ICMCTF2006 Session D1-1: Carbon Nitride, Boron Nitride and Group-III (Al, Ga, In) Nitride Materials

Thursday, May 4, 2006 1:30 PM in Room Sunset

Thursday Afternoon

Start	Invited?	Item
1:30 PM	Invited	D1-1-1 Thick c-BN Coatings - Preparation, Properties and Application Tests M. Keunecke (Fraunhofer IST, Germany); E. Wiemann (Institute for Machine Tools and Factory Management, Technical University Berlin, Germany); S.T. Park, K. Weigel, K. Bewilogua (Fraunhofer IST, Germany) Due to the outstanding properties of cubic boron nitride (c-BN), e.g. c-BN is the second hardest of all known materials, has a high wear resistance and a high thermal stability, this material is very desired for a broad range of application, especially as a cutting tool coating. The state-of-the-art is the use of sintered cutting inserts with c-BN grains. Such c-BN grains are synthesized in an expensive high-pressure, high-temperature process. The requirements to tools continuously increase in production engineering and this leads to a strong demand for new super hard tool coatings. c-BN coatings could be one solution. Unfortunately the preparation of thick c-BN coatings in µm scale is difficult, due to some serious drawbacks and succeeded only in the last years by different research groups. After a short remark to the relevance of c-BN bulk material in production engineering and future trends, an overview on the current status of development of c-BN coatings will be given. Different techniques for c-BN deposition and the synthesis of thick c-BN coatings (> 1 µm) will be discussed. PVD processes allow the preparation c-BN films thicker than 2 µm on silicon and 1 µm c-BN on pre-coated cemented carbide cutting inserts. Measurements of mechanical properties like hardness and Young's modulus reveal that the properties of the c-BN coatings, with hardness of about 60 GPa, are nearly identical to those of c-BN bulk material. Results of systematic turning and milling tests of different coatings in combination with a c-BN top-layer on cemented carbide cutting inserts will be presented in detail. The new results confirm the very high potential of c-BN coatings on tools.
2:10 PM		D1-1-3 Cubic Boron Nitride Thin Film Growth by Boron and Nitrogen Ion Implantation S. Eyhusen, H. Hofsaess, C. Ronning (University of Goettingen, Germany) Cubic boron nitride (c-BN) thin films were deposited on silicon substrates using mass seperated ion beam deposition (MSIBD). In order to investigate the influence of the ion energy on the growth of c-BN films, ¹¹B and ¹⁴N ions were implanted into c-BN with ion energies ranging from 5 keV to 43 keV and substrate temperatures T_S from room temperature (RT) to 250°C. A systematic study on the interplay of E _ION and T_S has revealed a characteristic energy-dependent temperature threshold for c-BN growth. This behavior is explained by dynamic annealing of defects caused by an impeding ion in a collison cascade. In this picture, the suppression of defect accumulation that is crucial for maintaining cubic phase formation is attributed to temperature-driven back-diffusion and subsequent annihilation of B and N interstitial recoils. The model is confirmed by analyzing the depth profile of implanted, isotopically pure ¹¹B, and its application for both c-BN nucleation and growth is discussed.
2:30 PM		D1-1-4 Structural Evolution of Boron Nitride Films Grown on Diamond Buffer-Layers P.C. Huang (National Dong Hwa University, Taiwan); T.S. Yang (Tzu Chi College of Technology, Taiwan); M.S. Wong (National Dong Hwa University, Taiwan) Nanostructured boron nitride thin films have been studied using cross-sectional high-resolution transmission electron microscopy (X-HRTEM) and FTIR. The films grown on silicon wafer and on buffer layers of micro-diamond and nano-diamond films are prepared under the same growth condition by microwave plasma-enhanced chemical vapor deposition (MPCVD) by the reaction of B₂H₆ and NH₃ in H₂ and Ar atmosphere. Various forms of boron nitride including hexagonal (h-BN), turbostratic (t-BN), amorphous-BN (a-BN), wurtzite (w-BN), explosion (e-BN or o-BN), rhombohedral (r-BN) and cubic (c-BN) were detected under the influence of substrates or buffer layers. For silicon substrate, a-BN layer grew first, followed by randomly nucleated t-BN layer, and finally e-BN (or o-BN) layer formed. Both turbostratic- and rhombohedral-like structures were observed at the interface between a-BN and c-BN on micro-diamond buffer layer, and were found to act as structural precursors and/or deposition sites for cubic boron nitride nucleation. In contrast, c-BN can grow directly on nano-diamond buffer layer without precursor layers. Thus, the c-BN formation was significantly promoted resulting in high c-BN content up to 90 at % in the BN film.
2:50 PM		D1-1-5 New Amorphous Si-B-C-N Materials: An Ab-Initio Study J. Houska (University of West Bohemia, Czech Republic); M.M.M. Bilek, O. Warschkow, D.R. McKenzie (University of Sydney, Australia); J. Vlcek, S. Potocky (University of West Bohemia, Czech Republic) In this contribution, we report ab-initio molecular dynamics (MD) simulations of the preparation of amorphous (Si)-(B)-C-N materials formed by energetic ion assisted deposition techniques. In our liquid-quench simulations, the Kohn-Sham equations for the valence electrons are expanded in a basis of plane wave functions, while core electrons were represented using Goedecker-type pseudopotentials. We simplify the ion bombardment process by assuming that the primary impact creates a localized region of high temperature, commonly referred to as a thermal spike. Thermal spikes have a cooling time sufficiently short to be simulated using ab initio MD methods. We show formation of N₂ molecules during liquid quench simulations and investigate how density, temperature and quench rate affect the number of N₂ molecules formed in the network. We find that a higher material density and shorter cooling times lead to reduced N₂ formation and thus to a higher nitrogen incorporation into the final structure. We investigate how the presence of Ar atoms in the sample affects the liquid quench and the final structure of the material. The presence of Ar leads to the formation of silicon enriched regions in the vicinity of implanted Ar atoms, which provides new insight into the role of implanted Ar in formation of structures in amorphous materials. It can also explain the ability of Si to relieve stress generated by these implanted Ar atoms. We calculate various data affecting material properties and compare them for previously deposited materials of different Si-B-C-N compositions. ¹J.Houska, M.M.M.Bilek, O.Warschkow et al., accepted for publication in Phys. Rev. B (2005). ²J.Houska, O.Warschkow, M.M.M.Bilek et al., submitted to J. Phys. C (2005). ³J.Vlcek, S.Potocky, J.Cizek et al., J. Vac. Sci. Technol. A, in print (12/2005). ⁴J.Houska, J.Vlcek, S.Potocky et al., submitted to Diamond Relat. Mater. (2005).
3:10 PM		D1-1-6 Water Adsorption on Lubricated Fullerene-Like CN_x Films E. Broitman, V.V. Pushkarev, A.J. Gellman (Carnegie Mellon University); J. Neidhardt (University of Leoben, Austria); A. Furlan, L. Hultman (Linköping University, Sweden) Humidity influences the tribological performance of the head-disk interface in magnetic data storage devices. In this work we compare the uptake of water of amorphous carbon nitride (a-CN_x) films, widely used as protective overcoats in computer disk drive systems, and fullerene-like carbon nitride (FL-CNx) films. Films were deposited on quartz crystal substrates by reactive dc magnetron sputtering in Ar/N2 discharges. After deposition, some of the films were coated with a 2 nm thick layer of Z-tetraol, a lubricant used in hard disk devices. A quartz crystal microbalance placed in a vacuum chamber was used to measure the adsorption of water at room temperature and pressures of water corresponding to relative humidity in the range 0 to 90 %. It was observed that adsorption and desorption is fast, indicating that equilibrium with ambient humidity is reached on timescales of minutes, much faster than the timescales for fluctuations in ambient humidity. In the case of non-lubricated coatings, measurements indicate the amount of water adsorbed by the amorphous films is significantly higher than the fullerene-like ones. The presence of the lubricant reduces the amount of adsorbed water, and the nanostructured FL-CN_x films have the lowest measured adsorption.
3:30 PM	Invited	D1-1-7 GaN Nanowires: CVD Synthesis and Properties X.M. Cai, A.B. Djurisic, M.H. Xie (University of Hong Kong, PR China) GaN is a wide band gap (3.4 eV) semiconductor, which is of great interest for short wavelength optoelectronic device applications, as well as high power/high temperature electronic applications. In recent years, in addition to research work on GaN thin films and devices, there has been increasing interest in the fabrication and characterization of GaN nanostructures. In this work, the growth of GaN nanowires from Ga and NH₃ sources in the flow of Ar carrier gas using a chemical vapor deposition (CVD) system was systematically studied. The substrates used were Si (111) and Si (100). Fabricated nanowires were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). We have investigated the influence of growth temperature, catalyst used, Ga amount, and the ratio of Ar and NH₃ flow rates on the morphology and properties of GaN nanowires. We found that the best results were obtained for growth temperature of 950 °C. Optimal catalysts were Au and metallic Ni, while the use of nickel nitrate was found to lead to formation of SiO_x nanowire bunches in addition to GaN nanowires. For the optimal temperature and catalyst used, the influence of Ga to N ratio on the nanowire growth was studied. It was found that different types of nanostructures are observed in relatively Ga-rich and in relatively N-rich conditions. Growth mechanisms of different types of nanowires, including the stacked-cone nanowires and the microscale structures formed by lateral growth under N-rich condition are discussed.
4:10 PM	Invited	D1-1-9 GaN Nanorods Grown by MBE L.-W. Tu, C.L. Hsiao, M. Chen, Y.J. Tu, T.W. Chi (National Sun Yat-Sen University, Taiwan); H.W. Seo, Q.Y. Chen, M.N. Iliev, W.K. Chu (University of Houston) Nano wind blows to change the crystal growth from pursuing a monotonous flat surface to exploring a variety of nano-structures. In this work, nitrogen-plasma-assisted molecular-beam epitaxy system was used to grow III-V nitrides in nanorod forms. As in two-dimensional epitaxial film growth, a right growth parameter window has to be located to ensure the wanted nano-structures. Si (111) wafer was used as the substrate. In addition to its hexagonal symmetry, it is conductive and easier for device process. Nanorods with different compositions and structures were grown. Characterizations of structure, composition, and optical properties were performed. Capillary condensation model is proposed to elucidate the initiation and the elongation of this nearly one-dimensional growth through detailed analyses. Nano-light-emitters were fabricated and their electroluminescence spectra were measured.
4:50 PM		D1-1-11 Near-Infrared Photoluminescence of Vertically Aligned InN Nanorods Grown on Si(111) by Plasma-Assisted Molecular-Beam Epitaxy H.-Y. Chen, C.-H. Chen, C.-H. Shen, H.-W. Lin, C.-Y. Wu, S. Gwo (National Tsing-Hua University, Taiwan) Vertically aligned InN nanorods have been grown on Si(111) substrates by nitrogen-plasma-assisted molecular-beam epitaxy at low and high growth temperatures (LT- and HT-InN). High-resolution SEM images clearly show that InN nanorods grown on Si(111) are hexagonal in shape, vertically aligned, well separated, and densely distributed on the substrate. The LT-InN rod size distribution is quite uniform, while the HT-InN nanorods show a bimodal distribution. The average aspect ratio (height/diameter) of the LT-InN nanorods has a constant value of ~5-6, independent of the growth time and nanorod height. Near-infrared (0.75-0.77 eV) photoluminescence (PL) from LT-InN nanorods was observed at room temperature. At a higher growth temperature (HT-InN), the PL efficiency becomes better and the PL peak position is closer to that of InN-on-Si epitaxial films (~0.65 eV). From the temperature-dependent PL measurements of InN nanorods, we observed an anomalous linear blue-shift of peak energy with increasing temperature from LT-InN nanorods and no obvious shift for the HT-InN nanorods. These PL properties are different from that of InN-on-Si epitaxial films.
5:10 PM		D1-1-12 Lasing Action in InN Nanotips Synthesized by Metalorganic Chemical Vapor Deposition J.-S. Hwang, G.-M. Hsu (National Taiwan Ocean University, Taiwan); S.-C. Shi, C.-F. Chen (National Chiao Tung University, Taiwan); L.-C. Chen (National Taiwan University, Taiwan); K.-H. Chen (IAMS, Academia Sinica, Taiwan) InN nano-tips were fabricated with gold as the catalyst using metalorganic chemical vapor deposition. The morphology dependence of the nano-tips on substrate temperature, pressure, and gas flow rate was investigated. Of particular interest is the photoluminescence from the nanotips, wherein apparently amplified spontaneous emission and lasing action were observed. After careful examination, the observed lasing action is very likely due to the random lasing mechanism related to the multiple scattering among the nanotips.