在扫描电子显微镜中原位操纵、加工和测量纳米结构

在电子显微镜中对纳米材料和纳米结构进行原位测量是了解纳米材料的结构与性能关系的最重要手段,并且,在电子显微镜中操纵和加工纳米材料与纳米结构还可研究新结构和新器件.由于扫描电镜有大的样品室、可较容易地引入多个多种测量和操纵探针、并可配备多种探测器从多个角度对同一个样品进行表征,使得扫描电镜中的原位研究在纳米材料和纳米器件...     

Vapor Phase Metal‐Assisted Chemical Etching of Silicon

This work introduces and explores vapor phase metal‐assisted chemical etching (VP‐MaCE) of silicon as a method to bypass some of the challenges found in traditional liquid phase metal‐assisted chemical etching (LP‐MaCE). Average etch rates for Ag, Au, and Pd/Au catalysts are established at 31, 70, and 96 nm/min respectively, and the relationship between etch rate and substrate temperature is examined experimentally. Just as with LP‐MaCE, 3D catalyst motion is maintained and three‐dimensional structures are fabricated with nanoparticle‐ and lithography‐patterned catalysts. VP‐MaCE produces less microporous silicon compared with LP‐MaCE and the diffusion/reduction distance of Ag⁺ ions is significantly reduced. This process sacrifices etch rate for increased etch uniformity and lower stiction for applications in micro‐electromechanical systems (MEMS) processing.     

单电子存储器

介绍了单电子存储器的发展情况和几种单电子存储器的基本特性,并将库仑阻塞效应作为存储器工作的理论基础进行了讨论。随着传统存储器集成度的不断提高,每个存储单元的电子数目不断减少,并逐渐接近其极限,使传统存储器的发展面临困难。采用单电子存储器有望解决这个困难,它们通常具有单个量子点或者是多隧穿结结构,存储一个比特的信息只需要精确控制增加或者减少一定数目的电子就可以实现。单电子器件的工作通常只需要很少的电子甚至一个电子就可以实现,具有高速和低功耗的特点,因此可以实现信息超高密度存储。与单电子逻辑电路相比,单电子存储器更容易解决随机背景电荷涨落的问题,因此从实际应用的角度来看,单电子存储器的应用前景更为光明。     

利用AFM动态电场在Si表面实现纳米氧化结构

讨论利用原子力显微镜(AFM)动态电场诱导阳极氧化作用下Si表面生成纳米氧化结构的特征,并进行相应的机理分析.实验表明,直流电压作用下的氧化结构表现出单峰特征,而电压脉冲和连续方波所得到的氧化结构具有中央凹陷特征和较高的纵横比.     

用AFM导电探针在n-Si(111)表面进行纳米加工的机理研究

本文介绍了在AFM针尖与氢钝化硅表面之间施加电场作用对硅表面进行修饰的纳米加工方法，重点讨论了加工机理。实验考虑了样品的表面状态，周围大气状况，所加电压的极性、大小和加压方式等影响纳米加工的因素。对机理的研究表明，针尖和样品之间发生的是场致电子发射而非热电子发射，电流热效应增强粒子的扩散能力，提高了电化学反应速度。最后给出了电场诱导阳极氧化扩散增强的加工机理。     

Nanoimprinted,Submicrometric, MOF‐Based 2D Photonic Structures: Toward Easy Selective Vapors Sensing by a Smartphone Camera

In this work, a soft‐lithographic approach to fabricate submicrometer metal organic framework (MOF)‐based 2D photonic structures is described. Nanometric zeolitic imidazole framework material ZIF‐8 (zinc) is chosen as the sensible MOF material because of its chemical stability and its vapor selective adsorption properties. Two different systems are fabricated: nanopatterned colloidal ZIF‐8 homo‐ and ZIF‐8/TiO₂ heterostructures. Several features (stripes, squares, etc.) with dimensions of 200 nm are replicated on different substrates such as silicon, flexible plastics, and even aluminum cans, over relatively large surfaces (up to 1 cm²). In addition, the use of these photonic MOF‐heterostructures as very low‐cost sensing platforms compatible with smartphone technology is demonstrated. This method relies on the evaluation of the change in diffraction efficiency of the photonic MOF‐patterns, induced by the MOF refractive index variation, which is simply detected by a charge coupled device (CCD) camera, as those integrated in smartphones, without need for complex optical instrumentations for transduction data processing. Performances of the sensors are first evaluated using isopropyl alcohol adsorption/desorption cycling as a model case. In addition, a “real” environmental issue is tackled. Selective detection of styrene in presence of interfering water is demonstrated at concentrations below the human permissible exposure limit. In situ ellispometric analyses are also carried out in order to confirm the sensor performances and to propose a mechanism for styrene uptake into the nanoMOFs.     

Picoliter volume glass tube array fabricated by Si electrochemical etching process

Fabrication process for picoliter volume SiO₂ glass tube array partially embedded in Si wafer was developed. As a template for the glass tubes, macropore array was formed at the surface of n-Si(1 0 0) wafer by photo-assisted electrochemical etching process. The area-selective formation of the array was achieved by applying Au/Cr micropatterns formed at the back-side surface of the substrate as the shade mask, which controls the illumination condition to optimize the etching reaction conditions. Subsequently, surface of the macropores was wet-thermally oxidized to form glass layer, and the bulk Si region was removed by alkaline etching, remaining the “glass tubes”. As a result of complete removal of the bulk Si, released glass tubes were obtained. By partial removal of the bulk Si part, the glass tubes were exposed, fixed in the remaining Si substrate in the form of well-ordered array. It was confirmed that the depth, the exposed region and the wall thickness of each glass tube were controllable by adjusting the parameters such as the duration of the Si electrochemical etching, the alkaline etching and the wet-thermal oxidation, respectively. In order to demonstrate microreaction in the glass tube, aqueous rhodamine B solution was injected into the tubes and excitation light was irradiated to them. As a result, the fluorescence of rhodamine B was clearly detected, confirming the applicability of the glass tubes for various kinds of devices and systems such as microreactors.     

Fabrication mechanism of friction-induced selective etching on Si(100) surface

As a maskless nanofabrication technique, friction-induced selective etching can easily produce nanopatterns on a Si(100) surface. Experimental results indicated that the height of the nanopatterns increased with the KOH etching time, while their width increased with the scratching load. It has also found that a contact pressure of 6.3 GPa is enough to fabricate a mask layer on the Si(100) surface. To understand the mechanism involved, the cross-sectional microstructure of a scratched area was examined, and the mask ability of the tip-disturbed silicon layer was studied. Transmission electron microscope observation and scanning Auger nanoprobe analysis suggested that the scratched area was covered by a thin superficial oxidation layer followed by a thick distorted (amorphous and deformed) layer in the subsurface. After the surface oxidation layer was removed by HF etching, the residual amorphous and deformed silicon layer on the scratched area can still serve as an etching mask in KOH solution. The results may help to develop a low-destructive, low-cost, and flexible nanofabrication technique suitable for machining of micro-mold and prototype fabrication in micro-systems.     

Generation and Evolution of Surface Oxide Layer of Amorphous Boron during Thermal Oxidation: A Micro/nanofabricated Slice Measurement

The generation and evolution of the surface oxide layer of boron were thoroughly investigated due to the key role of the oxide layer in ignition and combustion of amorphous boron (B). Samples in different oxidation degrees were obtained by heating B particles until 600, 650, and 700 °C, using a temperature programmed thermobalance. A dual beam focused ion beam micro/nanofabricator was used to etch and cut the samples into thin slices (ca. 327 nm). The slices were observed under a scanning transmission electron microscope, accompanied with energy dispersive X‐ray analysis. During the thermal oxidation process, B particles initially lost mass through dehydration. Then they began to get oxidized and gain weight markedly. The sample surface became more rough as the final temperature increased. Two different reaction modes took place in sequence during the thermal oxidation of the samples. Below 650 °C, the oxidation reaction occurred only on the surface of the particle (the surface reaction mode). However, when the samples were heated to 700 °C, the particle interior was also involved in the reaction (the global reaction mode), and a large number of pores were formed. The O content of the initial surface oxide layer was fairly high. The thickness distribution was uniform (average thickness 148.1 nm) and the two edges were both smooth. During the heating, the oxygen content of the surface oxide layer increased after an initial decrease. The average oxide layer thickness increased and the thickness distribution became irregular and unequal. The sample heated until 700 °C had an average surface oxide layer thickness of 379.3 nm, and the thickness span reached 354.3 nm. During the global reaction process (700 °C), the oxidation degree within the interior of the particle was lower than that on its surface. In the particle interior, pores near the center were smaller than those close to the edge, whereas the oxidation degree was uniformly distributed. Results in this work provide a deeper understanding of the surface oxide layer, which can potentially help improve the ignition and combustion features of B.     

基于AFM的Si纳米结构的加工

介绍了通过使用原子力显微镜,在H钝化Si(100)的表面局部阳极氧化反应的表面氧化图案上刻写的纳米级Si结构加工。这种氧化图形可被用作Si的可选择性蚀刻工艺的掩膜。带有临界特性的小到30nm的边门Si场效应晶体管也通过这种方法加工。