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Polarization induced degenerate $n$-type doping with electron concentrations up to $\sim$10$^{20}$\,cm$^{-3}$ is achieved in graded Al$_{x}$Ga$_{1-x}$N layers ($x$: 0\%$\rightarrow$37\%) grown on unintentionally doped and on $n$-doped…
Large area epitaxy of two-dimensional (2D) layered materials with high material quality is a crucial step in realizing novel device applications based on 2D materials. In this work, we report high-quality, crystalline, large-area gallium…
Precise control of the conductivity of semiconductors through doping has enabled the creation of advanced electronic devices, similarly, the ability to control the conductivity in oxides can enable novel advanced electronic and…
The nanoscale resistive switching characteristics of gallium phosphide (GaP) thin films directly grown on Si are investigated as a function of incident light. Firstly, as-grown GaP films show a high RON/ROFF (~10^4), shown to arise from the…
As an ultrawide bandgap semiconductor, beta-Ga2O3 has been attractive for its strong tolerance to irradiation damage and high n-type conductivity through ion implantation. Homoepitaxial (010) \b{eta}-Ga2O3 films grown by MOCVD were…
In the present Ph.D. Thesis we report an experimental investigation on the effects of gamma- and beta-ray irradiation and of subsequent thermal treatment on many types of a-SiO2 materials, differing in the production methods, OH- and…
An extensive theoretical study is performed for wide bandgap crystalline oxides and nitrides, namely, SiO_{2}, GeO_{2}, Al_{2}O_{3}, Si_{3}N_{4}, and Ge_{3}N_{4}. Their important polymorphs are considered which are for SiO_{2}:…
The inherent existence of multi phases in iron oxide nanostructures highlights the significance of them being investigated deliberately to understand and possibly control the phases. Here, the effects of annealing at 250 0C with a variable…
We present a study on the influence of strain-relieving InAlAs buffer layers on metamorphic InAs/InGaAs quantum wells grown by molecular beam epitaxy on GaAs. Residual strain in the buffer layer, the InGaAs barrier and the InAs wells were…
The electronic structure of the corundum-type transition-metal oxides V2O3 and Ti2O3 is studied by means of the augmented spherical wave method, based on density-functional theory and the local density approximation. Comparing the results…
Controlling the optical properties of rare-earth ions in wide-bandgap semiconductors remains a major challenge in the development of next-generation photonic materials. Here, we show that external hydrostatic pressure modulates the…
Density functional perturbation theory calculations of alpha-quartz using extended norm conserving pseudopotentials have been used to study the elastic properties and phonon dispersion relations along various high symmetry directions as a…
The creation of atomically thin layers of non-exfoliable materials remains a crucial challenge, requiring the development of innovative techniques. Here, confinement epitaxy is exploited to realize two-dimensional gallium via intercalation…
Potential structural modifications of graphene exposed to gaseous tritium are important for membrane-based hydrogen isotope separation. Such modifications cannot be explained by electron irradiation alone. Instead, tritiation, caused by the…
Ionic crystals terminated at oppositely charged polar surfaces are inherently unstable and expected to undergo surface reconstructions to maintain electrostatic stability. Essentially, an electric field that arises between oppositely…
Tantalum pentoxide (Ta2O5) is a polymorphic wide-bandgap semiconductor with outstanding dielectric properties and widespread use in optical and electronic technologies. Its rich structural diversity, arising from multiple polymorphs…
The VO2 polymorphs, i.e., VO2(A), VO2(B), VO2(M1) and VO2(R), have a wide spectrum of functionalities useful for many potential applications in information and energy technologies. However, synthesis of phase pure materials, especially in…
Gallium nitride (GaN), as a promising alternative semiconductor to silicon, is of well-established use in photoelectronic and electronic technology. However, the vulnerable GaN surface has been a critical restriction that hinders the…
The study of hexagonal silicon polytypes attracts special attention due to their unique physical properties compared to the traditional cubic phase of Si. Thus, for some hexagonal phases, a significant improvement in the emission properties…
Ge/Si(001) multilayer heterostructures containing arrays of low-temperature self-assembled Ge quantum dots and very thin Si$_x$Ge$_{1-x}$ layers of varying composition and complex geometry have been studied using Raman spectroscopy and…