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Aluminium nitride (AlN) nucleation layer (NL) is a useful nitride semiconductor for the growth of Gallium Nitride (GaN) on silicon. Major issues related to the fabrication of AlN films are on its crystallographic orientations and high processing temperatures. In order to fabricate AlN NL at low temperatures, radio frequency (RF) magnetron sputtering is used in this study. The aims are to deposit homogeneous and highly crystalline AlN NL with (100) and (002) preferential orientations at low processing temperatures. In this study, the homogeneous deposited AlN with highly crystalline along the (100) and (002) preferential orientations were successfully controlled using sputtering base pressure without any external heating. This will mitigate the presence of oxygen that presents during the deposition process. Moreover, the sputtering parameters such as target-to-substrate distance, working pressure, deposition times, and RF power were optimized. Thus, these highly crystalline AlN along the (100) and (002) preferential orientations were used in the Metal-Insulator-Semiconductor (MIS) structure to investigate their leakage currents. For the (002) preferential orientations of AlN, X-ray diffraction (XRD) showed that the full width at half maximum (FWHM) was smaller with low dislocation density and microstrain. Cross-sectional images from the field-emission scanning electron microscope (FESEM) showed that its exhibited grass-like columnar structures, showing it had a well-aligned structure. Meanwhile, its electrical properties showed that the (002)-oriented AlN NL had high electrical resistivity due to low dielectric permittivity, high capacitance, and low dielectric relaxation. The (100) and (002) preferential orientations leakage currents values in the MIS structure were 4.1 x 10-7 A and 2.0 x 10-8 A, respectively, indicating that (002) preferential orientations AlN NL displayed the lowest leakage current significantly. The effects of oxygen impurity in the layers played

Aluminium nitride (AlN) thin film is deposited by RF magnetron sputtering using Al sputtering target at room temperature. The sputter source was tilted 45° and the substrate holder was unrotated. The deposited AlN films were in the thickness range between 200 to 280 nm. The structural, elemental composition, morphological and topological properties of AlN with different thickness has been investigated. XRD analysis results revealed that all the AlN films deposited crystallize in hexagonal wurtzite phase (w-AlN). The crystal orientation of AlN (002) plane start to appear when the thickness of the AlN film increases and the thickest AlN film has a highest peak intensity of (002) plane with smallest FWHM indicated a good crystal quality of c-axis structure. The chemical composition of AlN analyze using EDS shows that all the films have AlN composition nearest to the stoichiometric and have a rice-like morphology regardless of the film thickness. The AFM analysis revealed that the surface roughness of the AlN films is increases along with the grain size as the thickness of the AlN films increased.

n this research, pure titanium dioxide (TiO2) and doped TiO2 thin film layers were prepared using the spin coating method of titanium(IV) butoxide on a glass substrate from the sol–gel method and annealed at 500 °C. The effects on the structural and chemical properties of these thin films were then investigated. The metal doped TiO2 thin film which exists as trivalent electrons consists of aluminium (Al), yttrium (Y) and gadolinium (Gd). The anatase phase of the thin films was observed and it was found that the crystal size became smaller when the concentration of thin film increased. The grain size was found to be 0.487 to 13.925 nm. The types of surface morphologies of the thin films were nanoporous, with a little agglomeration and smaller nanoparticles corresponding to Al doped TiO2, Y doped TiO2 and Gd doped TiO2, respectively. The trivalent doping concentration of the thin films increased with a rising of thickness of the thin film. This can contribute to the defects that give advantages to the thin film when the mobility of the hole carriers is high and the electrons of Ti can move easily. Thus, Ti3+ existed as a defect state in the metal doped TiO2 thin film based on lattice distortion with a faster growth thin film that encouraged the formation of a higher level of oxygen vacancy defects.

Titanium dioxide (TiO2) thin film gas sensors have been widely used and investigated in the detection of target gases. However, to obtain anatase phase for oxygen gas sensor with low and short annealing temperature is the obstacle in the fabrication of oxygen gas sensor. It is thus desirable to develop TiO2 thin film preparation technique that provides the anatase phase for oxygen gas sensor at low and short annealing temperature. In this study, the dip coating method was used to fabricate the TiO2 thin film. The parameters such as deposition layer, withdrawal speed of dip coating and annealing temperature were varied to optimize the properties of thin film. The optimum parameters are obtained from the I layer deposition film, IO mm/ min withdrawal speed of dip coating, and annealed the film at 400 °C in electrical furnace. Crystal structure studies showed that the optimized TiO2 thin film is anatase phase with tetragonal lattice structure and (101) plane is the dominant peak. Morphological studies indicated that the film is even and uniform in manner with grain size of 13.3 nm. The crystallite size obtained from HIGHSCORE software is 69.02 nm and calculated crystallite size using Scherrer's equation is 55.7 nm. The electrical studies showed that the film resistivity is 1.64 x I 0-3 n.cm. The gas sensor measurement revealed that the response and recovery time of TiO2 thin film sensor at room temperature is about 13.22 s and 2.67 s, respectively. Thus, proving that the potential to use the TiO2 thin film fabricated by dip coating as active layer in oxygen gas sensor.