扫描电—声显微镜及其应用

扫描电—声显微镜最近已在我们实验室研究制成功了,它是国际上近几年来发展起来的一种新的成像工具,它的成像机理是基于试样的微观热学和弹性性质的变化,特别是它具有非破坏性的亚表面剖面成像能力,这是常规扫描电镜所无法比拟的。本文主要介绍了扫描电一声显微镜的发展,工作原理,电—声成像的物理过程和优点。并显示了半导体材料、集成电路、金刚石复合片、硅片表面离子注入以及金属等试样的表面和亚表面电—声像,并与二次电子像作了比较,显示了电—声像的某些特点和潜在的应用价值。     

扫描探针声显微镜原理及其应用

将声学检测技术与扫描探针显微术相结合,构成的扫描探针声显微镜,不仅可以检测材料表面、亚表面和内部的微小缺陷,还可以分析样品的弹性特性、电特性等物理性能,同时还具有分辨率高的特点,在材料科学和生命科学等领域具有很高的应用价值.目前,得到实际应用的扫描探针声显微镜主要有扫描隧道声显微镜和原子力声显微镜.本文介绍了这两类显微镜的基本工作原理,并对扫描探针声显微镜今后的发展方向进行了探讨.     

红外激光光声光谱仪研制及应用概况

本文介绍了十年来(1978～1988年)红外激光光声光谱仪的研制及应用概况,并由此开拓了红外激光光声显微镜及红外激光光声功率计的研制和其他光声技术的应用研究。这些新的红外光声检测仪,有的已经投产,有的性能基本达到国外同类仪器的水平,对深入开展光声技术应用研究提供了新的研究和分析工具。     

激光扫描声学显微镜及应用

阐述了激光扫描声学显微镜(SLAM)的结构、工作原理，以及激光扫描声学显微镜的实际应用，结合电子科技大学光电声信息处理研究中心研制成功的SLAM说明这种新型无损检测设备具有的一些特殊功能，在电子、复合材料、生物医学等领域具有广泛的应用前景。     

扩声系统中设计、配置环绕和效果声应注意问题

说明了扩声系统设计中环绕声和效果声应注意的问题,指出了设计和配置环绕声（效果声）音箱的必要性,并介绍了如何设计和配置环绕声（效果声）音箱,为广大用户提供一个更加符合实际应用需要的扩声系统。     

扬声器阵列·声柱与声梁

介绍了扬声器阵列、扬声器线阵列、声柱的基本概念,以连续直线阵列为例,介绍其指向特性、波阵面传播特性、有效辐射率(ARF)概念及其估计方法,分析了点声源声柱和线声源声柱.提出了声梁的基本概念及一种利用二次剩余序列实现均匀声场的解决方案.     

用于脉冲压缩雷达的声表面波部件

介绍一种用于脉冲压缩雷达的声表面波部件。它包含了声表面波脉压线、声表面波振荡器和重要的电子线路。该部件产生一种脉冲展宽信号，其工作频率为９６０ＭＨｚ，信号带宽为６ＭＨｚ，色散时间为１０μｓ，杂波电平≤－５０ｄＢｃ。专门设置的９００ＭＨｚ本振输出电平≥７ｄＢｍ，杂散电平≤－８０ｄＢｃ     

国外声表面波传感器开发近况

以声表面波气体、温度和压力传感器为例，介绍了国外声表面波传感器的开发近况。指出了开发的重点、难点及今后的发展方向。     

扫描电子声显微镜在半导体材料分析中的应用

本文利用国际上近几年发展起来的一种新型显微成像工具──扫描电子声显微镜（ＳＥＡＭ－ＳｃａｎｎｉｎｇＥｌｅｃｔｒｏｎＡｃｏｕｓｔｉｃＭｉｃｒｏｓｃｏｐｅ）对几种类型的半导体材料进行了电子声成像观察与研究．文中简述了扫描电子声显微镜的电子声成像机理和其工作原理．从获得的电子声图像上，反映出扫描电子声显微成像技术在对半导体材料的亚表面缺陷和掺杂分布方面有着直接观察与显示的能力．同时与相应位置所获得的二次电子像进行了比较，显示出了电子声显微成像技术的独特之处和潜在的应用价值．     

声显微镜的现状和发展

本文综述了声显微镜(主要是机械扫描声显微镜)的特点、现状和进展。文中介绍了声显微镜的工作原理、常用结构,和设计公式。声显微镜观察到的象是物质的力学参量象,它是一种很有潜力的对物体内部结构进行观察的手段。当前的主要工作是扩展其基本功能,以及如何实现内部成象等。     

Effects of temperature and size on contact behavior of self-assembled alkanethiol cluster for dip-pen nanolithography

Molecular dynamics (MD) calculations are used to study the contact behavior of self-assembled monolayer (SAM) deposited on gold substrate in dip-pen nanolithography (DPN). The interaction of SAM atoms was described by a general universal force field, the tight-binding, second-moment approximation was used for Au substrate, and the Lennard-Jones potential function was employed to describe interaction between the SAM and the Au substrate atoms. The MD model consists of a planar Au substrate with n-hexadecanethiol SAM chemisorbed to the substrate. When the SAM clusters are brought closer to the substrate surface, the interaction normal force is induced. The normal force increases as the size of SAM clusters increases. In addition, the effect of the temperature and the size of SAM clusters on the contact angle between the alkanethiol SAM and the Au substrate in DPN are evaluated. Results show that the contact angles decreased as the temperature increased, and the smaller the cluster size, the smaller the contact angle.     

专业监听扬声器发展新技术简析

随着专业监听扬声器技术的不断升级、优化与改良,监听扬声器当前面临的技术挑战已不再是单纯地追求音质的高标准,而在于如何在严苛的声频技术标准与受到特定条件局限的工作环境下,仍然可以在监听环境中获得卓越的重放效果.旨在以Genelec 8351三分频声学同轴智能有源监听扬声器为例,阐述同轴扬声器研发的历史经验、设计思路及新技术特点,分析与探究专业监听扬声器在新时期下的发展现状与方向.     

Doping of Conjugated Polythiophenes with Alkyl Silanes

A strong modification of the electronic properties of solution‐processable conjugated polythiophenes by self‐assembled silane molecules is reported. Upon bulk doping with hydrolized fluoroalkyl trichlorosilane, the electrical conductivity of ultrathin polythiophene films increases by up to six orders of magnitude, reaching record values for polythiophenes: (1.1 ± 0.1) × 10³ S cm^?1 for poly(2,5‐bis(3‐tetradecylthiophen ‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) and 50 ± 20 S cm^?1 for poly(3‐hexyl)thiophene (P3HT). Interband optical absorption of the polymers in the doped state is drastically reduced, making these highly conductive films transparent in the visible range. The dopants within the porous polymer matrix are partially crosslinked via a silane self‐polymerization mechanism that makes the samples very stable in vacuum and nonpolar environments. The mechanism of SAM‐induced conductivity is believed to be based on protonic doping by the free silanol groups available within the partially crosslinked SAM network incorporated in the polythiophene structure. The SAM‐doped polythiophenes exhibit an intrinsic sensing effect: a drastic and reversible change in conductivity in response to ambient polar molecules, which is believed to be due to the interaction of the silanol groups with polar analytes. The reported electronic effects point to a new attractive route for doping conjugated polymers with potential applications in transparent conductors and molecular sensors.     

Advanced Characterization and Optimization of NiOx:Cu-SAM Hole-Transporting Bi-Layer for 23.4% Efficient Monolithic Cu(In,Ga)Se2-Perovskite Tandem Solar Cells

The performance of five hole-transporting layers (HTLs) is investigated in both single-junction perovskite and Cu(In, Ga)Se₂ (CIGSe)-perovskite tandem solar cells: nickel oxide (NiO_x,), copper-doped nickel oxide (NiO_x:Cu), NiO_x+SAM, NiO_x:Cu+SAM, and SAM, where SAM is the [2-(3,-6Dimethoxy-9H-carbazol-9yl)ethyl]phosphonic acid (MeO-2PACz) self-assembled monolayer. The performance of the devices is correlated to the charge-carrier dynamics at the HTL/perovskite interface and the limiting factors of these HTLs are analyzed by performing time-resolved and absolute photoluminescence ((Tr)PL), transient surface photovoltage (tr-SPV), and X-ray/UV photoemission spectroscopy (XPS/UPS) measurements on indium tin oxide (ITO)/HTL/perovskite and CIGSe/HTL/perovskite stacks. A high quasi-Fermi level splitting to open-circuit (QFLS-V_oc) deficit is detected for the NiO_x-based devices, attributed to electron trapping and poor hole extraction at the NiO_x-perovskite interface and a low carrier effective lifetime in the bulk of the perovskite. Simultaneously, doping the NiO_x with 2% Cu and passivating its surface with MeO-2PACz suppresses the electron trapping, enhances the holes extraction, reduces the non-radiative interfacial recombination, and improves the band alignment. Due to this superior interfacial charge-carrier dynamics, NiO_x:Cu+SAM is found to be the most suitable HTL for the monolithic CIGSe-perovskite tandem devices, enabling a power-conversion efficiency (PCE) of 23.4%, V_oc of 1.72V, and a fill factor (FF) of 71%, while the remaining four HTLs suffer from prominent V_oc and FF losses.     

Bottom‐Up Engineering of Subnanometer Copper Diffusion Barriers Using NH2‐Derived Self‐Assembled Monolayers

A 3‐aminopropyltrimethoxysilane‐derived self‐assembled monolayer (NH₂SAM) is investigated as a barrier against copper diffusion for application in back‐end‐of‐line (BEOL) technology. The essential characteristics studied include thermal stability to BEOL processing, inhibition of copper diffusion, and adhesion to both the underlying SiO₂ dielectric substrate and the Cu over‐layer. Time‐of‐flight secondary ion mass spectrometry and X‐ray spectroscopy (XPS) analysis reveal that the copper over‐layer closes at 1–2‐nm thickness, comparable with the 1.3‐nm closure of state‐of‐the‐art Ta/TaN Cu diffusion barriers. That the NH₂SAM remains intact upon Cu deposition and subsequent annealing is unambiguously revealed by energy‐filtered transmission electron microscopy supported by XPS. The SAM forms a well‐defined carbon‐rich interface with the Cu over‐layer and electron energy loss spectroscopy shows no evidence of Cu penetration into the SAM. Interestingly, the adhesion of the Cu/NH₂SAM/SiO₂ system increases with annealing temperature up to 7.2 J m^?2 at 400 °C, comparable to Ta/TaN (7.5 J m^?2 at room temperature). The corresponding fracture analysis shows that when failure does occur it is located at the Cu/SAM interface. Overall, these results demonstrate that NH₂SAM is a suitable candidate for subnanometer‐scale diffusion barrier application in a selective coating for copper advanced interconnects.     

Electrode Work Function Engineering with Phosphonic Acid Monolayers and Molecular Acceptors: Charge Redistribution Mechanisms

The uses of self‐assembled monolayers (SAMs) of dipolar molecules or of adsorbed molecular acceptors on electrode materials are common strategies to increase their work function, thereby facilitating hole injection into an organic semiconductor deposited on top. Here it is shown that a combination of both approaches can surpass the performance of the individual ones. By combined experimental and theoretical methods it is revealed that in a three‐component system, consisting of an indium‐tin‐oxide (ITO) electrode, a carbazole‐based phosphonic acid SAM, and a molecular acceptor layer on top of the SAM, charge transfer occurs from the ITO through the SAM to the acceptor layer, resulting in an electrostatic field drop over the charge‐neutral SAM. This result is in contrast to common expectations of either p‐doping the carbazole of the SAM or charge transfer complex formation between the carbazole and the acceptor molecules. A high work function of 5.7 eV is achieved with this combined system; even higher values may be accessible by exploiting the fundamental charge redistribution mechanisms identified here with other material combinations.     

Low temperature CuCu thermo-compression bonding with temporary passivation of self-assembled monolayer and its bond strength enhancement

Self-assembled monolayer (SAM) of alkane-thiol is formed on copper (Cu) thin layer coated on silicon (Si) wafer with the aim to protect the surface against excessive oxidation during storage in the room ambient. After 3 days of storage, the temporary SAM layer is desorbed with in situ anneal in inert ambient to uncover the clean Cu surface. A pair of wafers is bonded at 250 °C. Clear evidences of in-plane and out-of-plane Cu grain growth are observed resulting in a wiggling bonding interface. This gives rise to enhancement in shear strength in the bonded CuCu layer.     

The impact of self-assembled monolayer thickness in hybrid gate dielectrics for organic thin-film transistors

We have investigated the electrical characteristics of hybrid dielectrics with a thickness of 6 nm or less that are composed of a plasma-grown aluminum oxide (AlO_x) layer and a self-assembled monolayer (SAM) of an aliphatic phosphonic acid. The impact of the quality of the AlO_x layer on the insulating properties of the double-layer dielectrics was assessed by comparing two different oxidation procedures, and the influence of the thickness of the organic SAM was evaluated by employing molecules with five different chain lengths. In order to decouple the relative contributions of the oxide and the SAM to the performance of the double-layer dielectrics we have also performed cyclic voltammetry measurements on indium tin oxide (ITO)/SAM devices without AlO_x layer. Finally, we have evaluated how the quality of the AlO_x layer and the thickness of the SAM affect the performance of low-voltage organic thin-film transistors (TFTs) that employ the thin AlO_x/SAM dielectrics as the gate dielectric. The results confirm the important role of the SAM in determining the breakdown voltage, in limiting the current density, and in compensating the somewhat lower quality of AlO_x layers produced under mild plasma conditions.     

Vectorially Imprinted Hybrid Nanofilm for Acetylcholinesterase Recognition

Effective recognition of enzymatically active tetrameric acetylcholinesterase (AChE) is accomplished by a hybrid nanofilm composed of a propidium‐terminated self‐assembled monolayer (Prop‐SAM) which binds AChE via its peripheral anionic site (PAS) and an ultrathin electrosynthesized molecularly imprinted polymer (MIP) cover layer of a novel carboxylate‐modified derivative of 3,4‐propylenedioxythiophene. The rebinding of the AChE to the MIP/Prop‐SAM nanofilm covered electrode is detected by measuring in situ the enzymatic activity. The oxidative current of the released thiocholine is dependent on the AChE concentration from ≈0.04 × 10^?6 to 0.4 × 10^?6m . An imprinting factor of 9.9 is obtained for the hybrid MIP, which is among the best values reported for protein imprinting. The dissociation constant characterizing the strength of the MIP‐AChE binding is 4.2 × 10^?7m indicating the dominant role of the PAS‐Prop‐SAM interaction, while the benefit of the MIP nanofilm covering the Prop‐SAM layer is the effective suppression of the cross‐reactivity toward competing proteins as compared with the Prop‐SAM. The threefold selectivity gain provided by i) the “shape‐specific” MIP filter, ii) the propidium‐SAM, iii) signal generation only by the AChE bound to the nanofilm shows promise for assessing AChE activity levels in cerebrospinal fluid.     

Cu–Cu Hermetic Seal Enhancement Using Self-Assembled Monolayer Passivation

Low-temperature Cu–Cu thermocompression bonding enabled by self-assembled monolayer (SAM) passivation for hermetic sealing application is investigated in this work. Cavities are etched to a volume of 1.4 × 10^?3 cm³ in accordance with the MIL-STD-883E standard prescribed for microelectronics packaging. The wafer pairs (nonfunctional cavity wafer and cap wafer) are annealed and bonded at 250°C under a bonding force of 5500 N. The encapsulated cavities undergo helium overpressure in a bombing chamber, and the helium leak rate is detected by a mass spectrometer. The measurement results show that the cavities sealed with Cu–Cu bonding after SAM passivation exhibit excellent hermeticity with a leak rate below 10^?9 atm cm³/s, which is an improvement of at least 2× compared with the control sample without SAM passivation.