Semiconductor Samples Research Articles

Mechanochemical synthesis and characterization of poly[(aniline-co-N-(4-sulfophenyl) aniline] nanofibers and its nanocomposite with titanium dioxide nanoparticles and study of their efficiency in hybrid solar cell

The advantages of polyaniline for application in new generation solar cells include its cost-effectiveness, environmentally friendly synthesis, remarkable stability, and the ability to modify the bandgap through the synthesis of its nanocomposites. But a challenge for its nanostructures is the limited solubility in non-toxic solvents, including water, which limits their processability in coating techniques. We overcame this challenge by synthesizing its copolymer with diphenylamine-4-sulfonate and its nanocomposite with titanium dioxide nanoparticles (TiO2NPs). So through a solid-state and template-free technique and using sodium diphenylamine-4-sulfonate, aniline hydrochloride salt, TiO2NPs, and FeCl3∙6 H2O as an oxidant, poly(N-(sulfophenyl)aniline) nanoflowers (PSANFLs), poly [(aniline-co-N-(4-sulfophenyl) aniline] nanofibers (PAPSANFs), poly(N-(sulfophenyl)aniline) nanofibers/titanium dioxide nanoparticles (PSANFs/TiO2NPs), and poly (aniline-co-N-(4-sulfophenyl)aniline nanofibers/titanium dioxide nanoparticles (PAPSANFs/TiO2NPs) were synthesized. Characterization of the synthesized samples was carried out through field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectra, ultraviolet-visible spectra (UV-Vis), cyclic voltammetry (CV), and elemental analysis (CHNS). The FE-SEM images clearly illustrate that the synthesized samples are of nanoscale dimensions. The band gap values of 2.23 eV for PSANFs/TiO2NPs and 1.96 eV for PAPSANFs/TiO2NPs nanocomposites were determined through electrochemical calculations based on cyclic voltammetry curves, showcasing the complementary properties of n and p semiconductors. Using doctor blade method to prepare films from synthesized materials and the architectural pattern of ITO│TiO2NPs│semiconductor sample│Al, all hybrid solar cells are fabricated. The I-V characteristics and power conversion efficiency (PCE) of the samples were examined and discussed. The PCE values for the four samples were found to be in the range of 0.20–0.82 %.

Analyzing antimicrobial activity of ZnO/FTO, Sn-Cu-doped ZnO/FTO thin films: Production and characterizations.

In the developing field of nanotechnology, ZnO (zinc oxide) based semiconductor samples have emerged as the foremost choice due to their immense potential for advancing the development of cutting-edge nanodevices. Due to its excellent chemical stability, low cost, and non-toxicity to biological systems, it is also utilized in various investigations. In this study, the successive ionic layer adsorption and reaction (SILAR) method was used to generate FTO (fluorine-doped tin oxide)/ZnO, and tin (Sn)-copper (Cu)-doped ZnO thin films at varying concentrations on FTO substrates. After being stacked 40 times in varying concentrations on the FTO substrate, FTO/ZnO thin films and Sn-Cu-doped thin films were annealed at 300°C. Using Scanning Electron Microscopy (SEM) Energy Dispersive Spectroscopy-(EDS), the agar diffusion test, and the viability cell counting method, the minimum inhibitory concentration, structural properties, surface morphology, antibacterial properties, bacterial adhesion, and survival organism count of FTO/ZnO thin films and Sn-Cu-doped thin films were investigated. Both doped and FTO/ZnO films with varying Sn-Cu concentrations expanded harmonically on the FTO substrate, according to the SEM-EDS investigation. The doping concentration affected their morphological properties, causing changes depending on the doping level. Antibacterial activity was observed in the powder metals, but no antibacterial activity was found in the thin film form. The highest adhesion rate of bacterial organisms on the produced samples was observed when the FTO/ZnO/Sn-Cu doping rate was 1%. In addition, the lowest adhesion rate was observed when the FTO/ZnO/Sn-Cu additive ratio was 3%. RESEARCH HIGHLIGHTS: ZnO based semiconductors highlight significant potential in advancing nanodevice technology due to their chemical stability, cost-effectiveness, and biocompatibility. Employing the SILAR method, the study innovatively fabricates FTO/ZnO and Sn-Cu-doped ZnO thin films on FTO substrates, exploring a novel approach in semiconductor manufacturing. Post annealing at 300°C, the research examines the structural and surface morphological changes in the films, contributing to the understanding of semiconductor behavior under varying conditions. The study delves into the antibacterial properties of ZnO thin films, offering insights into the potential biomedical applications of these materials. SEM-EDS analysis reveals that doping concentrations crucially influence the morphological properties of ZnO thin films, shedding light on the optimization of semiconductor performance. Findings indicate a specific doping rate (1% Sn-Cu) enhances bacterial adhesion, while a 3% additive ratio minimizes it, suggesting implications for biomedical device engineering and antibacterial surface design.

Investigation of Thermo-Electrical Instabilities in a Semiconductor as 2D Dynamical Systems

A semiconducting sample placed in cryogenic media with applied electric field generates low frequency oscillations of electric current and sample temperature and known to be thermo-electrical instabilities. Although observation of current oscillations on oscilloscope is possible, change of sample temperature cannot be detected experimentally. Description of the phenomenon through mathematical equations helps to understand relationship of the two variables as well as their connection to deep trap behavior that are involved in supporting the instability. Mathematical model for thermo-electrical instabilities in an n type semiconductor based on the two deep trap level model with non-degenerate electron statistics has been introduced in order to investigate the unique relationship between the change in time of both electric current flowing through a semiconductor sample and the sample temperature. The 3D dynamical system of nonlinear inhomogeneous ordinary differential equations has been investigated as component 2D dynamical systems (n,T), (n,n<sub>t</sub>) and (n<sub>t</sub>,T) for local behavior at isolated equilibrium and at points on individual trajectories, where n, n<sub>t</sub> and T are free electron concentration at conduction band, electron concentration at deep traps and temperature of a semiconductor sample accordingly. Each of the planar systems is expressed in canonical form and investigated as a Cauchy problem with a set of appropriate initial values. This paper presents investigation results of phase trajectories of the planar systems depending on a single parameter – the temperature of cooling media T<sub>0</sub>. Based on obtained calculation results of time sequences of the three variables n, n<sub>t</sub> and T, phase differences among these variables have been determined for different values of T<sub>0</sub>. It has been established that the change in sample temperature lags behind change in current and this lag increases with T<sub>0</sub>. Clearly defined correlations among systems (n,T), (n,n<sub>t</sub>) and (n<sub>t</sub>,T) are seen, being the result of balance between field aided and thermal ionization mechanisms for charge carrier generation and recombination processes. Thermal and field assisted generation mechanisms compete with one another in achieving steady non equilibrium state in the system depending on temperature of cooling media T<sub>0</sub>.

Optoelectrical properties of the ternary chalcogenide SnSb2S5 as a new absorber layer for photovoltaic application

A new material, tin antimony sulfide (SnSb2S5) thin films, considering different thicknesses (200 nm, 312 nm and 431 nm), were obtained by thermal evaporation onto a glass substrate. The films were studied electrically (I–V dependence) and optically to highlight their properties as photoanodes in thin film photovoltaic devices. The I–V characteristic curves showed n-type semiconductor samples with an electrical conductivity of 10−3(ohm cm)−1 under white light excitation. The values of the absorption coefficient (α) and extinction coefficient (K) were found to be enlarged by increasing the layer thickness. The SnSb2S5 films displayed a high absorption coefficient of 105 cm−1. The studied physical characterizations of tin antimony sulfide (SnSb2S5) samples showed interesting optical and electrical properties for good absorber layers in thin film solar cell devices.

The Study of the Electrical Properties of Anisotropic Semiconductors in the Laboratory Workshop of the University Course in Physics

The purpose of the article is to develop a theoretically and experimentally substantiated specific laboratory work for studying the anisotropy of the electrical properties of semiconductors within the framework of the curricula of higher educational institutions, for such areas of training as “Physics”, “Technical Physics”, “Radiophysics” and “Electronics and Nanoelectronics”. The relevance of the problem is due to the desire of domestic electronics for technological sovereignty and high requirements for the training of qualified personnel for the production of structures of solid-state functional electronics. Based on the solution of the boundary electrodynamic problem, an expression is obtained for the electric potential in the region of a thin rectangular semiconductor sample with a tensor character of conductivity. The results of this work is the development of an original laboratory setup for the demonstration and practical study of the anisotropy of the electrical properties of semiconductor crystals. The proposed technique makes it possible to determine the main electrokinetic parameters of an anisotropic semiconductor – specific conductivity, concentration and Hall mobility of the main charge carriers. A schematic diagram of the installation and formulas for calculating the errors of the measured quantities are proposed. The results obtained may also be of scientific interest in the study of anisotropic semiconductor materials in laboratory conditions.

A simple new method for retrieving spectral changes of the refractive index of thin films from transmission spectra

A new method for calculating the refractive index spectral behaviour of thin films is presented. The method is based on introducing the idea of the order of appearance technique to accurately find the order of interference and Cauchy fitting parameters of the interference peaks observed in the transmission spectra of the thin film under investigation. A very simple mathematical relationship was found that relates the order of appearance and wavenumber of the interference peaks observed in the transmission spectrum. Fitting the data extracted from the measured transmission spectra to the newly found simple mathematical relation, we can extract the order of interference and Cauchy fitting parameters of the thin film under investigation. In addition, the thickness of the film was extracted and found to agree well with the thickness measured using the spectroscopic ellipsometery technique. The proposed method of calculation was successfully applied to five binary semiconductor samples, which are ZnO, ZnTe, ZnS, ZnSe, and SiO2. A very good agreement was found between the proposed method of calculation and the well-known method presented by Swanepoel. Finally, the effect of surface roughness on the FECO peak wavelength was discussed.

Investigation of semiconductor materials by the thermo-optical method in a magnetic field

The results of studying the effect of temperature and magnetic field on the relaxation of the thermo-optical signal in semiconductor samples with different electronic spectra n-Ge, n-InSb, ZnSe:Ni are presented. The results were obtained using a two-beam fiber-optic “pump–probe” method with a Fabry–Perot interferometer in the temperature range from 4.2 to 300 K with the application of a magnetic field up to 8 T. The significant change of behavior of reflected probing beam with wavelength of 1530 nm was found after the action of a pump pulse for the sample of n-Ge at temperatures below 30 K and a field induction of more than 2 T. This phenomenon is caused by transformation of electronic structure.

Field-dependent abundances of hydride molecular ions in atom probe tomography of III-N semiconductors.

We investigate the microscopic behaviour of hydrogen-containing species formed on the surface of III-N semiconductor samples by the residual hydrogen in the analysis chamber in laser-assisted atom probe tomography (APT). We analysed AlGaN/GaN heterostructures containing alternate layers with a thickness of about 20nm. The formation of H-containing species occurs at field strengths between 22 and 26V/nm and is independent of the analysed samples. The 3D APT reconstruction makes it possible to map the evolution of the surface behaviour of these species issued by chemical reactions. The results highlight the strong dependence of the relative abundances of hydrides on the surface field during evaporation. The relative abundances of the hydrides decrease when the surface field increases due to the evolution of the tip shape or the different evaporation behaviour of the different layers.

Analysis of plasma-elastic component of time-domain photoacoustic response

The plasma-elastic component of the photoacoustic response in the time-domain of thin semiconductor samples excited by long electromagnetic radiation pulses is analyzed in detail. The plasma-elastic component model assumes that ambipolar diffusion can be approximated by the minority carrier diffusion. The results obtained show that the plasma-elastic component in thin semiconductor samples affects photoacoustic measurements in the time domain, which is important for the photoacoustic determination of semiconductor electronic properties.

Thermo-Optical Measurements and Simulation in a Fibre-Optic Circuit Using an Extrinsic Fabry–Pérot Interferometer under Pulsed Laser Heating

Advantages of using an external Fabry–Pérot interferometer (EFPI) as a high-speed local temperature deformation sensor are demonstrated for the fibre-optic circuit combining a powerful laser beam for surface heating with a low-power probing radiation. The difference in the formation of the heating and probing radiation provides a simple basis for varying the gap between the fibre end and the surface in order to change the ratio between the heating and EFPI measuring areas. Using an example of modelling the laser heating by radiation from a standard single-mode fibre, we demonstrate the possibility of employing the EFPI to measure the temperature deformation of the surface on a quasi-isothermal area with the temperature close to the maximum at gap values of more than 100 μm. With the condition of preliminary calibration, the proposed scheme can be used to evaluate the heat treatment of the surface with the speed of the applied photodetector. The practical possibilities of the method are demonstrated on examples of heating some metal and semiconductor samples by laser pulses of microsecond duration.

Screened Coulomb interaction in insulators with strong disorder.

We study the effect of disorder on the excitons in a semiconductor with screened Coulomb interaction. Examples are polymeric semiconductors and/or van der Waals structures. In the screened hydrogenic problem, we consider the disorder phenomenologically using the so-called fractional Scrödinger equation. Our main finding is that joint action of screening and disorder either destroys the exciton (strong screening) or enhances the bounding of electron and hole in an exciton, leading to its collapse in the extreme case. Latter effects may also be related to the quantum manifestations of chaotic exciton behavior in the above semiconductor structures. Hence, they should be considered in device applications, where the interplay between dielectric screening and disorder is important. Our theoretical results permit one to predict the various excitonic properties in semiconductor samples with different degrees of disorder and Coulomb interaction screenings.

Size reduction process by novel TVA technique and its effect on enhancement of physical properties of oxide semiconductor pellets

ABSTRACT This work describes a novel approach that can reduce grain as well as particle size of semiconducting pellet samples in the nanoscale range with low-cost and less instrumentation. Herein an instrumental setup was designed and fabricated in-house, referred to as the ‘Thermo-Vibrational Annealing’ (TVA) setup. Here, the concept of grain confinement within the pellet during the recrystallisation phase of annealing was achieved by simultaneously applying both thermal and vibrational mechanical energy to the sample, followed by vibrational dry quenching. In this work, for the case study, ZnO pellets were prepared by using chemical route pyrophoric method followed by annealing at 800°C for 4 hours using this setup. The reduction of particle and grain size by this TVA, in comparison to without vibrational annealing, was confirmed by X-ray diffraction (XRD), high-resolution transmission electron microscopy and scanning electron microscopy studies. The expected changes in other microstructural and optical properties were examined by Raman and UV-Visible absorption spectroscopy studies. Moreover, this work gives references to improve the physical properties not only of ZnO but also of other oxide semiconductor samples using this technique, to be used in multiple sensors and optoelectronic devices.

Investigation of bulk magneto-resistance crossovers in iron doped zinc-oxide using spectroscopic techniques

Pellets of Pure and Fe-doped dilute magnetic semiconducting (DMS) samples are studied for bulk magneto-resistance (BMR) at room temperature and at low-temperatures ∼100K. Raman-, photoluminescence- and X-ray photoelectron-spectroscopic techniques are used to determine chemical and electronic structures of the samples. A broadband intense yellow-green-orange luminescence is observed in Fe-doped ZnO samples and emission red-shifts are investigated. Electrical transport is studied with and without applied magnetic field up to 9T and thermal activation and hopping modes of conduction is discussed in light of nature of Fe substitution in the host lattice. Several decremental- to incremental-BMR crossovers are obtained corresponding to experimental variables of Fe concentration 0.025 ≤ x ≤ 0.1, temperature and applied magnetic field. Several possible modes of magneto-transport are discussed to further elucidate the origin of the as-found BMR crossovers in our samples. Positive BMR in pure- and highly doped (x ≥ 0.1) ZnO is found to originate from F-centers and thermal fluctuations, respectively. However, modestly doped (x ≤ 0.05) ZnO exhibit thermally activated conduction and magnetic poloron mediated negative BMR.

High-low Kelvin probe force spectroscopy for measuring the interface state density.

The recently proposed high-low Kelvin probe force microscopy (KPFM) enables evaluation of the effects of semiconductor interface states with high spatial resolution using high and low AC bias frequencies compared with the cutoff frequency of the carrier transfer between the interface and bulk states. Information on the energy spectrum of the interface state density is important for actual semiconductor device evaluation, and there is a need to develop a method for obtaining such physical quantities. Here, we propose high-low Kelvin probe force spectroscopy (high-low KPFS), an electrostatic force spectroscopy method using high- and low-frequency AC bias voltages to measure the interface state density inside semiconductors. We derive an analytical expression for the electrostatic forces between a tip and a semiconductor sample in the accumulation, depletion, and inversion regions, taking into account the charge transfer between the bulk and interface states in semiconductors. We show that the analysis of electrostatic forces in the depletion region at high- and low-frequency AC bias voltages provides information about the interface state density in the semiconductor bandgap. As a preliminary experiment, high-low KPFS measurements were performed on ion-implanted silicon surfaces to confirm the dependence of the electrostatic force on the frequency of the AC bias voltage and obtain the interface state density.

The influence of temperature on the electrical conductivity of GaN piezoelectric semiconductors

GaN is an excellent material choice for power devices due to its excellent properties such as super wide bandgap width and high electron mobility. However, the problem of temperature affects the thermo reliability and hinders the potential of GaN devices. In this paper, the electrical properties of GaN under temperature have been studied by the combination of numerical simulation and experimental research. The electric current change and electrical resistivity of polarized and depolarized GaN semiconductor samples were tested in an environment-test cabinet. Based on the influence of temperature, the expression of the resistivity curve vs temperature was established for polarized and depolarized GaN samples. It is shown that the resistivity model predictions are consistent with experimental results. The I–V characteristic curves under different temperatures were also measured. Thus, such a model is instructive to the reliable design of GaN high-temperature devices. The findings will be instructive to the optimal design of GaN electronic components.

Simulation of the depth of the melted layer on the surface of a semiconductor using JAVA cross-platform application

The paper describes a method for obtaining p-n transitions due to the laser recrystallization of the surface of CdTe semiconductor samples, as well as a software application developed in Java that allows the simulation of thermal processes at the boundary of the epitaxial layer-substrate with laser irradiation of the semiconductor surface. It allows to make predictions regarding the thickness of the melted layer, which will affect the parameters of the devices made on the basis of the obtained barrier layers. The theoretical modeling of the processes taking place at absorption of laser radiation by the surface layer of a semiconductor is carried out.

Generation–recombination noise in uniformly doped semiconductors with contacts of finite surface recombination velocities

The formula for the voltage noise spectrum due to generation–recombination (G–R) rate fluctuations is derived for uniformly doped majority-carrier n-type semiconductor samples with contacts of finite surface recombination velocities. In the derivation of the formula, a new boundary condition with finite surface recombination velocities considered is used instead of the ohmic boundary condition. The G–R voltage noise spectra are calculated to become saturated and equal in the high electric field region irrespective of surface recombination velocities. However, the behaviors of slow surface recombination velocities in the low electric field region differ from those of fast ones. The profiles of the electron density fluctuations of slow ones differ significantly from those of fast ones in the low-field region. In the high field region, a steep rise in the magnitude of the electron density fluctuation occurs near the voltage contact toward which electrons drift. The various location dependencies of the contribution of noise sources to the voltage power spectral density are also derived for low and high field regions as well as low and high surface recombination velocities, and analytical expressions are developed for the voltage power spectral densities and electron density fluctuations.

Microwave acoustic studies of materials in diamond anvil cell under high pressure

This paper presents an integrated measuring system combining a diamond anvil cell (DAC) and a high overtone bulk acoustic resonator (HBAR) operating at the microwave frequency band as 2.8–8.8 GHz. We have studied several metallic (W, Zr) and semiconductor (Si) samples under pressure up to ∼16 GPa. As an HBAR, we have used the “Al/Al0.72Sc0.28N/Mo/(100) diamond” structure utilizing a piezoelectric aluminum–scandium nitride film. We have observed that under pressure, the Q-factor of the HBAR decreases but remains at the value of 2500–3000, which is suitable for our experiments. It is demonstrated that the above system can be used for studying the behavior of various solids under high pressure, the pressure-induced phase transition in Zr, the registration of plastic deformations, and their relaxation in metals. Here, we discussed the phenomenon of an acoustic wave passing through a tungsten layer under a pressure of ∼5.5 GPa. The integrated DAC&HBAR measuring system has demonstrated some practical advantages over known ultrasonic systems combined with the DAC as the possibility of applying a microwave operational frequency, the measurement of a Q-factor change under pressure, and the miniature size of a sensitive HBAR element. The application of the built-in DAC&HBAR system will hopefully allow more accurate studies on materials in the GPa pressure range of a DAC.

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Scanning Electron Microscopy Dopant Contrast Imaging of Phosphorus‐Diffused Silicon

AbstractPhosphorous dopant diffusion profiles feature in many silicon semiconductor devices, including the vast majority of silicon solar cells. Accurate spatially resolved dopant profiling is crucial for understanding the performance of these diffused regions, however, it is very challenging to obtain such profiles in non‐planar samples. Scanning electron microscopy for dopant contrast imaging (SEMDCI), where the secondary electron (SE) image contrast is used to determine the dopant level of a semiconductor sample, is an ideal candidate for Si dopant profiling, especially for silicon samples with surface nanotexturing or black silicon (BSi) technology. However, in previous SEMDCI studies, the dopant concentration of heavily doped n‐type layers in silicon samples have shown a poor correlation with the SE signal contrast. In this work, 1) good contrast for n‐type diffused silicon without contrast‐enhancing techniques; 2) a new contrast definition to account for imaging non‐uniformities; 3) clear correlations between SE contrast and sample work function for phosphorus‐diffused planar silicon specimens across a wide range of emitter profiles; 4) implementation of an empirical baseline correction to normalize scanning electron microscopy image condition variations, are presented. This SEMDCI method is subsequently used for the first time to obtain 2D electron concentration maps for both planar and BSi samples.