κ-phase Ga₂O₃ is a wide-bandgap semiconductor that has attracted attention for power and optoelectronic device applications. However, its crystal quality and optical properties are highly dependent on the growth temperature, which motivates the need for a systematic study. In this work, κ-Ga₂O₃ thin films were grown on AlN/sapphire templates using mist-CVD at different temperatures. At lower temperatures (400℃), films exhibited incomplete crystallization and partial opacity, whereas higher growth temperatures (500-700℃) produced transparent films with improved properties. The bandgap was found to increase with temperature, consistent with reported values for 600-700℃, and XRD/XRC analysis confirmed that crystal quality improved with higher growth temperature. AFM analysis further revealed reductions in surface roughness and grain size variation at elevated temperatures. These findings indicate that an optimal growth window of 600-700℃ enables high-quality κ-Ga₂O₃ films, with potential implications for integrating this material on other hexagonal substrates such as SiC and GaN.

An epitaxial GaN layer was grown on a cone-shape-patterned sapphire substrate (PSS) (Sample A) and an AlN-buffered PSS (Sample B) with two growth steps under the same process conditions by employing the hydride vapor phase epitaxy (HVPE) method. We have investigated the characteristics of the GaN layer grown on two kinds of substrates at each growth step. The cross-sectional SEM image of the GaN layer grown on the two types of substrates showed growth states of GaN layers formed during the 1st and 2nd growth steps with different growth durations. Dislocation density was obtained by calculation using the FWHM value of the rocking curve for (002) and (102). Sample A showed 2.62+08E and 6.66+08E and sample B exhibited 5.74+07E and 1.65+08E for two different planes. The red shift was observed is photoluminescence (PL) analysis and Raman spectroscopy results. GaN layers grown on AlN-buffered PSS exhibited better optical and crystallographic properties than GaN layers grown on PSS.

Aluminum nitride fibers were synthesized by carbothermal reduction and nitridation of precursor fibers obtained by electrospinning. The starting materials used to synthesize the AlN fibers were Al(NO₃)₃·9H₂O and urea. Polyvinylpyrrolidone with increasing viscidity was used as the carbon source to obtain a composite solution. The mixed solution was drawn into a plastic syringe with a stainless steel needle, which was used as the spinneret and connected to a 20 kV power supply. A high voltage was supplied to the solution to facilitate the formation of a dense net of fibers on the collector. The precursor fibers were dried at 100℃ and then heated to 1,400℃ for 1 h in a microwave furnace under N2 gas flow for the carbothermal reduction and nitridation. X-ray diffraction studies indicated that the synthesized fibers consisted of the AlN phase. Field emission scanning electron microscopy studies indicated that the diameter of the calcined fibers was approximately 100 nm.

The effects of TiO2 addition on the electrical insulation of AlN ceramics with 1 wt% Y₂O₃ as a sintering aid have been investigated. Some of TiO₂ has reacted with AlN powders and transformed to fine TiN particles during sintering, which was uniformly dispersed along grain boundaries of AlN. At a high electrical field (500 V/mm), the resistivity of AlN ceramics with TiO₂ addition of 0.2 wt% increased about 1000 times from 3x10¹⁰ Ω cm to 3.1×10¹³ Ωcm. Based on the impedance spectroscopy measurement, it was found that TiO₂ addition increased dramatically electrical resistivity of AlN grains much more than that of grain boundaries. Thus, TiO2 was believed to dissolve inside AlN grains to suppress ionic conduction of Al vacancies. This suppressed ionic conduction by Ti incorporation into AlN grains seems to contribute to more electrically insulating AlN ceramics.

In this paper, high quality AlN layers were regrown on AlN nanopillar structure with SiO2-dots by HVPE. Surface morphology of AlN layer regrown exhibited flatter than a conventional AlN template. The laterally overgrown AlN regions would consist of a continuous well coalesced layer with lower dislocation density than in the template because of the dislocation blocking and dislocation bending effects. Moreover, result of Raman spectroscopy suggest that the AlN nanopillar structure with SiO2-dots relieves the strain in the AlN layer regrown by HVPE.

Aluminum nitride (AlN) thin film and TiN film as a buffer layer were deposited on INCONEL600 substrate by reactive RF magnetron sputtering at room temperature(R.T.) under 25∼75% N2/Aratmosphere. The as-deposited AlN films at 25∼50% N2/Ar showed a polycrystalline phase of hexagonal AlN, and an amorphous phase. The peak of AlN (002) plane, which was determinant on a performance of piezoelectric transducer, became strong with increasing the N2/Ar ratio. Any change in the preferential orientation of the as-deposited AlN films was not observed within our N2 concentration range. The piezoelectric sensing properties of AlN module were performed using pressure-voltage measurement system. The output signal voltage of AlN module showed a linear behavior between 20∼80 mV in 1∼10MPa range, and the pressure-sensing sensitivity was calculated as 3.6 mV/MPa.

AlN thin films were deposited on p-type Si(100) substrates by RF magnetron sputtering method. This study showed the change of the preferential orientation of AlN thin films deposition with the change of the deposition conditions such as sputtering pressure and Ar/N2 gas ratio in chamber. It was identified by X-ray diffraction patterns that AlN thin film deposited at low sputtering pressure has a (002) orientation, however its preferred orientation was changed from the (002) to the (100) orientation with increasing sputtering pressure. Also, it was observed that the properties of AlN thin films such as thickness, grain size and surface roughness were largely dependent on Ar/N2 gas ratio and a high quality thin film could be prepared at lower nitrogen concentration. AlN thin films were investigated relationship between preferential orientation and deposition condition by using XRD, FE-SEM and PFM.

In this paper, heat-releasing sheets made of AlN powder and acryl binder as thermoset were prepared using tape casting method. The crystal structure and morphology, the thermal properties as nonvolatile solid content and thermal conductivity, and the surface resistance of heat- releasing sheet were measured by using X-ray diffractometer, field emission-scanning electron microscopy, thermo gravimetric analyzer and laser flash instrument, and surface resistance meter. It was proved that thermal conductivity is greatly affected by the content of binder in heat-releasing sheet. Superior thermal conductivity above 3.5W/mK and suface resistance were obtained at heat-releasing sheet with above 90% of AlN powder.

In this paper, heat-releasing composite sheets made of AlN, graphite, Al powder and acryl binder as thermoset were prepared using tape casting method, The crystal structure, morphology, thermal conductivity of heat-releasing composite sheet were measured by using X-ray diffractometer, field emission-scanning electron microscopy and laser flash instrument. It was found thermal conductivity of sheet was decided by solid content, composition including AlN, graphite, Al in heat-releasing composite sheets. As a result, 4.56W/mK of thermal conductivity could be obtained by using LFA 447.

In this study the (Alnico, Sm-Co) bonded magnets were fabricated by mixing the Sm-Co added alnico alloy powders with epoxy resin and binder, appropriately. Also, the hybrid ring magnets of (Alnico, Sm-Co)/Sr-ferrite were fabricated by coupling the Sr-ferrite composite layer with an (Alnico, Sm-Co) magnet. The magnetic properties of (Alnico, Sm-Co) ring magnets were varied with the amount of Sm-Co powders. The addition of Sm-Co powders increased a remanent induction(Br) and coercive force(BHC), while decreasing a surface flux density and repulsive distance. The surface flux density and repulsive distance for the (Alnico, Sm-Co) ring magnet increased with a magnetizing voltage up to about 160 V and reached an apparent saturation point. Also, the measurements of temperature and moisture characteristics showed that the surface flux densities of N-S poles and repulsive distance decreased a little within 4% after 10 days passed.