In this research,the growth of GaN thin films on c-plane sapphire（0001） substrates via two-step method without the assist of buffer layer and catalysts was demonstrated.First,gallium oxide（Ga_2O_3） ...thin films were deposited on sapphire substrates by radio frequency magnetron sputtering method.The deposited Ga_2O_3 thin films were then nitridated at various temperatures.In this research,attention is focused on the influence of nitridation temperatures on the structural and optical properties of the synthesized GaN thin films.It is revealed that 950 ℃ is the optimal nitridation temperature for synthesizing hexagonal wurtzite GaN thin film with preferential（0002） growth direction.
Spin coating growth and characterisations of c-oriented wurtzite structure gallium nitride (GaN) thin film on silicon (Si) substrate with (100) orientation was reported. The precursor solution ...consisted of a readily available gallium (III) nitrate hydrate powder, ethanol and diethanolamine as starting material, solvent and surfactant. All the structural and optical results showed that c-oriented wurtzite GaN thin film was deposited on Si (100) substrate. Compared with earlier reported work using sol-gel deposition, significant improvements in the structural quality of the GaN thin film were observed. The FWHM value of the thin film was approximately 2.60°. The framework described here is both an easy in setup and simple method as compared to other method such as MBE, MOCVD, and radio frequency sputtering to produce c-oriented wurtzite structure GaN thin film.
Ternary based aluminium doped zirconium oxide (AlxZryOz) was grown on silicon (Si) substrate after post-sputter oxidation of the AlZr film at different temperatures (400–1000 °C). Mixed phases ...(monoclinic + tetragonal) of AlxZryOz films were formed in all of the investigated films, accompanied with generation of oxygen vacancies (Vo). The presence of Vo favoured the hopping of oxygen molecules for oxidation to take place, leading to the formation of Al-Zr-Si-O interfacial layer (IL). The saturation of lattice with oxygen at high temperature (800 and 1000 °C) encouraged the trapping of additional oxygen as interstitials at the AlO network. Owing to the competition of both Vo and interstitials, microcracking was found on the film surface. Subsequent investigation was focused on the film obtained at 600 °C to study frequency dependent characteristics (dielectric constant, dielectric loss, interface state density, and series resistance) through capacitance-voltage and conductance-voltage measurements at different frequencies.
•Two-step growth route to produce ternary aluminium doped zirconium oxide films•Oxygen vacancies and interstitials were generated in the films.•Frequency dependent interface state density and series resistance happened.•Dielectric constant, dielectric loss, and loss tangent change with frequency.
Silicon-based metal-oxide-semiconductor (MOS) device was fabricated and investigated using cerium oxide (CeO
2
) films as the high dielectric constant passivation layers, which were produced by ...introducing a post-sputter oxidation process in a nitrogen infused oxygen ambient at 800ºC onto the direct current (DC) sputtered cerium films. Formation of cubic fluorite CeO
2
phases along with an increase in crystallite size was obtained with the increase on nitrogen gas flow rate from 0 to 0.7 slm in the nitrogen infused oxygen ambient. Although the implementation of nitrogen gas flow rates has improved densification of CeO
2
films as well as impeding the growth of the silicon dioxide interfacial layer, bandgap narrowing happened when the flow rate of the nitrogen gas increased beyond/at 0.5 slm, which could be associated with the presence of larger amount of nitrogen ions in the samples, resulting in an overlapping of the nitrogen 2p states and O2p states, and hence reducing the bandgap width. In comparison, CeO
2
film subjected to post-sputter oxidation in 0.3 slm nitrogen gas flow rate could be the optimum parameter to be considered for further investigation in future work.
Ga
2
O
3
film deposited by RF magnetron sputtering was subjected to annealing in different ambient (N
2
–O
2
–N
2
, argon, and oxygen ambient) at 800 °C. Results divulged the formation of ...polycrystalline phases ascribed to
β
-Ga
2
O
3
phases in all samples while an additional
γ
-Ga
2
O
3
phase was present for the film annealed in argon ambient. Although oxygen vacancies are present in the film annealed in argon ambient, nitrogen incorporation in the film subjected to annealing in N
2
–O
2
–N
2
has generated more oxygen vacancies and this brought to a degradation of the film quality by yielding the highest leakage current density, the lowest critical electric field, and the smallest bandgap. An improvement was achieved for the film annealed in oxygen ambient through the repairing of broken bonds in the film. However, a decrease in the critical electric field was obtained due to the existence of oxygen interstitials in the film that might serve as a scattering center.
Co-sputtering and post-sputter oxidation were incorporated as a two-step growth route for the formation of ternary aluminium doped zirconium oxide (AlxZryOz) films on silicon (Si) substrate using ...Al-Zr alloy film as the template film. Post-sputter oxidation at 400, 600, 800, and 1000 °C has transformed the amorphous as-deposited Al-Zr film to crystalline AlxZryOzfilms. A mixed monoclinic-tetragonal phase of AlxZryOz films was formed at 400 and 600 °C, while above which, tetragonal phase was obtained. The increase of oxidation temperature has also encouraged the formation of aluminium zirconium silicate (Al-Zr-Si-O) interfacial layer (IL), owing to an increase in the adsorption and diffusion of oxygen molecules from the ambient. The presence of excess oxygen in the film oxidized at the highest temperature (1000 °C) has translated into the formation of oxygen interstitials residing in the lattice, which have induced mid-gap states at the band gap of the film. As a result, a degradation in leakage current density-voltage (J-V) characteristic was obtained and the corresponding structural, optical, and capacitance-voltage characteristics were presented in comparison to the films oxidized at lower temperatures.
•Formation of ternary aluminium doped zirconium oxide film via two-step growth.•Transformation from amorphous Al-Zr alloy films to crystalline AlxZryOz films.•Oxygen interstitials induced mid-gap states in the band gap of AlxZryOz film.•Metal-oxide-semiconductor characteristics of AlxZryOz film on silicon substrate.
Properties of indium gallium zinc oxide (In2Ga2ZnO7) thin films on silicon (Si) substrate prepared using sol-gel method in response to annealing time were thoroughly studied. Post-annealing treatment ...for 5, 15, 30 and 60 min has revealed changes on surface morphologies, film roughness, film thickness and optical energy bandgap. InGaZnO (IGZO) structure was determined to be polycrystalline after annealing at 500 °C temperature regardless of annealing time. The increase in annealing time to 60 min successfully encouraged the formation of interfacial layer (IL) on the underlying Si substrate, owing to a build-up of oxygen molecules diffused from the ambient that resided in the lattice. As a result, a larger leakage current was obtained from leakage current density-voltage (J-V) characteristic. Corresponding properties of the films in comparison to 60 min annealing were further elaborated in terms of optical and electrical characterization.
•Crystallization of In2Ga2ZnO7 film took place at minimum of 5 min annealing at 500 °C in room ambient.•Amount of oxygen vacancy decreased as annealing temperature increased causing changes in energy bandgap indirect transition.•Interfacial layer formed on underlying substrate when annealed for 60 min.•Incorporation of interfacial layer increased leakage current of IGZO film.
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