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采用微波等离子体增强化学气相沉积(MPECVD)法,在涂有FeCl3的硅衬底上制备出了纳米非晶碳薄膜.通 过SEM、XRD和拉曼光谱分析了薄膜材料的形貌和结构.并研究了薄膜材料的场发射特性.结果表明:薄膜的开启电场仅为0.39 V/μm;当电场强度为1.85 V/μm时,电流密度高达3.06 mA/cm2;且场发射点均匀、密集、稳定.迭代法计算表明薄膜材料的功函数为3.1 eV,发射点密度约为1.7×105个/cm2.这些均表明该薄膜是一种性能优良的场发射阴极材料. 相似文献
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利用磁过滤等离子体结合氧化铝模板(AA0)技术在室温下制备了具有优异场发射性能的铜掺杂类金刚石(DLC)纳米点阵列.微观分析表明,铜掺杂类金刚石纳米点阵列分布均匀,密度高达109cm-2;利用X射线光电子能谱对制备的铜掺杂类金刚石纳米点阵列进行结构分析,测得铜的掺杂量为3.6;且sp3键含量高达60;;通过对铜掺杂类金刚石纳米点阵列的场发射性能测试,试验结果表明,铜掺杂类金刚石纳米点阵列开启电场和阈值电场分别为0.08V/μm,0.42V/μm,并且在电场值为0.67V/μm时,发射电流密度高达95mA/cm2,场发射性能明显优于无掺杂类金刚石纳米点阵列. 相似文献
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采用微波等离子体化学气相沉积法在经研磨处理后的Si(111)面上制备出了纳米非晶碳薄膜.为改善薄膜的场发射性能,在研磨好的Si基底上运用直流磁控溅射法沉积了一层金属过渡层.本文分别选择三种常见金属:钛(Ti)、鉬(Mo)、镍(Ni)来作对比试验.结果发现用钛作为过渡层时薄膜场发射效果最好,主要表现为开启电场低,同一电场下发射电流大,发射点密度较大且分布均匀等.利用迭代法计算了钛作为过渡层时制备的纳米非晶碳薄膜的有效发射面积和功函数. 相似文献
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对电化学沉淀法制备的氧化锌纳米棒阵列,通过室温下真空场发射电流密度与外加电压关系的测量,研究其场发射特性.根据测量数据,基于 Fowler-Nordheim 方程,估算了样品场发射效应的增强因子,观察到其取值随外加电压变化具有反常的两阶段性,即当外电场强度在3.3 V/μm 场发射开启值到4.3 V/μm之间时,增强因子值为1339,外加场强大于4.3V/μm 时,增强因子锐减至296;结合样品的光致发光谱和能量散射谱,应用半导体中强电场效应、掺杂半导体中温度对费米能级、载流子浓度和迁移率影响,通过场发射电流密度测量系统的串联电路等效,分析了样品缺陷态对此两阶段性的决定和影响. 相似文献
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WO3/TiO2复合薄膜具有许多特性,是一种优良的光电功能薄膜材料.利用先进的制膜技术获得性能优异的纳米结构WO3/TiO2复合薄膜,对提高光电器件的性能及应用具有重要意义.本文着重介绍了溶胶-凝胶法、水热法、电沉积法和磁控溅射法制备纳米结构WO3/TiO2复合薄膜.总结了纳米结构WO3/TiO2复合薄膜在电致变色智能窗、光催化技术、湿度传感器上的应用.最后,针对纳米结构WO3/TiO2复合薄膜现状提出了未来发展趋势. 相似文献
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本文综述了近年来国内外研究者在纳米金刚石薄膜的掺杂、导电性能、场发射性能和电化学性能等方面的工作,涉及化学气相沉积法制备n型纳米金刚石薄膜,离子注入掺杂纳米金刚石晶粒提高薄膜的n型导电性能,金属离子注入制备场发射性能良好的纳米金刚石薄膜,低剂量离子注入和晶粒表面氧终止态获得高迁移率n型电导,纳米金刚石/石墨烯复合结构的调控对其电学及电化学性能的影响,以及硼掺杂金刚石薄膜电极的微结构和电化学性能研究等。综合分析发现,晶粒掺杂和表界面协同调控可以提升薄膜的电学性能、场发射性能及电化学性能,为纳米金刚石薄膜在纳米电子器件、电化学电极等领域的应用提供了理论基础。 相似文献
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本文针对模具对陶瓷材料的要求,从提高陶瓷模具材料的综合力学性能出发,采用纳米复合方法制备出具有较高综合力学性能的纳米陶瓷模具材料.研究了纳米Ti(C7N3)和Y2O3的组分含量对纳米陶瓷模具材料微观结构和力学性能的影响,结果表明添加纳米Ti(C7N3)和Y2O3的氧化锆纳米陶瓷模具材料的力学性能优于纯氧化锆陶瓷材料,纳米颗粒的添加改善了材料的微观结构和力学性能.当纳米Ti(C7N3)和Y2O3的添加量分别为17.15vol;和5 mol;时,材料的综合性能最好,其抗弯强度为814MPa、断裂韧性6.35 MPa· m1/2、维氏硬度11.87 GPa. 相似文献
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采用全浮区模型数值研究了旋转磁场作用下熔区内热毛细对流流动特性,分析了磁场强度对流场及浓度场的影响.研究发现,无磁场时,熔体内杂质浓度场和流场呈现三涡胞对称振荡特征;温度场主要由扩散作用决定,呈对称分布.旋转磁场作用下,Ma数基本保持不变.当磁场强度B0≤1 mT时,熔体内杂质浓度场和流场与无磁场时结构类似,但旋转磁场的搅拌作用使得熔体内周期性振荡提前出现,且当旋转磁场产生的洛伦兹力相对较大时,表面张力产生的三维振荡对流得到很好地抑制.B0=5 mT时,周向波动被完全抑制,熔区内流场和浓度场呈二维轴对称分布.旋转磁场对熔体流动产生的轴向抑制作用和周向搅拌作用,都有助于熔体流动的稳定性、浓度分布以及温度分布的均匀性,从而有利于高质量晶体的生长. 相似文献
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HFCVD系统中衬底温度场及气相空间场的数值分析 总被引:2,自引:2,他引:0
探讨了典型气氛中热丝辐射、气体热传导与对流、化学反应生热等因素对衬底温度的影响,建立了三维热丝辐射和二维热流耦合有限元模型,研究了各工艺参数对衬底温度场及气相空间场的影响.结果表明H2占主导地位的气氛中衬底表面的氢原子重组放热对衬底温度有较大影响,氩气气氛中原子重组放热对衬底温度影响很小;热丝温度对衬底温度的影响最大;进气口到衬底的距离及进气口气体流速对衬底附近的流场影响最大,适当提高进气口到衬底的距离有助于提高衬底附近流场均匀性,增大进气速度有助于突破热障提高衬底表面流速,但同时加剧了衬底附近流场的不均匀性. 相似文献
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Connections between continuum, mean-field, adiabatic Peierls-fröhlich theory in the half-filled band limit and known field theory results are discussed. Particular attention is gi en to the Φ4 model and to the solvable N +2 Gross-Neveu model. The later is equivalent to the Peierls system at a static, semi- classical level. Based on this equivalence we note the prediction of both kink and polaron solitions in models of trans-(CH)x. Polarons in cis-(CH) are compared with those in the trans isomer. Optical absorption from polarons is described, and general experimental consequences of polarons in (CH)x and other conjugated polymers is discussed. 相似文献
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本文采用有限元法建立了KDP晶体线锯切割的仿真模型,仿真分析了切割过程中晶体内部应力场分布的变化规律.结果表明,线锯切割加工过程应力变化整体平稳,属低应力锯切方式,当晶体即将切断时,最大拉应力显著增加;随着被加工材料的去除,晶体初始内应力释放,晶体内部距离待加工表面越近的点,切割过程中应力变化越剧烈;锯切切口处,锯切应力与内应力相互耦合,应力集聚,并且晶体初始内应力越大,应力集聚越明显,晶体切割开裂几率越大.仿真结果为保证KDP晶体线锯切割加工过程中避免开裂提供了理论基础. 相似文献
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This paper presents calculations of the internal field constants γe for four homologous liquid crystal materials in their nematic and crystalline phases. We find that for the nematic phase, the γe ~ S 2 curve is nearly a straight line for each compound. When one extrapolates the straight line to S 2 = 1, the corresponding γe value is nearly equal to γ∥, the crystalline internal field constant. The birefringence data used are those reported by Somashekar et al.4 The four compounds studied are: (1) p(p'-ethoxyphenylazo)phenyl valerate; (2) p(p'-ethoxyphenylazo)phenyl hexanote; (3) p(p'-ethoxyphenylazo)phenyl heptanoate; (4) p(p'-ethoxyphenylazo)phenyl undecylenate. 相似文献
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P. Palffy-muhoray D. A. Balzarini D. A. Dunmur 《Molecular Crystals and Liquid Crystals》2013,570(1-4):315-330
The anisotropy of the local electric field in the interior of ordered fluids provides a measure of the anisotropy of the molecular distribution. In nematics, both the orientational order parameter and the anisotropy of the local field can be calculated from refractive index and density measurements; results are presented for the liquid crystal butyl p-(p-ethoxyphenoxycarbonyl) phenyl carbonate. It is found that the anisotropy of the local field is very nearly proportional to the orientational order parameter. A simple model incorporating steric intermolecular repulsion predicts this behaviour. The ratio of the local field anisotropy to the uniaxial and biaxial order parameters is simply related to the length-to-breadth ratio of the effective molecular hard core. 相似文献
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J. Linhart 《Crystal Research and Technology》2002,37(8):849-867
This article is devoted theoretical and experimental researches of temperature fields which are formed in area semi‐transparent, diffusely transmitting and scattering boundary of two optical environments. It is revealed, that thus can arise non‐monotonic or at certain conditions completely an inverse temperature field. The phenomenon of inversion of a stationary temperature field is revealed theoretically and subsequently is experimentally confirmed. The specific conditions of occurrence of the phenomenon of inversion are determined. During the crystal growth process behind the front of crystallization there can be a congestion of impurities or micro‐bubbles which are grasped by the moving front of crystallization. It results in occurrence diffusely transmitting and scattering boundary on which the radiating thermal flux going from the melt is dissipated in a growing crystal. In turn under the certain conditions it could result in non‐monotonic of temperature field in area of phase boundary and even in full inversion. The experimental equipment was developed and results of experimental measurements which completely confirm theoretical conclusions are given. The described phenomenon could be meet in growing of such optical crystals as sapphire, ruby, fluorides etc. It is specified, that the similar conditions can arise as well on boundary of solid‐gas and liquid‐gas. 相似文献
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利用ANSYS有限元模拟超重力反应合成TiB2-TiC陶瓷凝固过程中温度场分布及各区域温度随时间变化曲线,并对制备的陶瓷进行显微组织分析.由模拟结果可知,陶瓷熔体自边缘向心部迅速降温、凝固,且不同区域的温度变化速率差异明显.XRD、FESEM和EDS分析表明,陶瓷基体主要由TiB2片晶与不规则的TiC球晶组成,但各区域的组织形态有所变化,这主要是由于凝固速率差异造成的.同时,超重力反应合成TiB2-TiC陶瓷显微组织分布验证了ANSYS有限元模拟陶瓷凝固过程中温度场变化箱势的有效性. 相似文献