Effect of Fe metal on the growth of silicon oxide nanowires

Silicon oxide (SiO_x) nanowires are generally grown on Si substrate under the catalysis of Au in N₂ atmosphere at elevated temperatures. Because the price of Au metal is quite high, Fe metal is then used to replace a part of Au for catalyzing the growth of SiO_x nanowires. The results show that the Fe film can be used as the diffusion barrier of Au. SiO_x nanowires are grown on Au/Fe/Si substrate at 1030℃. Under the catalysis of Fe/Au, the efficiency for the growth of SiO_x nanowires is promoted.     

温度对硅纳米线生长结构的影响

以硅烷为反应气体,温度为850～1100℃,在（100）取向的单晶硅片上,采用化学气相沉积法生长了一维硅纳米线．用扫描电子显微镜观察了硅纳米线的表面形貌,用X射线衍射仪研究了硅纳米线生长结构与反应温度的关系．分析了不同实验条件对硅纳米线生长结构的影响,并对一维硅纳米线与块体硅的光致发光（PL）特性进行了分析比较．     

硅纳米线表面喷墨打印纳米银油墨的SERS性能研究

在金属辅助化学刻蚀法制备的硅纳米线表面,通过喷墨打印纳米银油墨制备了银纳米粒子/硅纳米线复合结构基底.通过调节刻蚀时间和刻蚀温度,探究硅纳米线的微观形貌变化,及其对基底表面增强拉曼散射(SERS)活性的影响.实验结果表明,硅纳米线的长度随着刻蚀时间的延长而增加.当刻蚀温度为40℃、刻蚀时间为8 min时,能够激发更强的SERS信号.银纳米粒子/硅纳米线对探针分子罗丹明6G的最低检测限为10^-7mol·L^-1.     

Abnormal Raman spectral phenomenon of silicon nanowires

The Raman spectra of two one-dimensional silicon nanowire samples with different excitation wavetengths were measured and an abnormal phenomenon was discovered that the Raman spectral features change with the wavetengths of excitation. Closer analysis of the crystalline structure of samples and the changes in Raman spectral features showed that the abnormal behavior is the result of resonance Raman scattering setection effect.     

Enhanced thermoelectric performance of rough silicon nanowires

Approximately 90 per cent of the world's power is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30-40 per cent efficiency, such that roughly 15 terawatts of heat is lost to the environment. Thermoelectric modules could potentially convert part of this low-grade waste heat to electricity. Their efficiency depends on the thermoelectric figure of merit ZT of their material components, which is a function of the Seebeck coefficient, electrical resistivity, thermal conductivity and absolute temperature. Over the past five decades it has been challenging to increase ZT > 1, since the parameters of ZT are generally interdependent. While nanostructured thermoelectric materials can increase ZT > 1 (refs 2-4), the materials (Bi, Te, Pb, Sb, and Ag) and processes used are not often easy to scale to practically useful dimensions. Here we report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20-300 nm in diameter. These nanowires have Seebeck coefficient and electrical resistivity values that are the same as doped bulk Si, but those with diameters of about 50 nm exhibit 100-fold reduction in thermal conductivity, yielding ZT = 0.6 at room temperature. For such nanowires, the lattice contribution to thermal conductivity approaches the amorphous limit for Si, which cannot be explained by current theories. Although bulk Si is a poor thermoelectric material, by greatly reducing thermal conductivity without much affecting the Seebeck coefficient and electrical resistivity, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.     

掺杂和应变对硅纳米线电子结构与光学性质的调制影响

为了研究掺杂和应变对[111]晶向硅纳米线的电子结构与光学性质的调制影响,基于密度泛函理论体系下的广义梯度近似(general gradient approximation,GGA),采用第一性原理方法开展了相关计算。能带计算表明：空位掺杂和元素掺杂均引入杂质能级,形成了N型和P型半导体材料。单轴应变则进一步减小了带隙,增强了掺杂硅纳米线的导电性,但由于应变也修饰了费米面附近能级的形貌,能带曲率突变影响了体系的导电性能。光学性质计算表明：相比于空位掺杂,元素掺杂更有效地改变了SiNWs的介电函数、吸收系数、折射率与反射率等光学参数,而单轴应变则削弱了元素掺杂的影响。拉应变提升了光吸收的范围和强度,尤其是可见光波段,使掺杂硅纳米线成为优质光伏材料,压应变则降低了对紫外光波段的吸收效率。在紫外区域,拉应变和压应变对掺杂硅纳米线的折射率与反射率的影响相反,在红外和可见光区域影响则一致。本文研究结果为基于应变和掺杂硅纳米线的光电器件设计与应用提供一定的理论参考。     

Si纳米线光伏器件的研究进展

Si纳米线具有良好的光吸收和减反射特性,能够和现有Si工艺较好地兼容以及降低电池成本等优势,在太阳电池方面具有潜在的应用.介绍了Si纳米线径向p-n结、轴向p-n结、聚合物混合异质结和肖特基结等太阳电池的结构、制备、光伏特性等研究进展,同时指出Si纳米线结构太阳电池研究中需要解决的一些问题,并对今后的发展方向进行了展望.     

H2 sensing properties of modified silicon nanowires

It has been found that the silicon nanowires modified with noble metals can be used to fabricate an effective H2 gas sensor in the present study.The preparation and surface modification of silicon nanowires(Si NWs) were carried out by chemical methods. The morphology of the silicon nanowires unmodified and modified with nanoparticles of platinum, palladium, silver and gold was investigated using scanning electron microscopy(SEM). The chemical composition of the silicon nanowire layers was studied by secondary ion mass spectroscopy(SIMS) and energy dispersive X-ray analysis(EDX). The structures of type metal/Si NWs/p-Si/Al were fabricated. The electrical characterization(I–V) was performed in primary vacuum and H2 at different concentrations. It was found that the metal type used to modify the Si NWs strongly influenced the I–V characteristics. The response of these structures toward H2 gas was studied as a function of the metal type. Finally, the sensing characteristics and performance of the sensors were investigated.     

沉积温度对微晶硅薄膜结构特性的影响

采用PECVD技术,在玻璃衬底上沉积μc-Si:H薄膜.用拉曼光谱、SEM和UV分光光度计对不同沉积温度下沉积的薄膜的结构特性进行分析.研究发现:沉积温度较低时,随着沉积温度的升高,薄膜的晶化率增加;当沉积温度超过某一温度值时,随着温度的进一步升高,薄膜的晶化率降低.这时,表面反应由表面扩散限制转变为流量控制.该温度值随着硅烷含量的降低而降低.     

The influence of ridge migration on the magmatic segmentation of mid-ocean ridges

The Earth's mid-ocean ridges display systematic changes in depth and shape, which subdivide the ridges into discrete spreading segments bounded by transform faults and smaller non-transform offsets of the axis. These morphological changes have been attributed to spatial variations in the supply of magma from the mantle, although the origin of the variations is poorly understood. Here we show that magmatic segmentation of ridges with fast and intermediate spreading rates is directly related to the migration velocity of the spreading axis over the mantle. For over 9,500 km of mid-ocean ridge examined, leading ridge segments in the 'hotspot' reference frame coincide with the shallow magmatically robust segments across 86 per cent of all transform faults and 73 per cent of all second-order discontinuities. We attribute this relationship to asymmetric mantle upwelling and melt production due to ridge migration, with focusing of melt towards ridge segments across discontinuities. The model is consistent with variations in crustal structure across discontinuities of the East Pacific Rise, and may explain variations in depth of melting and the distribution of enriched lavas.     

热蒸发SiO大量合成硅纳米线及其可控p型掺杂

文章采用化学气相沉积法,以一氧化硅粉末为硅源,于1 350℃进行高温热蒸发,成功合成了大量单晶硅纳米线;并利用X-射线衍射、场发射扫描电子显微镜以及透射电子显微镜等手段对产物的形貌和微结构进行了系统表征.硅纳米线具有良好的结晶质量,直径在20～80 nm之间,长度为数十微米至数百微米,其外层通常为一层非晶硅氧化层所包裹...     

Self-interstitials generated on silicon bulk surface

Pentacene for p-channel organic field effect transistors(OTFTs) and perfluoropentacene for n-channel OTFTs have attracted strong attentions to be used as CMOS type organic semiconductor materials for flexible organic displays.n-channel OTFTs with different gate insulators of polyimide(PI) and SiO_2 and perfluoropentacene as a semiconductor layer were fabricated,and their instability of the transistor characteristics measured in air,vacuum and oxygen was investigated.The results show that both of the tran...     

基于金纳米线构建电化学传感器间接检测碱性磷酸酶活性

在临床实践中,碱性磷酸酶（ALP）是最常检测的酶之一,已被广泛用作肝病、骨病、乳腺癌、前列腺癌以及糖尿病等多种疾病的重要检测指标.通过自组装方法在氧化铟锡（ITO）导电玻璃上制备金纳米线（AuNWs）,利用4-巯基苯甲酸（4-MBA）修饰AuNWs,对其进行改性,与铜离子（Cu²⁺）螯合形成Cu²⁺-AuNWs/ITO电极.在ALP活性检测中,电解液中的焦磷酸根阴离子（PPi）与电极表面Cu²⁺结合,湮灭了Cu²⁺的电化学信号.ALP的加入使底物PPi水解并释放出Cu²⁺,电化学信号增加.构建的Cu²⁺-AuNWs/ITO电极对ALP活性检测范围为60~180 U·L^-1,且抗干扰性能良好.     

表面修饰的金纳米粒子的制作及表征

通过硼氢化钠NaBH4还原金氯酸HAuCl4，成功地制作了羧酸酯表面修饰的金纳米粒子，并用丁二酸硫醇作为硫醇配体稳定剂，抑制了纳米粒子的进一步生长，这种方法有效地把粒径控制在纳米范围内并且粒径分布范围小，只需通过一次反应就可大量地制得1－20nm、具有量子效应的纳米料，用X射线衍射仪、透射式电子显微镜和隧道扫描显微镜对这些粒子进行了检测，证实了大量的粒子都是面心立方结构，硫醇配体在金粒子在表面由化学吸附形成一层单分子膜，隧道扫描显微镜观察到了这一层单分子膜。     

保护蛋白对聚苯乙烯微珠表面抗体固定化的影响

分别利用糖基固定化方法和生物素—亲和素系统在聚苯乙烯微珠表面固定了小鼠单克隆抗体,并考察了抗体中保护蛋白牛血清白蛋白(BSA)对抗体固定化的影响.结果表明,BSA会严重干扰抗体固定化,通过使用不合BSA的缓冲溶液和超滤离心的方法去除掉抗体中的BSA再进行抗体固定化时,抗体的固定化效果得到明显改善.利用流式细胞仪对微珠的...     

晶体硅太阳电池表面钝化的研究

文章从理论上分析了太阳电池的表面复合及重掺杂效应。在实验上采用二氧化硅作为钝化膜,比较了两种不同表面浓度的太阳电池片钝化效果,得出低表面浓度的太阳电池片比高表面浓度的太阳电池片的开路电压要高,短波光谱响应要好。开路电压和短波光谱响应的提高主要来自于前表面的钝化和适当地降低了表面浓度。     

Cylindrical PCL brushes on the surface of lanthanum hydroxide nanowires by ring-opening polymerization

A core-shell hybrid nanostructure,a hard core of single-crystalline lanthanum hydroxide nanowires and a soft shell of brushes of poly (ε-caprolactone) (PCL), has been successfully prepared by ring-opening polymerization (ROP) on the surface of nanowires. Such special structures were proved by TEM images. Meanwhile, the thickness of polymer layers was measured. The chemical component and the grafted PCL quantity of the sample were characterized by FTIR and TGA, which provides a simple and universal method to...     

Direct electroless nickel plating on silicon surface

Direct electroless nickel plating on n-Si(100) wafers in alkaline solutions was demonstrated without any activation procedure in advance, the effect of pH and temperature of the solutions on size of metal particles in deposits was examined, and also the element contents of deposits were analyzed by energy disperse spectroscopy (EDS). The results indicated that the size of metal particles increases with increasing temperature or decreasing pH. The possible mechanism of nickel deposition on n-Si(100) was discussed in terms of semiconductor electrochemistry, and the formation of nickel seed crystal on Si was mainly attributed to the generation of atomic hydrogen by electron capture of water molecule from the semiconductor in alkaline solutions.     

Self-directed growth of molecular nanostructures on silicon

Advances in techniques for the nanoscale manipulation of matter are important for the realization of molecule-based miniature devices with new or advanced functions. A particularly promising approach involves the construction of hybrid organic-molecule/silicon devices. But challenges remain--both in the formation of nanostructures that will constitute the active parts of future devices, and in the construction of commensurately small connecting wires. Atom-by-atom crafting of structures with scanning tunnelling microscopes, although essential to fundamental advances, is too slow for any practical fabrication process; self-assembly approaches may permit rapid fabrication, but lack the ability to control growth location and shape. Furthermore, molecular diffusion on silicon is greatly inhibited, thereby presenting a problem for self-assembly techniques. Here we report an approach for fabricating nanoscale organic structures on silicon surfaces, employing minimal intervention by the tip of a scanning tunnelling microscope and a spontaneous self-directed chemical growth process. We demonstrate growth of straight molecular styrene lines--each composed of many organic molecules--and the crystalline silicon substrate determines both the orientation of the lines and the molecular spacing within these lines. This process should, in principle, allow parallel fabrication of identical complex functional structures.     

Unidirectional molecular motor on a gold surface

Molecules capable of mimicking the function of a wide range of mechanical devices have been fabricated, with motors that can induce mechanical movement attracting particular attention. Such molecular motors convert light or chemical energy into directional rotary or linear motion, and are usually prepared and operated in solution. But if they are to be used as nanomachines that can do useful work, it seems essential to construct systems that can function on a surface, like a recently reported linear artificial muscle. Surface-mounted rotors have been realized and limited directionality in their motion predicted. Here we demonstrate that a light-driven molecular motor capable of repetitive unidirectional rotation can be mounted on the surface of gold nanoparticles. The motor design uses a chiral helical alkene with an upper half that serves as a propeller and is connected through a carbon-carbon double bond (the rotation axis) to a lower half that serves as a stator. The stator carries two thiol-functionalized 'legs', which then bind the entire motor molecule to a gold surface. NMR spectroscopy reveals that two photo-induced cis-trans isomerizations of the central double bond, each followed by a thermal helix inversion to prevent reverse rotation, induce a full and unidirectional 360 degrees rotation of the propeller with respect to the surface-mounted lower half of the system.