Bensong Chen

A General Synthetic Approach to Interconnected Nanowire/Nanotube and Nanotube/Nanowire/Nanotube Heterojunctions with Branched Topology

Heterojunctions between nanotubes (NTs) and nanowires (NWs) could provide building blocks for nanoelectronics and nanophotonics, with other applications in barcodes, optical readout, biomolecular separation, catalysis, selfassembly, and magnetic manipulation. Although hybrid NWs (metal/polymer, semiconductor/semiconductor, 9] metal/semiconductor, and metal/metal ), hybrid NTs (metal/metal), NT/NW heterojunctions, and tree-like nano-heterojunctions have beenmade, the corresponding studies demonstrated limited control over the geometry and complexity of the nano-heterojunctions, which ultimately are central to the design of building blocks for nanocircuits, nanodevices, and nanosystems. Herein we show a general synthetic approach to various branched two-segment NW/NT and three-segment NT/NW/NT heterojunctions, based on a combinatorial process of electrodepositing NWs within the branched channels of anodic aluminum oxide (AAO) templates, selectively etching part of the electrodeposited NWs, and growing NTs on the ends of the NWs. The NWs can be metallic or semiconducting, while the NTs can consist of carbon, silicon, and silica; the two NT segments in threesegment NT/NW/NT nanoarchitectures can comprise either the same or different materials. This approach enables excellent control over the geometry, chemical composition, and complexity of the hetero-nanoarchitectures that can be the framework for nanoscale devices and systems. Figure 1 shows schematic depictions of the basic heteronanoarchitectures we have made, which consist of various NT and NW segments placed combinatorially in a Y-shaped topology. The synthesis scheme follows a typical buildingblock concept in which a set of different nanoscale components (NTs and NWs of different materials with distinct properties, in linear and branched topologies) can be connected in a predetermined fashion inside the branched

Crystalline Silicon Nanotubes and Their Connections with Gold Nanowires in Both Linear and Branched Topologies

Silicon, being in the same group in the periodic table as carbon, plays a key role in modern semiconductor industry. However, unlike carbon nanotube (NT), progress remains relatively slow in silicon NT (SiNT) and SiNT-based heteroarchitectures, which would be the fundamental building blocks of various nanoscale circuits, devices, and systems. Here, we report the synthesis of linear and branched crystalline SiNTs via porous anodic aluminum oxide (AAO) self-catalyzed growth and postannealing, and the connection of crystalline SiNTs and gold nanowires (AuNWs) via a combinatorial process of electrodepositing AuNWs with predesired length and location in the channels of the AAO template and subsequent AAO self-catalyzed and postannealing growth of SiNTs in the remaining empty channels adjacent to the AuNWs. Using the approach, a large variety of two-segment AuNW/SiNT and three-segment SiNT/AuNW/SiNT heteronanostructures with both linear and branched topologies have been achieved, paving the way for the rational design and fabrication of SiNT-based nanocircuits, nanodevices, and multifunctional nanosystems in the future.

Growth kinetics controlled rational synthesis of germanium nanotowers in chemical vapor deposition

This study demonstrated a simple method for gold (Au) catalyzed atmospheric pressure chemical vapor deposition (CVD) of tower-like germanium (Ge) nanostructures (denoted as Ge nanotowers) on silicon substrate. The Ge nanotowers have quasi- hexagonal cross-section with a diameter gradually decreasing from the bottom to the top end and sawtooth-faceted sidewalls. The Ge nanotowers are formed in a competitive growth process involving an Au-catalyzed axial growth and lateral growth, which can be controlled by the varied reagent vapor pressure in the CVD growth. The relationship between CVD growth kinetics and the complex morphologies was carefully examined for Ge nanostructures ranging from cylindrical and tapered nanowires to moniliform-shaped and sawtooth faceted hexagonal nanotowers in different deposition zones. The resultant complex Ge nanotowers not only enrich the family of Ge-based nanostructures, but also have potentials as building blocks for Ge-based functional nanodevices.中文摘要本文以简单的金催化常压化学气相沉积法,在单晶硅片上合成了塔状锗纳米结构(简称锗纳米塔). 这种锗纳米塔的横截面为准六边形,从底端至顶端的尺寸逐渐减小,侧面含有锯齿状边缘.研究表明, 锗纳米塔的形成主要是由相互竞争的生长过程决定的:在化学气相沉积过程中,由反应物蒸汽压调控的金催化的轴向生长与径向生长之间的竞争.这种生长动力学与产物复杂形貌之间的关系可以通过不同沉积区域获得的圆柱状、圆锥状锗纳米线以及念珠状、六角锥状锗纳米塔得到验证.这种锗纳米塔不仅丰富了锗纳米结构家族,而且在锗基功能纳米器件中有潜在的应用前景.

ERRATUM: Nanocontainers made of Various Materials with Tunable Shape and Size

Nanocontainers have great potentials in targeted drug delivery and nanospace-confined reactions. However, the previous synthetic approaches exhibited limited control over the morphology, size and materials of the nanocontainers, which are crucial in practical applications. Here, we present a synthetic approach to multi-segment linear-shaped nanopores with pre-designed morphologies inside anodic aluminium oxide (AAO), by tailoring the anodizing duration after a rational increase of the applied anodizing voltage and the number of voltage increase during Al foil anodization. Then, we achieve nanocontainers with designed morphologies, such as nanofunnels, nanobottles, nano-separating-funnels and nanodroppers, with tunable sizes and diverse materials of carbon, silicon, germanium, hafnium oxide, silica and nickel/carbon magnetic composite, by depositing a thin layer of materials on the inner walls of the pre-designed AAO nanopores. The strategy has far-reaching implications in the designing and large-scale fabrication of nanocontainers, opening up new opportunities in nanotechnology applications.