Using optical properties of semiconductor structures for modulators realization

Cathodoluminescence (CL) is a very powerful technique for studying the optical properties of semiconductor structures, especially low-dimensional structures (structures with sub-micron features). We will give a number of examples of studies, where CL has been used to study a variety of low-dimensional semiconductor structures. We will also compare the CL technique with other techniques for studies of luminescence with high spatial resolution.

Many-body Coulomb interactions dominate nonlinear optical properties of semiconductor structures in many respects. Resulting effects show up most distinct in the temporal evolution of transient four-wave mixing signals. The simplest example in systems with homogeneously broadened absorption is the static exchange interaction, which prevents the occurrence of pure free polarization decay and gives rise to an additional interaction induced signal. For inhomogeneous broadening one obtains photon echo-like behaviour. The temporal duration of the signal, however, is not determined by the width of the inhomogeneous broadening, as is predicted by theory if interaction effects are neglected, but is much smaller due to exciton-exciton interaction. Additional to the static interaction effects electron-electron correlations give rise to laser induced renormalization and dephasing processes which depend sensitively on the polarizations of the driving fields. These effects are analyzed on the basis of quantum-kinetic equations, which allow to describe the temporal evolution of the nonlinear polarizations. Numerical results are presented for various excitation conditions and material systems.

First principle study of structural and optoelectronic properties of ZnLiX3 (X = Cl or F) perovskites

The ion beam assistance during the film growth is one of the most useful method to obtain dense film along with improved optical and structural properties. Afnia material is widely used in optical coating operating in the UV region of the spectrum and its optical properties depend on the production method and the physical parameters of the species involved in the deposition process. In this work afnia thin films were evaporated by an e-gun and assisted during the growth process. The deposition parameters, ion beam energy, density of ions impinging on the growing film and the number of arrival atoms from the crucible, have been related to the optical and structural properties of the film itself. The absorption coefficient and the refractive index were measured by spectrophotometric technique while the microstructure has been studied by means of x-ray diffraction. A strictly correlation between the grain size, the optical properties and the laser damage threshold measurements at 248 nm was found for the samples deposited at different deposition parameters.

Aims: To address the physical properties of the growing research topic based on inorganic and organic composite materials under the glassy regime. The incorporation of a small amount of organic content in inorganic chalcogenide alloy could be an interesting topic for the investigation. Such composite materials' optical and structural properties could define their prospective use. Objectives: Considering the prospective utility of the inorganic and organic composite materials, this report’s key goal was to demonstrate the structural and optical properties, like, absorption spectra, extinction coefficient (k), real dielectric constant (εʹ), imaginary dielectric constant (εʹʹ), refractive index (n), absorption coefficient (α) and optical energy band (Eg ) for the Se 55 Te 25 Ge 20 (GTS) alloy, Se 55 Te 25 Ge 20 +0.025% multiwalled carbon nano tubes (MWCNT) and Se 55 Te 25 Ge 20 +0.025 % bilayer graphene (GF) composites. Methods: To synthesize the materials, a direct melt-quenched technique was adopted. Materials microstructural and UV/Visible optical absorption were performed from the Field Emission Scanning Electron Microscope and UV/Visible optical spectrometer equipment’s. Results: The obtained experimental evidences revealed that materials’ optical properties and microstructures slightly altered owing to the incorporation of multi walled carbon nano tubes and bilayer graphene in Se 55 Te 25 Ge 20 regime. To correlate the inorganic-organic material interactions, a schematic has also interpreted based on the bond formation in the solids. Conclusion: The experimental evidences have revealed the existence of MWCNT and GF in diffused form in GTS glassy configuration. The evidences have also revealed the diffused morphologies of the MWCNT and GF could not developed the specific structure within the complex configuration (although they have exhibited rather distinct morphologies), but they influenced the optical properties of the composite materials.

In this paper, the preparation of the harmful cadmium CdS on glass bases, prepared by thermal evaporation in the vacuum and study of optical and structural properties. The thickness and structural of the films were determined by (FESEM cross section). The results of the X-ray diffraction (XRD) showed that the films had a single crystal the hexagonal structure and the roughness and granular size were studied by using the (AFM) in two dimensions and three dimensions. The surface of the films was formed from clusters of granules called cluster and the roughness rate increased . The optical properties were studied through the (T) permeability spectrum of cadmium sulfide (CdS) prepared in wavelength range (400,650,750) nm. It was noted hat the permeability of cadmium sulfide was low and when the permeability decreased, the energy gap increased. And the value of the optical energy gap is(2.6eV) for cadmium sulfide. The optical properties were calculated as a function of the photon energy, which includes the absorption coefficient. The optical properties suggest that the prepared had a direct energy gap of 2.5,2.2,1.95eV where the energy gap was observed by increasing the thickness of the prepared the films was studied for the manufacture of electronic devices such as solar cells. The morphology of the surface was studied through (AFM) ,and the study of the optical properties of the films by UV-visible, and the CdS of the (PVD) thermal discharge were prepared in vacuum. http://dx.doi.org/10.25130/tjps.24.2019.114

The aim of the research was to modify the surface of construction textiles by means of the use of thin silver oxide films, investigate the structure and optical and mechanical properties, and determine the structure, optical and mechanical properties of the aged composites. Thin films of silver oxide (Ag2O) were synthesized on a flexible PET/PVC construction textile (CT); the structural, optical, and physical properties, as well as the effect of artificial aging on these properties, were investigated. The SILAR method (successive ionic layer adsorption and reaction) was used to synthesize thin Ag2O films on the CT surface. Before the thin films were deposited, the CT surface was mechanically roughened and pretreated with acidic and alkaline solutions at an elevated temperature. XRD analysis showed that the deposited films were a polycrystalline mixed phase material consisting of Ag2O, AgO, and metallic Ag. Diffuse reflectance spectra in the ultraviolet and visible ranges (UV-Vis) were used to study the optical properties of the deposited thin films. The synthesized Ag2O/CT composites were direct-gap semiconductors (the optical band gap (Eg) was 0.89 ± 0.02 eV). Eg and refractive indices (n) increased as the aging tests were carried out. Higher Eg and n meant that the composites were a good material for optoelectronic applications. The results showed that, after modification, the structural properties and tear strength of the PET/PVC fabric remained the same while the tensile strength decreased. The same tendencies remained after artificial aging.

The structural properties (radial distribution function, small angle scattering, density), optical properties (complex dielectric function versus energy), and other characterizing parameters (scanning electron microscope examination, chemical analysis, recrystallization behaviour, transport phenomena), have been determined for a series of amorphous Ge films sputtered at different substrate temperatures. Various of these properties (e.g. refractive index, density, room temperature conductivity) show only slowly varying values for low and high substrate temperatures, with a rapid changeover in a critical temperature range. A model has been developed which relates this behaviour to the probability that an adatom configuration be able to change to a configuration of lower local free energy in the time for the deposition of a monolayer, and it is suggested that such behaviour may be a general feature of disordered films prepared by any deposition method. The structural and optical properties at a give...

Carbon dots (PCs) are nanoparticles produced from carbon sources and have attracted great attention in recent years due to their photoluminescence properties, as well as biocompatibility, low cost in the synthetic route, and photostability. Currently, some studies are being developed with the objective of better understanding the structural and optical properties, since there are numerous methodologies for obtaining PCs, which directly influence the aforementioned properties. Therefore, in our work, we sought to evaluate the structural and optical properties using carbonaceous precursors such as o-phenylenediamine (OPDA) to obtain PCs-OPDA and 3,4-diaminobenzoic acid (3,4-DABA) to obtain PCs 3,4-DABA, in which they were submitted to the same synthetic route condition via irradiation in domestic microwaves. The PCs-OPDA and PCs 3,4-DABA were initially characterized in terms of their structural properties by spectroscopy in the Infrared (IR) region, inferring that the functional groups present on the surfaces of the synthesized PCs are different, Raman spectroscopy made it possible to discuss information on the graphitization of the carbon core of PCs, in which the results obtained showed incomplete carbon core, by powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA), a character of polycrystalline PCs was obtained, indicating that the PCs in our work presented structures referring to the carbonized polymer dots (CPDs), in the atomic force microscopy (AFM) the sizes of the nanoparticles were in the order of 5.02 ± 1.03 nm for PCs-OPDA and 14.01 ± 1.21 nm for PCs 3,4-DABA. The optical properties were studied using ultra and visible violet (UV/Vis) spectroscopy and fluorescence spectroscopy, confirming the formation of CPDs, since the fluorescence emission presented a profile independent of the excitation wavelength for both the PCs. The emission is in the region of yellow for PCs-OPDA and green for PCs 3,4-DABA. Other studies on fluorescence emission were carried out, such as evaluation of fluorescence intensity as a function of pH, evaluation of the fluorescence region in solvatochromism, evaluation of fluorescence intensity about temperature, the quantum yield of fluorescence for PCs-OPDA was 17% and for PCs 3,4-DABA of 2.98% and the cell viability studies of the synthesized PCs showed cytotoxicity for B16F10 and A375 tumor lines in the study concentration range.

Effect of temperature and D-sorbitol reducing agent content on the structural and optical properties of copper oxide thin films deposited by ultrasonic spray pyrolysis

Structural and optical properties of 30Li2O–55B2O3–5ZnO–xTiO2–(10 − x)V2O5, (0 ≤ x ≤ 10) glasses

Nickel foam of various pore-size coated graphene thin film of 200 nm thickness was investigated as a function of the pore size. The structural properties were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The optical properties were analyzed through the UV–Visible reflectance and Photoluminescence spectra. Hall Effect and Electrochemical impedance spectroscopy techniques were used to study the electrical and dielectric properties. The thermal properties were measured through the photothermal deflection technique. By decreasing the pore size, the electrical conductivity was increased from 9.42 × 107 to 33.26 × 107 S m−1, volume and surface carrier densities were decreased from −8.66 × 1021 to −2.05 × 1021 cm−3 and from −1.13 × 1014 cm−2 to −0.41 × 1014 cm−2; respectively, the specific capacitance was increased from 15.52 × 106 F to 19.65 × 106 F and the dielectric permittivity of value in the order of 1.5 × 103 F m−1 was decreased with the frequency. It was developed the photothermal deflection technique and discussed its sensitivity to the determination of thermal properties which show that the thermal conductivity decreased from 4.12 to 3.58 W m−1 K−1 and the thermal diffusivity decreased from 0.146 to 0.109 cm2 s−1. It was established semi-empirical relationships which allow to deduce the thermal properties and optical band gap without needing to measure them. These results introduce the graphene coated on Nickel foam sheets as good candidate for potential use in photoelectric and thermoelectric devices.

Effect of annealing temperature on properties of ZnO:Al thin films prepared by pulsed DC reactive magnetron sputtering

Tin oxide pure and manganese oxide doped (SnO2:Mn2O3) films were grown on a glass substrate in vacuum by pulsed laser deposition (PLD) technique (using Nd: YAG Laser) at different ratios of Mn2O3 (0, 3, 5, 7, 9) % wt. The structural and optical properties were studied. The X-ray diffraction (XRD) studies showed the structure nature of the films to be polycrystalline and rutile tetragonal. The optical transmittance spectra and optical constants of the prepared thin films, such as extinction coefficient (k), refractive index (n), and real (εr) and imaginary parts (εi) of the dielectric constant, were investigated. The values of the energy band gap increased from 3.5 eV to 3.55 eV with increasing the doping concentration.

TiO2:Ag nanocomposites have been prepared by sol-gel method with varying silver concentration. Different technological approaches are employed to study the formation of Ag nanoparticles in titanium dioxide matrix. The obtained thin films are either thermally treated at temperatures from 300 to 600oC or UV irradiated for 15 minutes between layer deposition. XRD and FTIR studies reveal that Ag is incorporated in TiO2 films as nanoparticles and no Ag oxide phases are detected. Optical characterization performed by UV-VIS spectroscopy confirms the formation of silver nanoparticles. The influence of thermal treatment and UV radiation on the optical and structural properties is studied.