Papers by Keyword: Energy Band Gap

Abstract: An artificial algorithm using a machine learning approach could be used to determine the energy band gap, E_g which would simply the process of synthesizing ZnO properties. This paper proposes to develop machine learning models that can accurately predict the energy band gap of ZnO. This study used PSO-SVR model utilizing three kernel functions: linear, polynomial, and RBF. The PSO-SVR with RBF resulted in the lowest RMSE of 0.0395eV. This analysis also showed that the combination of lattice constant a and c, crystallite size, D and grain size of ZnO datasets had contributed to high accuracy of predicting E_g.

Abstract: Zinc oxide nanorods zinc oxide nanowire has been deposited on quartz employing a hydrothermal method. The ZnO nanoroad as a seed layer were prepared for the growth process using the drop-casting method. The zincoxide nanomaterials produced were characterized by UV–Visible spectrophotometers, x-ray diffraction, Scanning electron microscopy ,. The crystal structure was calculated from the XRD data and it was confirmed the growth of wurtzite crystalline crystal structures of ZnO NRs. The SEM images revealed high-density nanowires were grown via drop cast coated seed layer. The bandgap in the ZnO NRs film was found to be 3.28 eV. This result was confirmed the formation of ZnO nanostructure. The thermal and electrical properties of ZnO NRs were measured also and analyzed. The conductivity of the ZnO NRs film was modified with the addition of gold nanoparticles using the sputtering technique. These modified films were promising and give an optimized temperature sensor performance.

Abstract: Effect of defect - through observation of energy absorption Urbach, on deposition rate, energy band gap, and surface roughness of intrinsic thin film are investigated using Radio Frequency Plasma Enhance Chemical Vapor Deposition (RF-PECVD). Films are grown on ITO (Indium Tin Oxide) glass substrate. Analysis of energy band gap is conducted to determine changes in the structure of a thin film of a-Si:H. Energy band gap is important to determine the portion of the spectrum of sunlight that is absorbed solar cells. From the characterization using UV-Vis spectrometer and the Tauc’s plot method, the width of the resulting energy band gap is greater if the hydrogen dilution is increased. It can be shown that the increase of the hydrogen dilution, will increase the energy band gap, and the surface roughness of thin layers. Instead, the improvement of the hydrogen dilution decrease the rate of deposition and Urbach energy. It is estimated that with greater hydrogen dilution, an intrinsic thin film of a-Si:H is more conductive for more reduction in residual of band tail defects or dangling bond defects.

Abstract: We report on the growth of zinc oxide/polyaniline (ZnO/PANI) nanocomposites deposited on platinum (Pt)–coated glass substrate via chemical bath deposition and dip–casting technique is reported. Scanning electron micrographs of the nanocomposites revealed that etching of ZnO nanorods takes place during growth which turn into plate–like and distorted nanostructures. We found out that increasing the concentration of NH₄OH triggered increase in nanostructure diameter. The surface morphology of nanocomposites significantly changed as the molar concentration of NH₄OH precursor varies. Fast fourier transform infrared spectroscopy results showed the interaction of ZnO and PANI by observing the shift of peaks to the higher wavenumbers. The measured optical band gap of the nanocomposites are in good aggreement with the reported values. This result indicates that the grown ZnO/PANI nanocomposites is a good material for solar cell device.

Abstract: Fe-doped NiO nanoparticles was prepared by the co-precipitation method. The precipitation solution were used the concentration of FeSO₄ mixing NiCl₂ for 0.5 M. The precipitation process was used a magnetic stirrer of 1100 rpm, a temperature of 30-60 ^OC for 0.5 h and the dropping a NaOH of 0.5 M in the mixing solution. The precipitate product was dried at the temperature of 120 ^OC for 9 h and calcined in a furnace at the temperature of 400 ^OC for 4 h in air atmosphere. The powder product was analyzed a crystal structure by a x-rays diffractometer, calculated an energy band gap by UV-VIS spectrophotometer, measured a magnetic properties by a vibrating sample magnetometer and explained morphology by a scanning electron microscope. It was found that the crystal structure was shown face center cubic. The nanoparticles in the range of 30-100 nm was observed the morphology of the optimum product. However, the coercive, the magnetic moment and the energy band gap was found the optimum at the doping Fe of 8 wt% at the precipitation temperature of 40 ^OC.

Abstract: Antimony sulfide (Sb₂S₃) nanostructure was synthesized using a 600 W microwave irradiation technique. The precursors including Sb(CH₃CO₂)₃ and Na₂S₂O₃.5H₂O were dissolved into 50 mL ethylene glycol (EG) solution with containing 0 and 1 g of hydroxyethyl cellulose (HEC). Phase, morphology and optical properties of the as-synthesized products were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy and photoluminescence (PL). Energy band gap of Sb₂S₃ nanostructure exhibits the value of 1.90 and 2.06 eV for synthesizing condition with and without HEC containing, respectively.

Abstract: Conjugated polymers have been widely used for electronic purpose applications due to their numerous advantages. This has led many researches to pay their major attention in studying on characteristics of conjugated polymer thin films. The purpose of this study was to investigate the effect of undoped conjugated polymer thin films on their optical and electrical properties. Poly(3-thiophene acetic acid), Polypyrrole and Polythiophene thin film was fabricated on ITO glass substrate by using EIS. Film thickness, energy band gap and electrical conductivity of thin films were characterized by using profilometer, ultraviolet-visible spectrometer and four point probe method respectively. The thickness of each thin film varied between 50.534 nm to 97.03 nm. The result has shown that thicker film has lower energy band gap compared to the thinner one. However the electrical conductivity showed an opposite behavior.

Abstract: The purpose of this work is to search reduced graphene oxide (RGO) phase by identifying the molecular bonding, energy band gap and phase of old coconut shell. The characterization was performed by using FTIR, Uv-Vis and XRD spectroscopy. The heating temperature used in this work was 400°C and 600°C. Furthermore, the type of heating atmosphere used in this research covers nitrogen, ambient air with and without rinsing step. The XRD analysis shows that the RGO phase is formed by turbostatic structure which is a pile of random arrangement of parallel layers that make up the graphite structure with cliftonite phase at temperature 400°C and 600°C. In the inert nitrogen gas treatment, there are two impurity phases such as potassium chlorate (KClO₄) and sulfur (S₁₁). The molecular bondings of C=C, C-C, C-O, C=O, C-H and O-H appeared on the FTIR spectra of the samples were indentified. Analysis by using linear regression and absorbance edge methods was conducted to result in energy gap in the range from 0.14 to 0.67 eV, indicating that the produced samples are semiconducting materials.

Abstract: Tin Oxide (SnO₂) thin film is one of the important transparent conducting oxides (TCOs) due to its electrical and optical transparency in visible light spectrum. This study presents the best model in estimating optical properties of tin oxide thin film which is performed using the absorption coefficient of the film. The annealing temperature is at 473 K prepared by radio frequency sputtering technique. Twelve multiple regression (MR) models with interactions are generated from three independent variables (transmission spectra, energy band gap and the wavelength of light). They are developed from data sets of 50. The best model M8.0.0 is chosen from the 6 selected models based on the Eight Selection Criterion (8SC). Best model will have the majority criteria with the least value. Factors affect the absorption coefficient are found to be X₁ (transmission spectra), X₂ (energy band gap) and X₁X₂ (interaction between transmission spectra and energy band gap).

Abstract: . Achieving tunable optical properties of inorganic glasses via optimized doping of rare earth ions is ever-demanding in photonics. Control and inhibition of luminescence quenching, nonradiative decay and multi-phonon relaxation responsible of reduction of optical performance remains challenging. Doping/co-doping of different rare earth ions, variation of modifiers and embedding metallic nanoparticles (NPs) are thought as alternative routes to enhance optical response are still underway. We examine the influence of samarium ion concentrations on the optical properties of oxy-chlorite tellurite glasses of the form (70-x)TeO₂-15MgO-5Li₂O-10LiCl-xSm₂O₃ with 0.0 x 2.5 mol% prepared using melt-quenching method. The structural and optical characterizations are performed via X-ray diffraction (XRD), Ultraviolet-Visible (UV-Vis) absorption and photoluminescence (PL) spectroscopy. The glass density increased from 4.509 - 4.770 with the increase of Sm₂O₃ contents from 0.0 2.5 mol %. The XRD spectra confirm the amorphous nature of the glass. The absorption spectra exhibit nine prominent peaks corresponding to the transitions from the ground to excited states and the PL spectra reveal four peaks. The optical energy band gap for direct and indirect transitions are increased and Urbach energy decreased from 3.448 - 3.497, 3.165 - 3.232 and 0.217 - 0.175, respectively with the increase of Sm³⁺ ion concentrations. Furthermore, the significant enhancement in UV-Vis and PL response display the strong influence of samarium ion on optical and structural properties. The mechanism responsible for enhanced optical properties are analyzed and discussed. The results suggest that our careful experimental studies may contribute towards the development of tellurite glass based solid state lasers.