rich Oxides (SRO) has repeatedly generated a huge interest due to their possible applications in optoelectronic devices. However, a plausible emission mechanism has not yet widespread acceptance of the scientific community. In this research, we employed the Density Functional Theory with a functional B3LYP and a basis set 6 - 31G* to calculate the optical and electronic properties of small (six to ten silicon atoms) and medium size clusters of silicon (constituted of eleven to fourteen silicon atoms). With the theoretical calculation of the structural and optical properties of silicon clusters, it is possible to evaluate the contribution of silicon agglomerates in the luminescent emission mechanism experimentally found in thin SRO films.

<i>Ab Initio</i> Molecular Orbital Calculation for Optical and Electronic Properties Evaluation of Small and Medium Size Silicon Nano-Clusters Found in Silicon Rich Oxide Films

In systems in atomic and nano scales such as clusters or agglomerates constituted of particles from a few to less than one hundred of atoms, quantum confinement effects are very important. Their optical and electronic properties are often dependent on the size of the systems and the way in which the atoms in these clusters are bonded. Generally, these nano-structures display optical and electronic properties significantly different of those found in corresponding bulk materials. Silicon agglomerates found in Silicon Rich Oxide (SRO) films have optical properties, which have reported as depended directly on nano-crystal size. Furthermore, the room temperature photoluminescence (PL) of Silicon Rich Oxides (SRO) has repeatedly generated a huge interest due to their possible applications in optoelectronic devices. However, a plausible emission mechanism has not yet widespread acceptance of the scientific community. In this research, we employed the Density Functional Theory with a functional B3LYP and a basis set 6 - 31G* to calculate the optical and electronic properties of small (six to ten silicon atoms) and medium size clusters of silicon (constituted of eleven to fourteen silicon atoms). With the theoretical calculation of the structural and optical properties of silicon clusters, it is possible to evaluate the contribution of silicon agglomerates in the luminescent emission mechanism experimentally found in thin SRO films.

Growth and characterization of wurtzite ZnO nanocombs and nanosaws

Using direct oxidation of Zn powder as a source material, zinc oxide comb and saw structures were fabricated by vapor phase transport and condensation. X-ray diffraction pattern showed that the samples had a wurtzite crystal structure. Different structures such as comb-like nano- and microstructures and saw-like structures have been studied by scanning electron microscopy. ZnO comb-like nanostructures with an average size of 15–20nm and 50nm were observed, as well as comb-like and saw-like microstructures. Photoluminescence (PL) spectra of these ZnO samples at room temperature were discussed. PL spectra showed strong UV and green emissions that indicate their possible application in optoelectronic devices. Also, the I–V behavior of a single nanowire was investigated. Approximately linear current versus voltage was observed for this nanowire, which showed good ohmic contacts to structure.

Characterization of optical transitions of Eu 3+ in lanthanum oxychloride nanophosphor

This paper presented the studies on the optical properties and calculation of spectral parameters of europium doped lanthanum oxychloride nanophosphor for their possible applications in optoelectronic devices. The compound was doped with 0.1 mol% Eu 3+ ions. The X-ray diffraction study of prepared sample suggested the tetragonal structure with particle size in the range of 18-21 nm. The photoluminescence (PL) emission spectra showed the bright emission in orange-red region from 580 to 630 nm. The most intense emission peak at 621 nm was due to transition 5D 0→ 7F 2 in energy levels of Eu 3+ ions. The spectral parameters were calculated from the absorption and emission spectra using Judd-Ofelt intensity parameters. The calculated values of the oscillator strength corresponding to the three transitions 7F 1→ 5D 1, 7F 1→ 5D 2 and 7F 0→ 5D 2 observed at 535, 472 and 465 nm in absorption spectra were 0.30×10 −6, 1.36×10 −6 and 0.63×10 −6, respectively. The value of transition probability ( A), stimulated emission cross-section (σ E P) and radiative lifetime ( τ rad) corresponding to 621 nm emission peak (transition 5D 0→ 7F 2) were 308 s −1, 1.22×10 −21 cm 2 and 3.24×10 −3 s, respectively.