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Relationship between the orientation of texture and heteroepitaxy of diamond and related materials films on silicon single crystal and the valence electron structure of the interface

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Science China(Technological Sciences) 2007年第5期50卷 664-673页

作者： LI ZhiLin LI ZhiFeng HUANG Qin College of Materials Science and Engineering Beijing University of Chemical Technology Beijing 100029 China College of Materials Science and Engineering Beijing University of Chemical Technology Beijing 100029 China College of Materials Science and Engineering Beijing University of Chemical Technology Beijing 100029 China

Diamond and cubic boron nitride films have already been applied practically be- cause of their excellent properties. The specific orientations of the films have spe- cial meaning on their application in optics and microelectronics fields. In this paper, the relative electron density differences of the interface between the different crystal planes of silicon substrate and those of diamond and cubic boron films are calculated with the empirical electron theory in solids and molecules. Analyses on the calculation results show that in the range of the researched films, the smaller the relative electron density difference between the film and the substrate is, the stabler the film is in thermodynamics. Therefore, the electron density difference is the essential factor of determining the orientation of the texture and heteroepitaxy of the films. The deductions accord well with the experimental facts. The calcula- tion methods and the theory not only provide a new angle of view for the research of the growth mechanism of diamond film and cubic boron nitride film on the sili- con substrate, but also provide a possible direction for the prediction of the orien- tation of other films.

关键词： films, interface electron density, texture, heteroepitaxy, diamond, cubic boron nitride

Structures and properties of [CoPt/Ag]_(n) multilayer films

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Science China(Technological Sciences) 2005年第2期48卷 214-219页

作者： XU Xiaohong YANG Zhiguang WU Haishun School of Chemistry and Material Science Shanxi Normal University Linfen 041004 China School of Chemistry and Material Science Shanxi Normal University Linfen 041004 China School of Chemistry and Material Science Shanxi Normal University Linfen 041004 China

The magnetic properties and structures of [CoPt/Ag]n multilayer films deposited by DC magnetron sputtering have been studied. During the deposited process, two kinds of deposited sequences, that is Ag layer (FDAG) first deposited or CoPt layer (FDCP) first deposited, have been chosen. The results show that the microstructures and coercivities were strongly influenced by the deposited sequence and the thickness of films. The coercivities of [Ag/CoPt]n with FDAG are obviously higher than those of [CoPt/Ag]n with FDCP. Especially, when the thickness of films is 8 nm, the difference of coercivities between the FDAG film and the FDCP film is the largest. It is possibly because Ag plays a role of underlayer in FDAG multilayers, which can induce both the transformation from fcc to fct and the oriented growth along c-axis. In addition, δ M curves reveal that the [CoPt/Ag]8 multilayer film has a lower intergrain interaction than the CoPt/Ag bilayer film.

关键词： [CoPt/Ag]n multilayer films, deposition sequence, magnetic properties, X-ray diffraction.

FeS_(2) (pyrite) electrodeposition thin films and study of growth mechanism

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Science China(Technological Sciences) 2005年第6期48卷 601-611页

作者： DONG Youzhong1, ZHENG Yufeng1, ZHANG Xiaogang2, DUAN He1, SUN Yanfei1 & CHEN Yanhua1 1. Department of Physics, Xinjiang University, Urumqi 830046, China 2. Institute of Applied Chemistry, Xinjiang University, Urumqi 830046, China 1. Department of Physics Xinjiang University 830046 Urumqi China 2. Institute of Applied Chemistry Xinjiang University 830046 Urumqi China

Ferrous sulfide (FeS) thin films were initially electrodeposited on indium-tin oxide (ITO) substrates in the aqueous solution containing iron, sulfur elements and then annealed in the sulfur atmosphere. Thereby, we successfully obtained the single-phased iron pyrite (FeS2) thin films with good quality. The experimental parameters for electrodeposition and the post-growth thermal-dynamical conditions have been calculated so that more details about the effect of thermal-dynamical conditions on the micromechanism concerned with the iron pyrite crystal growth as well as the properties of the samples have been discussed.

关键词： electrodeposition, FeS2 (pyrite), thin films, growth dynamics.

Preparation and properties of GaN films on Si(111) substrates

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Science China(Physics,Mechanics & Astronomy) 2003年第2期46卷 173-177页

作者：杨莺歌马洪磊郝晓涛马瑾薛成山庄惠照 School of Physics and Microelectronics Shandong UniversityJinan 250100China Institute of Semiconductor Shandong Normal UniversityJinan 250014P.R.China

High-quality gallium nitride (GaN) films were prepared on Si(111) substrates by sputtering post-annealing-reaction technique. XRD, XPS, and SEM measurement results indicate that polycrystalline GaN with hexagonal structure was successfully prepared. Intense room- temperature photoluminescence that peaked at 354 nm of the films is observed. The bandgap of these films has a blueshift with respect to bulk GaN.

关键词： photoluminescence, gallium nitride films, Si (111).

Fabrication of sub-micro size PZT array and their ferroelectric properties

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Science China(Technological Sciences) 2006年第6期49卷 693-700页

作者： ZHAO Gaoyang1, ZHANG Weihua1, XU Guomin1, DENG Xiaocui1, JIANG Bailing1 & ZHAO Wei2 1. School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048, China 2. Xi’an Institute of Optics and Precision Mechanics of CAS, Xi’an 710048, China School of Materials Science Engineering Xi’an University of Technology Xi’an 710048 China Xi’an Institute of Optics Precision Mechanics of CAS Xi’an 710048 China

The photosensitive PZT sols and their gel films were prepared by sol-gel process. Based on the photosensitivity of the PZT gel films, two-dimensional (2D) array of the PZT gel film was fabricated using twice-exposure of double-beam interference on the gel film. PZT gel films coated on ITO/quartz substrate were exposed to an interference fringe of 325 He-Cd laser beams, the substrate was rotated by 90° between the first and second irradiation steps. Island type periodic 2D array structures with a pitch of 1 μm and cell size of about 480 nm × 480 nm × 40 nm were formed after the irradiation, and followed by leaching with organic solvent, and then by heat treatment at 600°C for 15 min. The hysteresis loops of the cell in PZT array were in-situ measured by the online-operation of TF analyzer and atomic force microscope (AFM). The probe can be located on the locked cell of PZT array in the AFM image. The alternating voltage applied to the locked cell is supplied by the TF analyzer through the conductive coating probe, and then the test signal is fed back to the TF analyzer to obtain the hysteresis loop of the locked cell of array in the absence of top electrode. The results show that the sub-micro size PZT arrays prepared in this way are of polarization reversal characteristics with the alternating electric fields, thereby exhibiting obvious ferroelectricity.

关键词： PZT, ferroelectric films, photosensitivity, hysteresis loop.

Improvement of luminescent stability from carbon nanotube field emission display based on printed CNT film

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Science China(Technological Sciences) 2006年第3期49卷 283-290页

作者： ZENG Fanguang ZHU Changchun LIU Xinghui LIU Weihua School of Electronics and Information Engineering Xi'an Jiaotong University Xi'an 710049 China School of Electronics and Information Engineering Xi'an Jiaotong University Xi'an 710049 China School of Electronics and Information Engineering Xi'an Jiaotong University Xi'an 710049 China School of Electronics and Information Engineering Xi'an Jiaotong University Xi'an 710049 China

Aiming at the influences of poor contact at carbon nanotube (CNT)/electrode interface on luminescence stability in printed CNT film, a new co-sintering process for cathode fabrication was presented to improve the luminescent stability of fully printed CNT-FED. By co-sintering the printed silver and CNT layers, CNTs geometrically matched with Ag surface and/or embedded into Ag layer at the bottom of the co-sintered film, large CNTs block and bulk silver nested each other at the top of the co-sintered film. All these structures increased the contact area at CNT/Ag interface, which could increase the probability of forming ohmic contact at CNT/Ag interface. The luminescent stability of printed CNT-FED with co-sintered cathode could be improved as 5.6 times high as that of common devices.

关键词： printed CNT films, field emission display, luminescent stability, co-sintering process.

Interfacial behaviors of PMMA-PEO block copolymers at the air/water interface

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Science China Chemistry 2005年第6期48卷 567-573页

作者： CHENG Caixia1, JIAO Tifeng2, TANG Rupei1, LIU Minghua2 & XI Fu1 1. State Key Laboratory of Polymer Physics and Chemistry, Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China 2. CAS Key Laboratory of Colloid and Interface Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China 1. State Key Laboratory of Polymer Physics and Chemistry Joint Laboratory of Polymer Science and Materials Institute of Chemistry Chinese Academy of Sciences 100080 Beijing China 2. CAS Key Laboratory of Colloid and Interface Science Institute of Chemistry Chinese Academy of Sciences 100080 Beijing China

Diblock copolymer of PMMA291-b-PEO114 and triblock copolymer of PMMA120-b- PEO227-b-PMMA120 were synthesized and their interfacial properties at the air-water interface were investigated, where both blocks of polyethylene oxide (PEO) and poly(methyl methacrylate) (PMMA) are surface active but the former is soluble in water while the latter is not. Both the block copolymers could form monolayers with two obvious transition regions. The first transition point is around 10 mN/m, which could be assigned to the pancake-brush change of the PEO chains. The other is around 18 mN/m, which could be ascribed to the condensed packing of PMMA. The surface morphological changes during the compression of the Langmuir monolayers are inves-tigated by using the AFM and SEM methods for the films deposited at different surface pressure or molecular areas. At a lower surface pressure, a typical morphology of PEO-con- taining lipopolymers is observed. Upon compression, sphere-dominant morphologies were observed. While the diblock copolymer is easy to folding, the triblock copolymer is in favor of formation of circular domains through vesiculation.

关键词： PMMA-PEO, block copolymers, monolayer, Langmuir-Blodgett films, AFM.

How linear molecules resist to shear:the origin of nanoscale friction

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Science China(Physics,Mechanics & Astronomy) 2004年第z1期47卷 15-20页

作者： Linmao QIAN G.Luengo E.Perez Laboratoire de Physique Statistique de I’Ecole Normale Superieure associee au CNRS et aux Univer-sites Paris Vl et Paris Vll24rue Lhomond75231 Paris Cedex 05France Key Laboratory of Advanced Technologies of Materials(Ministry of Education) Tribology Research InstituteSouthwest Jiaotong UniversityChengdu 610031China

Friction force measurements between smooth surfaces across two layers of linear alkanes over five decades of speeds are presented. A maximum friction dissipation is observed at a characteristic speed. The behaviour is described by a new approach: the formation and destruction of molecular bridges between confined alkane layers. The bridges interdigitated between the layers exhibit a thermally activated resistance to *** analytical model involving activation barriers accounts for the overall behaviour of the forces over four decades of speed. This first simple semi-quantitative description sheds new light on the subtle mechanisms of friction at the nanoscale level and shows how the molecular length influences the tribological properties of the liquid.

关键词： nanotribology, friction, surface force apparatus, interface molecular films, linear alkanes.