Papers by Keyword: Nitridation

Abstract: We present the improvement of SiO₂/4H-SiC interface quality and high field-effect (FE) mobility (µ_FE) in 4H-SiC MOSFETs. This is achieved by introducing a nitrous oxide (N₂O) plasma in-situ pre-treatment before gate stack formation using plasma enhanced chemical vapour deposition (PECVD) oxide followed by a post deposition anneal (PDA) in diluted N₂O for times ranging from 30 to 120 minutes thereby creating an ultra-thin thermally grown SiO₂ layer at the SiO₂/4H-SiC interface. MOS capacitors with SiO₂ deposited on in-situ pre-treated SiC surfaces had a lower density of interface traps (D_IT) for all PDA durations, compared with devices having untreated PECVD oxides or control devices with 30 nm thermally grown oxide. After PDA for 90 minutes, a minimum D_IT value of 1.2×10¹¹ cm^-2·eV^-1 was measured. A peak µ_FE value reaching 94 cm²/(V·s) was measured in n-channel planar MOSFETs fabricated with PECVD oxide on in-situ pre-treated devices, which significantly exceeds a maximum µ_FE of 6 cm²/(V·s) in control devices.

Abstract: The synthesis of aluminum nitride (AlN) powders is traditionally completed through a thermal nitridation process, in which the reacting aluminum powders are combined with nitrogen at high temperatures with a long reaction time (usually several hours). Moreover, the occurrence of agglomeration within the melting Al particles results in a poor dispersibility of AlN powders, with a low efficiency of nitridation. In this study, an atmosphere-pressure microwave plasma preceded the rapid gas-gas synthesis process. In the reactor, the gaseous aluminum chloride (AlCl₃) reactant was fed at different positions (R1, R2, R3) to react with nitrogen at various reaction temperatures (690~1150°C) to rapidly produce AlN nano powders (in several seconds). The process was operated at a total flow rate of 13 slm with NH₃ gas content of 0 or 0.77% and an applied power of 1200/1400 W. Results showed that the high purity and dispersibility of AlN powders were found at a AlCl₃ feeding position closer to the resonant cavity of the reactor (R3, 1150°C). The AlN particle size was in the range of 25-50 nm. The experiments indicated that the gas-gas reaction for rapidly synthesizing AlN nanopowders can be successfully carried out via an AlCl₃-N₂ plasma-chemical approach.

Abstract: The study highlights the effects of growth temperatures ranging from 500 to 650 °C on the properties of indium nitride (InN) thin films prepared by sol-gel spin coating method followed by nitridation, also, the growth mechanism was studied in depth. The findings revealed that the InN crystal growth was promoted at the growth temperature of 600 °C, by which the crystalline quality of the deposited thin films was improved and the densely packed InN grains were formed. However, thermal decomposition of InN was observed at increasing temperature to 650 °C. Apart from that, the infrared (IR) reflectance measurement shows the presence of transverse and longitudinal-optical phonon modes of wurtzite structure InN. These vibrational modes were found to be slightly shifted from the theoretical values as a result of the incorporation of oxygen contamination in the deposited thin films.

Abstract: In this study, aluminum nitride (AlN) thin films were grown on p-type silicon (100) substrate by sol-gel spin coating method. Two types of ethanol-based precursors were prepared, namely, precursors with and without the aid of diethanolamine (DEA). The objective of this work is to investigate the effects of the DEA on the surface morphology, structural and optical properties of the deposited thin films. The coating films were undergone nitridation process under ammonia ambient at 1100 °C for 60 min. The surface morphology and structural properties of the deposited AlN thin films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD results revealed that both samples have AlN (100) preferred orientation. In addition, the crystallinity of sample without the aid of DEA is higher compared to the sample prepared with DEA. While, the AFM results showed that both samples have uniform and smooth surface. The optical properties of AlN thin films was investigated by Raman spectroscopy. For sample without DEA, Raman results showed the present of wurtzite AlN characteristics phonon modes of E₂(high) and A₁(LO) at 660 cm^-1 and 892 cm^-1, respectively. Whereas only E₂(high) is observed for sample with the aid of DEA. Finally, all the results revealed that the present of DEA has a strong influence on the properties of deposited AlN thin films and film prepared without DEA have better quality.

Abstract: Fiber-like SiCN was found in the product from the nitridation of silicon by foaming and reaction sintering. The mixture slurry was comprised of silicon powder and cornstarch as raw material, yttrium oxide as sintering additive and some foams. The casted sample was sintered at 1650oC in nitrogen. The phase composition of the as-prepared sample was determined by X-ray powder diffractometer, and the microstructure of the sample was observed by scanning electron microscope and transmission electron microscope equipped with energy dispersive spectrometer. The results show that fiber-like SiCN with micron scale grown along [100] direction, and the interplanar spacing was 0.655 nm.

Abstract: β-Sialon powders were synthesized via salt-assisted nitridation synthesis from Al, Si, SiO₂ powders and molten salt medium (NaCl and NaF) with the addition of different content of NaN₃ at different temperature for 3 h. NaN₃ were employed as auxiliary nitrogen source which effectively provide sufficient nitrogen. The results indicated that the growth of β-Sialon powders had better effect when the NaN₃ was added. And the β-Sialon powders grew more completely and the morphology of β-Sialon powders showed the rod-like crystal with hexagonal smooth tips instead of conical tips. In addition, the products displayed different sizes when the content of NaN₃ was changed. These results of this work suggested that β-Sialon could be synthesized with specific morphology by adding different content of NaN₃.

Abstract: This paper presents and analyse the experimental results of 4H-SiC(0001) lateral MOSFETs and MOS capacitors with gate oxides grown directly in N₂O environment or in O₂ ambient followed by a N₂O post oxidation annealing process. Different nitridation temperatures of 1200°C, 1300°C, 1400°C and 1500°C have been investigated. Results have demonstrated that at high temperature (>1200°C) there is a significant improvement in the interface trap density (~1.5×10¹¹ cm^-2eV^-1 at 0.2 eV) and field effect channel mobility (19 cm²/V.s) of 4H-SiC MOSFET compare with those at lower temperature (1×10¹² cm^-2eV^-1 at 0.2 eV and 4 cm²/V.s). Among those nitridation temperatures, 1300°C has found to be the most effective in increasing the field effect channel mobility and reducing threshold voltage.

Abstract: In this study, 4H–SiC inversion layers were experimentally evaluated by Hall and split C–V measurements, and scattering mechanisms related to gate oxide nitridation were analyzed. Three typical samples with different crystal plane directions and gate oxidation conditions were prepared, and their total trap density and Hall mobility were compared. Based on the temperature dependence of the Hall mobility, we found that scattering mechanisms differed for each sample. The sample C-face oxynitride which had a high nitrogen density at the metal–oxide–semiconductor (MOS) interface, showed a similar temperature dependency to that of ionized impurity scattering. This result suggests that high-density nitrogen acts as donors that supply free carriers and cause ionized impurity scattering, just like in a bulk crystal. In addition, the sample C-face wet has lowest influence of the Coulomb scattering because of the lowest temperature dependence of Hall mobility and the lowest total trap density.

Abstract: The proposed paper deals about the heat treatment of two types of chromium tool steels that are assigned to work in specific conditions of abrasion wear. The materials are heat treated to achieve high hardness for higher abrasion wear resistance. An additional increase of the materials abrasion wear resistance can be achieved by applying nitridation with diffusion annealing of the material surface. The paper deals about the influence of the material purity, his chemical composition on the process of diffusion, the quality of the nitrided layer of a vacuum smelted steel Bӧhler W400 VMR and a chromium steel X210Cr12.

Abstract: 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.