Study on A.C properties of tin selenidethin films

A.c properties of tin selenide thin films prepared by an encapsulated selenization method are investigated. The measurements obtained from al/snse/al sandwich structures showed strong indication of frequency and temperature dependence of capacitance, dielectric loss and conductance over the ranges of 5-200 khz and 228-373 k, respectively. Dielectric behaviour was expected to be due to space charge polarization which contributed to a.c conduction. This was generally explained in terms of hopping of the charge carriers between localized states with activation energies 0.03-0.08 ev. Parameters such as trap binding energy (0.94 ev) and minimum hopping distance (1.01 nm) were also predicte

Hydrostatic pressure studies of semiconductor heterostructures and Schottky diodes

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN004148 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Growth parameters of InAs/GaAs quantum dots grown by MOVPE

Quantum dots are zero dimensional structures and therefore have superior transport and optical properties compared to either 2-dimensional or 3-dimensional structures. Quantum dots show promise for use in diode lasers, amplifiers, and biological sensors. They are also vigorously researched for use in solid-state quantum computing. Indium arsenide quantum dots are currently studied for their use in the photoelectronic and semiconductor fields. In our research, Indium Arsenide (InAs) quantum dots are grown on Gallium Arsenide (GaAs) substrate using Metal Organic Vapor Phase Epitaxy (MOVPE) in the Stranski-Krastanov Growth mode. Several parameters influence the growth of InAs quantum dots greatly. We will be describing these growth parameters, which we have identified in our current growth attempts. We are currently trying to achieve device quality InAs/GaAs quantum dots by varying these parameters we have identified. These growth parameters include the V/III ratio of both InAs and GaAs, In/As growth temperature, and quantum dot growth time. By carefully fine tuning the parameters above, we will be able to grow device quality quantum dots. Deviations from the optimized value will result in either no formation of quantum dots, or the formation of large islands which are particularly susceptible to dislocations. The effects of differing growth parameters are observed by using an Atomic Force Microscope (AFM) located at Faculty of Science, UTM. The MOVPE is located at Ibn Sina Institute for Fundamental Science Studies, UTM

Growth of binary, ternary and quatenary III-V compounds nanowores by MOCVD

Various III-V compounds semiconductor Nanowires (NWs) have been grown by using vertical camber MOCVD. The morphology of the NWs has been characterized using FESEM and SEM. In addition to binary and ternary NWs such as GaAs, InP, InxGa1- xAs and AlyGa1-yAs NWs, the quaternary compounds InGaAsP NWs have been successfully grown. The growth of NWs has been assisted by gold nanocolloids as seed particles. Besides this technique, seed free-assisted growth of NWs has also been demonstrated. InxGa1-xAs NWs have been successfully grown without gold seedparticle assisted

Influence of InxGa1−xAs Underlying Layer on the Structural of the In0.5Ga0.5As Quantum Dots Grown by MOCVD

The single layer In0.5Ga0.5As quantum dots (QDs) were grown on a thin InxGa1−xAs underlying layer by metal-organic chemical vapour deposition (MOCVD) via Stranski-Krastanow growth mode. The effect of different indium composition in the In − xGa1−xAs underlying layer was investigated using atomic force microscopy (AFM). AFM images show that the QDs structures were formed on the surface. The dots formation onthe surface changes with different composition of InxGa1−xAs underlying layer. Increasing indium composition in the underlying layer resulted to formation of higher density and smaller size dots. Several large dots were also formed on the surface. Growing of underlying layer reduces the lattice mismatch between In0.5Ga0.5As and GaAs, and decreases the critical thickness of the dots. This strongly influences the dots nucleation on the surface. Growth of quantum dots using underlying layer is one way to modify dot formation in order to achieve uniform QDs of right size and high density, which are essential for QDs device applications

Estimation of Crystallite Size, Density, and Compositional of the Ti: Al2O3 Single Crystal

The purposes of this research were to estimate the crystallite size, density, and chemical composition of the ingot Ti: Al2O3  crystal grown by the Czochralski method. The crystallite size and composition of Ti: Al2O3 crystals had been determined using x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDXS). Based on the Archimedes principle, the density of the crystals had been determined. The XRD patterns showed a single central peak with high intensity for all samples. It indicated that all samples had a single crystal. The average value of the samples' crystallite size was in the range of 20.798 nm to 34.294 nm. The ingot crystal density and Ti composition increased from the top to the bottom part because the solid solution was distributed unevenly during the growth process

The effect of annealing temperature on gold catalyst and substrate surface in the growth of gaAs nanowire

Annealing temperature plays an important role in the formation of Au-Ga alloy eutectic. Effect of annealing temperature on gold catalyst and substrate surface were studied using AFM, FE-SEM and TEM. With a temperature of 600°C, the layer of gold colloids particle formed an islands in the state of molten eutectic alloy and absorbed evaporated metal-organics to formed nanowire underneath the alloy. Pit formed on the substrate surface due to the chemical reactions during the pre-annealing process have an impact on the direction of nanowire growth Without pre-annealing temperature, the nanowire formed vertically on the GaAs (100) surface, meanwhile the growth direction depends on the intact nucleation facets and surface energy, when annealing is applied. With pre-annealing temperature, the wire base is large and curve due to the migration of Ga atoms on the substrate surface towards the tip of the wire and line tension between the substrate surface and gold particle

Resistivity measurement of ZnO:AI films for solar cell

Aluminium doped Zinc Oxide films were deposited on glass slide by RF magnetron sputtering using a ZnO target mixed with A120J. All the films were growth in room temperature without intentional heating. The resistivity of the ZnO:AI films were measured using van der Pauw method in terms of the preparation conditions such as RF power, working pressure, deposition time, O2 content in sputtering gas and target-substrate distance. Resistivity of the deposited films shows the following behaviours: decreases with the increasing RF power and film thickness while increase with increasing target substrate distance, and O2 content in sputtering gas. Resistivity for films prepared in different working pressure decreases with the Argon pressure but increased after the optimal pressure of 45mTorr

Synthesis and analysis of silicon nanowire below Si-Au eutectic temperatures using very high frequency plasma enhanced chemical vapor deposition

Silicon nanowires (SiNWs) were synthesized from pure silane precursor gas and Au nanoparticles catalyst at below Au-Si eutectic temperature. The SiNWs were grown onto Si (1 1 1) substrates using very high frequency plasma enhanced chemical vapor deposition via a vapor-solid-solid mechanism at temperatures ranging from 363 to 230 degrees C. The morphology of the synthesized SiNWs was characterized by means of field emission scanning electron microscope equipped with energy dispersive X-ray, high resolution transmission electron microscopy, X-ray diffraction technique and Raman spectroscope. Results demonstrated that the SiNWs can be grown at the temperature as low as 250 degrees C. In addition, it was revealed that the grown wires were silicon-crystallized