磁控溅射制备碳化硼薄膜的结构与成分分析

近年来国际上³He资源的短缺造成了基于³He的中子探测器高昂的成本,而以碳化硼薄膜作为中子转换层的硼基中子探测器逐渐成为了最有前景的替代方案。通过直流磁控溅射制备了Ti/B₄C多层膜,并使用透射电子显微镜（TEM）、飞行时间二次离子质谱（ToF-SIMS）、X射线光电子能谱（XPS）等手段对薄膜的结构与成分进行表征。结果表明：Ti层存在结晶情况;H、O、N元素为薄膜内部的主要杂质,且多分布于Ti层与B₄C-on-Ti过渡层中;更高的本底真空度能够降低碳化硼薄膜内的杂质含量,提高B含量占比;中子探测效率测试结果证明本底真空度的提高能够有效提高碳化硼中子转换层的效率。     

厚度效应对Pb(Zr0.53Ti0.47)O3薄膜微结构、铁电、介电性能的影响

用改进的溶胶-凝胶法在Pt(111)/Ti/SiO₂/Si(100)衬底上制备了不同厚度的高度(111)取向的Pb(Zr_0.53Ti_0.47)O₃薄膜.运用X射线衍射(XRD)和原子力显微镜(AFM)分析了薄膜的微结构,原子力显微镜表明厚度为0.3μm和0.56μm的PZT薄膜的晶粒尺寸和表面粗糙度分别为0.2～0.3μm、2～3μm和0.92nm、34nm.0.3μm和0.56μm PZT薄膜的剩余极化(Pr)和矫顽场(Ec)分别为32.2μC/²、79.9kV/cm, 27.7μC/cm²、54.4kV/cm;在频率100KHz时,薄膜的介电常数和介电损耗分别为539、0.066,821、0.029.     

钨镍共掺杂V2O5薄膜的光电特性研究

利用溶胶–凝胶旋涂法和后退火工艺在FTO导电玻璃上制备了钨镍共掺杂V₂O₅薄膜,研究了薄膜在不同温度和不同偏压下的光电特性和相变特性。利用X射线衍射仪（XRD）、扫描电子显微镜（SEM） 和X射线光电子能谱仪（XPS） 测试了钨镍共掺杂V₂O₅薄膜的晶体结构、表面形貌和组分,分析了不同钨镍共掺杂浓度对V₂O₅薄膜相变光电特性的影响。结果表明,当钨和镍的掺杂质量分数分别为3 %和1.5 %时,钨镍共掺杂的V₂O₅薄膜的相变温度为218.5 ℃,在可见光范围内有较高的透过率,在近红外1310 nm波长处的光学透过率达48.83%,与未掺杂V₂O₅薄膜的光学透过率相比提高了10.29%,薄膜电阻降低了30.53%,热致回线宽度收窄为15 ℃,说明钨镍共掺杂的V₂O₅薄膜具有良好的可逆相变光电特性,有望在新型光电器件领域得到较好的应用。     

单价银离子在 CaO-P2O5 系统玻璃中的发光特性

在弱还原气氛下制备了单价银离子(Ag⁺)掺杂的CaO-P₂O₅系统玻璃,测试了其在室温下的吸收光谱、激发光谱和发射光谱。Ag⁺-CaO-P₂O₅玻璃的吸收光谱表明两个吸收峰。高能峰位于220nm波长,由4d¹⁰→4d⁹5P¹跃迁引起,低能峰中心位于240nm波长,归因于4d¹⁰→4d⁹5s¹跃迁,该吸收与其发射特性有关。紫外波段的宽带吸收产生了可见波段强烈的荧光发射,发光峰位于440nm波长,半宽度为130nm.研究了掺质浓度与发光特性的关系,随着掺质浓度的增加(0.05～0.25mol%),发光峰向较长波段移动。在Ag₂O含量为0.5mol%时,出现了浓度猝灭现象。为了比较起见,同时还研制了Cu⁺-CaO-P₂O₅及Cu⁺-Ag⁺-CaO-P₂O₅玻璃。     

纳米半导体复合薄膜的非线性光学性质及其在激光器中的应用

采用射频磁控溅射技术制备了Ge掺二氧化硅（Ge-SiO₂）和Ge,Al共掺二氧化硅（Ge/Al-SiO₂）两种复合薄膜,并进行了热退火处理形成了纳米Ge镶嵌结构。通过紫外-可见吸收谱测量,确定了两种薄膜中纳米Ge的光学带隙,并采用皮秒激光Z-扫描技术研究了薄膜的非线性光学性质。测试结果显示,在1 064 nm激发下得到的Ge-SiO₂和Ge/Al-SiO₂薄膜的非线性吸收系数分别为-1.23×10^-7 m/V和4.35×10^-8 m/W,前者为饱和吸收,而后者为双光子吸收。把两种薄膜作为可饱和吸收体均可实现1.06 μm激光的被动调Q和被动锁模运转。与Ge-SiO₂薄膜比较,采用Ge/Al-SiO2薄膜可以获得较窄的调Q脉冲和锁模脉冲。最后,理论分析和实验比较了两种薄膜实现被动调Q和锁模的机理。     

基于Ge2Sb2Se4Te1的可重构光开关的仿真

光开关是集成光路上一个重要的元器件。提出了一种用在L和C波段基于硫系相变材料（Ge₂Sb₂Se₄Te₁）的片上2×2定向耦合器式的可重构光开关,可通过改变相态切换开关。利用仿真软件Lumerical中的Mode Solutions和FDTD Solutions模块设计器件,得到在1500~1625 nm内耦合长度为24.9 μm的Ge₂Sb₂Se₄Te₁非晶态下插入损耗（IL）>-0.36 dB,串口对比度（CT）<-24 dB;Ge₂Sb₂Se₄Te₁晶态下IL>-0.44 dB,CT<-30.46 dB。利用仿真软件COMSOL模拟532 nm波长激光加热Ge₂Sb₂Se₄Te₁,结果显示：一个25 ns、峰值功率45 mW的高斯短脉冲可以使材料由晶态转化为非晶态;施加多个峰值功率20 mW、周期1 μs且占空比0.03%的高斯脉冲阵列可重回晶态。仿真结果表明,设计的光开关在通信波段通过激光加热可以快速实现切换光路的作用。     

CsPbBr3纳米片–萘之间的高效三线态能量传递

铯铅卤化物钙钛矿纳米晶是光伏和发光应用领域中理想化的三线态敏化材料,具有较高的荧光量子产率和量子限域效应。以三层厚度的CsPbBr₃纳米片（NPLs）为三线态给体,实现了从NPLs到1-萘甲酸（NCA）分子的高效三线态能量传递（TET）。CsPbBr₃ NPLs采用配体辅助再沉淀方法制备,其与NCA分子结合后,稳态荧光被大幅淬灭,荧光寿命从复合前的6.743 ns缩短到0.995 ns,TET效率达到85.3%。通过与大尺寸纳米立方体对比发现,对于CsPbBr₃-多环芳烃复合体系,量子限域效应是获得高效TET的关键。研究结果表明,CsPbBr₃ NPLs作为三线态敏化剂,可应用在基于TET的光子上转换、光催化氧化-还原反应和室温磷光等领域。     

推拉式小车法制备单层硒化钨薄膜

为了提升单层硒化钨（WSe₂）薄膜的制备质量，在传统化学气相沉积（CVD）法制备的基础上进行改进，通过引入推拉式小车来制备单层WSe₂薄膜，从而构造出可以调控沉积区域、精确控制生长时间，并可实现快速降温的生长方式。采用光学显微镜和原子力显微镜来表征制备材料的尺寸、荧光强度、形貌结构等特性，证明了利用推拉式小车法可成功制备出高质量的单层WSe₂薄膜。推拉式小车法可以稳定制备大面积、高质量、单层的WSe₂薄膜，为其在信息、能源、生物等前沿领域的应用提供参考。     

ZrTe5的太赫兹辐射研究

为了研究层状ZrTe₅（五碲化锆）在飞秒脉冲激发下的超快瞬态太赫兹辐射,利用太赫兹时域反射系统对其进行了测试分析。通过分析层状ZrTe₅太赫兹电场幅度与飞秒激光泵浦功率及泵浦脉冲偏振关系,获得了层状ZrTe₅产生太赫兹辐射的主要机理。同时还对比了相同泵浦条件下层状ZrTe₅和本征GaAs（砷化镓）太赫兹辐射强度。研究表明,层状ZrTe₅具有带隙结构窄、吸收深度浅、光生电子剩余能量较大、载流子迁移率较高等优势,在太赫兹产生方面比传统半导体具有更好的性能。该研究可为发现高效、高度集成化太赫兹辐射源提供参考。     

高分子聚合物封装对(PEA)2PbI4荧光稳定性的改善

采用聚苯乙烯（PS）、聚甲基丙烯酸甲酯（PMMA）、环烯烃聚合体（COP）三种高分子聚合物封装技术改善二维钙钛矿（(PEA)₂PbI₄）薄膜荧光的稳定性。将液相合成获得的二维钙钛矿用PS、PMMA、COP三种高分子聚合物进行封装,研究结果表明,三者分别对二维钙钛矿实现3倍、4倍与8倍的稳定性改善,有效地减弱了光照引发的晶格畸变,降低了有机分子的扩散与挥发,从而减缓了二维钙钛矿的降解。该方法简单、成本低,是一种改善二维钙钛矿荧光稳定性的有效方法。     

Effects of morphological control on the characteristics of vertical-type OTFTs using Alq3

We have fabricated vertical-type organic thin-film transistors (OTFTs) using tris-(8-hydroxyquinoline) aluminum (Alq₃) as an n-type active material. Vertical-type OTFT using Alq₃ has a layered structure of Al(source electrode)/Alq₃(active layer)/Al(gate electrode)/Alq₃(active layer)/ITO glass(drain electrode). Alq₃ thin films containing various surface morphologies could be obtained by the control of evaporation rate and substrate temperature. The effects of the morphological control of Alq₃ thin layer on the grain size and the flatness of film surface were investigated. The characteristics of vertical-type OTFT significantly influenced the growth condition of Alq₃ layer.     

Influence of substrate orientation on the morphologyand orientation of LaNiO3 thin films

LaNiO₃ thin films were successfully prepared by a chemical method from citrate precursors. The LNO precursor solution was spin‐coated onto Si (100) and Si (111) substrates. To obtain epitaxial or highly oriented films, the deposited layers were slowly heated in a gradient thermal field, with a heating rate of 1° min^?1, and annealed at 700°C. The influence of different substrate orientations on the thin film morphology was investigated using atomic force microscopy and X‐ray diffraction analysis. Well‐crystallized films with grains aligned along a certain direction were obtained on both substrates. Films deposited on both substrates were very smooth, but with a different grain size and shape depending on the crystal orientation. Films deposited on Si (100) grew in the (110) direction and had elongated grains, whereas those on Si (111) grew in the (211) direction and had a quasi‐square grain shape.     

A study on friction and wear characteristics of nanometer Al2O3 /PEEK composites under the dry sliding condition

The friction and wear properties of the polyetheretherketone (PEEK) based composites filled with 5 mass% nanometer or micron Al₂O₃ with or without 10 mass% polytetrafluroethylene (PTFE) against the medium carbon steel (AISI 1045 steel) ring under the dry sliding condition at Amsler wear tester were examined. A constant sliding velocity of 0.42 m s⁻¹ and a load of 196 N were used in all experiments. The average diameter 250 μm PEEK powders, the 15 or 90 nm Al₂O₃ nano-particles or 500 nm Al₂O₃ particles and/or the PTFE fine powders of diameter 50 μm were mechanically mixed in alcohol, and then the block composite specimens were prepared by the heat compression moulding. The homogeneously dispersion of the Al₂O₃ nano-particles in PEEK matrix of the prepared composites was analyzed by the atomic force microscopy (AFM). The wear testing results showed that nanometer and micron Al₂O₃ reduced the wear coefficient of PEEK composites without PTFE effectively, but not reduced the friction coefficient. The filling of 10 mass% PTFE into pure PEEK resulted in a decrease of the friction coefficient and the wear coefficient of the filled composite simultaneously. However, when 10 mass% PTFE was filled into Al₂O₃/ PEEK composites, the friction coefficient was decreased and the wear coefficient increased. The worn scars on the tested composite specimen surfaces and steel ring surfaces were observed by scanning electron microscopy (SEM). A thin, uniform, and tenacious transferred film on the surface of the steel rings against the PEEK composites filled with 5 mass% 15 nm Al₂O₃ particles but without PTFE was formed. The components of the transferred films were detected by energy dispersive spectrometry (EDS). The results indicated that the nanometer Al₂O₃ as the filler, together with PEEK matrix, transferred to the counterpart ring surface during the sliding friction and wear. Therefore, the ability of Al₂O₃ to improve the wear resistant behaviors is closely related to the ability to improve the characteristics of the transfer film.     

Influence of Mg doping on the morphology and optical properties of ZnO films for enhanced H2 sensing

Highly oriented ZnO and Mg doped ZnO thin films were fabricated on Al₂O₃ substrate by sputtering at room temperature. The effect of Mg doping on the structural, optical, and morphological properties of ZnO film was investigated. The intensity of (002) peak in X‐ray diffraction measurements revealed the influence of Mg doping on the crystallinity and orientation of ZnO film. Photoluminescence (PL) results show that the Ultraviolet (UV) emission peak was shifted to lower wavelength side for Mg:ZnO film indicating the possibility for quantum confinement. UV–vis–NIR optical absorption revealed an improvement in optical transmittance from 70 to 85%, and corresponding optical band gap from 3.25 to 3.54 eV. Atomic force microscope (AFM) images revealed the nano‐size particulate microstructure of the films. The surface topography of Mg doped ZnO film confirmed decreased grain size with large surface roughness and increased surface area, favorable for sensing. Pure ZnO and Mg doped ZnO film were used as active layer and tested for its sensing performance to hydrogen. Compared to undoped ZnO, 22 at.% Mg doped ZnO film showed much higher sensor response to H₂ at a concentration as low as 200 ppm and at a lower operating temperature of 180°C. A linear sensor response was observed for H₂ concentration in the range of 100–500 ppm. Microsc. Res. Tech. 76:1118–1124, 2013. © 2013 Wiley Periodicals, Inc.     

Tribological investigation of CaF2 nanocrystals as grease additives

Calcium fluoride (CaF₂) nanocrystals with average grain size of 60 nm were synthesized via a precipitation method. The morphology and structure of nanocrystals were characterized by means of transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). TEM and XRD showed that CaF₂ nanocrystals are cubic particles in submicron scale. The tribological properties of the prepared CaF₂ nanocrystals as an additive in lithium grease were evaluated with a four-ball tester. The results indicated that these nanocrystals exhibit excellent antiwear, friction reduction and extreme pressure (EP) properties. It was also found that the EP and antiwear capabilities of the grease are not proportional to the content of CaF₂ nanocrystals but there existed a certain value. The rubbed surface after friction test was investigated with X-ray photoelectron spectroscopy and scanning electron microscopy to understand the action mechanism. The results show that a boundary film mainly composed of CaF₂, CaO, iron oxide and some organic compounds was formed on the rubbed surface after friction test and the thickness of boundary film was about 12 nm. The disproportion of stoichiometric ratio of Ca and F in boundary lubrication film indicates that tribochemical reaction of CaF₂ nanocrystals occurred on the worn steel surface at severe tribological conditions.     

Atomic force microscopy imaging of polycrystalline CuInSe2 thin films

In this study, atomic force microscopy (AFM) imaging has been used to study the structural properties of polycrystalline CuInSe₂ films, which are widely used as absorber materials in thin film solar cell devices. This technique demonstrated an excellent capability for the reproducible imaging of these rough polycrystalline materials. AFM imaging in combination with statistical analysis revealed distinct differences in the structural properties (i.e. grain width and height distributions, root‐mean‐square (RMS) and peak to valley (R_(p–v)) roughness values) as a function of the specific growth technique used and the bulk composition of the films. In the case of Cu‐rich films, prepared by the H₂Se/Ar treatment of Cu/In/Cu alloys, rough surface structures were in general observed. Statistical analysis revealed two distinct distribution of grains in these samples (1.0–2.5 μm and 3–5.5 μm) with large RMS and R_(p–v) roughness values of 380 nm and 2.6 μm, respectively. In‐rich films were characterized by the presence of much smaller, roughly circular clusters with a significant reduction in both the width and height distributions as well as RMS and R_(p–v) roughness values. The most successful growth techniques, in terms of producing homogeneous and dense films, were in the cases of H₂Se/Ar treated metallic InSe/Cu/InSe alloys and the coevaporation of all materials to form CuInSe₂. Both these techniques produced absorber films with very narrow grain width and height distributions as well as small roughness values. It was possible to establish that high efficiency devices are associated with the use of absorber films with narrow width distributions between 0.5 and 2 μm and small RMS (> 300 nm) roughness values. These values are used as a figure of merit in our laboratories to evaluate the structural properties of our CuInSe₂ thin films.     

A Two-Chamber Facility for Depositing Thin Films in a Transverse High-Frequency Discharge

A facility for depositing thin films in a transverse high-frequency discharge is described. The facility consists of two (basic and auxiliary) chambers. The basic chamber is intended for sputtering targets and depositing a thin film on the prepared substrate. The auxiliary chamber contains a system of replaceable electrodes and serves for the preliminary processing of a substrate and the subsequent action on the thin film obtained. The device was tested in an oxygen discharge at pressures of 1.0 to 15 hPa and a deposited specific high-frequency power of up to 6.5 W/cm³ at a frequency of 10 MHz with targets of Pb(Zr _x Ti _{x– 1})O₃ ferroelectric ceramics and showed satisfactory results.     

Effect of CH4/H2 plasma ratio on ultra-low friction of nano-crystalline diamond coating deposited by MPECVD technique

Nano-crystalline diamond coatings were deposited on the silicon substrate using Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD). Experiments were performed by varying the H₂ content in CH₄/H₂ plasma during synthesis. Raman spectral analysis revealed that with decrease in hydrogen content in the CH₄ plasma, the I_D/I_G ratio decreases with the formation of smaller crystallites. Such a film possesses a large grain boundary fraction containing hydrogenated amorphous carbon (a-C:H). During tribological test, sufficient amount of hydrogen present in the grain boundary passivates the dangling σ-bond causing ultra-low friction and extremely low wear evident by improvement in microstructure.     

Optical transition process in AgOx super-resolution near-field structure

A sandwiched 15 nm AgO_x thin film of the super‐resolution, near‐field optical disk was studied using a confocal Z‐scan system. Nonlinear optical properties of quartz glass/ZnS–SiO₂ (170 nm)/AgO_x (15 nm)/ZnS–SiO₂ (40 nm) were measured using a Q‐switch Nd : YAG pulse laser of wavelength 532 nm, pulse width 0.7 ns, and 15.79 kHz repetition rate. Transmittance and reflectance of the sandwiched AgO_x thin film show important optical responses at the focused position of Z‐scan. The dissociation processes of AgO_x, recombination of the silver and oxygen, and the resonance of the localized surface plasmon of the nano‐composites of the AgO_x thin film are correlated to transmittance and reflectance at the focused position of the Z‐scan for different input laser powers. An irreversible upper threshold intensity of 4.40 × 10⁶ mW cm^?2 at the focused position was found. A reversible working window of the focusing intensity between 1.86 × 10⁶ and 4.40 × 10⁶ mW cm^?2 was measured with sandwiched AgO_x thin film alone. The near‐field interactions of the AgO_x thin film and the recording layers of super‐resolution near‐field optical disk are also discussed.     

Electrostatic force microscopy study on the domain switching properties of the Pb(Zr0.2Ti0.8)O3 thin films with different crystallographic orientations for the probe-based data storage

The domain switching properties of the ferroelectric Pb(Zr_0.2Ti_0.8)O₃ (PZT) thin films with two types of crystallographic orientations were investigated by electrostatic force microscopy (EFM). The crystallographic orientations of the PZT thin films were random on the (1 1 1)Pt/MgO(1 0 0) and c-axis preferred on the (1 0 0)Pt/MgO(1 0 0), respectively. When dc bias was applied to the films for writing in micro-scale area, electrostatic force images showed that the domain switching was hard in the PZT thin films with random orientation, while the pattern could clearly be written in the PZT films with c-axis orientation. The differences in the domain switching properties of each PZT thin film were investigated in the crystallographic orientations point of view, and the domain switching dynamics were also measured by investigating the nano-sized dot switching behavior with respect to the width of the applied voltage pulse.