两种微结构阵列上碳纳米管薄膜强流脉冲发射比较

为比较不同微结构对于碳纳米管冷阴极电流发射能力的增强效果,采用酞菁铁高温热解方法,以化学镀铜层为缓冲层在两种不同单元尺度的微结构阵列的硅基底上制备了CNTs薄膜,并在20 GW脉冲功率源系统中采用二极结构对其强流脉冲发射特性进行了比较研究.基底微结构阵列的单元尺度为10 μm×20μm(其中微锥底边长为20μm,单元节距为30 μm)和20 μm × 20 μm.结果表明:在相同的峰值电场下,基底微结构阵列的单元尺度越小,CNTs薄膜的强流脉冲发射电流越大;且随着峰值电场的增加,单元尺度越小,CNTs薄膜的发射电流的增长速度越快.     

过渡层对纳米非晶碳薄膜场发射性能的影响

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.     

氧氩比及基底温度对脉冲磁控溅射Cu2O薄膜结构和光学性能的影响

利用脉冲磁控溅射制备技术,采用单质金属铜靶作为溅射靶,在氧气(O2)和氩气(Ar)的混合气氛下在石英玻璃基底上制备Cu2O薄膜,研究了O2和Ar流量比(O2/Ar)及基底湿度对沉积的Cu2O薄膜结构、表面形貌及光学性能的影响.结果表明:在O2/Ar为30∶80的气氛条件下,基底温度在室温(RT)和100℃时均可获得单相的Cu2O＜ 111＞薄膜;薄膜表面致密、颗粒呈球状,粗糙度的均方根(RMS)值随基底温度增加而增大;薄膜的光谱吸收范围为300～ 650 nm,紫外区吸收较强,可见光区吸收强度较弱,吸收强度随基底温度的增加而增强,光学带隙(Eg)随基底温度的增加而减小.     

基于直流磁控溅射晶种层的ZnO纳米阵列的制备及性能研究

采用直流反应磁控溅射法制备品种层薄膜,研究O2/Ar气体分压比和退火温度对品种层结构和微观形貌的影响.通过化学水浴沉积,在预制有晶种层的薄膜上制备ZnO纳米阵列结构,研究不同前驱体浓度和预制晶种层对纳米阵列生长的影响.结果表明,当O2/Ar中O2分压减少,薄膜均匀性较差,当Ar分压增加薄膜由于扩散而趋于平整.退火温度增加,晶粒尺寸增大,内应力降低.磁控溅射法预制的晶种层上生长的纳米棒垂直于衬底生长,(002)晶面的衍射峰强最高,说明纳米棒沿c轴择优取向.生长液的浓度对纳米棒的形貌影响显著,随着生长液浓度的升高,ZnO纳米阵列直径增大,顶端趋于平整的六棱柱结构.     

衬底温度对nc-Si∶H薄膜微结构和氢键合特征的影响

采用射频等离子体增强型化学气相沉积(RF-PECVD)技术,以H2和SiH4作为反应气体源,在不同的衬底温度下沉积了nc-Si∶H薄膜.采用Raman散射、X射线衍射、红外吸收等技术分析了薄膜的微结构和氢键合特征.结果表明,随衬底温度的升高,nc-Si∶H薄膜的沉积速率不断增大,晶化率和晶粒尺寸增加,纳米硅颗粒呈现出Si(111)晶面的择优生长趋势.键合特性显示,薄膜中的氢含量随衬底温度升高而逐渐减小,薄膜均匀性先增大后减小.     

F掺杂对溶胶-凝胶法制备的ZnO∶ Fe薄膜结构及光学性质的影响

采用溶胶-凝胶法在玻璃衬底上制备了Zn0.98-xFe0.02FxO(x =0,0.01,0.02,0.03,0.04)薄膜,进而利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、紫外-可见透过谱(UV-VIS)、光致发光(PL)多种测试手段研究了不同掺F浓度对ZnO∶ Fe薄膜的表面形貌、微结构、禁带宽度及光致发光的影响.结果表明:样品均为六角纤锌矿结构,当F掺杂浓度为2at;时,薄膜的结晶度最好且表现出明显的c轴择优取向.随着F掺杂浓度的进一步增大,薄膜的结晶性逐渐变差,c轴择优取向消失.F掺杂ZnO∶ Fe薄膜在可见光区均有很高的透过率,平均可达93;.样品的禁带宽度随着掺F浓度的增加而减小.PL谱观察到Zn0.98-xFe0.02FxO薄膜的发射峰主要由紫外发射峰和蓝光发射峰组成,其中2at;F掺杂样品的紫外发射强度最大,同时蓝光发射强度随着F含量的增大逐渐减小.     

数值模拟p/i界面对微晶硅薄膜太阳电池性能的影响

采用美国宾州大学开发的AMPS(Analysis of Microelectronic and Photonic Structures)软件模拟了p/i界面缺陷态密度(Npt/i)和非晶孵化层厚度(d)对pin型氢化微晶硅(μc-Si:H)薄膜太阳电池性能的影响.结果表明:随着Npt/i的增大,电池的开路电压Voc和填充因子FF单调减小,短路电流Jsc基本不变;随着d的增大,Jsc和FF单调减小,Voc反而增大;Npt/i和d值的增大均会导致电池光电转换效率η下降.通过对电池内部的电场及能带的分析,对上述模拟结果进行了解释.     

平栅型双层膜的场致发射性能研究

通过在平栅型基板上,分别溅射氧化铋薄膜和氧化锡薄膜,形成阴极场发射阵列,并在阴极和栅极之间加载脉冲电流,使阴栅级之间的薄膜形成裂缝,并进行场致发射性能测试,测试结果表明,平栅型双层膜发射器件的开启电压随阳极电压增加而降低.在阳压为3000 V,隔离子高度为500 μm时,平栅型双层膜场发射器件的开启电压为110 V,在栅压为110 V时的发射效率为1;左右,随着栅压的增大,发射效率逐渐减小.该双层膜阴极具有均匀的发射性能、良好的栅控能力以及场发射特性.     

非晶 Ti-Al 过渡层对 Pt/Ba0.6Sr0.4TiO3/Pt电容器结构和性能的影响

应用磁控溅射法在 Pt/Ti/SiO2/Si(001)衬底上制备 5 mm 厚超薄非晶 Ti-Al 薄膜作为过渡层,利用脉冲激光沉积法制备 Ba0.6 Sr0.4TiO3 薄膜,构造了 Pt/Ba0.6Sr0.4TiO3/Pt(Pt/BST/Pt)和 Pt/Ti-Al/Ba0.6Sr0.4TiO3/Ti-Al/Pt(Pt/Ti-Al/BST/Ti-Al/Pt)结构的电容器,研究了 Ti-Al 过渡层对 Pt/BST/Pt 电容器结构及其性能的影响.实验表明,过渡层的引入有效地阻止了 Pt 电极和 BST 薄膜的互扩散,降低了 BST 薄膜氧空位的浓度,提高了铁电电容器的介电性能.当测试频率为 1 kHz、直流偏压为0 V时,介电常数由引入过渡层前的 530 增大到引入后的 601,介电损耗则由0.09减小到0.03.而且过渡层的引入有效地降低了 BST 薄膜的漏电流,使正负向漏电流趋于对称,在测试电压为5 V 时,漏电流密度由3.8×10-5 A/cm2 减小到 8.25 ×10-6 A/cm2.     

热蒸发法原位生长-维氧化锌纳米材料及其场发射特性研究

利用磁控溅射在ITO电极上沉积氧化锌薄膜,以氧化锌薄膜为种子层,采用热蒸发法合成ZnO一维纳米材料,利用XRD和SEM方法对氧化锌一维纳米材料的微观结构进行分析,测试其场发射性能.结果显示,氧化锌纳米材料为钉子状结构,每个氧化锌纳米钉由几微米大的钉帽和细棒组成,垂直于基底生长.场发射性能研究表明它具有较低的开启场强,高的发射电流和好的稳定性,是一种优良的冷阴极电子发射源.     

A review of measurement of thermophysical properties of silicon melt

Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi₃ existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species.     

Mesomorphism Dependence on the Position of Substitution of a Pair of Esters

A novel homologous series of ethylene derivatives of thermotropic liquid crystals has been synthesized. The methoxy to octyloxy derivatives are nematogenic, the decyloxy to tetradecyloxy derivatives are smectogenic, in addition to nematogenic, and the hexadecyloxy homologue is smectogenic only. All the members of the series are enantiotropically mesogenic. Thermotropic behavior was determined by an optical polarizing microscope equipped with a heating stage and Differential Scanning Calorimetry (DSC) study. Analytical and spectral data confirm the molecular structures of homologues (infrared, nuclear magnetic resonance, mass spectra, X-ray, and DSC data). Textures of the nematic phase are threaded or Schlieren and that of smectic phase are focal conic fan-shaped of smectic A or C. Transition curves of the phase diagram behave in a normal manner except one or two deviations from the normal trend. The mesophase range (Sm+N) varies from 3°C to 44°C. The average thermal stability for smectic is 93°C and that for nematic 117.4°C. The LC behavior of the novel series is compared with a structurally similar known series.     

Effect of alumina on enthalpy of mixing of mixed alkali silicate glasses

The enthalpy of mixing of mixed alkali (Na₂O and K₂O) silicate glasses containing various concentrations of alumina was determined using an ion-exchange equilibrium method. For glasses with a constant alkali concentration, the enthalpy of mixing was found to become less negative with alumina addition. Consistent with our previous results on the enthalpy of mixing of alumina-free mixed alkali silicate glasses, the magnitude of enthalpy of mixing exhibited a good correlation with the molar volume mismatch of the corresponding two single alkali glasses as well as with the extent of conductivity mixed alkali effect, e.g. excess activation energy of conductivity, ΔE. The reduction of the magnitude of the enthalpy of mixing with alumina addition can be attributed to the reduction of non-bridging oxygen and ionic field strength. Combining the present results with results obtained earlier, the magnitude of the enthalpy of mixing for all mixed alkali (Na₂O and K₂O) silicate glasses with and without alumina was expressed by a simple function of a modified Tobolsky parameter, which takes into account the alkali concentration and the difference in cation-to-effective anion distances. The enthalpy of mixing data of the mixed alkali glasses was then compared with reported experimental data on the conductivity of mixed alkali aluminosilicate glasses. What appears to be conflicting experimental data can be understood in terms of the magnitude of the enthalpy of mixing and we can conclude that the mixed alkali effect is closely correlated with the negative enthalpy of mixing.     

立方晶系晶体本征铁弹相变序参量的选取

在本征铁弹相变的软模理论的基础上,依据弹性本构关系和居里原理,给出了立方晶系晶体所有可能的自发应变的种类,研究了立方晶系晶体本征铁弹相变序参量的选取问题.以Th群和Oh群为例,阐明了不同类的序参量导致晶体对称性变化相同的的原因,提出了该情况下序参量选取的“就少不就多”的原则.得到了发生本征铁弹相变时所有可能的序参量及晶体的对称性的变化.     

On the influence of structural features of DNA on the possibility of metabolic transfer of electrons

Abstract

A fragment of a DNA molecule is considered as one of the channels of metabolic electron transfer. The heterogeneity of the complementary chains is effectively taken into account. This made it possible to find the speed of the electron injected into the DNA conduction band and the current density that it creates. Estimates of electron mobility in nucleic acid chains are made. They were an order of magnitude smaller than that of typical semiconductors. For the specific conductivity of nucleic acid chains, estimates provide a conductivity of one to two orders of magnitude lower than in graphite.     

原位氮化法制备TiN纳米粉体

用溶胶凝胶法合成的纳米TiO2粉体作为原料,将该粉体在氨气中进行原位氮化制备了TiN纳米粉体.用XRD,TEM,化学分析等手段对合成的TiN纳米粉体的物相组成、形貌、成分进行了分析.实验分析表明:在1000℃和1100℃下分别氮化5h,可以制备粒径大约为40nm和80nm的TiN粉体,其TiN的含量分别为95.40;和98.37;;而在1000℃条件下氮化时间减少到2h时,TiN的含量仅为58.36;.氮化温度和氮化时间是合成纳米TiN的重要因素,提高合成温度和延长氮化时间均可形成纯度较高的TiN纳米粉体,但延长氮化时间更有利于获得粒径小的氮化钛粉体.     

Features of transformations in REE-containing systems of nitrate precursors in preparatory processes of formation of multifunctional oxide materials

Abstract

The complex study provides a reliable idea of ??the trends in the joint behavior of structural components in the water-salt systems of nitrate precursors of REE, alkaline, alkaline earth metals in the preparatory stages of the processes of forming multicomponent oxide polyfunctional materials on their basis with thermal activation. Stages of such transformations are revealed; The regularities of complex and phase formation in systems and factors influencing them are determined; A number of physicochemical properties of the intermediate phases formed - coordination lanthanides nitrates: their composition, types of compounds, atomic-crystalline structure, regularities of transformations during heat treatment were studied.     

Growth and characterization of semicarbazone of cyclohexanone

A new organic single crystal of semicarbazone of cyclohexanone (SCCH) has been synthesized and grown as a bulk single crystal by low temperature solution growth technique for the first time in the literature. The grown crystal has been confirmed by X‐ray diffraction and proton nuclear magnetic resonance spectral analyses and also characterized by FT‐ir and FT‐Raman studies. Thermal properties of the grown crystals were studied by thermogravimetric and differential thermal analyses. Optical transmittance was studied by ultraviolet‐visible spectrum and the second harmonic generation property was tested by using Q switched Nd: YAG laser as a source. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of density of states on optical properties of GaSe thin film

A systematic investigation on the effect of substrate temperature on the structure, optical absorption and density of states of vacuum evaporated gallium monoselenide (GaSe) thin films is reported. The X‐ray diffraction analysis shows an occurrence of amorphous to polycrystalline transformation in the films deposited at higher‐temperature substrates (573K). The compositional analysis is made with Auger Electron Spectroscopy (AES). The thickness of the film (175nm) is measured by a multiple beam interferometery. Optical characteristics of the GaSe sample have been analyzed using spectrophotometer in the photon energy range of 1.0 ‐ 4 eV. The absorption mechanism has been recognized and the allowed indirect as well as forbidden direct transitions have been found. As‐deposited films show two indirect and allowed transitions due to spin‐orbit splitting of the valence band, as reported here for the first time. Low field conduction have enabled us to determine the density of states in amorphous and poly‐GaSe films. The amorphous and polycrystalline GaSe thin films have localized states density values of N (E_F) = 1.686 × 10¹⁷ cm^‐3 eV^‐1 and 1.257 × 10¹⁵ cm^‐3 eV^‐1 respectively. The experimental results are interpreted in terms of variations in the density of localized states due to progressive decrease of the unsaturated bonds during deposition. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

电子显微分析在表征纳米晶体化学组分中的应用

纳米材料的化学组分及含量影响其光、电、声、热、磁等物理性能,电子显微分析是表征纳米晶体化学组分的重要方法之一.本文综述了X-射线能谱(EDS)、X-射线波谱(WDS)、电子能量损失谱(EELS)和选区电子衍射(SAED)等现代电子显微分析技术在表征纳米晶体化学组分、形貌、尺寸和结构等方面的应用及其研究进展,并比较了这些分析方法存在的差异,提出了其应用中存在的不足及今后的研发方向.