Optical and photoelectrical properties of β-In2S3 thin films prepared by two-stage process

β-In₂S₃ films were grown on glass as well as on quartz substrates by rapid heating of metallic indium films in H₂S atmosphere. The effect of sulfurization temperature and time on the growth, structural, electrical and photoelectrical properties of β-In₂S₃ films has been investigated. Highly oriented single-phase β-In₂S₃ films were grown by the sulfurization technique. The morphology and composition of films have been characterized. The optical band gap of β-In₂S₃ is found to vary from 1.9 to 2.5 eV when the sulfurization temperature is varied from 300 to 600 °C or by increasing the sulfurization time. The electrical properties of the thin films have also been studied; they have n-type electrical conductivity. The photoelectrical properties of the β-In₂S₃ films are also found to depend on the sulfurizing temperature. A high photoresponse is obtained for films prepared at a sulfurizing temperature of 600 °C. β-In₂S₃ can be used as an alternative to toxic CdS as a window layer in photovoltaic technology.     

Study on sulfur diffusion in CuInSe2 thin films using two thermal profiles

An insurmountable disadvantage of CuInSe₂ is the low band gap, which limits the open-circuit voltage to value well below 500 mV in solar cells. The incorporation of sulfur into CuInSe₂ thin film was investigated to establish a scientific basis for the graded band gap CuIn(Se_1 − x,S_x)₂ thin films. CuIn(Se_1 − x,S_x)₂ thin films were obtained by reactive annealing of Cu₁₁In₉ precursors in a mixture of sulfur and selenium atmosphere while post-sulfurization of single phase CuInSe₂ did not result in CuIn(Se_1 − x,S_x)₂ thin films. A band gap of 1.36 eV, was obtained for the prepared CuIn(Se_1 − x,S_x)₂.     

Coarsening of Inter- and Intra-granular Proeutectoid Cementite in an Initially Pearlitic 2C-4Cr Ultrahigh Carbon Steel

Metallurgical and Materials Transactions A - We have examined spheroidization and coarsening of cementite in an initially pearlitic 2C-4Cr ultrahigh carbon steel containing a cementite network....     

Linearly polarized emission from PTCDI-C8 one-dimensional microstructures

Linearly polarized emission has been observed from a crystalline one-dimensional (1D) microstructure fabricated from N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C₈) molecules via solution phase self-assembly. Rotating microscopy imaging of a 1D microstructure under crossed polarization was performed for the investigation of polarized emission. The anisotropy birefringence was maximum only when the 1D microstructure was aligned 45° to the direction of the polarizer and it was minimum when aligned parallel to the polarizer implying that the transmission axis of the 1D microstructure is perpendicular to its π–π stacking direction. A model has been proposed to explain linearly polarized emission from the microstructure.     

Low Latency Fog-Centric Deduplication Approach to Reduce IoT Healthcare Data Redundancy

In today’s highly computerized society, detection and recognition of text present in natural scene images is complex and difficult to be properly recognized by human vision. Most of the existing algorithms and models mainly focus on detection and recognition of text from still images. Many of the recent machine translation systems are built using the Encoder-Decoder framework which works on the format of encoding the sequence of input and then based on the encoded input, the output is decoded. Both the encoder and the decoder use an attention mechanism as an interface, making the model complex. Aiming at this situation, an alternative method for recognition of texts from videos is proposed. The proposed approach is based on a single Two-Dimensional Convolutional Neural Network (2D CNN). An algorithm for extracting features from an image called the crosswise feature extraction is also proposed. The proposed model is tested and shows that crosswise feature extraction gives better recognition accuracy by requiring a lesser period of time for training than the conventional feature extraction technique used by CNN.

     

Identifying threading dislocations in GaN films and substrates by electron channelling

Electron channelling contrast imaging of threading dislocations in GaN (0002) substrates and epitaxial films has been demonstrated using a conventional polepiece-mounted backscatter detector in a commercial scanning electron microscope. The influence of accelerating voltage and diffraction vector on contrast features denoting specific threading dislocation types has been studied. As confirmed by coordinated transmission electron microscopy analysis, electron channelling contrast imaging contrast features for edge-type threading dislocations are spatially smaller than mixed-type threading dislocations in GaN. This ability to delineate GaN edge threading dislocations from mixed type was also confirmed by defect-selective etch processing using molten MgO/KOH. This study validates electron channelling contrast imaging as a nondestructive and widely accessible method for spatially mapping and identifying dislocations in GaN with wider applicability for other single-crystal materials.     

Imaging Dislocations in Single-Crystal SrTiO<Subscript>3</Subscript> Substrates by Electron Channeling

Electron channeling contrast imaging (ECCI) using a conventional pole-mounted backscatter detector in a commercial scanning electron microscope (SEM) has been implemented to analyze extended defects. In-grown extended defects in bulk SrTiO₃ (001) substrates such as dislocation loops, subsurface dislocations parallel to the surface, and surface-penetrating dislocations have been distinguished by ECCI. The techniques of dislocation-selective etching and ECCI have been compared side-by-side, where surface-penetrating dislocations have been shown to have one-to-one correspondence with ECCI spot features. g·b and g·b × u have been implemented for subsurface portions of intrinsic dislocations, being identified as screw dislocations with Burgers vector in the 〈100〉 direction.     

On‐Demand Nanoscale Manipulations of Correlated Oxide Phases

Controlling material properties at the nanoscale is a critical enabler of high performance electronic and photonic devices. A prototypical material example is VO₂, where a structural phase transition in correlation with dramatic changes in resistivity, optical response, and thermal properties demonstrates particular technological importance. While the phase transition in VO₂ can be controlled at macroscopic scales, reliable and reversible nanoscale control of the material phases has remained elusive. Here, reconfigurable nanoscale manipulations of VO₂ from the pristine monoclinic semiconducting phase to either a stable monoclinic metallic phase, a metastable rutile metallic phase, or a layered insulating phase using an atomic force microscope is demonstrated at room temperature. The capability to directly write and erase arbitrary 2D patterns of different material phases with distinct optical and electrical properties builds a solid foundation for future reprogrammable multifunctional device engineering.     

Oxygen Vacancy Creation,Drift, and Aggregation in TiO2‐Based Resistive Switches at Low Temperature and Voltage

Transmission electron microscopy with in situ biasing has been performed on TiN/single‐crystal rutile TiO₂/Pt resistive switching structures. Three elementary processes essential for switching: i) creation of oxygen vacancies by electrochemical reactions at low temperatures (<150 °C), ii) their drift in the electric field, and iii) their coalescence into planar faults (and dissociation from them) have been documented. The faults have a form of vacancy discs in {110} and {121} planes, are bound by partial dislocation loops, and are identical to Wadsley defects observed in nonstoichiometric TiO₂ annealed at high temperatures. The faults can be regarded as a precursor to the formation of oxygen‐deficient Magnéli phases, but 3D secondary phase inclusions have not been detected. Together, the observations shed light on the behavior of oxygen vacancies in relatively low electric fields and temperatures, suggesting that, in addition to the rather accepted notion of oxygen vacancy motion during the writing processes in resistive switching devices, such motion may occur even during reading, and may be accompanied by significant oxygen vacancy creation at modest device excitation levels.     

Epitaxial SiC Growth Morphology and Extended Defects Investigated by Electron Backscatter Diffraction and Electron Channeling Contrast Imaging

Electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) were employed to investigate epitaxial SiC growth on 4H-SiC mesa structures. SiC polytypes were identified by indexing Kikuchi maps recorded from various points on the mesa surfaces. Orientation contrast was observed between different polytype surfaces using ECCI by forescattered electron detection. Extended defects in 3C-SiC were imaged directly by ECCI. Additionally, the ECCI technique was utilized to correlate dislocations with atomic step morphologies for various mesa surfaces. Evidence of vertical growth enhancement in the form of additional faceting was attributed to the presence of threading screw dislocations at mesa surfaces. Atomic steps were observed very near the edges of some mesa surfaces free of dislocations.