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

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

Solid oxide fuel cell: an overview

This paper will review the area of interest in fuel cell, especially in solid oxide fuel cell (SOFC). This area of interest covers SOFC operational reaction, its advantages and limitations, type of cell structure and configuration, and the requirement of SOFC. The review also looks into the development and fabrication of a research towards low temperature SOFC. There is also a review made by professional organizations that contribute to the research on fuel cell both locally and globally

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

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

The synthesis of cuprous oxide nanowires in the presence of oxygen using a hot tube thermal evaporation method

Cuprous oxide nanowires have been synthesized by heating copper foil in the presence of oxygen rich environment using a hot tube vacuum thermal evaporation method. The effect of growth parameters such as growth time, temperature and oxidative environment on the morphology of the nanowires is investigated. The growth of cuprous oxide nanowires from copper foils thermally oxidized in the presence of oxygen rich at temperatures between 300 and 500 0C. The nanowires were formed within the temperature range of 400 – 500 0C with diameters and length between 25 - 100 nm and length 1 - 4 µm, respectively. This gave an estimate of aspect ratio around 40. Observation from FESEM results revealed the optimal growth of cuprous oxide nanowires which occurred at oxidation times for 1h, 1/2h and 25 minutes and flow rates of oxygen at 0.09 psi, 0.12 psi and 0.08 psi. The atom% of copper and oxygen were measured using EDX and their existence were later confirmed by XRD, essentially indicated by 40% an 60% of copper and oxygen contents, respectively

Synthesis and analysis of silicon nanowires grown on Si (111) substrate at different silane gas flow rate

Silicon nanowires were grown on Si (111) substrates by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). The nanowires were grouted at 450 °C and 21 watt RF power. Pure silane (99.9995%) and gold colloid were used as precursor and catalyst respectively for growth of wires. The nanowires were investigated using scanning electron microscopy (SEM). Their crystallity and compositions were studied using X-ray diffraction method and energy dispersive X-ray (EDX) spectroscopy. The growth of Si nanowires is controlled by conventional vapor- liquid-solid (VLS) mechanism. The results show ed that there were gold particle on the top of wires. The silane flow rates does effect the quantity of Si nanowire. The Si nanowires length changes from 350 nm to 5.5 μm for Si flow rate of 5 to 20 sccm, respectively. XRD and EDX results revealed that the nanowires composed of mainly Si with small percent of Au and oxygen

Ultra-sharp pointed tip Si nanowires produced by very high frequency plasma enhanced chemical vapor deposition via VLS mechanism

Needle-like silicon nanowires have been grown using gold colloid as the catalyst and silane (SiH4) as the precursor by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). Si nanowires produced by this method were unique with sharpness below 3 nm. High resolution transmission electron microscopy (HRTEM) and X-ray diffraction technique (XRD) confirmed the single crystalline growth of the Si nanowires with (111) crystalline structure. Raman spectroscopy also has revealed the presence of crystalline Si in the grown Si nanowire body. In this research, presence of a gold nanoparticle on tip of the nanowires proved vapor–liquid–solid growth mechanism

The formation of nanoscale clusters-nanofilms/quantum dots predicted using a capillary model of nucleation

This paper describes the theoretical and simulation studies of both homogenous and heterogeneous nucleation, the phenomena that refers to the formation of stable nuclei prior to the growth of nanoclusters including nanofilms and quantum dots. Essentially, a single cluster may contain few thousand of atoms, and interaction with the surface may be preceded via processes, such as diffusion, hopping, sorption and coalescences. These complicated physical-chemical phenomena require in-depth theoretical understanding on how the various interacting quantities can be formulated and then resolved using specific mathematical approximation. In the case of a capillary model for heterogeneous nucleation, the nuclei are assumed to be in spherical shapes, which increase in both energies and diameters, and finally reach their critical points and settled to oval shapes prior to dome-like wetting on the substrate, essentially just like water droplet resting on a surface. The net change of energy, ∆G for the formation of cluster is found to be the functions of nucleus volume, surface area of atomic-nucleus interface, surface area of nucleus-surface interface and energy lost at substrate-atomic interface. The results for ∆G, ∆G*, r* and Ω and their respective changes with r, s and T were obtained and experimentally verified using existing data

Excess silicon concentration dependence of the structural and optical properties of silicon nanocrystals embedded in silicon oxide matrix

Silicon (Si) nanocrystals embedded in Si oxide matrix have been formed by rapid thermal annealing of sub-stoichiometric Si oxide films (SiOx with x < 2). The SiOx films were deposited by co-sputtering of Si oxide and Si target using magnetron RF sputtering technique. The Si-to-SiO2 ratio was controlled by varying the number of Si chips being placed on the pure SiO2 target during sputtering. Rapid thermal anneal in nitrogen gas at 1100°C lead to the decomposition of SiOx into Si nanocrystals and SiO2. The structural (size of nanocrystals) and optical properties (absorption and luminescence) of Si nanocrystals embedded in oxide matrix, were found, strongly depend on the initial excess Si concentration in SiOx films