Effects of Substrate Radial-Position Relative to the Sputter-Gun Axis on the Electrical, Optical and Structural Properties of ZnO Thin Films Deposited by Reactive Direct Current Magnetron Sputtering

ZnO thin films were deposited using reactive direct current (dc) magnetron sputtering on glass substrates placed at seven variable radial positions (-1, 0, 1, 2, 3, 4 and 5 cm)  relative to the sputter-gun (target) axis. A pure zinc target was used and sputtering carried out in argon and oxygen atmosphere with flow rates of 50 sccm and 6 sccm, respectively. XRD characterization showed that, all films crystallized homogeneously in the wurtzite phase with a strong (002) and a weak (004) orientations. Film crystallinity was very low at substrate positions located less than or equal to 1 cm from the target axis but rapidly improved as substrate position increased beyond 1 cm. Film thickness decreased steadily (from 320 to 160 nm) with increase in substrate position from 1 to 5 cm. Film resistivity was much higher (over ~104 Ω cm) at substrate positions located less than 2 cm from the target axis and rapidly decreased with increase in substrate position reaching the order ~10– 3 Ω cm at 3 cm and leveled out. Optical transmittance was homogeneous with 86% in the wavelength range 380 – 2500 nm. Band gap increased dramatically (from 3.15 eV to 3.28 eV) with increase in substrate position.Keywords: Magnetron sputtering, substrate radial position, properties of ZnO thin films

Compositional and Thickness Effects on the Optical Properties of Zinc–Doped Selenium–Antimony Thin Films

Chalcogenide system of antimony (Sb)-selenium (Se)-zinc (Zn) system is a promising semiconductor for phase change memory devices due to its thermal stability and low power consumption. The study investigated the effect of film thickness and zinc content on the optical properties of thermally evaporated Sb10Se90-xZnx (x = 0, 5, 10 & 15 at. %) thin films. It was found that transmittance (T~ 85-40%) and optical band gap energy (Eopt ~ 1.60 eV – 1.22 eV) decreased but absorption coefficient (α~0.840–2.031 104 cm–1) increased with increase in zinc content. Furthermore, as the film thickness increased from 53 ± 5 nm to 286 ± 10 nm, transmittance decreased but band gap energy increased due to zinc defects and localized states in the Sb10Se90-xZnx system.Keywords: Selenium; phase change memory; localized state

First-principle investigation of structural, electronic and magnetic properties of Co2VIn and CoVIn Heusler compounds

Investigation of the structural, electronic and magnetic properties of full-Heusler Co2VIn as well as half-Heusler CoVIn Cobalt based Heusler compounds using density functional theory (DFT) leads to the general conclusion that Co2VIn and CoVIn are half-metallic materials with a gap at the Fermi level in the minority states and majority states respectively. A Hubbard-like Coulomb correlation term U has been included in the DFT (DFT+U) for the computation of the electronic and magnetic properties of the compounds. The structural properties have been calculated for the paramagnetic and ferromagnetic phases, and both Co2VIn and CoVIn are found to be stable in the ferromagnetic phase. The calculated magnetic moments are 2 μB and 0.9 μB per formula unit for Co2VIn and CoVIn respectively

First-principle investigation of structural, electronic and magnetic properties of Co2VIn and CoVIn Heusler compounds

Investigation of the structural, electronic and magnetic properties of full-Heusler Co2VIn as well as half-Heusler CoVIn Cobalt based Heusler compounds using density functional theory (DFT) leads to the general conclusion that Co2VIn and CoVIn are half-metallic materials with a gap at the Fermi level in the minority states and majority states respectively. A Hubbard-like Coulomb correlation term U has been included in the DFT (DFT+U) for the computation of the electronic and magnetic properties of the compounds. The structural properties have been calculated for the paramagnetic and ferromagnetic phases, and both Co2VIn and CoVIn are found to be stable in the ferromagnetic phase. The calculated magnetic moments are 2 μB and 0.9 μB per formula unit for Co2VIn and CoVIn respectively

Device Simulation of Sb2S3 Solar Cells by SCAPS-1D Software

Antimony sulphide (Sb2S3) has drawn research interest due to its promising properties for photovoltaic applications. The progress in developing highly efficient Sb2S3 solar cells has stimulated this study to a great extent. In this paper, we present the results of a simulation of solar cell processing parameters on the performance of the solar cell through theoretical analysis and device simulation using SCAPS software. The results of this simulation show that the solar cell performance can be enhanced to a great extent by adjusting the thickness, doping concentration and defect density of both the TiO2 buffer layer and Sb2S3 absorber layer and also the electron affinity of the TiO2 buffer layer. Optimized parameters were found to be: doping concentration of (1.0 X 1017CM3 for TiO2 and 3.0 X 1016 CM3 for Sb2S3), defect density of the Sb2S3 absorber at (1.0 X 1015.....3) and the electron affinity of the buffer layer at (4.26 eV). The results obtained were as follows: Voc of 750 mV, Jsc of 15.23 mA/cm2, FF of 73.55% and efficiency of 8.41%. These results show that Sb2S3 is a potential earth-abundant compound that can yield highly efficient solar cells

Teacher’s preparedness for implementing competency based curriculum in primary schools in Kiambu County, Kenya

Paper presented at the 5th Strathmore International Mathematics Conference (SIMC 2019), 12 - 16 August 2019, Strathmore University, Nairobi, KenyaThis article is based on a study that investigated teachers’ preparedness for implementing the competency-based curriculum in primary schools in Kiambu County, Kenya. The government of Kenya has rolled out the competency-based curriculum (CBC) amid concerns by education stakeholders regarding preparedness of teachers. CBC emphasizes the significance of developing skills, knowledge, and attitudes and applying them to real-life situation. The study measured teachers’ preparedness and readiness regarding teachers technological skills required for the implementation, and teachers perception regarding implementation of the competencybased curriculum. The study involved the use of a descriptive survey design. The research participants included 15 head teachers and 50 primary school teachers. Analysis of the data involved the use of descriptive statistics. Presentation involved the use of figures, frequency tables, and percentages. The study findings indicate that the primary school teachers are not prepared for implementing the competency-based curriculum in the early childhood education and lower primary education. It was evident that the teachers experienced challenges due to limited in-service training, inadequate parental support, inadequate information and communications technology skills, and a heavy workload. Based on the findings, it was recommended that the Ministry of Education need to organize additional in-service training workshops for primary school teachers to impart them with information and communications technology skills, subject content knowledge, and improve teachers’ perceptions regarding competency-based curriculum.Kenyatta University, Kenya

The effect of guanidinium tetrafluoroborate surface passivation on the stability of 2D-PEA2SnI4 perovskite thin films prepared by sequential physical vapor deposition

DATA AVAILABILITY : Data will be made available on request.Please read abstract in the article.Partnership for Skills in Applied Sciences, Engineering and Technology (PASET)-RSIF and South African Research Chair (SARChI).https://www.elsevier.com/locate/physbhj2024PhysicsSDG-09: Industry, innovation and infrastructur

Stability Investigation in the Optical Properties of Thermally Evaporated Ge5Se95-x Znx Thin Films

Selenium-based chalcogenides are useful in telecommunication devices like infrared optics and threshold switching devices. The investigated system of Ge5Se95-xZnx (0.0 ‰¤ x ‰¤ 4 at.%) has been prepared from high purity constituent elements. Thin films from the bulk material were deposited by vacuum thermal evaporation. Optical absorbance measurements have been performed on the as-deposited thin films using transmission spectra. The allowed optical transition was found to be indirect and the corresponding band gap energy determined. The variation of optical band gap energy with the average coordination number has also been investigated based on the chemical bonding between the constituents and the rigidity behaviour of the systems network

First principle study of ATiO 3 (A=Ti,Sr) materials for photovoltaic applications

DATA AVAILABILITY : The authors will provide the source files and data upon request.Please read abstract in the article.Open access funding provided by University of Pretoria. The Partnership for Skills in Applied Sciences, Engineering, and Technology (PASET)-Regional Scholarship Innovation Fund provided funding for this project (RSIF). The Center for High-Performance Computing, CHPC, Cape, is acknowledged by the authors as a source of HPC resources.https://link.springer.com/journal/894hj2024PhysicsNon