Mmantsae Diale

Mmantsae Diale
University of Pretoria | UP · Department of Physics

PhD

About

107
Publications
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883
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Publications

Publications (107)
Preprint
Full-text available
A comparative study was conducted between methylammonium lead tri-iodide (MAPbI3)/zinc oxide (ZnO) nanorods (NRs) on fluorine-doped tin oxide (FTO) and indium tin oxide (ITO) substrates for the first time. X-ray diffraction micrographs confirmed pure tetragonal MAPbI3 phase with I4/mcm space group and highly textured wurtzite hexagonal ZnO structur...
Preprint
Full-text available
We have studied the crystal growth and degradation of sequential physical vapor deposited thin methylammonium lead tri-bromide (MAPbBr 3) perovskite films on glass, aluminum (Al), tin (Sn), silver (Ag), gold-zinc (Au-Zn), and gold (Au) substrates. The structural and morphological properties of the MAPbBr 3 were observed as-deposited and 60 days lat...
Article
Full-text available
First-principles calculations based on density functional theory (DFT) have been carried out to study the energetic stability and electronic properties of bimetallic doped {0001} α-Fe2O3 photoanode surface with (Zn, Ti) and (Zn, Zr) pairs for enhanced PEC water splitting. The doped systems showed negative formation energies under both O-rich and Fe...
Presentation
Full-text available
Convener: Martina Della Togna Purpose and relevance of study This chapter investigates the capacity and effectiveness of government's communications strategy as the country went through the various stages of lockdown under the Covid-19 pandemic. The study probes the working relationship between government communications (at national, provincial, di...
Article
Full-text available
Lead iodide (PbI 2 )-rich methylammonium lead bromide-iodide (MAPb(I 1– x Br x ) 3 ) thin-films were prepared by sequential physical vapor deposition of methylammonium lead tri-bromide (MAPbBr 3 ) on methylammonium lead tri-iodide (MAPbI 3 ) bottom layer. The structural, optical, morphological, and electrical properties of the thin-films were studi...
Article
Full-text available
In this research, three different sets of hematite (α-Fe 2 O 3 ) films of various thicknesses were prepared using dip, spin, and combined dip/spin coating methods. α-Fe 2 O 3 films of 450–500, 740–800 and 920–980 ± 30 nm thicknesses were prepared using each of the coating methods, and their photoelectrochemical (PEC) behaviour was investigated. Dip...
Article
Full-text available
We have studied the crystal growth and degradation of sequential physical vapor deposited thin methylammonium lead tri-bromide (MAPbBr3) perovskite films on glass, aluminum (Al), tin (Sn), silver (Ag), gold-zinc (Au-Zn), and gold (Au) substrates. The structural and morphological properties of the MAPbBr3 were observed as-deposited and 60 days later...
Article
In this research, nanostructured heterojunction of hematite (α-Fe2O3) and porous copper (II) oxide (CuO) composites represented as α-Fe2O3/CuO was prepared and used as photoanode for photoelectrochemical (PEC) water splitting. X-ray diffraction (XRD) and Raman spectroscopy studies confirmed the high purity of α-Fe2O3/CuO heterostructures produced....
Article
Full-text available
Transitional metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS2) have found application in photovoltaic cells as a charge transporting layer due to their high carrier mobility, chemical stability, and flexibility. In this research, a photovoltaic device was fabricated consisting of copper phthalocyanine (CuPc) as the active layer, exf...
Article
Elemental doping of hematite has been widely performed to improve its mobility, electrical conductivity as well as to suppress electron–hole recombination in photoelectrochemical applications. When hematite is doped with high titanium concentrations, above 5%, pseudobrookite layers may be formed as overlayers leading to improved photocurrent while...
Article
Full-text available
Indium tin oxide (ITO) thin films were rapid thermal annealed (RTA) for 5 min at a temperature of 550 °C in different exposures of nitrogen gas. Effects of these exposures on the structural, morphological, electrical, and optical properties of these films were investigated using X-ray diffraction, atomic force microscopy and field emission-scanning...
Article
Methylammonium lead tri-iodide perovskite (MAPbI3) thin film for solar cells, chemical formula CH3NH3PbI3, is synthesized in situ via sequential thermal vapor deposition of lead (II)iodide (PbI2) and methylammonium iodide (MAI) single layers. The structural, morphological, optical, and electrical attributes are highly dependent on annealing time an...
Article
Hematite nanoparticles were synthesized using chemical spray pyrolysis. Precursor concentrations of 30, 40, and 50 mM, deposition temperatures of 250, 340, and 400°C were used. X-ray diffraction measurements confirmed the purity of hematite with no other phases of iron oxide. The (104) and (110) diffraction peaks associated with corundum structure...
Article
Multi-layered hematite (α-Fe2O3) films were prepared on fluorine-doped tin oxide (FTO) using the dip coating method. The first three layers of the films were annealed at 500 °C and fourth layers at 500, 600, 700, 750 and 800 °C respectively, and their photoelectrochemical (PEC) performance was investigated. Films annealed at 750 °C recorded the bes...
Conference Paper
Full-text available
Methylammonium lead tri-bromide (MAPbBr3) thin films were grown by sequential physical vapor deposition of lead(II)bromide and methylammonium bromide (MABr). X-ray diffractograms confirmed the cubic MAPbBr3 structure with Pm¯3 m space group. UV-Vis spectra revealed a red shift in absorption onset from 540 to 550 nm as the thickness of MABr increase...
Book
Full-text available
This book captures the 10-year science and technology collaboration between Switzerland and South Africa, and the impact of the 61 projects that emanated therefrom. It is proudly produced by the Embassy of Switzerland, in collaboration with the Department of Science and Innovation. A PDF version is available at www.eda.admin.ch/pretoria Photograp...
Article
We report on the properties of hematite thin films prepared by spray pyrolysis on fluorine-doped tin oxide (FTO)-coated glass substrates and investigated the effect of the spray volume, tetraethoxysilicate treatment of the hematite, and post-annealing at 500 °C for 2 h with 10 °C/min ramping. Raman spectroscopy confirmed the characteristic Raman sp...
Article
Nanostructured hematite films were synthesized using spray pyrolysis and chemical bath deposition. X-ray diffraction measurements revealed sharp diffraction peaks of (012), (104) and (110), describing corundum hexagonal structure of hematite. Raman spectroscopy confirmed polycrystalline hematite symmetry with two Eg and five A1g vibrational phonon...
Article
Full-text available
Methylammonium lead tri-bromide (MAPbBr3) thin films were grown by sequential physical vapor deposition of lead(II)bromide and methylammonium bromide (MABr). X-ray diffractograms confirmed the cubic MAPbBr3 structure with Pm¯3 m space group. UV-Vis spectra revealed a red shift in absorption onset from 540 to 550 nm as the thickness of MABr increase...
Article
Hematite (α-Fe2O3) thin films were deposited by dip, spin and combined coating techniques on fluorine-doped tin oxide (FTO)/glass substrates. Structural properties observed from X-ray Diffraction (XRD) and Raman spectra analysis suggest better crystallinity for films prepared by dip and combined coating techniques as compared to the ones prepared b...
Article
Full-text available
First-principles calculations of Zinc (Zn) doped {0001} and {011‾2} hematite surfaces for improved photoelectrochemical water splitting have been studied. The single Zn-doped systems were found to be energetically favourable (negative formation energies) and the stability increased with increasing concentration of Zn atoms. Our results show that ev...
Article
Plasmonic coupling of metallic nanoparticles and adjacent pigments can dramatically increase the brightness of the pigments due to the enhanced local electric field. Here, we demonstrate that the fluorescence brightness of a single plant light-harvesting complex (LHCII) can be significantly enhanced when coupled to a gold nanorod (AuNR). The AuNRs...
Article
Hematite, a common type of iron oxide, is a promising material for solar technologies, due to its small bandgap that allows for solar radiation absorption in the visible region, low toxicity in aqueous solutions, easy synthesis and natural abundance. However, fast electron–hole recombination has been hampering full applicability of hematite in sola...
Conference Paper
Full-text available
Physics still has a long way to go in addressing acceleration of women to higher ranks of research and leadership. The general trend shows that the personal choices affect the acceleration of women to the top in both research and academia. My reference is on women who already obtained PhDs and are in positions in South Africa. Women in academia has...
Preprint
Plasmonic coupling of metallic nanoparticles and adjacent pigments can dramatically increase the brightness of the pigments due to the enhanced local electric field. Here, we demonstrate that the fluorescence brightness of a single plant light-harvesting complex (LHCII) can be significantly enhanced when coupled to single gold nanorods (AuNRs). The...
Article
Ni/4H-SiC Schottky barrier diodes have been irradiated by 5.4-MeV helium ions at cryogenic temperatures and their electrical characteristics investigated. Only the prominent native defects (E0.11, E0.16, and E0.65) were observed before and after low-temperature irradiation at 50 K, with a baseline on the spectrum observed starting at 190 K. Low-tem...
Article
We have used confocal Raman spectroscopy, atomic force microscopy (AFM), Binary collision approximations and Deep level transient spectroscopy (DLTS) to study the defects introduced in n-type 4H-SiC by 167 MeV Xe²⁶⁺ ions (swift heavy ions (SHIs)). Moderately doped epitaxial layers were irradiated with SHIs to a fluence of 5 × 10¹¹ cm⁻² at room temp...
Article
Full-text available
We compare the structural, morphological and electrical properties of two variants of the ITO/ZnO/(Formula presented.)/PDOT:PSS/Au thin film perovskite device made using two structurally different forms of lead iodide. The first device was based on a commercially sourced, common 12R polytype. The second device uses the rarer 6R polytype, as recentl...
Article
Defects introduced by the solid state reactions between tungsten and silicon carbide have been studied using deep level transient spectroscopy (DLTS) and Laplace DLTS. W/4H-SiC Schottky barrier diodes were isochronally annealed in the 100–1100 °C temperature range. Phase composition transitions and the associated evolution in the surface morphology...
Article
We have characterised the deep level defects present before and after annealing the proton-irradiated Ni/nitrogen-doped 4H-SiC Schottky barrier diodes (SBDs) using deep level transient spectroscopy. The bombardment of the sample was carried out at a fluence of 1.0 × 10¹² cm⁻². The quality of the Ni/4H-SiC SBDs was evaluated before and after proton...
Article
We have studied the defects introduced in n-type 4H-SiC during sputter deposition of tungsten using deep-level transient spectroscopy (DLTS). Current-voltage and capacitance-voltage measurements showed a deterioration of diode thermionic emission characteristics due to the sputter deposition. Two electrically active defects E0.29 and E0.69 were int...
Article
Full-text available
Density Functional Theory (DFT) calculations study of Cu doped {0001} and {01-12} surfaces of hematite for enhanced water splitting have been carried out. The doping was restricted to planes in the vicinity of the surface, specifically from the top most layers to the third inner layer of Fe atoms. Thermodynamic stabilities were evaluated based on s...
Article
Full-text available
Jan van der Merwe held numerous academic and research positions in South Africa in addition to various appointments overseas. His last appointment as Professor emeritus was with University of Pretoria. Prof Jan H van der Merwe passed away on Sunday, February 28, 2016, on his 94th birthday. At this old age he still frequently attended seminars. This...
Chapter
Full-text available
It is widely recognised that sustainable energy at low cost would contribute to poverty alleviation and arrest climate change. Fossil fuels for energy contribute directly to global warming by adding carbon dioxide to the atmosphere, as well as to deforestation and climate change. The growing world population adds further urgency to the need to deve...
Article
Nanostructured zinc oxide synthesized using an easy and low temperature chemical bath deposition method are among the most promising low cost semiconducting nanostructures investigated for a variety of applications. We successfully report the effects of ammonia solution in the growth of ZnO nanorods at a temperature of 60 °C. Successive addition of...
Article
We report the preparation, characterization, and property evaluation of molecularly imprinted polyaniline nanoparticles that can be used for the selective recognition of aldrin. The molecularly imprinted polyaniline nanoparticles were prepared by inverted emulsion polymerization using aldrin as a template and aniline as a functional monomer. The pr...
Article
Full-text available
We present a measurement of the energies and capture cross-sections of defect states in methylammonium lead bromide (MAPbBr3) single crystals. Using Laplace current deep level transient spectroscopy (I-DLTS), two prominent defects were observed with energies 0.17 eV and 0.20 eV from the band edges, and further I-DLTS measurements confirmed that the...
Article
Full-text available
Hematite is a widely investigated material for applications in solar water oxidation due primarily to its small bandgap. However, full realization of the material continues to be hampered by fast electron-hole recombination rates among other weaknesses such as low hole mobility, short hole diffusion length and low conductivity. To address the probl...
Article
We report on effect of surface morphology on the optical and electrical properties of chemical bath deposited Zinc oxide (ZnO) nanostructures. ZnO nanostructures were deposited on the seeded conducting indium doped tin oxide substrate positioned in three different directions in the growth solution. Field emission scanning electron microscopy was us...
Article
Using x-ray spectroscopy to analyze a photoelectrochemical cell during water oxidation and hydrogen formation sheds light on the physics and chemistry of photoelectrodes. http://spie.org/newsroom/6793-hydrogen-production-with-holes-what-we-learn-from-operando-studies?highlight=x2358&ArticleID=x126181
Article
The deep level transient spectroscopy (DLTS) technique was used to investigate the effects of electron beam exposure (EBE) on n-GaN. A defect with activation energy of 0.12 eV and capture cross section of 8.0×10–16 cm² was induced by the exposure. The defect was similar to defects induced by other irradiation techniques such as proton, electron, an...
Article
In this study n-type GaN was subjected to irradiation. This irradiation was performed by Xe⁺²⁶ of 167 MeV to a fluence of 10¹⁰ cm⁻² at room temperature. Irradiation resulted in an increase in the reverse current by about 10 orders of magnitude. This has been explained by the generation/recombination centers formed during irradiation. Using the deep...
Article
Nanostructured hematite thin films prepared by dip coating technique were investigated for their photoelectrochemical activity for generation of hydrogen from water splitting. Structural, morphological and optical analyses of the doped/undoped films were performed by X-ray diffraction, high resolution field emission-scanning electron microscopy, UV...
Article
Deep level transient spectroscopy (DLTS) was used to characterise Cs implanted GaN grown by hydride vapour phase epitaxy (HVPE). This implantation was done at room temperature using energy of 360 keV to a fluence of 10–11 cm⁻². A defect with activation energy of 0.19 eV below the conduction band and an apparent capture cross section of 1.1 × 10–15...
Article
We have used deep level transient spectroscopy (DLTS) and Laplace DLTS (L-DLTS) to characterize the electrically active point defects introduced in n-type gallium arsenide by electron beam exposure prior to Schottky metallization. The GaAs crystals were exposed to incident electrons at sub-threshold energies which are deemed low and insufficient to...
Article
The effect of high energy electron (HEE) irradiation on nickel Schottky contacts fabricated on lowly-doped n-type 4H-SiC was investigated by deep level transient spectroscopy (DLTS) and high resolution Laplace-DLTS. The Schottky contacts were deposited by resistive evaporation of nickel and were observed to be of good rectification quality from cur...
Book
https://www.cambridge.org/core/journals/journal-of-materials-research/call-for-papers-jmr-focus-issue-in-honor-of-jan-van-der-merwe Fabrication of well-ordered semiconductor thin lms by precise deposition control of atomic layers is known to semiconductor engineers and device physicists as epitaxy and Frank-van der Merwe growth. Understanding and...
Article
Undoped and copper doped zinc oxide (ZnO) nanorods have been synthesized by a simple chemical bath deposition (CBD) method at a temperature of 90 °C. Structural, morphological, optical and electrical properties of the synthesized ZnO nanorods were found to be dependent on the Cu doping percentage. X-ray diffraction (XRD) patterns revealed strong di...
Conference Paper
Full-text available
Large scale facilities pose a potential risk and threat because with one isolated attack large damage can be obtained, for example in a city, potentially with a large number of human casualties. We present a solar energy harvesting strategy which allows for the generation of fuel for housing and mobility in a decentralised form. A city or a part of...
Article
Influence of anodization time on the surface modifications on α-Fe2O3 photoanode upon anodization – ERRATUM - Volume 31 Issue 11 - Kelebogile Maabong, Yelin Hu, Artur Braun, Augusto G.J. Machatine, Mmantsae Diale
Article
Full-text available
The effect of high energy electron irradiation on Ni/4H-SiC Schottky barrier diodes was evaluated by current–voltage (I–V) and capacitance–voltage (C–V) measurements at room temperature. Electron irradiation was achieved by using a radioactive strontium source with peak emission energy of 2.3 MeV. Irradiation was performed in fluence steps of 4.9 ×...
Article
Defects induced by electron irradiation in n-GaAs have been studied using deep level transient spectroscopy(DLTS) and Laplace DLTS (L-DLTS). The E0.83 (EL2) is the only defect observed prior to irradiation. Ru/n-GaAs Schottky diodes were irradiated with high energy electrons from a Sr-90 radionuclide up to a fluence of 2.45 × 1013 cm−2. The promine...
Article
Full-text available
From August 17–19, 2015, the Swiss Federal Laboratories for Materials Science and Technology (Empa) and the Swiss Light Source (SLS) at the Paul Scherrer Institut (PSI) held an international workshop on photoelectrochemistry, catalysis, and X-ray spectroscopy at Empa in Dübendorf, Switzerland. Thirty scientists from Austria, China, Germany, Italy,...
Article
Full-text available
In searching for a suitable semiconductor material for hydrogen production via photoelectrochemical water splitting, α-Fe2O3 received significant attention as a promising photoanode due to its band gap (∼2.1 eV), good stability, low cost, and natural occurrence. α-Fe2O3 thin films were prepared by economic and facile dip coating method and subseque...
Conference Paper
Full-text available
Efforts by the group Women in Physics in South Africa are described, ranging from informal networking in departmental lunches, to programs to increase the visibility and entrepreneurial skills of women physicists, to outreach and community engagement. The current president of the South African Institute of Physics is female, and the arrival of the...
Poster
Full-text available
Photovoltaics is a mature technology for the conversion of sunshine into electric energy. But less than 20% of the world energy use is electric. The other >80% world energy use is in all sorts of fuels: fossil fuels, nuclear fuels, biomass, … . We make “solar fuels” by combining photovoltaics, electrocatalysis and photoelectrochemistry: www.sun2fue...
Article
We report on the analysis of current voltage (I–V) measurements performed on Pd/ZnO Schottky barrier diodes (SBDs) in the 80–320 K temperature range. Assuming thermionic emission (TE) theory, the forward bias I–V characteristics were analysed to extract Pd/ZnO Schottky diode parameters. Comparing Cheung’s method in the extraction of the series resi...
Article
Full-text available
In this study, the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Au/n-GaAs Schottky diodes have been measured over a wide temperature range, 80-480K. The diodes were rectifying throughout the range and showed good thermal stability. Room temperature values for the ideality factor, I-V barrier height and C-V barrier height w...