金纳米粒子LB单层膜的制备及其I-V特性

在不同条件下采用LB技术制备了金纳米粒子单层膜,并利用SEM对所得到的薄膜的表面形貌进行表征。结果表明决定薄膜质量的关键因素是表面压。将表面压控制在22~26mN/m的范围内以较慢的拉膜速度在Si(100)基底上进行拉膜,可以得到大面积金纳米粒子的均匀致密单层膜。在室温下测量两点之间单层膜的I-V特性,得到了非欧姆特性,这是由电子在电场作用下发生隧穿产生的。     

FePt纳米粒子有序膜结构的SPM研究

采用化学合成方法制备了单分散的FePt磁性纳米粒子，通过对纳米粒子的操纵与排布制得了磁性纳米粒子单层膜和多层膜，并利用扫描探针显微技术(SPM)和X射线粉末衍射(XRD)考察了磁性纳米粒子膜中FePt纳米粒子的形貌、粒度分布和表面聚集状态。研究结果表明在磁性纳米粒子单层膜中，磁性纳米粒子分布均匀、排列紧密，且多层膜在膜累加方向是具有周期结构的有序组合体。     

多元等离子体共振纳米结构的飞秒激光加工与拉曼检测应用

以多元金属纳米薄膜(金、银)为基底,利用飞秒激光加工技术制备得到多元等离子体纳米结构,并研究了其局域表面等离子体共振效应(Local Surface Plasmon Resonance,LSPR)和表面增强拉曼散射(Surface Enhanced Raman Scattering,SERS)性能。利用时域有限差分(Finite Difference Time Domain,FDTD)软件模拟了不同情况下(单层金膜、金银双层金属薄膜的平面以及阵列结构)的电场分布情况。根据仿真结果,相较于平面金属膜来说,飞秒激光制备的微纳结构阵列附近区域产生电磁场增强,集中在结构边缘处,且其强度变化与预期结果基本保持一致。此外,使用浓度为10-4 M和10-6 M的罗丹明(R6G)溶液进行SERS性能测试。测试的结果表明,单层平面金膜基本没有SERS峰值信号出现,而单层金膜上制备的等离子体纳米结构附近出现峰值信号,双层金属薄膜上制备的等离子体纳米结构展现出更高的SERS峰值信号。多元金属等离子体纳米结构展示出更强的局域表面等离子体共振效应,从而在表面增强拉曼散射、光催化、生物传感等领域具有广泛的应用。     

微型球状光学免疫传感器的构建及其在CA125检测中的应用

金纳米粒子(AuNP)和银纳米粒子(AgNP)受到光子作用发出强烈的散射光,在暗场显微镜中可观察到清晰的单纳米粒子图像。以金纳米粒子耦合抗体分子作为球状传感器核心,银纳米粒子作为抗原标记物,构建微型球状光学免疫传感器。研究结果显示,在暗场显微镜中观察到抗体耦合的金纳米粒子为金黄色光点,银纳米粒子为绿色光点。当溶液中癌抗原CA125浓度为35 U/mL时,银纳米粒子耦合到金纳米粒子表面,金黄色的暗场图像转变成绿色,散射光强度增强至68 720,表明通过暗场显微镜观察传感器的颜色变化可定量检测生物分子。该光学免疫传感器体积小、灵敏度高,可进一步应用于临床疾病诊断。     

Cu/Ta/SiO2/Si薄膜在纳米压痕下的分层现象研究

采用磁控溅射技术在热氧化单晶硅衬底上先后淀积了厚度分别为50nm的Ta膜和400 nm的Cu膜.使用纳米压入仪在样品表面进行压入测试,在薄膜表面制造出残留压痕.使用扫描电镜(SEM)、聚焦离子束(FIB)、透射电镜(TEM)和X射线能谱仪(EDX)对残留压痕形貌、剖面上的分层现象进行观察,确定分层所在的位置.发现在69 mN的最大载荷作用后,在TA/SiO2界面处发生分层.分层的原因主要归结为在应力作用下,多层膜中各种材料的应变、弹性恢复能力不同.     

LB膜与AFM技术研究磷脂酰乙醇胺单分子膜结构

用LB膜技术对磷脂酰乙醇胺(PE)单分子膜的影响因素进行了研究。实验发现溶液浓度、亚相温度、pH值以及胆固醇含量等因素对磷脂酰乙醇胺单分子膜成膜条件有一定的影响。当溶液浓度为0.32 mg/mL,加入量在100~500μL范围内,随着加入量的增多,磷脂分子越易形成致密的单分子层;温度升高对单分子膜有一定的破坏作用,在39.1℃时,亚相的pH值在中性或接近中性的弱酸条件下,PE分子排列更有序;胆固醇的加入降低了PE分子膜的流动性,对单分子膜有显著的稳固作用。用Y型LB提膜法将单分子膜转移到新解离的云母表面,用原子力显微镜技术对其进行了分子结构的观察研究,实验结果表明,膜压低于1 mN/m时,液面上磷脂分子的烃链自由弯曲运动,取向性呈无序随机排列。但在大于1 mN/m时,PE分子较易形成有序分子膜,膜压为33 mN/m,形成高质量的LB膜。     

基于表面等离子体的微纳光刻技术

首先介绍了光刻技术的发展及其面临的挑战。随着纳米加工技术的发展,纳米结构器件必将成为未来集成电路的基础,而纳米光刻技术是纳米结构制作的基础,基于表面等离子体的纳米光刻作为一种新兴技术有望突破45nm节点从而极大提高光刻的分辨力。介绍了表面等离子体的特性,对表面等离子体(SPs)在光刻中的应用作了回顾和分析,指出在现有的利用表面等离子体进行纳米光刻的实验装置中,或采用单层膜的超透镜(Superlens),或采用多层膜的Super-lens,但都面临着如何克服近场光刻这一难题;结合作者现有课题分析了表面等离子体光刻的发展方向,认为结合多层膜的远场纳米光刻方法是表面等离子体光刻的发展方向。     

SnO2纳米薄膜的自组装制备及表征

利用自组装单层膜法,在单晶硅基底上生长有机硅烷单分子膜层,并在硅烷的功能性基团上,诱导生成二氧化锡纳米薄膜,通过XPS、AFM、SEM及XRD等手段对膜材料的表面形貌和结构进行了分析。结果表明:自组装单层法制备的SnO2薄膜为晶态膜,膜层致密、均一,厚度约为20 nm,结构为金红石结构。     

硅烷偶联剂对太阳电池铝浆性能的影响及分析

在晶体硅太阳电池制造过程中,铝电极是通过丝网印刷-烘干-烧结制成的。该过程中铝电极膜层与传送网带发生相对摩擦,易导致铝膜表面产生划痕、起灰。重点研究了添加不同质量分数w(硅烷偶联剂)(0.5%~3.0%)对铝浆有机载体的表面张力、铝膜表面划痕、起灰、导电性能的影响规律。结果表明:当w(硅烷偶联剂)为2.5%时,有机载体的表面张力可从约30mN/m降低至25.69mN/m,提高了铝粉颗粒之间以及铝膜与硅片之间的黏附作用,从而减少划痕和灰化,进而可使铝电极的接触电阻由0.60?降低至0.19?。     

Ag纳米粒子等离子体共振增强太阳能电池吸收

针对薄膜太阳能电池硅薄膜层吸收效率较低的问题,提出了运用金属纳米粒子局域表面等离子体共振(LSPR)增强太阳能电池的吸收效率,采用时域有限差分(FDTD)法,模拟计算了太阳能电池中不同厚度的硅薄膜层吸收特性,分析了不同几何参数的矩形Ag纳米粒子与Ag背反射膜对增强太阳能电池吸收效率的影响作用。计算结果表明,硅薄膜层厚度为500nm的太阳能电池具有较高的吸收效率,通过调整Ag纳米粒子的相关参数,有效地降低了太阳电池硅薄膜表面的反射损耗,取得最大吸收增强因子为1.35。Ag背反射膜有效地降低了Ag纳米粒子硅薄膜结构的透射损耗,其最大的吸收增强因子达到1.42。     

Facile Fabrication of High‐Density Sub‐1‐nm Gaps from Au Nanoparticle Monolayers as Reproducible SERS Substrates

The fabrication of ultrasmall nanogaps (sub‐1 nm) with high density is of significant interest and importance in physics, chemistry, life science, materials science, surface science, nanotechnology, and environmental engineering. However, it remains a challenge to generate uncovered and clean sub‐1‐nm gaps with high density and uniform reproducibility. Here, a facile and low‐cost approach is demonstrated for the fabrication of high‐density sub‐1‐nm gaps from Au nanoparticle monolayers as reproducible surface‐enhanced Raman scattering (SERS) substrates. Au nanoparticles with larger diameters possess lower surface charge, thus the obtained large‐area nanoparticle monolayer generates a high‐density of sub‐1‐nm gaps. In addition, a remarkable SERS performance with a 10¹¹ magnitude for the Raman enhancement is achieved for 120 nm Au nanoparticle monolayers due to the dramatic increase in the electromagnetic field enhancement when the obtained gap is smaller than 0.5 nm. The Au nanoparticle monolayer is also transferred onto a stretchable PDMS substrate and the structural stability and reproducibility of the high‐density sub‐1‐nm gaps in Au monolayer films are illustrated. The resultant Au nanoparticle monolayer substrates with an increasing particle diameter exhibit tunable plasmonic properties, which control the plasmon‐enhanced photocatalytic efficiency for the dimerization of p‐aminothiophenol. The findings reported here offer a new opportunity for expanding the SERS application.     

The Bond Strength of Au/Si Eutectic Bonding Studied by IR Microscope

The interface of Au/Si(100) eutectic bonding was investigated by infrared (IR) microscope and related to the bond strength. A strong relationship between the IR images and the bond strengths was found. Bond strength test showed that a strong bond has many square black spots in the IR images, whereas a poor bond has fewer or no square black spots. In order to study the nature of the relationship, the dissolution behavior of the bare Si(100) surface after bonding was investigated. During the Au/Si(100) eutectic reaction, the dissolution of the bare Si(100) surface primarily occurs by the formation of the craters which result in many square black spots in the IR images. The formation of the craters is ascribed to the anisotropic nature of Au/Si reaction that results in three-dimensional dissolution behavior on the bare Si(100) side. In order to further test the anisotropy hypothesis, Au/Si(111) bonding was also studied. Under the same bonding conditions, triangular black spots were observed in the IR images and triangular pits were found on the bare Si(111) surface. The analysis suggests that the craters on the bare Si(100) surface, in other words the square black spots in the IR images, are the indication of Au/Si(100) eutectic reaction. More craters mean a reaction between Au and Si(100), which occurs uniformly at the Au/Si(100) bonding interface compared to the case of fewer craters. No crater indicates that there is no eutectic reaction in the region. Therefore, the IR microscope may be used to evaluate and compare the different bond strengths qualitatively.      

Au/SiO_2复合纳米颗粒膜的制备及退火行为研究

室温下用磁控溅射法在Si(111)衬底上生成Au/SiO2复合纳米颗粒膜。用扫描电子显微镜(SEM)和X射线衍射方法(XRD)对不同温度退火后的Au/SiO2复合薄膜的表面形貌、微观结构进行了表征。SEM结果表明,随着退火温度升高,Au纳米颗粒先形成大的聚集后出现分布均匀的超微颗粒。XRD结果显示700℃时Au的衍射峰最强,随后峰强有所减弱,这与SEM检测结果相吻合。另外实验结果证实在1000℃退火时自组装生成空间分布均匀(直径约为70nm)的Au纳米点,可以用来作为生长一维纳米材料的模板。     

Modification of metal/semiconductor junctions by self-assembled monolayer organic films

Two new metal/molecule/semiconductor contacts, Au/n-Si/TDA/Au and Au/p-Si/ODM/Au, were fabricated to understand effect of organic compounds, tridecylamine and octadecylmercaptan self-assembled monolayer (SAM) films, on electrical charge transport properties of the metal/semiconductor junctions. The morphology of the organic monolayers deposited on Si substrates was investigated by atomic force microscopy. The molecular coverage of ODM deposited on p-Si is poorer than that of TDA on n-Si substrate. The ideality factors of the p-Si/ODM and n-Si/TDA diodes were found to be 1.66 and 1.48, respectively. The electrical results show that the tridecylamine monolayer passivated junction has a lower ideality factor. The ideality factor indicates clear dependence on two different type functional groups R-SH (Thiol) and R-NH₂ (Amin) groups and it increases with different functional groups of organic molecule. The barrier height φ_b value of the n-Si/TDA diode is smaller than that of p-Si/ODM diode, as a result of chain length of the SAM organic molecules. The interface state density D_it values of the diodes were determined using conductance technique. The n-Si/TDA diode has the smaller interface state density according to p-Si/ODM diode.We have evaluated that the organic molecules control the electronic parameters of metal/semiconductor diodes and thus, organic modification helps to get one step closer towards to new organic assisted silicon based microelectronic devices.     

Symmetric Large‐Area Metal‐Molecular Monolayer‐Metal Junctions by Wedging Transfer

A method is described for fabricating and electrically characterizing large‐area (100–400 μm²) metal‐molecular monolayer‐metal junctions with a relatively high overall yield of ≈45%. The measurement geometry consists of ultra‐smooth (template‐stripped) patterned Au bottom electrodes, combined with ultra‐smooth top Au electrodes deposited using wedging transfer. The fabrication method is applied to the electrical characterization of Au‐alkanethiol self‐assembled monolayer‐Au junctions. An exponential decay of the current density is found for increasing the chain length of the alkanethiols, in agreement with earlier studies. The symmetric device geometry, and flexibility for contacting monolayers with various end groups are important advantages compared to existing techniques for electrically characterizing molecular monolayers.     

Atomic Layer Deposition of TiO2 Thin Films on Mixed Self‐Assembled Monolayers Studied as a Function of Surface Free Energy

Mixed self‐assembled monolayers (SAMs) with different ratios of –OH to –CH₃ groups were used to modify the surface free energies of the Si substrates from 64 to 29 mN m^–1. The TiO₂ thin films were grown on the mixed SAM‐coated Si substrates by atomic layer deposition (ALD) from titanium isopropoxide and water. A two‐dimensional growth mode is observed on the SAMs‐coated substrates possessing high surface free energies. As the surface free energy decreases, a three‐dimensional growth mode begins to dominate. These observations indicate that the mixed SAMs can control the growth modes of the atomic layer deposition by modifying of the surface free energies of the substrates.     

STM Lithography in an Organic Self‐Assembled Monolayer

We describe the suitability of ultra‐high vacuum scanning tunneling microscopy (UHV‐STM) based nanolithography by using highly ordered monomolecular organic films, called self‐assembled monolayers (SAMs), as ultrathin resists. Organothiol‐type SAMs such as hexadecanethiol (SH–(CH₂)₁₅–CH₃) and N‐biphenylthiol (SH–(C₆H₆)₂–NO₂) monolayers have been prepared by immersion on gold films and Au(111) single crystals. Organosilane‐type SAMs such as octadecyltrichlorosilane (SiCl₃–(CH₂)₁₇–CH₃) monolayers have been prepared on hydroxylated Si(100) surfaces as well as hydroxylated chromium film surfaces. Dense line patterns have been written by UHV‐STM in constant current mode for various tunneling parameters (gap voltage, tunneling current, scan speed, and orientation) and transferred into the underlying substrate by wet etch techniques. The etched structures have been analyzed by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). Best resolution has been achieved without etch transfer for a 20 nm × 20 nm square written in hexadecanethiol/Au(111) with an edge definition of about 5 nm. Etch transfer of the STM nanopatterns in Au films resulted in 55 nm dense line patterns (15 nm deep) mainly broadened by the isotropic etch characteristic, while 35 nm wide and 30 nm deep dense line patterns written in octadecyltrichlorosilane/Si(100) and anisotropically etched into Si(100) could be achieved.     

CdZnTe heteroepitaxy on 3″ (112) Si: Interface, surface, and layer characteristics

Tellurium adsorption studies were made on clean and arsenic passivated (112) silicon surfaces. Quantitative surface coverage values for tellurium were determined by Auger electron spectroscopy. Saturation coverage of up to 1.2 monolayers of tellurium could be obtained on a clean (112) silicon surface. On an arsenic passivated (112) Si surface however, the tellurium saturation coverage was limited to only ∼0.3 monolayer. Analysis of the adsorption behavior suggested that tellurium and arsenic chemisorption occurs preferentially at step edges and on terraces, respectively. The study revealed that arsenic passivation led to a significant decrease in the sticking coefficient of tellurium and an increase in it’s surface mobility. A model describing zinc telluride nucleation on a (112) Si surface is proposed. Thin templates of ZnTe followed by Cd_1−xZn_xTe layers were deposited on (112) Si by molecular beam epitaxy (MBE). The characteristics of the MBE Cd_1−xZn_xTe layers were found to be sensitive to the initial ZnTe nucleation and Si surface preparation.     

沉积时间对Au/Si-NPA电学特性的影响

采用浸渍法在硅纳米孔柱阵列(Silicon Nanoporous Pillar Array,Si-NPA)衬底上制得了一系列金/硅纳米孔柱阵列(Au/Si-NPA),不同Au/Si-NPA所用沉积时间不同.通过测试分析所制Au/Si-NPA的,I-V特性曲线,研究了沉积时间对Au/Si-NPA电学特性的影响.结果表明:...