Papers by Keyword: Aluminum Nitride (AlN)

Abstract: Novel simple route to prepare AlN nanoparticles was proposed in this study. Aluminum nitride powder was synthesized by microwave-assisted urea route. Aluminum chloride was dissolved in ethanol and urea was added to this solution considering molar concentration with Aluminum chloride. The solution was heated under microwave (MW) irradiation from 60°C to 80°C for 5-10 minutes. And then heat treatment was performed in N₂ atmosphere with various temperatures and time to obtain AlN particles. While microwave was irradiated to the mixed solution with Aluminum chloride, urea and ethanol, the solvent was eliminated and polymerization reaction was accelerated to formmetal-organic complex. AlN particles were successfully synthesized after heat treatment above 1600°C under N₂ or N₂-H₂ mixed gas atmosphere in the molar ratio (urea/Aluminum chloride) of 6.

Abstract: High density graphite disks and aluminum nitride ceramics powders have been utilized to obtain joints by Spark Plasma Sintering technique. The joining was carried out in vacuum, at temperatures of 1700°C, 1800°C and 1900°C, under the pressure of 50 MPa with a constant dwelling time of 5 minutes The AlN ceramics to be joined were also synthesized by ceramic technology standard route by using AlN powders and 2.5 % wt.Y₂O₃ powders as sintering additive, which were added in order to increase densification rate and by thus, thermal conductivity. The joining of AlN/C was performed both without and with the aid of a ceramic powder composite AlN+Y₂O₃+C film, as interlayer. Besides the crystalline phases (AlN and C), the Al₅Y₃O₁₂ compounds with a cubic crystallographic structure were identified by X-ray diffraction. The optical microscopy images revealed that all samples, both without and with film as interlayer, had strong joined areas, without any defects and discontinuities at interfaces. The Vickers microhardness and Young Modulus values measured by nanoindentation have shown that using of the film as intermediary layer was leading to the highest values of mechanical properties (HV = 8 – 23 GPa and E= 227-512 GPa) at the AlN/C joints interfaces.

Abstract: Structural investigations of Si quantum dots (QDs) grown by CVD on two different heterostructures: AlN/Si (111) and 3C-SiC/Si (100) are conducted. The Si QDs have been grown using silane as precursor, diluted in hydrogen, at fixed temperature and pressure (830°C - 800mbar). High densities of dots can be obtained (up to 10¹¹ cm^-2) with typical heights below 10nm. The kinetic of deposition lets suppose the presence of an initial wetting layer before the dots formation. Different durations are required for nucleating dots on AlN and 3C-SiC. Si QDs on AlN present a luminescence band which can be attributed to quantum confinement.

Abstract: Aluminum nitride (AlN) bulk crystals, approximately 50.8mm in diameter and up to 5mm thickness, were grown by a physical vapor transport (PVT) method in a tantalum crucible. To investigate the effect of crucible materials, various crucible materials, a graphite and TaC-coated graphite and tantalum crucible were used for the AlN growth. XRD pattern of AlN crystal grown on SiC seed in the Ta-crucible exhibited only (00l) peaks, indicating that AlN single crystal was successfully grown on SiC seed. The interface structure between AlN and SiC crystals was observed by a high resolution TEM.

Abstract: We report on the growth method and the structural characterization of freestanding AlN crystals. An AlN layer is grown on a gradually decomposing SiC substrate yielding a freestanding crack free 2H single crystal with dislocation density 5×10⁴ cm^–2 and without grain boundaries as confirmed by synchrotron radiation phase contrast imaging and topography data. Wafers of 600–1000 μm thick and up to 15 mm in diameter are obtained. The thermal stress distribution in a conventional AlN/SiC structure is discussed. Theoretical estimates show that cracking of AlN layers is a natural result of their growth on undecomposed SiC substrates.

Abstract: AlN has been widely used as the piezoelectric thin film layer in film bulk acoustic wave resonator (FBAR). The performance of FBAR is influenced by various geometrical parameters and losses from piezoelectric material such as thermoelastic damping and material damping. This research focuses on the estimation of material damping coefficients (α and β) of the AlN by using the Akhieser approximation to estimate more accurate values of the coefficients, thus a more realistic value of the quality (Q) factor is achieved for FBAR operating at Ku-band frequency ranges (12 GHz-18 GHz).

Abstract: This study signifies the growth and characterization of aluminium nitride (AlN) thin film deposited on the atmospheric plasma treated n-type silicon [n-Si (100)]. Basically, the low cost spin coating technique which emphasized the production of a thin and uniform film on a flat substrate through a dilute solution is adopted. For the precursor preparation, the main ingredient of aluminium nitrate hydrate is dissolved with an organic solvent. The nitridation process is carried out on the deposited coating at 1100 °C for 1 hour. The surface morphology and structural properties of the thin film were investigated by field-emission scanning electron microscope, atomic force microscopy energy, dispersive X-ray spectroscopy and X-ray diffraction; while the optical properties of the deposited thin film was determined by using Fourier transform infrared spectrometer. All the results revealed that AlN thin film was successfully deposited on n-Si (100) substrate.

Abstract: Thermoplastic slip from commercial powders of yttrium nitride and yttrium oxide. The scheme of making the slip is proposed, the casting properties are determined. The influence of sintering additives dispersion and molding conditions (pressure, temperature) on slip properties is researched.

Abstract: Liquid crystalline epoxy, 4,4’-Diglycidyloxy-α-methylstilbene (DOMS) was synthesized and Aluminum Nitride reinforced DOMS composites were fabricated by melt blending with sulfanilamide (SAA) as a curing agent. Thermal degradation behavior was investigated by thermogravimetric analysis (TGA) under nitrogen atmosphere at the temperature range from 30 to 1000°C. Activation energies for decomposition (Ed) by TGA were determined as a function of conversion by weight loss process.

Abstract: Using melamine and aluminum nitrate as raw material, we prepared aluminum nitride whiskers by precursor method and studied the effect of reactants and concentration to AlN precursor. The results showed that when the Molar ratio is 1:3, and the concentration is 0.2mol/l, whisker precursor produced is relatively uniform and have large length diameter ratio.