硅纳米线的制备与生长机理

硅纳米线是一种新型的一维半导体光电材料.本文较系统地介绍了硅纳米线在制备技术、生长机理方面的研究现状与最新进展,主要就激光烧蚀法、化学气相沉积法、热气相沉积法及溶液法等制备方法和基于气-液-固机理的生长机理、氧化物辅助生长机理及固-液-固生长机理等作了较为详尽的论述.     

化学刻蚀两步法制备硅纳米线(英文)

采用化学刻蚀两步法制备硅纳米线。在制作过程的不同阶段,通过金相显微镜,扫描电子显微镜及透射电子显微镜分别对其表面形态进行观察。结果表明,通过两步法制作的硅纳米线比传统刻蚀方法制作的样品具有更细的直径。光致发光的测量结果表明,两步法制备的硅纳米线在可见光领域有较强的红光发射。     

针尖状SiC纳米线的合成与机理分析

采用热蒸发硅的方法,于1650℃反应不同的时间,在聚丙烯腈(PAN)碳纤维上原位生长碳化硅纳米线。通过X射线衍射,场发射扫描电镜及透射电子显微镜分析和观察,发现制得的产物为β-SiC单晶纳米线,具有明显的针尖状头部,且呈放射状生长在碳纤维上,形成试管刷状阵列。基于在反应不同阶段所得到产物的不同形貌,结合对制备条件和制备原料的分析,提出不同于传统VLS机理的VL’S机理。     

氧化物辅助生长硅纳米线

氧化物辅助生长机理是近年来在合成硅纳米线的过程中发展起来的一种研究一维纳米材料生长的机理,根据此机理已经制备出了多种一维纳米材料.介绍了氧化物辅助生长机理及其根据此机理制备硅纳米线的制备方法,载气、压力及原料等不同条件对合成硅纳米线的影响等进展情况,并对其发展作了展望.     

Impurity Doping in Silicon Nanowires

Silicon nanowires (SiNWs) have considerable potential to assist the realization of next‐generation metal‐oxide semiconductor field‐effect transistors (MOSFETs) with vertical structures. Impurity doping and its control is a key technique in the creation of SiNW devices, which renders it necessary to develop characterization methods for dopant atoms in SiNWs. In this Research News, we described how the states of the dopant atoms boron and phosphorus can be detected.     

碳化硅纳米线的湿腐蚀研究

使用湿腐蚀法即氢氟酸和硝酸的混合酸(体积比为3:1),于100℃对所制备的具有周期性孪晶结构的碳化硅纳米线进行腐蚀,采用SEM、HRTEM、FTIR、PL对所得的样品进行表征,并讨论了纳米线腐蚀的反应机理.结果表明,混合酸对具有周期性孪晶结构纳米线的腐蚀具有选择性,形成了不同于原材料的特殊形貌.同时,腐蚀改变了纳米线的光致发光性能.     

适用于纳米电子器件的超长硅纳米线合成

采用SiO为起始原料、Ar为载气,蒸发温度1300℃、压力1～2×104Pa的生长条件下,成功地合成了超长的单晶硅纳米线;以SiO和P205混合粉末为起始原料时在相同的生长条件下实现了对硅纳米线的掺杂;借助电感耦合等离子体质谱仪（ICPMS）分析了硅纳米线P掺杂效果;利用扫描电镜（SEM）、高分辨透射电镜（HRTEM）、X射线衍射仪（XDR）等检测手段对硅纳米线进行了形貌和结构的表征,测试结果表明在不同的沉积区域硅纳米线具有大致相同的直径,但其长度随着温度的升高而变长,在1180℃的生长区域,硅纳米线的长度达到了150μm;硅纳米线表面氧化层经HF和NH4F混合溶液处理后被完全剔除。     

Rapid Low‐Temperature 3D Integration of Silicon Nanowires on Flexible Substrates

The vertical integration of 1D nanostructures onto the 2D substrates has the potential to offer significant performance gains to flexible electronic devices due to high integration density, large surface area, and improved light absorption and trapping. A simple, rapid, and low temperature transfer bonding method has been developed for this purpose. Ultrasonic vibration is used to achieve a low temperature bonding within a few seconds, resulting in a polymer‐matrix‐free, electrically conducting vertical assembly of silicon nanowires (SiNWs) with a graphene/PET substrate. The microscopic structure, and mechanical and electrical characteristics of the interface between the transferred SiNW array and graphene layer are subsequently investigated, revealing that this creates a mechanically robust and electrically Ohmic contact. This newly developed ultrasonic transfer bonding technique is also found to be readily adaptable for diverse substrates of both metal and polymer. It is therefore considered as a valuable technique for integrating 1D vertical nanostructures onto the 2D flexible substrates for flexible photovoltaics, energy storage, and water splitting systems.     

Modulation of Agglomeration of Vertical Porous Silicon Nanowires and the Effect on Gas‐Sensing Response

Porous silicon nanowires (PSiNWs) array is a promising material for development of integrated gas sensors operating at room temperature. This work reports the fabrication of PSiNWs assembly with different structural features and its effect on gas‐sensing performance. Bundling and well separating PSiNWs arrays are fabricated by MACE method, respectively, based on the effective modulation of surface wettability of the initial Si substrate. The HF pretreatment creates a hydrophobic surface favorable for deposition of irregular Ag nanoflakes and then for the formation of bundling PSiNWs array. In contrast, the PSiNWs with well lateral separation are formed based on the predeposited uniform Ag nanoparticles on a hydrophilic Si surface. The PSiNWs array featured by tip‐clusters is proved to be highly effective in achieving highly sensitive and rapid response to NO₂ gas at room temperature. Satisfying dynamic characteristic and selectivity are meanwhile observed for the bundling array. The formation of the bundling or separating of PSiNWs is discussed in terms of the force balance of individual nanowire, which is further correlated with non‐uniform distribution of Ag nanoclusters caused by H‐termination. Meanwhile, high sensing performance of bundling nanowires is analyzed based on the structural promotion of the unique configuration of tip‐cluster to sensing response.

     

Nanowires enabling signal-enhanced nanoscale Raman spectroscopy

Silicon nanowires grown by the vapor-liquid-solid (VLS) mechanism catalyzed by gold show gold caps (droplets) approximately 20-500 nm in diameter with a half spherical towards almost spherical shape. These gold droplets are well suited to exploit the surface-enhanced Raman scattering (SERS) effect and could be used for tip-enhanced Raman spectroscopy (TERS). The gold droplet of a nanowire attached to an atomic force microscopy (AFM) tip could locally enhance the Raman signal and increase the spatial resolution. Used as a SERS template, an ensemble of self-organizing nanowires grown bottom up on a silicon substrate could allow highly sensitive signal-enhanced Raman spectroscopy of materials that show a characteristic Raman signature. A combination of a nanowire-based TERS probe and a nanowire-based SERS substrate promises optimized signal enhancement so that the detection of highly dilute species, even single molecules or single bacteria or DNA strands, and other soft matter is within reach. Potential applications of this novel nanowire-based SERS and TERS solution lie in the fields of biomedical and life sciences, as well as security and solid-state research such as silicon technology.     

Spectromicroscopy Studies of Silicon Nanowires Array Covered by Tin Oxide Layers

The composition and atomic and electronic structure of a silicon nanowire (SiNW) array coated with tin oxide are studied at the spectromicroscopic level. SiNWs are covered from top to down with a wide bandgap tin oxide layer using a metal–organic chemical vapor deposition technique. Results obtained via scanning electron microscopy and X-ray diffraction showed that tin-oxide nanocrystals, 20 nm in size, form a continuous and highly developed surface with a complex phase composition responsible for the observed electronic structure transformation. The “one spot” combination, containing a chemically sensitive morphology and spectroscopic data, is examined via photoemission electron microscopy in the X-ray absorption near-edge structure spectroscopy (XANES) mode. The observed spectromicroscopy results showed that the entire SiNW surface is covered with a tin(IV) oxide layer and traces of tin(II) oxide and metallic tin phases. The deviation from stoichiometric SnO₂ leads to the formation of the density of states sub-band in the atop tin oxide layer bandgap close to the bottom of the SnO₂ conduction band. These observations open up the possibility of the precise surface electronic structures estimation using photo-electron microscopy in XANES mode.     

一维硅纳米材料的研究进展

作为微电子领域最重要的半导体材料,硅的一维纳米结构在器件组装、纳米尺寸磁性器件、光电子等领域具有重要的作用,已经成为国际上材料科学研究的一个热点.从制备方法、应用前景等方面综述了国际上关于纳米硅丝和纳米硅管的研究进展,并提出今后的研究方向.     

超长单晶硅纳米丝的化学气相沉积法制备

采用化学气相沉积法在镀金硅片上制备出了大量直径均匀、长度大于100肿的单晶纳米硅丝。采用场发射扫描电镜（FESEM）、能谱分析（EDX）、透射电镜（TEM）和拉曼光谱（Rarnan）对样品进行了表征和分析，并对超长纳米硅丝的生长机理进行了讨论。     

图形化硅纳米线阵列的制备

本文主要研究了在常态(常温、常压等)条件下,利用金属催化化学腐蚀方法在硅片表面上大面积制备排列整齐、取向一致的硅纳米线阵列.同时,出于对后续制作硅纳米线传感器考虑,利用微电子标准加工工艺,以氮化硅做掩膜,通过选择合适的实验参数,在硅片表面选择性生长纳米线阵列,得到图形化的硅纳米线阵列.     

Hybrid Anodic and Metal‐Assisted Chemical Etching Method Enabling Fabrication of Silicon Carbide Nanowires

Silicon carbide (SiC) is one of the most important third‐generation semiconductor materials. However, the chemical robustness of SiC makes it very difficult to process, and only very limited methods are available to fabricate nanostructures on SiC. In this work, a hybrid anodic and metal‐assisted chemical etching (MACE) method is proposed to fabricate SiC nanowires based on wet etching approaches at room temperature and under atmospheric pressure. Through investigations of the etching mechanism and optimal etching conditions, it is found that the metal component plays at least two key roles in the process, i.e., acting as a catalyst to produce hole carriers and introducing band bending in SiC to accumulate sufficient holes for etching. Through the combined anodic and MACE process the required electrical bias is greatly lowered (3.5 V for etching SiC and 7.5 V for creating SiC nanowires) while enhancing the etching efficiency. Furthermore, it is demonstrated that by tuning the etching electrical bias and time, various nanostructures can be obtained and the diameters of the obtained pores and nanowires can range from tens to hundreds of nanometers. This facile method may provide a feasible and economical way to fabricate SiC nanowires and nanostructures for broad applications.