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Current-voltage characteristics of polycrystal cubic nitride samples are studied at various temperatures. The samples were undoped crystals obtained by the method of direct phase transformation of pyrolytic graphite-like boron nitride and crystals doped with sulfur to obtain n-type conductivity. The current-voltage characteristics consist of three different parts: linear and quadratic segments and the region of dramatic increase in the current, which indicates the existence of space-charge-limited currents. The activation energy, Et, and concentration of the trapping centers, Nt, are determined. The experimental data obtained allowed us to calculate, for the first time, the mobility and concentration of free carrier in the conduction band. Possible mechanisms giving rise to a dramatic increase in are made the current on the current-voltage characteristics are discussed. 相似文献
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Takanori Hirano Takeo Oku Masayuki Kawaguchi Katsuaki Suganuma 《Molecular Crystals and Liquid Crystals》2013,570(1):787-792
Abstract Boron nitride nanocapsules with gold, iron oxide and germanium nanoparticles were produced. High-resolution electron microscopy and electron energy-loss spectroscopy showed the gold, iron oxide and germanium nanoparticles were encapsulated in the boron nitide sheets. Weak peaks of photoluminescence spectrum were observed from the nanocapsules with germanium nanoparticles. The present work indicates that the boron nitide nanocapsules with conducting, magnetic and semiconductor nanoparticles can be produced by are melting method, and models for the formation mechanism and nano-structures of the boron nitide nanocapsule were proposed. 相似文献
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Xuxin Yang Hongdong LiYingai Li Xianyi LüShiyong Gao Pinwen ZhuQing Zhang Tiechen ZhangGuangtian Zou 《Journal of Crystal Growth》2009,311(14):3716-3720
Cubic boron nitride (cBN) thick films deposited on mainly c-axis-oriented graphite substrate at room temperature and zero bias by radio frequency (RF) magnetron sputtering were studied. In the growth process, RF power plays a key role in determining the content of cubic phase in films, while the conventional substrate heating and biasing have been neglected. With increase in RF power, the dominated content of films converts from explosion boron nitride (eBN) to cBN. The transformation mechanism has been discussed. The unique structural properties of the “soft” graphite are favorable to propose simple conditions for growing “hard” cBN films. Furthermore, the optical band gap of BN films having ∼90% cubic phase is of ∼5.8 eV obtained from ultraviolet–visible optical transmission measurement. The electron field emission examination shows that cBN film on graphite has a high emission current density of 2.8×10−5 A/cm2 at an applied field of ∼30 V/μm. 相似文献
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化学气相沉积法生长的单层石墨烯具有卓越的力学、热学和电学特性,成为新一代纳米器件的首选材料。对石墨烯电子特性的理论研究有利于推动纳米器件的发展与应用。本文基于密度泛函理论与非平衡格林函数相结合的方法,系统地研究了石墨烯及石墨烯/氮化硼的电子结构特性。结果表明,在高对称K点,带隙为零。在50~400 K范围内,由于费米面的电声子散射作用,单层石墨烯的迁移率随着温度增加呈现显著下降趋势。此外,通过对不同层间距的石墨烯/氮化硼结构的能带、态密度、电子密度等特性分析,发现随着层间距增加,能带间隙减小,导带与价带间的能量差减小。随着原子个数的增加,石墨烯/氮化硼超胞结构与原胞结构的带隙开度变化规律一致,这对石墨烯基器件的结构设计具有一定的指导意义。 相似文献
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Crystallography Reports - The real structure of ultradispersed powders of sphalerite boron nitride synthesized under shock compression has been studied by X-ray diffraction. The lattice microstrain... 相似文献
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Energetic and kinetic characteristics of charge carrier trapping and recombination centres in graphite-like boron nitride produced by gas-phase deposition are discussed. Local levels in X-ray excited PBN are studied using the method of thermally activated spectroscopy of luminescence and conduction, and their position in the band gap is determined from the temperature dependences of the diffusive current and depolarization current. Acceptor and donor level models for different PBN are developed. Their influence on conduction and on luminescence is determined. The scheme of hole-electron transitions by luminescence is suggested. The carbon influence on the nature of the defects creating local levels is discussed. 相似文献
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G. Bhikshamaiah P. V. Mohan Rao S. V. Suryanarayana S. V. Nagender Naidu 《Crystal Research and Technology》1994,29(3):403-408
Ni3Al and Ni3Al alloys containing varying amounts of boron in L12 phase were prepared. All the samples were suitably annealed and then cold-worked by hand filing. X-ray diffraction data are collected on annealed and cold-worked samples. The deformation fault probabilities have been evaluated by two methods, viz. peak shift analysis of powder pattern X-ray reflections of annealed and cold-worked samples, and lattice parameter change between annealed and corresponding cold-worked samples. The values obtained by both the methods are in reasonable agreement. It has been found that the deformation fault probability of Ni3Al and Ni3Al containing boron alloys are very high compared to Ag and Cu base alloys. Further the deformation fault probability of Ni3Al is more sensitive to boron addition. It has been found that at least 1.22 at. % of boron goes into the Ni3Al lattice. 相似文献
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V. I. Ponomarev I. D. Kovalev S. V. Konovalikhin V. I. Vershinnikov 《Crystallography Reports》2013,58(3):422-426
Boron carbide crystals have been obtained in the entire compositional range according to the phase diagram by self-propagating high-temperature synthesis (SHS). Based on the results of X-ray diffraction investigations, the samples were characterized by the unit-cell metric and reflection half-width in the entire range of carbon concentrations. A significant spread in the boron carbide unit-cell parameters for the same carbon content is found in the data in the literature; this spread contradicts the structural concepts for covalent compounds. The SHS samples have not revealed any significant spread in the unit-cell parameters. Structural analysis suggests that the spread of parameters in the literary data is related to the unique process of ordering of carbon atoms in the boron carbide structure. 相似文献
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Muhammed Oz Namik Kemal Saritekin Cetin Bozkurt Erhan Budak Gurcan Yildirim 《Crystal Research and Technology》2016,51(12):708-717
This study is interested in the effect of lithium carbonate on the formation of hexagonal boron nitride (hBN) by means of the available experimental methods including TGA, XRD, FTIR, SEM and HR‐TEM. hBN samples were synthesized at the 1450 °C with different molar ratios of lithium carbonate by modified O'Connor routine. The crystalline hBN formation tended to improve with the increment of the Li2CO3 concentration level (especially after more 20 %). The dopant quantity decreased the residual stresses due to the presence of possible relaxation mechanisms along with the nanocrystal structure, even favored by XRD experimental findings regarding the enhancement of crystal plane alignments, crystallite sizes and lattice parameters. As for the FTIR surveys, the Li2CO3 foreign impurities strengthened more and more the covalent bonds between boron and nitrogen atoms. At the same time, the samples with 40 % lithium carbonate were annealed at the varied temperatures of 1000, 1150, 1300 and 1450 °C to determine the optimum annealing temperature. The XRD+FTIR investigations indicated that the degree of hexagonality improved with the increased annealing temperature. Similarly, the surface morphology confirmed not only the formation of regularity and flaky hexagonal BN structures, but also the strengthening of covalent bonds between the atoms. 相似文献
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X-ray crystallography and Mössbauer spectroscopy were used to investigate the crystallization of the amorphous Fe100−xBx alloys, 14 x 20 annealed at 615 K. As a result of the heat treatment, the formation of crystalline -Fe and Fe3B were observed. Variations in the values of the isomer shift and the orientation of the axis of magnetization indicate changes in the iron-boron bonding and the local atomic arrangement.
Formation of the -Fe phase was determined as a function of boron concentration and annealing time. Crystallization rates of that phase were observed to be dependent on boron concentration and on the annealing time. The average hyperfine field of the untreated samples was observed to increase till x = 17 after which it decreased. This is explained in terms of the Invar behavior of Fe83B17. The anomalous crystallization of Fe86B14 is proposed to be due to the existence of interstitial-like boron sites in a near bcc short range atomic structure. 相似文献
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《Journal of Non》2006,352(9-20):1246-1249
This study presents the processing of micro-bridges used in suspended gate field effect transistor. Micro mechanical structures were processed using different materials. To ensure the mechanical stability, boron doped polysilicon films, showing positive mechanical stress, had to be embedded between two negatively stressed silicon nitride layers. These micro-bridges are used as suspended gate with a gap as low as 500 nm in the field effect transistor process. The pH sensitive membrane is a silicon nitride layer. The device characteristics are sensitive to any electrical charge in the air-gap because of the local high electrical field. It is then possible to detect any charge variation with higher sensitivity than the one reached using other non electrical technique. For example the present structure was used as pH sensor with a sensitivity five times greater than the ISFET usual Nernstian response. 相似文献
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M. Chandra Sekhar B. Gopalakrishna M. M. Kumar S. V. Suryanarayana 《Crystal Research and Technology》1995,30(3):345-352
Samples with the stoichiometric composition Bi2−xPbxSr2Ca2Cu3−yByOz (x = 0.3, y = 0.2, 0.25, 0.3, 0.4) ceramics were prepared by a solid state reaction method. The samples were annealed at 850 °C for 100 hours (treatment A), and the other at 850 °C for 200 hours (treatment B). From the X-ray diffraction data of a ceramic sample it is revealed that all the samples were mixed phases of 2212 and 2223. The variation of the lattice parameters with the dopant level are represented. From the D.C. four-probe electrical resistivity data it was found that for the samples subjected to treatment B the Tc(0) values were higher than those with treatment A. The A.C. susceptibility data were collected by change in the inductance method. The effect of boron doping on the phase formation and Tc(0) is presented and the volume fraction of the phases estimated from the X-ray data. The presence of boron in the samples was confirmed by the inductive coupled plasma method. The microstructure of the samples was studied by scanning electron microscopy. 相似文献
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Yu. S. Perets L. Yu. Matzui L. L. Vovchenko V. Yu. Serdyuk 《Molecular Crystals and Liquid Crystals》2014,589(1):195-201
This paper presents the results of changes in electrical resistivity and thermal conductivity of polymer composites (CMs) with two-component filler. It is shown that thermal conductivity of epoxy CMs strongly depends on structural and morphological characteristics of carbon fillers. The synergistic effect in electrical and thermal conductivities of the studied CMs is observed upon addition of boron nitride BN. The presence of a sufficiently large number of BN particles in CMs promotes a more efficient formation of chains of carbon filler and reduces thermal (electrical) contact resistance between the filler particles by decreasing the distance between particles of the filler. 相似文献
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Muhammed
z Namk Kemal Saritekn etin Bozkurt Gürcan Yildirim 《Crystal Research and Technology》2016,51(6):380-392
This comprehensive study declares experimentally the effects of IA/IIA metal carbonates on the formation of hexagonal boron nitride (hBN) with the aid of the available experimental methods as regards Fourier transform infrared spectroscopy (FT‐IR), powder X‐ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (TEM). hBN is synthesized in the existence of the metal carbonates at the low temperature by modified O'Connor method. The experimental findings of FT‐IR and XRD investigations show that the addition of metal carbonates affects considerably the crystallization of hBN powder during the synthesis process. The presence of the high concentration level of the additions improves harshly the crystallinity. In this respect, the graphitization index deduced from the XRD patterns reduces with the enhancement in the amount of the dopant content. At the same time, the differentiation between the products is analyzed by the SEM surveys. According to the results, the materials synthesized by the Li2CO3 powder exhibit both the tubular form and rod‐like while the other samples prepared by the CaCO3 chemical dopant display the homogeneous plates. Even, the TEM images confirm the nanowires and nanotubes structures such as multi‐walled cylindrical, bamboo nanotubes in all the materials studied in this work. 相似文献
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Amorphous Si–(B–)C–N polymer-derived ceramics (PDCs) with a boron content ranging from 0 to 8.3 at.%, were synthesized by thermolysis of boron-modified poly(methylvinylsilazane). Correlation of the boron content and the thermal stability of these materials in the course of annealing were investigated using high temperature thermal gravimetric analysis (HT-TGA). Furthermore, the initial crystallization of the as-thermolyzed amorphous ceramics was studied by X-ray diffraction (XRD) measurements. The increase of boron content promotes the crystallization of SiC, and inhibits the crystallization of Si3N4. Moreover, the ratio of α-Si3N4/β-Si3N4 in crystalline ceramic decreases with increasing boron content. Thermodynamic modeling proves the influence of boron content on driving force for crystallization. The available thermodynamic model of amorphous Si–C–N domains, nano-crystalline silicon nitride, and nano-crystalline silicon carbide treated as the separated phases has been used to interpret these results. 相似文献
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采用等离子体增强化学气相沉积技术,以NH3、SiH4和N2为反应气体制备富硅-氮化硅薄膜.在优化了其它沉积参数条件下,研究氨气流量对富硅-氮化硅薄膜的结构和光学性质的影响.利用傅立叶变换红外光谱、紫外可见光谱和X射线衍射谱分析了薄膜的键合情况、带隙结构.结果表明,随着NH3流量的增大,薄膜中的Si-N键和N-H键增强,Si-H键减小并向高波数方向移动,薄膜逐渐由非晶SiNx相向小晶粒Si3 N4相转变.同时随着NH3流量的增大,薄膜的光学带隙逐渐展宽,微观结构的有序度降低.XRD图谱分析表明薄膜内的平均晶粒尺寸也随着氨气流量的增加而在逐渐增大.结合以上结果分析,适当增加NH3流量有助于薄膜由非晶SiNx向包含小晶粒的Si3 N4转变. 相似文献