Kamarulazizi Ibrahim

Optical and Structural Properties of Thermally Evaporated Zinc Oxide Thin Films on Polyethylene Terephthalate Substrates

Zinc oxide thin films of different thicknesses ranging from 100 to 300 nm were prepared on polyethylene terephthalate substrates with thermal evaporation in a vacuum of approximately Torr. X-ray diffraction patterns confirm the proper phase formation of the material. From atomic force microscopy (AFM) images, it was found that the root mean square roughness of the film surface increased as the film thickness increased. The optical properties of ZnO on PET substrates were determined through the optical transmission method using an ultraviolet-visible spectrophotometer. The optical band gap values of ZnO thin films slightly decreased as the film thickness increased.

Effect of sulfurization time on the properties of copper zinc tin sulfide thin films grown by electrochemical deposition.

We report growth of quaternary Cu2 ZnSnS4 (CZTS) thin films prepared by the electrochemical deposition from salt precursors containing Cu (II), Zn (II) and Sn (IV) metals. The influence of different sulfurization times t (t = 75, 90, 105, and 120 min) on the structural, compositional, morphological, and optical properties, as well as on the electrical properties is studied. The films sulfurized 2 hours showed a prominent kesterite phase with a nearly stoichiometric composition. Samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and Raman and UV-VIS-NIR spectrometer at different stages of work. X-ray diffraction and Raman spectroscopy analyses confirmed the formation of phase-pure CZTS films. (FESEM) shows that compact and dense morphology and enhanced photo-sensitivity. STEM - EDS elemental map of CZTS cross-section confirms homogeneous distribution. From optical study, energy gap was enlarged with a changed sulfurization times in the range of 1.37–1.47 eV.

The effect of porosity on the properties of silicon solar cell

Purpose – The purpose of this paper is to describe how fabricate solar cell based‐on porous silicon (PS) prepared by electrochemical etching process is fabricated and the effect of porosity layer on the solar cell performance is investigated.Design/methodology/approach – The techniques used include SiO2 thermal oxidation, ZnO/TiO2 sputtering deposition and PS prepared by electrochemical etching. Surface morphology and structural properties of porous Si were characterized by using scanning electron microscopy. Photoluminescence and Raman spectroscopy measurements were also performed at room temperature. Current‐voltage measurements of the fabricated solar cell were taken under 80 mW/cm2 illumination conditions. Optical reflectance was obtained by using optical reflectometer (Filmetrics‐F20).Findings – Pore diameter and microstructure are dependent on anodization condition such as HF: ethanol concentration, duration time, temperature, and current density. On other hand, a much more homogeneous and uniform d...

Computer simulation of collection efficiency of a-Si : H tandem solar cells interconnected by transparent conductive oxide

Abstract In tandem solar cells, the interconnection between the cells is one of the factors limiting the performance of the photovoltaic device. For high performance, the interconnection must have good ohmic contact as well as good utilization of solar radiation to the bottom cells. Thin film of transparent conductive oxide with high conductivity and optical transparency is useful for this interconnection. In this paper, we made computer simulation of reflectance, transmittance and absorbance as a function of the wavelength of incident photons in single cell as well as two junction tandem solar cells. The collection efficiency was calculated for different thickness of transparent conductive oxide (TCO) TiO2 interposed as interconnection between the two cells.

Investigation of CIGS Solar Cells on Polyethylene Terephthalate Substrates

CIGS nanoparticles ink with composition of Cu (Ga0.3 In0.7) Se2 was prepared by using dissolved copper, indium, gallium acetylacetonate, and Se powder in oleylamine using hot injection methods. The structural properties of the CIGS films deposited on the polyethylene terephthalate (PET) substrate were studied using an X-ray diffraction technique. The as-deposited CIGS films were found to be a chalcopyrite-type structure with crystallite grain size of about 43.8 nm. An optical study shows that the band-gap energy of the CIGS film is 1.25 eV. The flexible CIGS solar cell on a PET substrate with the best conversion efficiency of 4.21% is demonstrated.

PROPERTIES OF AMORPHOUS GAN GROWN ON SILICON

The success of crystalline GaN as an optical and electronic material has motivated an enormous effort to explore all aspects of the material. Little is known and reported about the amorphous phase of this semiconducting wide band gap material. In this paper, we report on the properties of amorphous GaN (a-GaN) grown on p-Si at 443K using electron cyclotron resonance (ECR) plasma-assisted metalorganic chemical vapor deposition (MOCVD). Silicon is a potential alternative to sapphire due to its high quality and readily available as a large diameter and low cost substrates. The film was analyzed by a variety of methods, including scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray diffraction (XRD). The current-voltage characteristics of a-GaN/Si heterojunction were measured from room temperature to 363K. Rectification behavior and photovoltaic effect were observed for this anisotype heterojunction. The electrical characteristics of Ni Schottky barriers on a-GaN were also investigated.

Development with a difference: neo-disaster risk management for sustainable development

Sustainable development (SD) or sustainability is the imperative of the 21st century. Protecting our planet, lifting people out of poverty and advancing economic growth are interconnected aspects of the same principle – sustainability. Global change research and global environmental policy summits have repeatedly asserted that the current developmental paradigm that puts considerable pressure on natural resources, resulting in environmental degradation, change climate and widening of the gap between the poor and rich further, is simply not sustainable. While developed countries will continue efforts to sustain their living standards and maintain economic growth, developing countries are on a fast track to become ‘developed’. Is there a paradox in the development trajectories that the two groups have been following in that they are inherently unsustainable? It depends. Either we contradict the principles and practices of SD or now we have a unique opportunity to embrace an altogether new course of action to realize the dreams of our generation and those who will follow us, traversing the less travelled pathway of sustainability. This is what we dub as development with a difference, a big difference! While many idealize SD, we propose actually to practice it. While skeptics question the validity of the multiple risk-based scenarios developed in scientific assessments such as Intergovernmental Panel on Climate Change (IPCC), Millennium Declaration and United Nations mediated global sustainability summits, we could pursue a new way of building resilience to avoid undesired outcomes in the future through reducing current risks posed by human actions that are changing significantly Earth and its environment. We could define risk more inclusively to cover both ‘rapid onset–high impact’ events such as floods and heat waves, and ‘slow onset–high impact’ events such as climate change and poverty, acknowledging that most of the present-day sustainability challenges belong to the latter category at this stage. The need for a set of sustainable development goals (SDGs) as highlighted in the Rioþ20 outcome, the ‘future we want’, is urgent to pursue through focused and coherent action to address sustainability challenges. A recent article (Griggs et al. 2013) proposed six such SDGs – thriving lives and livelihoods, sustainable food

Investigation on Molybdenum Thin Films Deposited by DC-Sputtering on Polyethylene Terephthalate Substrate

Molybdenum (Mo) films were prepared by DC sputtering on a polyethylene terephthalate (PET) substrate with different thicknesses. The molybdenum finds use in a very broad spectrum of applications in widely different forms. The obtained results of thin films of molybdenum deposited on PET are characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD) and (EDX). It was found that the thickness increases with the time of deposition and reduces the resistivity and sheet resistance. The lowest resistivity value we found for the Mo films was 1.3 × 10−5 Ω · cm at thickness (210 nm).

Simulation of Two-Dimensional 50 nm Vertical Metal Oxide Semiconductor Field-Effect Transistor Incorporating a Dielectric Pocket

A vertical metal oxide semiconductor field-effect transistor (VMOST) incorporating a dielectric pocket (DP) with epitaxial growth has been presented using two-dimensional simulation tools. A comparison between the non-DP VMOST and DP-VMOST was performed. It was shown that DP-VMOST had a better output than non-DP VMOST. The DP-VMOST with a body doping concentration of 2 ×1018 cm-3 and a spacing between the pocket and the gate oxide, WC, of 5 nm resulted in a threshold voltage of 0.35 V, an off-state leakage current of 1.31 ×10-8 A/µm, a subthreshold slope of 76.2 mV, and a drain current of 1069.77 µA/µm. For non-DP VMOST, the results showed a lower threshold voltage and a higher off-state leakage current. The dielectric pocket allowed the suppression of short-channel effects and punchthrough drain to the body. A comparison of the simulation results with experimental results by other researchers has also been performed with ISE simulation software.

Structural and surface analysis of AlInN thin films synthesized by elemental stacks annealing

This paper presents the synthesis of AlInN thin films on Si (100) substrates using elemental stacks annealing (ESA) process. Single stack InN films were grown on Si (100) substrates by reactive radiofrequency (RF) magnetron sputtering using pure indium target in Ar–N2 environment and then an Al stack layer was deposited on the InN films by direct current (dc) sputtering of pure aluminum target in Ar atmosphere at room temperature. Annealing of the deposited films was carried out at 400 °C for 2, 4 and 6 h in a tube furnace under N2 atmosphere. X-ray diffraction (XRD) results reveal that annealing for 2 h does not produce a well-defined AlInN film, however, with the increase of annealing time to 4 h and to 6 h, (002) and (103) oriented highly crystalline AlInN films are formed with wurtzite structures. Field emission scanning electron microscopy (FESEM) results indicate a uniform film structure with grains growth by increasing the annealing time. Energy dispersive x-ray (EDX) analysis shows higher Al (atomic %) in the film as compared to In and N. Atomic force microscopy (AFM) results show a decrease in the surface roughness with increase of the annealing time.