Characterization of Crystalline Carbon Nitride Films Deposited on Si and Si3N4/Si Substrate by RF Magnetron Sputtering System with DC Bias

Crystalline carbon nitride films were deposited on Si and Si₃N₄/Si substrate by reactive RF magnetron sputtering system with chamber heating and DC bias. The deposited films showed -C₃N₄, -C₃N₄ and lonsdaleite phase by XRD, XPS and FTIR. The crystalline morphology was found to gave a hexagonal structure, which has theoretical unit cell of carbon nitride observed in SEM photographs. When nitrogen gas ratio is 70%, RF power is 300 W and DC bias is –80 V, the growth rate of carbon nitride film on Si₃N₄ substrate is 2.2 m/hr, which is a relatively high growth rate compared with those in previously reported papers. The deposited films have thermally stable properties in the range of 650_C to 1,400_C.     

Synthesis of new boron-rich building blocks for boron neutron capture therapy or energy-filtering transmission electron microscopy

The synthesis of a new ortho-carborane derivative, tetracarboranylketone 4, is reported here. Ketone 4 was prepared from a tetraalkynylated ketone by the addition of decaborane. The keto group was then easily modified to yield the glycosides 17alpha and 18beta, which contain glucose or galactose, respectively, and the nucleotide 13b. In addition to ketone 4, which is acyclic, cyclic ketone 8 was also synthesised. X-ray diffraction analysis of compound 4 indicated the presence of two toluene guest molecules per molecule of the host compound. Furthermore, compound 4 displays a rather low cytotoxicity. These novel products can be used as building blocks to create a new class of biomolecules containing high-density carborane clusters. Such molecules may constitute powerful tools for applications like Boron Neutron Capture Therapy or Energy-Filtering Transmission Electron Microscopy.     

Properties of wurtzite GaN MESFETs studied by two-dimensional full band Monte Carlo approach

The properties of a GaN Metal-Semiconductor Field Effect Transistor were studied based on two-dimensional full band Monte Carlo simulations. The dependences of the distributions of the electric potential, electron concentration, electric field, drift velocity, and average electron energy on the gate-source voltage (V_GS) and drain-source voltage (V_DS) were obtained, then the characteristics of the drain current (I_DS) versus the drain-source voltage (V_DS) and the transconductance (G_m) versus V_GS characteristics were determined. At and I_DS is 5.03 A/cm, which is higher value. The G_m−V_GS curve shows bell shaped and the maximum G_m is 112 ms/mm at and The current gain cutoff frequency (f_T) is 98 GHz at and      

碳氮纳米管薄膜及其场致电子发射特性

利用微波等离子体增强化学气相沉积技术,在玻璃衬底上600℃～650℃的低温下制备出了碳氮纳米管薄膜,氮含量为12％,采用扫描电子显微镜(SEM)、X射线光电子谱(XPS)和Raman光谱等测试手段对所制备薄膜的表面形貌、微结构和成分进行了分析,并研究了其场致电子发射特性,阈值电场为3．7V／μm。当电场为8V／μm时,电流密度为413．3μA／cm^2,实验表明该薄膜具有优异的场发射性能,而且用这种方法制备的薄膜将大大简化平板显示器件的制作工艺。     

Some Characteristic Features of Formation of Ceramics Based on Composite Powders SiC ― Si3N4 ― Si2N2O

We have studied the characteristic features of synthesis of composite powders SiC Si₃N₄ Si₂N₂O. We have investigated processes involving hot pressing of these powders without activating additives and a protective atmosphere. We consider the mechanical properties of ceramics obtained on the basis of these composite powders.     

Detailed structural analysis of semiconductors with X-ray scattering

Some of the most important material systems, GaInN alloys and quantum dot structures create interesting and complex challenges for structural analysis. This paper concentrates on the interpretation of the microstructure of both these materials, the former to assess the defect separation and the latter to obtain the shape and composition of the quantum dots. The methods used are based on mapping the X-ray intensity in reciprocal space and simulating proposed models to achieve good agreement with the experimental results. An indication of the reliability of these methods is presented.The simulation of the 0002 reciprocal space map of a 0 0 0 1 orientated InGaN/GaN sample yielded a range of dimensions of the perfect regions between defects of 60 and 220 μm. This comes from careful fitting of the tails of the scattering parallel to the surface plane. The average composition within an InGaAs quantum dot has been determined to a reliability of ±3% and the dimensions of these buried dots evaluated from simulating the reciprocal space maps using the in-plane scattering geometry.     

高能机械化学法制备超微氮化钼粉体

在室温下通过自行设计的高能机械化学球磨机,使钼粉在NH3气氛下经过高能球磨得到超微氮化钼粉体.分别利用X射线衍射仪、扫描电镜和透射电镜对制得的粉体结构和粒度进行分析.结果表明,在球料质量比为8∶1的情况下经过30 h球磨,得到了FCC结构的Mo2N粉体,粉体平均粒度在100 nm以内.机械化学反应过程中,一方面,NH3分子在清洁的钼金属表面的化学吸附起着重要的作用,为球磨过程中由于介质球碰撞所产生的储存于钼粉中的能量(界面能和缺陷能)提供了Mo-N化学吸附向氮化钼转变所需的激活能.另一方面,钼粉晶粒细化改变了Mo原子表面电子的不饱和性,从而促进了Mo与N的键合作用.在Mo与NH3的高能机械化学反应过程中,球磨转速的高低对整个反应的速度起决定性作用.     

Explosion energy in the synthesis of superhard phases

This article reviews works of the Institute for Problems of Materials Science evoted to the application of explosion energy for the synthesis of superhard phases (SHPs) based on phase transformations of layered structures of carbon and boron nitride at high pressures. Major attention is given to the development and application of the high-temperature shock compression method, which made it possible to synthesize a new structural form of carbon and to attain, for the first time, a 70% yield of cubic BN under shock compression. The diagram of BN phase transformations by different mechanisms is discussed, which demonstrates the dependence of the phase composition of shock compression products on the ordering degree of the starting graphite-like structure. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 3–10, 2007.     

Adsorption-chemical activity and interaction in the boron nitride-titanium hydride system

The paper examines the effect of physicochemical properties of starting boron nitride and titanium hydride on their reactive activity in the synthesis of the TiN-TiB_x composite. There are kinetic data on thermal desorption of the active adsorbate from the BN surface, which precipitated from the gas mixture (20 vol.% O₂-80 vol.% N₂ under the relative humidity of 80%). Kinetics of hydrogen release from titanium hydride in isothermal conditions and controlled rate of temperature increase in the reactive system is researched. A possible mechanism of chemical transformations of starting compounds and synthesis of the TiN-TiB_x composite is considered. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 5–6 (455), pp. 102–110, 2007.     

40MnB钢硼含量的控制

莱钢特钢厂用50t电炉-50t（LF＋VD）精炼炉工艺流程生产含硼钢，钢中B元素控制非常重要。通过分析影响硼元素收得率的因素，对电炉及精炼炉各环节制定了严格生产工艺要点，保证了钢中有效酸溶硼含量控制在合格范围内。