Si纳米线表面Ni薄膜生长工艺

研究了Si纳米线表面Ni薄膜生长工艺。采用热蒸发法以SiO为起始原料制备自组生长的Si纳米线,再以5%(体积分数)HF剔除Si纳米线表面硅氧化合物,采用氩离子磁控溅射的方法在Si纳米线表面溅射一定厚度的无定形Ni颗粒,此后对镀Ni的Si纳米线进行完整晶体结构的退火处理。应用高分辨透射电镜(HRTEM)等结构表征工具分析了Si纳米线表面Ni薄膜的形成过程,HRTEM结果表明,在350℃左右退火得到的Si纳米线表面能形成连续的、结构完整的Ni薄膜;退火温度低于300℃时,表面溅射的Ni结晶效果较差;退火温度在800℃时,表面Ni薄膜发生团聚,形成了分立的纳米颗粒。     

自组装法合成导电聚吡咯纳米线

以多孔氧化铝为模板,合成导电聚吡咯纳米线。利用SEM对聚吡咯进行了表征,结果表明:在吡咯单体浓度为0.2 mol/L,电压1.0 V,时间1 600 s的条件下,制得的聚吡咯会有大量的微触手结构出现,且表面光滑,比表面积较大,并初步探究了聚吡咯微触手结构的形成机理。     

银纳米线表面等离子体波导的传输损耗特性研究

通过远场聚焦光斑激发银纳米线表面等离子体激元(SPP: Surface Plasmon Polariton),并搭建银纳米线路由传输结构改变SPP的传输距离,研究了SPP的传输损耗特性。实验上测量了置于玻璃衬底表面的银纳米线在不同激发波长时SPP的传输损耗系数,发现SPP的传输损耗具有波长依赖性：632.8nm激光激发时,传输损耗系数为0.115 ,780nm激光激发时,传输损耗系数为0.0923 ,即传输损耗系数在长波激发时小,而在短波激发时大。测量结果对基于银纳米线波导的集成微纳光学系统设计有很好的指导作用。     

银纳米线与二氧化硅衬底表面摩擦力的测量

银纳米线是制作纳米光电子器件的理想材料,了解银纳米线与特定衬底间的摩擦特性对于器件的设计和制备工艺具有重要参考价值.本文利用原子力显微镜(AFM)研究银纳米线与二氧化硅衬底表面的摩擦特性,为提高摩擦力测量准确性,依次借助斜面法和横向力曲线分别标定了AFM探针的扭转弹性常数和光杠杆横向灵敏度,同时对扫描器引入的横向误差进行了补偿.利用AFM纳米操纵技术记录了单根银纳米线由静止到整体滑动的全过程,实验测得直径50 nm银纳米线与二氧化硅衬底表面的最大静摩擦线密度和滑动摩擦线密度分别为1.07 nN/nm和0.56 nN/nm.     

8通道-1.6nm Si纳米线阵列波导光栅的设计与制作

设计了基于绝缘层上硅(SOI)材料的8通道Si纳米线阵列波导光栅(AWG),器件的通道间隔为1.6nm,面积为420μm×130μm。利用传输函数法模拟了器件传输谱,结果表明,器件的通道间隔为1.6nm,通道间串扰为17dB。给出了结合电子束光刻(EBL)和感应耦合等离子(ICP)刻蚀技术制备器件的详细流程。光谱测试结果分析表明,器件通道间隔为1.3～1.6nm,通道串扰为3dB,中心通道损耗为11.6dB。     

Si纳米线阵列波导光栅制备

采用绝缘层上Si(SOI)材料设计制备了3×5纳米线阵列波导光栅(AWG),器件大小为110μm×100μm。利用简单传输法模拟了器件的传输谱,并采用二维时域有限差分(FDTD)模拟中心通道输出光场的稳态分布,模拟结果表明,器件的通道间隔为11 nm,通道间的串扰为18 dB。通过电子束曝光(EBL)和感应耦合等离子(ICP)刻蚀制备了所设计的器件,光输出谱测试分析表明,器件中心通道的片上损耗为9 dB,通道间隔为8.36～10.40 nm,中心输出通道的串扰为6 dB。在误差允许范围内,设计和测试的结果一致。     

缓冲层温度对Si(111)上GaN表面形貌影响

用不同温度的Al N缓冲层在Si(111)衬底上外延GaN薄膜。通过对薄膜表面扫描电子显微镜(SEM)和高分辨率双晶X射线衍射(DCXRD)的分析,研究了缓冲层生长温度对外延层表面形貌的影响,分析解释了表面形貌中凹坑的形成及缓冲层生长温度对凹坑的影响。结果表明:缓冲层生长温度通过影响缓冲层初始成核密度和成核尺寸来影响外延层表面形貌。较低温度下的Al N缓冲层,在衬底表面形成的成核颗粒因温度太低,无法运动到相邻的颗粒而结合成大的成核颗粒,因此成核密度高,成核尺寸小;高温生长的Al N缓冲层,成核颗粒有足够的能量运动到相邻的成核颗粒,因此使成核颗粒的尺寸增大,成核密度低。这种初始成核密度和尺寸的不同,造成外延层形貌的差异,如表面形貌中凹坑的密度和大小就是受初始成核的直接影响。通过实验和分析,提出了外延生长的物理模型。     

基于金银合金纳米线SERS活性基底的制备

首先采用液相软模板方法合成银纳米线,然后采用静电吸附法将带负电荷的银纳米线和带正电荷的金纳米颗粒组装形成金银合金纳米线。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线能谱分析仪(EDS)对材料的形貌和成分进行表征,结果表明金纳米颗粒被均匀吸附在银纳米线的表面。之后将金银合金纳米线偶联到氨基化处理后的硅片抛光面上,组装得到均匀、致密排列的金银合金纳米线表面增强喇曼散射(SERS)基底,该基底具有良好的重现性、均一性和SERS活性。使用尼罗蓝A (NBA)作为喇曼信号分子,SERS基底的最低检测浓度为7.93×10~(-10)mol/L,其分析增强因子(AEF)为6.31×10~7,SERS增强效应很高。此外金银合金纳米线具有高稳定性和良好的生物相容性,因此该基底在SERS生物传感方面具有广阔的应用前景。     

Influence of arsenic on the atomic structure of the Si(112) surface

The surface science techniques of low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), and scanning tunneling microscopy (STM) have been used to characterize the clean Si(112) surface and the influence of an As monolayer on the properties and structure of the surface. In agreement with previous studies, the clean surface is found by both LEEd and atomically resolved STM images to be unstable with respect to faceting into other stable planes. Procedures for in-situ deposition of As onto clean Si surfaces were devised and XPS results show that approximately one monolayer of As can be deposited free of any contamination. The As/Si(112) surface is characterized by a sharper LEED pattern than for the clean surface and by STM images characterized by long rows along the direction with a regular width of 1.9 nm. This is consistent with a doubling of the periodicity in the direction of the bulk-terminated unit cell. This implies that As yields a stable but reconstructed Si(112) surface.     

Evaluation of PZT thin films on Ag coated Si substrates

Fabrication characteristics of hybrid thin film components are investigated. Lead zirconate titanate (PZT) films, thickness 10 μm, are fabricated by using laser ablation on the Ag electrode (about 1 μm thick) which is deposited on 200 μm Si substrates by evaporation. Composition close to the target material is obtained in PZT films even in air and without substrate heating. Low surface energy in the Ag−Si system causes spheroidization of the Ag layer on the fresh Si substrate, but the surface can be modified by grinding and oxidization. Only some cavities exist at the interface. The interface between the Ag electrode and PZT layer is physically continuous, as revealed by electron microscopy. After annealing at 750°C for 2 h, the PZT layer consists of the rhombohedral perovskite phase with a fraction of the pyrochlore phase. Detrimental interdiffusion between Pb and Si occurs during annealing if the PZT thin film is directly on the Si substrate. This is retarded by the presence of the Ag layer.     

Surface-enhanced Raman scattering of sulfate ion based on Ag/Si nanostructure

Silicon nanowires (SiNWs) with tens of micrometer in length have been synthesized and modified with Ag nanoparticles,which were confirmed by X-ray diffractometer (XRD),scanning electron microscopy and ...     

Arsenic deposition as a precursor layer on silicon (211) and (311) surfaces

We investigate the properties of arsenic (As) covered Si(211) and Si(311) surfaces by analyzing data from x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) images. We then create a model using total surface energy calculations. It was found that both Si(211) and Si(311) had 0.68±0.08 surface As coverage. Si(211) had 0.28±0.04 Te coverage and Si(311) had 0.24±0.04 Te coverage. The Si(211) surface replaces the terrace and trench Si atoms with As for a lower surface energy, while the Si edge atoms form dimers. The Si(311) surface replaces all terrace atoms and adsorbs an As dimer every other edge site. These configurations imply an improvement in the mean migration path from the bare silicon surface by allowing the impinging atoms for the next epitaxial layer, tellurium (Te), to bind at every other pair of edge atoms, and not the step terrace sites. This would ensure a nonpolar, B-face growth.     

The Growth of Transition Metals on H‐Passivated Si(111) Substrates

The growth of Co and Ag layers on wet‐processed H‐passivated Si(111) substrates by molecular beam epitaxy (MBE) has been studied using high resolution scanning tunneling microscopy (STM) with regard to possible applications of the layers in magnetoelectronic devices. Roughness and intermixing at interfaces as functions of deposition temperature and layer thickness are key parameters for the performance of such devices. The initial growth of Co and Ag and the influence of Ag atoms on the Si(111) surface reconstructions provide insight into adatom–substrate interactions.     

Growth of (111) HgCdTe on (100) Si by MOVPE using metalorganic tellurium adsorption and annealing

(lll)B CdTe layers free of antiphase domains and twins were directly grown on (100) Si 4°-misoriented toward<011> substrates, using a metalorganic tellurium (Te) adsorption and annealing technique. Direct growth of (lll)B CdTe on (100) Si has three major problems: the etching of Si by Te, antiphase domains, and twinning. Te adsorption at low temperature avoids the etching effect and annealing at a high temperature grows single domain CdTe layers. Te atoms on the Si surface are arranged in two stable positions, depending on annealing temperatures. We evaluated the characteristics of (lll)B CdTe and (lll)B HgCdTe layers. The full width at half maximum (FWHM) of the x-ray double crystal rocking curve (DCRC) showed 146 arc sec at the 8 |im thick CdTe layers. In Hg_1−xCd_xJe (x = 0.22 to 0.24) layers, the FWHMs of the DCRCs were 127 arc sec for a 7 (im thick layer and 119 arc sec for a 17 (im thick layer. The etch pit densities of the HgCdTe were 2.3 x 106 cm2 at 7 ^m and 1.5 x 106 cm-2 at 17 um.     

Comparison of the agglomeration behavior of Ag(Al) films and Ag(Au) films

It is essential to suppress agglomeration of Ag films caused by thermal treatment for their successful application as new metallization materials. Co-sputtered Ag(Al) and Ag(Au) films were investigated, with regard to their change in morphology and electrical resistivity after vacuum annealing. As a result, agglomeration of the Ag(Al) film (Al: 4.3 at.%) was not recognized even after annealing at 600 °C. However, void formation followed by de-wetting was observed for the Ag(Au) film after annealing, similar to that for a pure Ag film. The morphological change was accompanied by an increase in the resistivity of the Ag(Au) films with annealing temperature. On the other hand, the resistivity of the Ag(Al) films did not increase by annealing at temperatures from 400 to 600 °C. However, the film with the highest Al content, which was most resistive to agglomeration, had too high resistivity for use as a metallization material. By analysis of the Auger depth profile, the presence of very thin oxide layers at the surface of the film and at the interface with the substrate was confirmed for Ag(Al) films after annealing. This was considered to be the reason for the large difference in agglomeration behavior between the Ag(Au) and Ag(Al) films.     

The structure of the Si (211) surface

Silicon (211) has been proposed as an alternative substrate for CdTe/HgCdTe molecular beam epitaxial growth. Silicon has a clear advantage over other substrates because of its low cost, high strength, and thermal-expansion coefficient, which matches that of the silicon readout integrated circuit. The (211) orientation has been shown to yield high-quality CdTe and HgCdTe/CdTe layers over other orientations. The reconstruction and faceting of the Si (211) surface is poorly understood despite the importance of the (211) orientation. The results of low-energy electron diffraction (LEED) studies have been contradictory, and their conclusions are inconsistent with recent scanning tunneling microscopy (STM) studies. LEED and STM images were used to determine the most probable Si (211) surface facet structure as a function of annealing temperature. Samples annealed at a high temperature (i.e., >1260°C) allowed the formation of ordered LEED spot patterns as opposed to the typically reported $[\bar 111]$ streaks. The pattern in the $[0\bar 11]$ direction gave a consistent 2× (7.68 Å) reconstruction.     

Si(113)表面的原子结构

利用LEED研究了Si(113)表面的原子结构.清洁表面是采用离子轰击和退火方法制备的.实验发现:当温度高于600℃时表面为1×1结构,随着温度缓慢下降,表面原子结构发生1×1(?)3×1(?)3×2的可逆相变.