Nanoimprint lithography for nanophotonics in silicon

A novel inverse imprinting procedure for nanolithography is presented which offers a transfer accuracy and feature definition that is comparable to state-of-the-art nanofabrication techniques. We illustrate the fabrication quality of a demanding nanophotonic structure: a photonic crystal waveguide. Local examination using photon scanning tunneling microscopy (PSTM) shows that the resulting nanophotonic structures have excellent guiding properties at wavelengths in the telecommunications range, which indicates a high quality of the local structure and the overall periodicity.     

Polymer micromachining for micro- and nanophotonics

Polymeric materials have been used in the fabrication of many high-performance, low cost photonic devices for optical communications, interconnects and sensors. The paper presents two low cost techniques for polymer based photonic components fabrication, such as waveguides, diffractive optical elements and optical modulators.We used both photopatternable (metal doped PVA) and nonphotopatternable polymers (PMMA and silicone polymers).The photosensitivity and, in the same time, refractive index of the poly(vinyl-alcohol) were modified through the addition inorganic/organic materials. These new light-sensitive nanocomposites can be easily spin coated onto variety of semiconductor substrates, and directly patterned to obtain channel waveguides and photonic integrated circuits.For nonphotopatternable polymers, two types of molds have been used: grooves etched in silicon or in silicon dioxide and photoresist molds. Rib waveguides and tunable modulators, voltage actuated, have been obtained using these techniques.     

endo-Fullerene and doped diamond nanocrystallite-based models of qubits for solid-state quantum computers

Models of encapsulated nuclear spin 1/2 1H and 31P atoms in fullerene and diamond nanocrystallite, respectively, are proposed and examined with an ab initio local density functional method for possible applications as single quantum bits (qubits) in solid-state quantum computers. A 1H atom encapsulated in a fully deuterated fullerene, C20D20, forms the first model system and ab initio calculation shows that the 1H atom is stable in its atomic state at the center of the fullerene with a barrier of about 1 eV to escape. A 31P atom positioned at the center of a diamond nanocrystallite is the second model system, and 31P atom is found to be stable at the substitutional site relative to interstitial sites by 15 eV. Vacancy formation energy is 6 eV in diamond, so the substitutional 31P atom will be stable against diffusion during the formation mechanisms within the nanocrystallite. The coupling between the nuclear spin and the weakly bound (valance) donor electron in both systems is found to be suitable for single qubit applications, whereas the spatial distributions of (valance) donor electron wave functions are found to be preferentially spread along certain lattice directions, facilitating two or more qubit applications. The feasibility of the fabrication pathways for both model solid-state qubit systems within practical quantum computers is discussed within the context of our proposed solid-state qubits.     

量子神经计算和量子遗传算法的理论分析和应用

经过比较研究发现,在量子计算与神经网络和遗传算法之间,不论在计算思想上还是模型表达上,都存在着许多相似之处,这些相似性启发人们去研究基于量子理论的神经网络和遗传算法模型,一方面探索神经网络和遗传算法在量子系统上的实现方法,另一方面研究量子理论启发下的新的神经网络与遗传算法模型。本文总结了本课题组近年来在量子计算与神经网络和遗传算法相结合领域的研究工作,包括量子系统实现神经计算的理论分析,量子神经网络物理模型的研究,基于量子概率表达的量子遗传算法及其应用研究等,并对今后的发展提出了展望。     

Direct visualization of near-fields in nanoplasmonics and nanophotonics

Electric fields of nanoscale particles are fundamental to our understanding of nanoplasmonics and nanophotonics. Success has been made in developing methods to probe the effect of their presence, but it remains difficult to directly image optically induced electric fields at the nanoscale and especially when ensembles of particles are involved. Here, using ultrafast electron microscopy, we report the space-time visualization of photon-induced electric fields for ensembles of silver nanoparticles having different sizes, shapes, and separations. The high-field-of-view measurements enable parallel processing of many particles in the ensemble with high throughput of information. Directly in the image, the evanescent fields are observed and visualized when the particles are polarized with the optical excitation. Because the particle size is smaller than the wavelength of light, the near-fields are those of nanoplasmonics and are precursors of far-field nanophotonics. The reported results pave the way for quantitative studies of fields in ensembles of complex morphologies with the nanoparticles being embedded or interfacial.     

Two-dimensional noble transition-metal dichalcogenides for nanophotonics and optoelectronics:Status and prospects

An emerging subclass of transition-metal dichalcogenides(TMDs),noble-transition-metal dichalcogenides(NMDs),has led to an increase in nanoscientific research in...     

Integrated all-optical infrared switchable plasmonic quantum cascade laser

We report a type of infrared switchable plasmonic quantum cascade laser, in which far field light in the midwave infrared (MWIR, 6.1 μm) is modulated by a near field interaction of light in the telecommunications wavelength (1.55 μm). To achieve this all-optical switch, we used cross-polarized bowtie antennas and a centrally located germanium nanoslab. The bowtie antenna squeezes the short wavelength light into the gap region, where the germanium is placed. The perturbation of refractive index of the germanium due to the free carrier absorption produced by short wavelength light changes the optical response of the antenna and the entire laser intensity at 6.1 μm significantly. This device shows a viable method to modulate the far field of a laser through a near field interaction.     

Nanoelectronics and nanophotonics at the first international forum on nanotechnologies

Some of the scientific results presented in the “Nanoelectronics” and “Nanophotonics” sessions at the First International Forum on Nanotechnologies “Rusnanoforum-2008” (Rusnanotech08) are reviewed briefly.     

Integrated availability model based on performance of computer networks

An efficient computer network can realize bulk data transfer and real time control with high reliability and precision. Its availability is dependent on its topological structure and network services performed simultaneously. To explore the dynamic interactions between software and hardware failures, generalized stochastic petri net (GSPN) is adopted to model the availability of nodes in the network, and then the study is developed through path selection and service performance evaluation. Network performance indices such as throughput and time delay can be obtained by modeling the network service with queueing theory. With Power formula, this paper presents an integrated availability model. This model considers both topological connectivity and operational performance, developing the availability analysis from the viewpoint of a user.     

Concepts for diamond electronics

The present status in the development of diamond as electronic semiconductor material with wide band-gap (5.45 eV) is reviewed. Since diamond cannot be doped with shallow impurities, specific doping concepts and related diode and FET structures had to be developed, restricted to p-type boron doping. The results allow to predict that diamond high voltage switching diodes, high power RF FET sources and operation at high temperature will surpass the capability of devices designed in competing wide band-gap materials like SiC and GaN.     

Structural and optical properties of ultrananocrystalline diamond / InGaAs/GaAs quantum dot structures

The combination of the unique properties of ultrananocrystalline diamond (UNCD) films and of semiconductor quantum dot (QD) structures could significantly improve the performance of different electronic and optoelectronic devices, where e.g. good thermal management and advanced mechanical parameters are required. In the current work quantum dot InGaAs/GaAs heterostructures have been grown by molecular beam epitaxy (MBE) with different densities between 1.6 × 10¹⁰ cm^− 2 and 1.6 × 10¹¹ cm^− 2 controlled by the substrate temperature in the range between 490 and 515 °C. These structures were overgrown with UNCD by microwave plasma chemical vapor deposition (MWCVD) using methane/nitrogen mixtures at 570 °C. Scanning electron microscopy (SEM) reveals that without ultrasonic pretreatment the diamond nucleation density on QD structures is low and only separate islands of UNCD are deposited, while after pretreatment thin closed films are formed. From the cross-section SEM images a growth rate of ca. 3 nm/min is estimated which is very close to that on silicon at the same deposition conditions. The UNCD coatings exhibit a morphology consisting of two types of structures as shown by atomic force microscopy (AFM). The first one includes nodules with diameters between 180 and 350 nm varying with the density of the underlying QDs; the second is formed by a kind of granular substructure of these nodules with diameters of about 40 nm for all QD densities. The optical properties were investigated by photoluminescence (PL) spectroscopy before and after the deposition of UNCD. The PL signals of QD structures overgrown with UNCD, although with decreased intensity, remain almost unchanged with respect to the peak positions and widths, revealing that the UNCD/QD structures retain the optical properties of uncoated InGaAs/GaAs quantum dots.     

Optical setups for probabilistic bipartite and tripartite entanglement generation and quantum teleportation in optical networks

In this work we present optical setups for a polarization encoded qubit, based only on common linear optical devices, which implement probabilistic bipartite and tripartite entanglement generation, as well probabilistic quantum teleportation. The setups can be implemented with current technology and they permit the realization of several quantum communication protocols.     

Diamond at the nanoscale: applications of diamond nanoparticles from cellular biomarkers to quantum computing

Although nanocrystalline diamond powders have been produced in industrial quantities, mainly by detonation synthesis, for many decades their use in applications other than traditional polishing and grinding have been limited, until recently. This paper presents the wide-ranging applications of nanodiamond particles to date and discusses future research directions in this field. Owing to the recent commercial availability of these powders and the present interest in nanotechnology, one can predict a huge increase in research with these materials in the very near future. However, to fully exploit these materials, fundamental as well as applied research is required to understand the transition between bulk and surface properties as the size of particles decreases.     

CVD diamond layers for electrochemistry

Diamond electrodes of different morphologies and qualities were manufactured by hot filament chemical deposition (HF CVD) techniques by changing the parameters of diamond growth process. The estimation of diamond quality and identification of different carbon phases was performed by Raman spectroscopy measurements. The effect of diamond quality and amorphous carbon phase content on the electrochemical response of an obtained diamond electrode in 0.5 M H₂SO₄ as supporting electrolyte was investigated by cyclic voltammetry with [Fe(CN)₆]^4?/3? as a redox probe. The kinetic parameters such as catalytic reaction rate constant k₀ and electron transfer coefficient α were determined. The obtained results show that the analytical performance of undoped diamond electrodes can be implemented just by the change of diamond layers quality.     

The apparatus for diamond synthesis

A high-pressure apparatus, whose cavity is formed by openings of two oppositely located calipers surrounded by an angular body, has been considered. Parameters, at which the pressure created in the cavity is kept by the forces of friction without the use of a press, have been defined. A scheme of a plant that allows a group of apparatuses to be driven by one press has been suggested.     

Integrated analysis of the gene neighbouring impact on bacterial metabolic networks

Different levels of abstraction are needed to represent a living system. Unfortunately information of different nature is not superposable in an obvious way, but requires a dedicated framework. Because biological abstractions, i.e., genomic or metabolic information, can be easily represented as graphs, it is intuitive to integrate them into a unique graph, in which one can perform graph analysis for investigating a given biological assumption. This study follows such a philosophy and completes a genome and metabolome combination. In a such integrated framework and as illustration, we applied a graph analysis that automatically investigates impacts of the gene adjacency to predict functional relationships between genes and reactions. Our approach, called SIPPER, creates a weighted graph, in which the weights rely on the given relationship between genes, and computes (alternative) chains of reactions catalysed by genes. This method, as a generalisation of methods already published, can be easily adapted to several biological assumptions, properties or measures. This paper evaluates SIPPER on Escherichia coli. We automatically extract subgraphs, called k-SIPs, and quantify their interest in both genomic and metabolic contexts by showing functional compounds like operons or functional modules.     

金刚石薄膜抗激光破坏研究

介绍了金刚石优异的光学和力学特性,对金刚石薄膜在从紫外到红外波段以及不同脉宽激光参数下的激光损伤行为和损伤阈值进行了评述。分析了不同激光工作参数对金刚石薄膜的激光损伤机理,认为石墨化导致晶格失稳是金刚石薄膜激光损伤的主要原因。金刚石薄膜石墨化有两种方式:垂直表面向体层方向石墨化和平行表面按分层的方式逐层石墨化。     

Nanocrystalline diamond films for nanotechnology applications

Abstract

Nanocrystalline diamond films with rms roughnesses in the order of 50 nm have been prepared by microwave plasma enhanced chemical vapour deposition. Ar-CH₄ gas mixtures have been used in a coaxially bladed reactor, and Ar-H₂-CH4 gas mixtures have been used in a reactor with a dual mode microwave applicator. These films have been examined by ultraviolet and visible Raman spectroscopy. They have been subjected to nanotribological investigation, with a view to their incorporation into microelectromechanical systems (MEMS). Comparisons with other diamond and hard carbon films are made, and the advantages of nanocrystalline diamond films are discussed.