A general lithography-free method of microscale/nanoscale fabrication and patterning on Si and Ge surfaces

Here, we introduce and give an overview of a general lithography-free method to fabricate silicide and germanide micro-/nanostructures on Si and Ge surfaces through metal-vapor-initiated endoepitaxial growth. Excellent controls on shape and orientation are achieved by adjusting the substrate orientation and growth parameters. Furthermore, micro-/nanoscale pits with controlled morphologies can also be successfully fabricated on Si and Ge surfaces by taking advantage of the sublimation of silicides/germanides. The aim of this brief report is to illustrate the concept of lithography-free synthesis and patterning on surfaces of elemental semiconductors, and the differences and the challenges associated with the Si and the Ge surfaces will be discussed. Our results suggest that this low-cost bottom-up approach is promising for applications in functional nanodevices.     

A direct-write,resistless hard mask for rapid nanoscale patterning of diamond

We introduce a simple, resist-free dry etch mask for producing patterns in diamond, both bulk and thin deposited films. Direct gallium ion beam exposure of the native diamond surface to doses as low as 10¹⁶ cm^?2 forms a top surface hard mask resistant to both oxygen plasma chemical dry etching and, unexpectedly, argon plasma physical dry etching. Gallium implant hard masks of nominal 50 nm thickness demonstrate oxygen plasma etch resistance to over 450 nm depth, or 9:1 selectivity. The process offers significant advantages over direct ion milling of diamond including increased throughput due to separation of patterning and material removal steps, allowing both nanoscale patterning resolution as well as rapid masking of areas approaching millimeter scales. Retention of diamond properties in nanostructures formed by the technique is demonstrated by fabrication of specially shaped nanoindenter tips that can perform imprint pattern transfer at over 14 GPa pressure into gold and silicon surfaces. This resistless technique can be applied to curved and non-planar surfaces for a variety of potential applications requiring high resolution structuring of diamond coatings.     

The pharmaceutical biochemistry group: where pharmaceutical chemistry meets biology and drug delivery

Successful drug discovery and development of new therapeutics is a long, expensive multidisciplinary process needing innovation and the integration of smart cutting edge science and technology to overcome the challenges in taking a drug from the bench to the bedside. The research activities of the Pharmaceutical Biochemistry group span the drug discovery and development process, providing an interface that brings together pharmaceutical chemistry, biochemistry, structural biology, computational chemistry and biopharmaceutics. Formulation and drug delivery are brought into play at an earlier stage when facing the perennial challenge of transforming a potent molecule in vitro into a therapeutic agent in vivo. Concomitantly, drug delivery results can be understood at a molecular level. This broad range of interdisciplinary research activities and competences enables us to address key challenges in modern drug discovery and development, provides a powerful collaborative platform for other universities and the pharmaceutical industry and an excellent training platform for pharmacists and pharmaceutical scientists who will later be involved in drug discovery and development.     

Metal-assisted chemical etching of Ge(100) surfaces in water toward nanoscale patterning

We propose the metal-assisted chemical etching of Ge surfaces in water mediated by dissolved oxygen molecules (O₂). First, we demonstrate that Ge surfaces around deposited metallic particles (Ag and Pt) are preferentially etched in water. When a Ge(100) surface is used, most etch pits are in the shape of inverted pyramids. The mechanism of this anisotropic etching is proposed to be the enhanced formation of soluble oxide (GeO₂) around metals by the catalytic activity of metallic particles, reducing dissolved O₂ in water to H₂O molecules. Secondly, we apply this metal-assisted chemical etching to the nanoscale patterning of Ge in water using a cantilever probe in an atomic force microscopy setup. We investigate the dependences of probe material, dissolved oxygen concentration, and pressing force in water on the etched depth of Ge(100) surfaces. We find that the enhanced etching of Ge surfaces occurs only when both a metal-coated probe and saturated-dissolved-oxygen water are used. In this study, we present the possibility of a novel lithography method for Ge in which neither chemical solutions nor resist resins are needed.     

软化学法制备纳米铁氧体的研究进展

介绍了近几年国内外以软化学方法制备纳米铁氧体的研究进展,分析了液相沉淀法、溶胶-凝胶法、低热固相法、微乳液法、流变相法等的特点,并对软化学法在纳米铁氧体制备中的应用进行了展望。     

Towards characterisation of millimetre length waveguides and new fabrication method for nanoscale diamond photonic structures

We present a novel approach to achieving in-plane coupling for ridge waveguides fabricated in single crystal diamond through a modification to the graphitic implant process. The etched cross-section of a diamond ridge structure is examined to confirm roughness estimates and the trenching effect. Finally nanoscale optical cavities are fabricated in polycrystalline diamond using a new method of exposure using focussed ion beam as a hard mask to pattern the structures.     

On the nature and importance of the transition between molecules and nanocrystals: towards a chemistry of "nanoscale perfection"

This paper discusses the importance of the transition between molecular compounds and nanocrystals. The boundary between molecular and nanocrystals/nanoclusters can be defined by the emergence of the bulk phase; atoms in the core of the nanoclusters that are not bound to ligands. This transition in dimensions and structural organization is important because it overlaps with the boundary between atomically defined moieties (molecules can be isolated with increasing purity) and mixtures (nanocrystals have a distribution of sizes, shapes, and defects; they cannot be easily separated into batches of structurally identical species). Passing through this boundary, as the size of a structure increases beyond a few nanometres, the information about the position of each atom gradually disappears. This loss of structural information about a chemical structure fundamentally compromises our ability to use it as a part of a complex chemical system. If we are to engineer complex functions encoded in a chemical language, we will need pure batches of atomically defined (truly monodisperse) nanoscale compounds, and we will need to understand how to make them and preserve them over a broad range of length scales, compositions, and timeframes. In this review we survey most classes of monodisperse nanomaterials (mostly nanoclusters) and highlight the recent breakthroughs in this area which might be spearheading the development of a chemistry of "nanoscale perfection".     

In situ nanoscale wet imaging of the heterogeneous catalyzationof nitriles in a solution phase: novel hydrogenation chemistry through nanocatalysts on nanosupports

Wet-environmental transmission electron microscopy studies of heterogeneous hydrogenation of complex nitriles in a liquid phase over new mesoporous cobalt-promoted ruthenium nanocatalysts on reducible nanotitania supports are presented. The desorbed organic products in the dynamic liquid phase hydrogenation are imaged situ on the nanoscale. The direct studies on the “nanocomposite” catalysts are correlated with parallel reaction chemistry measurements. They demonstrate high hydrogenation activity at low operating temperatures in the presence of atomic scale anion vacancy defects associated with Lewis acid sites at the nanosupport surface and an electronic and synergistic contribution to the promoter mechanism. The combined synergistic effect between the two metals and the interaction with the reduced nanosupport leading to an electronic modification lead to highly reactive site for the hydrogenation catalysis. The results illustrate novel selective hydrogenation chemistry with mesoporous nanocatalyst systems on nanosupports.     

Graphene: nanoscale processing and recent applications

One of the most interesting features of graphene is the rich physics set up by the various nanostructures it may adopt. The planar structure of graphene makes this material ideal for patterning at the nanoscale. The breathtakingly fast evolution of research on graphene growth and preparation methods has made possible the preparation of samples with arbitrary sizes. Available sample production techniques, combined with the right patterning tools, can be used to tailor the graphene sheet into functional nanostructures, even whole electronic circuits. This paper is a review of the existing graphene patterning techniques and potential applications of related lithographic methods.     

Nanoscale ear drum: graphene based nanoscale sensors

The difficulty in determining the mass of a sample increases as its size diminishes. At the nanoscale, there are no direct methods for resolving the mass of single molecules or nanoparticles and so more sophisticated approaches based on electromechanical phenomena are required. More importantly, one demands that such nanoelectromechanical techniques could provide not only information about the mass of the target molecules but also about their geometrical properties. In this sense, we report a theoretical study that illustrates in detail how graphene membranes can operate as nanoelectromechanical mass-sensor devices. Wide graphene sheets were exposed to different types and amounts of molecules and molecular dynamic simulations were employed to treat these doping processes statistically. We demonstrate that the mass variation effect and information about the graphene-molecule interactions can be inferred through dynamical response functions. Our results confirm the potential use of graphene as a mass detector device with remarkable precision in estimating variations in mass at the molecular scale and other physical properties of the dopants.     

Fluid catalytic cracking: chemistry

Fluid catalytic cracking (FCC) is the major catalytic refinery process and the chemistry of some of the complex reactions occurring during FCC processing is reviewed and discussed. Experimental results for catalysts based on zeolite Y, and its modifications, and for comparison of zeolite Y and shape-selective catalysts are used to explain features of the underlying chemistry involved in the FCC process.     

Protective space coatings: a ceramer approach for nanoscale materials

There is a concerted and focused push to develop protective space coatings for vehicles in low earth and geosynchronous orbit. The space environment is not suitable for organic materials due to atomic oxygen, high energy particles, and deep UV light being able to degrade polymeric organic resins. An inorganic/organic hybrid coating, known as a ceramer, will be fabricated using a polysiloxane binder and nanophase silicon/metal-oxo-clusters derived from sol–gel precursors. The binder of the coating will be a substituted polysiloxane terminated with a cyclohexyl epoxide. The cyclohexyl epoxide will be cured at ambient temperature via a cationic UV curing mechanism. PDSC will also be used to investigate the effects of temperature, UV light intensity, sol–gel precursor concentration, and exposure time have on the rate of polymerization. Nuclear magnetic resonance and Fourier transform infrared spectroscopy were used to characterize the synthesis of the polysiloxanes. The rate of polymerization was found to increase as temperature, intensity, sol–gel precursor concentration, and exposure time were increased.     

Magnetically actuated propulsion at low Reynolds numbers: towards nanoscale control

Significant progress has been made in the fabrication of micron and sub-micron structures whose motion can be controlled in liquids under ambient conditions. The aim of many of these engineering endeavors is to be able to build and propel an artificial micro-structure that rivals the versatility of biological swimmers of similar size, e.g. motile bacterial cells. Applications for such artificial "micro-bots" are envisioned to range from microrheology to targeted drug delivery and microsurgery, and require full motion-control under ambient conditions. In this Mini-Review we discuss the construction, actuation, and operation of several devices that have recently been reported, especially systems that can be controlled by and propelled with homogenous magnetic fields. We describe the fabrication and associated experimental challenges and discuss potential applications.