共查询到20条相似文献,搜索用时 15 毫秒
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V.S. Pavelyev S.A. Borodin N.L. Kazanskiy G.F. Kostyuk A.V. Volkov 《Optics & Laser Technology》2007,39(6):1234-1238
The fabrication of diamond-based optical elements for high-power CO2 lasers is of particular interest because of low optical absorption, high thermal conductivity and weak temperature dependence of the refractive index of diamond. In earlier publications, we presented the results of the implementation of ion-chemical etching technology for generating a diffraction grating on the surface of a diamond film. The results on generating diamond diffractive optical elements and a sub-wavelength antireflection structure by plasma etching were also presented. In this paper, we study the generation of the grating on the diamond surface by ion-chemical etching. The choice of (Ar+O2) mixture as a working gas and use of niobium as a masking layer are substantiated. The results of studying a diffraction microrelief generated on the diamond-film surface through ion-chemical etching are discussed. 相似文献
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By using first-principles density functional theory, we investigate the charge distribution of a potassium-doped layered combined system of graphene and hexagonal boron nitride. Two configurations of potassium-doped hexagonal boron nitride layers on graphenes and the reverse geometry of graphenes on hexagonal boron nitride layers are considered. We find that the charge distribution exhibits different features in these two situations. In the former case, the outmost hexagonal boron nitride layer cannot screen the external charges offered by potassium atom completely and most of the transferred charges reside on the two bounding layers. In contrary, the outmost graphene layer near the potassium atom can accept almost all of the transferred charges and only a few of them stay at interior layers in the latter case. A more amazing result is that the characteristics of charge transfer are independent of the number of hexagonal boron nitride layers and graphenes. 相似文献
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金刚石薄膜红外椭圆偏振参量的计算与拟合 总被引:2,自引:0,他引:2
用红外椭圆偏振仪对热丝化学气相沉积法制备的金刚石薄膜的光学参量进行了测量。由于表面状态和界面特性的差异,分别对镜面抛光硅片和粗糙氧化铝基片上的金刚石薄膜建立了不同的模型,并在此基础上进行了测试结果的计算拟合。为了综合反应诸如表面粗糙度等表面界面因素对测试结果的影响,根据衬底特性将表面层和界面层分离出来,并采用Bruggeman有效介质方法对它们的影响进行了近似处理。结果表明,硅衬底上金刚石薄膜的椭偏数据在模型引入了厚度为879nm的表面粗糙层之后能得到很好的拟合。而对于氧化铝衬底上的金刚石薄膜而言,除了在薄膜表面引入了粗糙层之外,还必须在衬底和金刚石界面处加入一层由体积分数为0.641的氧化铝、体积分数为0.2334的金刚石和体积分数为0.1253的空隙组成的复合过渡层(厚度995nm),才能使计算值与实验参量很好地吻合。 相似文献
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X. D. Wang W. D. Hu X. S. Chen J. T. Xu X. Y. Li W. Lu 《Optical and Quantum Electronics》2011,42(11-13):755-764
The spectral responsivity characteristics have been numerically studied for visible blind GaN/AlGaN p-i-n ultraviolet detector. The effects of the absorption layer and the n-layer thicknesses on the photoresponse have been investigated. It is shown that the absorption layer and n-layer thicknesses have notable impacts on the peak value of photoresponse and the rejection ratio of short-wavelength side, respectively. Finally, the effect of doping concentration of the absorption layer on photoresponse is discussed in detail. It is demonstrated that mobility degradation, Radiative and Auger recombinations are jointly responsible for the decrease of photoresponse with increasing doping concentration of the absorption layer. 相似文献
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Diamond is a very persistent metastable form of carbon. At low pressure, graphitization of the diamond surface is observed at temperatures lower than 1700 °C. The basic cause of this is known to be interaction with oxygen. In the present paper, the microphysics of the phenomenon of diamond surface graphitization was studied. It has been shown that surface graphitization proceeds in several stages. First, a thin surface layer of graphite is developed due to interaction with oxygen (and probably other substances). As temperature is increased, nuclei of 5–10 nm in size are formed within it. The graphite nuclei are capable of migrating along the surface of diamond. They form ‘nests,’ where they are coalesced into aggregates 10–100 nm in size. These ‘nests’ give rise to diamond surface layer graphitization, which proceeds along diamond {211} crystallographic planes and forms graphitization figures. At this stage, the factor that determines the transformation is the pressure exerted on graphitizing material by the surrounding diamond. 相似文献
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Jürgen Ristein 《Surface science》2006,600(18):3677-3689
The crystal structure of diamond is identical with that of its more common semiconductor relatives silicon and germanium. Consequently, a number of surface properties in terms of reconstructions, surface states and surface band diagrams are similar as in the case of Si or Ge. But diamond also exhibits a number of unusual and potentially very useful surface properties. Particularly when the surface dangling bonds are saturated by monovalent hydrogen atoms (donor-like), surface states are removed from the gap, the electron affinity changes sign and becomes negative, and the material becomes susceptible to an unusual type of transfer doping where holes are injected by acceptors located at the surface instead of inside the host lattice. These surface acceptors can in the simplest case be adsorbed molecules conveniently chosen by their electron affinity, but they can also be solvated ions within atmospheric water layers or electrolytes in contact with the hydrogenated diamond surface. In this article the surface properties of diamond will be reviewed with special emphasis on this new kind of doping mechanism. 相似文献
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摘 要:金属钛原子在金刚石表面的结合强度直接影响金刚石真空介电窗口的使用性能和寿命. 本文通过基于密度泛函理论的第一性原理方法研究了Ti原子与不同氮掺杂位置的金刚石(001)界面的结合能、电荷分布和稳态几何结构. 结果表明:Ti原子与N原子取代掺杂在第二层C原子处金刚石表面的结合能比未掺杂和掺杂在第三层的结合能都高,达到-7.293 eV,使得金刚石表面形成的界面结构更加稳定,结合强度更好;通过电荷分布分析,N原子掺杂在第二层金刚石表面的Ti原子上的电荷转移最明显,对金刚石表面碳原子吸附最强,也具有更好的结合强度. 与未掺杂金刚石表面形成的Ti-C键键长相比,N掺杂在第二层和第三层C原子处金刚石表面形成的Ti-C键键长比前者分别长0.051 Å和0.042 Å,略有增加. 相似文献
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L. A. Alekseeva V. D. Natsik R. V. Romashkin L. A. Vashchenko A. S. Garbuz V. Yu. Lyakhno 《Physics of the Solid State》2006,48(8):1513-1520
The plastic and strength properties of polycrystals obtained as a result of rapid crystallization of a N2 + n-H2 gas mixture were studied. Samples were stretched under low loads at liquid-helium temperatures. A qualitative difference was revealed between the strain-stress curves for polycrystals of a N2 + n-H2 mixture and pure n-H2. It was established that the N2 impurity leads to a substantial increase in the plasticity resource and to a small increase in the strength of normal hydrogen. The experimental results are interpreted assuming a two-phase structure of the mixed polycrystals (namely, the presence of fine N2 crystallites in large n-H2 crystallites). The specific features of the formation of dislocation ensembles in this heterogeneous polycrystal and the evolution of these ensembles during deformation are discussed. 相似文献
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《Comptes Rendus Physique》2019,20(6):583-592
During the growth of a single-crystal diamond by MPCVD, polycrystalline diamonds are prone to grow in the edge regions. This substantially reduces the usable area of the grown diamond film. In addition, the inhomogeneous distribution of internal stress causes diamond to crack during continuous growth. In recent years, a series of experimental studies have been carried out to solve these problems and some achievements have been obtained. However, in order to understand fundamentally the growth mechanism of diamond, the relationship between growth quality and various influencing factors still needs to be quantitatively studied through integrated simulations and experiments. Electron number density and substrate temperature are important factors affecting diamond crystallization quality. In this paper, the growth conditions of the diamond were simulated and analyzed. Simulation results were compared with the experimental results. This evidences that the surface temperature distribution is relatively homogeneous, and that the significant electron number density gradient in the axial direction is the main reason for the formation of polycrystals in the edge regions. Therefore, substrate holders with different cavity depths were designed and the substrates grew in the same temperature range. The surface morphologies, crystalline qualities, and internal stress distributions of the grown diamonds were measured, and it was found that the quality of growth increased first and then decreased with the depth of the cavity, while the growth rate decreased with increasing the latter. These results are in good agreement with the simulation results. Finally, suggestions on the selection of the substrate holder for film growth with different thicknesses are proposed. 相似文献
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MOCVD法生长SAWF用ZnO/Diamond/Si多层结构 总被引:4,自引:2,他引:4
使用等离子体辅助MOCVD系统在金刚石,硅衬底上成功地制备了氧化锌多层薄膜材料,通过两步生长法对薄膜质量进行了优化。XRD测试显示优化后的样品具有c轴的择优取向生长,PL谱测试表明样品经优化后不仅深能级发射峰消失,同时紫外发射峰增强。对优化后的样品的表面测试显示出较低的表面粗糙度。比较氧化锌多层薄膜结构的声表面波频散曲线,ZnO薄膜声表面滤波器受膜厚和衬底材料的影响较大。当ZnO薄膜较薄时,在它上面的传播速度将与衬底上的传播速度接近,与其他衬底上生长的薄膜相比,以金刚石这种快声速材料为衬底的ZnO多层薄膜结构,声表面波滤波器的中心频率将提高1倍左右。 相似文献
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本文利用迁移率谱分析了离子束刻蚀后的碲镉汞晶体, 发现180 μm的p型碲镉汞晶体在刻蚀后完全转为n型, 且由两个不同电学特性的电子层组成:低迁移率的表面电子层和高迁移率的体电子层. 通过分析不同温度下的迁移率谱, 表明表面电子层的迁移率不随温度而变化, 而体电子层的迁移率随温度的变化与传统的n型碲镉汞材料一致. 不同厚度下的霍尔参数表明体电子层的电学性质均匀. 另外, 通过计算得到表面电子层的浓度要比体电子层高2-3个数量级. 相似文献
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G.A. Shafeev E.D. Obraztsova S.M. Pimenov 《Applied Physics A: Materials Science & Processing》1997,65(1):29-32
2 O, (CH3)2SO). Diamond samples are virtually transparent at this wavelength, and the coupling of laser radiation to diamond is via the
formation of a thin graphitized layer at the diamond surface. The etching rate in liquid media is slightly higher than in
air at otherwise equal conditions and is as high as 50 μm/s for etching with a scanning laser beam. Raman spectra measurements
carried out on diamond samples etched in air show the presence of glassy carbon on the surface, whereas for samples etched
in a liquid the diamond peak at 1332 cm-1 dominates with significantly lower intensity of the glassy carbon peak. Electroless copper deposition on the laser-etched
features is studied to compare the catalytic activity of the diamond surface etched in air with that etched in liquids. Possible
mechanisms responsible for the observed difference both in the structure of the etched area and in the electroless Cu deposition
onto the surface etched in various media (air or liquids) are discussed.
Received: 2 August 1996/Accepted: 7 January 1997 相似文献
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Diamond is well known as the hardest material in nature. It also has other unique bulk physical and mechanical properties, such as very high thermal conductivity and broad optical transparency, which enable a number of new applications now that large areas of diamond can be fabricated by the new diamond plasma chemical vapor deposition (CVD) technologies. However, some of the most interesting properties of diamond, including the ability to be grown over large areas by CVD processes, result not from its bulk properties but from its special and unique surface chemistry. The surface chemistry derived properties are as remarkable as the bulk properties, and in the end may enable the development of new applications, technologies, and industries which are at least as important as those based on the bulk properties. Some of these surface properties are extreme chemical inertness, low surface energy, low friction coefficients, negative electron affinity, biological inertness, and high over-voltage electrode behavior. The surface science and some of the interesting ongoing research in these areas are explored and illustrated, and unresolved questions are highlighted. 相似文献
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采用化学气相沉积(CVD)技术,以高温高压(HTHP)合成的(100)金刚石和p型(100)Si为衬底制备了硫掺杂和硼-硫共掺杂金刚石薄膜,利用原子力显微镜(AFM)、扫描隧道显微镜(STM)及隧道电流谱(CITS)等手段分析同质和异质外延CVD掺杂金刚石薄膜的结构和性能.结果表明:异Si衬底上CVD金刚石的形核密度低,薄膜表面比较粗糙,粗糙度达到18.5nm;同质HTHP金刚石衬底上CVD金刚石薄膜晶粒尺寸约为10—50nm,表面平整,表面粗糙度为1.8nm.拉曼测试和电阻测量的结果显示,在HTHP金刚
关键词:
金刚石
掺杂
外延 相似文献
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Structure and energy related properties of neutral and charged vacancies on relaxed diamond (1 0 0) (2 × 1) surface were investigated by means of density functional theory. Calculations indicate that the diffusion of a single vacancy from the top surface layer to the second layer is not energetically favored. Analysis of energies in charged system shows that neutral state is most stable on diamond (1 0 0) (2 × 1) surface. The multiplicity of possible states can exist on diamond (1 0 0) surface in dependence on the surface Fermi level, which supports that surface diffusion of a vacancy is mediated by the change of vacancy charge states. Analysis of density of states shows surface vacancy can be effectively measured by photoelectricity technology. 相似文献
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Marián Varga Tibor I?ák Alexander Kromka Marian Vesely Karel Hru?ka Miroslav Michalka 《Central European Journal of Physics》2012,10(1):218-224
In this study we have investigated diamond nucleation on Si substrates by ultrasonic seeding with different liquid solutions
of Ultradispersed Detonation Diamond (UDD) powder in a mixture of metal nano- or microparticles (Ni, Co, Y). The influence
of different solutions on nucleation efficiency was investigated. For highlighting nucleation centers and better evaluation
of the nucleation process the nucleated samples were moved into a Microwave Plasma Enhanced Chemical Vapor Deposition (MW
CVD) reactor and a ”short-time” (10 min), then followed by a ”long-time” (+1 hour), diamond deposition was performed. The
morphology of samples was characterized by Scanning Electron Microscopy (SEM) and the chemical composition of grown diamond
layer was investigated by Raman Spectroscopy. From the measurements we found out that microsized metal particles positively
influenced nucleation and the uniformity of the deposited diamond thin film. The lowest surface roughness was achieved in
the case of nanodiamond powder mixed with Co and Y metal powder. The influence of Ni, Co and Y to the nucleation and early
growth stage are discussed. 相似文献
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K. V. Reich 《JETP Letters》2011,94(1):22-26
The optical properties of nanodiamond suspensions have been calculated. The main supposition is that carbon dimers, which
in many aspects are analogous to Pandey chains (2 × 1) on the surface of bulk diamond, are formed on the surface of nanodiamonds
due to the surface reconstruction. All experimentally observed features of the absorption of nanodiamond suspensions have
been explained on the basis of these ideas. Whereas the diamond nucleus does not absorb light in the visible spectral range,
dimers on the surface of the diamond core absorb light in the entire range of optical wavelengths. In addition, there are
two features at energies close to 1.5 and 5 eV in their absorption spectrum. 相似文献