Wavelength-scanning surface plasmon resonance imaging

A new surface plasmon resonance (SPR) imaging technique was proposed. After measurements were conducted at varying wavelengths, the wavelength affording the minimum brightness (SPR wavelength) was determined at each pixel of the image. A two-dimensional map of the SPR wavelength could be converted to a thickness profile by use of a nonlinear calibration curve, which was obtained by Fresnel calculation. An array of protein thin layers on a gold film was evaluated in air to present the layers' surface structure in nanometer scale.     

Multiple-wavelength focusing of surface plasmons with a nonperiodic nanoslit coupler

A novel type of multiple-wavelength focusing plasmonic coupler based on a nonperiodic nanoslit array is designed and experimentally demonstrated. An array of nanoslits patterned on a thin metal film is used to couple free-space light into surface plasmon polaritons (SPPs) and simultaneously focus different-wavelength SPPs into arbitrary predefined locations in the two-dimensional plane. We design and fabricate a compact triplexer on a glass substrate with an integrated silicon photodetector. The photocurrent spectra demonstrate that the incident light is effectively coupled to SPPs and routed into three different focal spots depending on the wavelength. The proposed scheme provides a simple method of building wavelength-division multiplexing and spectral filtering elements, integrated with other plasmonic and optoelectronic devices.     

Two-dimensional direct-reading fluorescence spectrograph for DNA sequencing by capillary array electrophoresis

We report a compact, two-dimensional direct-reading fluorescence spectrograph and demonstrate its application to DNA sequencing by capillary array electrophoresis. The detection cuvette is based on sheath flow, wherein the capillaries terminate in a two-dimensional array in a fluid-filled chamber that is pressurized with buffer. A thin metal plate is located downstream from the capillaries. This barrier plate has an array of holes that precisely matches the location of the capillaries. Buffer flows through the holes, drawing analyte from the capillaries in a well-defined array of thin filaments. Fluorescence is excited in the upper chamber with an elliptically shaped laser beam. The bottom chamber is sealed with a glass window and drained from the side. Fluorescence is detected by imaging the illuminated sample streams through the holes in the barrier plate. A prism is used to disperse fluorescence from each sample across a CCD camera so that the emission spectrum is monitored simultaneously from each capillary. The instrument is demonstrated in a 32-capillary configuration but can be scaled to several thousand capillaries.     

The "millipede" - nanotechnology entering data storage

Present a new scanning-probe-based data-storage concept called the "millipede" that combines ultrahigh density, terabit capacity, small form factor, and high data rate. Ultrahigh storage density has been demonstrated by a new thermomechanical local-probe technique to store, read back, and erase data in very thin polymer films. With this new technique, nanometer-sized bit indentations and pitch sizes have been made by a single cantilever/tip into thin polymer layers, resulting in a data storage densities of up to 1 Tb/in². High data rates are achieved by parallel operation of large two-dimensional (2-D) atomic force microscope (AFM) arrays that have been batch-fabricated by silicon surface-micromachining techniques. The very large-scale integration (VLSI) of micro/nanomechanical devices (cantilevers/tips) on a single chip leads to the largest and densest 2-D array of 32×32 (1024) AFM cantilevers with integrated write/read/erase storage functionality ever built. Time-multiplexed electronics control the functional storage cycles for parallel operation of the millipede array chip. Initial areal densities of 100-200 Gb/in² have been achieved with the 32×32 array chip     

Piezoelectrically actuated flextensional micromachined ultrasound droplet ejectors

This paper reports a variation on the design of the flextensional transducer for use in ejecting liquids. The transducer is constructed by depositing a piezoelectric thin film to a thin, edge-clamped, circular annular plate. By placing a fluid behind one face of a vibrating compound plate that has an orifice at its center, we achieve continuous or drop-on-demand ejection of the fluid. We present results of ejection of water and isopropanol. The ejector is harmless to sensitive fluids and can be used to eject fuels as well as chemical and biological samples. Micromachined two-dimensional array piezoelectrically actuated flextensional droplet ejectors were realized using planar silicon micromachining techniques. Typical resonant frequency of the micromachined device ranges from 400 kHz to 4.5 MHz. The ejection of water through a 5-μm diameter orifice at 3.5 MHz was demonstrated by using the developed micromachined two-dimensional array ejectors     

Field-programmable smart-pixel arrays: design, VLSI implementation, and applications

A smart-pixel array is a two-dimensional array of optoelectronic devices that combine optical inputs and outputs with electronic processing circuitry. A field-programmable smart-pixel array (FP-SPA) is a smart-pixel array capable of having its electronic functionality dynamically programmed in the field. Such devices could be used in a diverse range of applications, including optical switching, optical digital signal processing, and optical image processing. We describe the design, VLSI implementation, and applications of a first-generation FP-SPA implemented with the 0.8-microm complementary metal-oxide semiconductor-self-electro-optic effect device technology made available through the Lucent Technologies-Advanced Research Projects Agency Cooperative (Lucent/ARPA/COOP) program. We report spice simulations and experimental results of two sample applications: In the first application, we configure this FP-SPA as an array of free-space optical binary switches that can be used in optical multistage networks. In the second, we configure the device as an optoelectronic transceiver for a dynamically reconfigurable free-space intelligent optical backplane called the hyperplane. We also describe the testing setup and the electrical and the optical tests that demonstrate the correct functionality of the fabricated device. Such devices have the potential to reduce significantly the need for custom design and fabrication of application-specific optoelectronic devices in the same manner that field-programmable gate arrays have largely eliminated the need for custom design and fabrication of application-specific gate arrays, except in the most demanding applications.     

Forward-viewing CMUT arrays for medical imaging

This paper reports the design and testing of forward-viewing annular arrays fabricated using capacitive micromachined ultrasonic transducer (CMUT) technology. Recent research studies have shown that CMUTs have broad frequency bandwidth and high-transduction efficiency. One- and two-dimensional CMUT arrays of various sizes already have been fabricated, and their viability for medical imaging applications has been demonstrated. We fabricated 64-element, forward-viewing annular arrays using the standard CMUT fabrication process and carried out experiments to measure the operating frequency, bandwidth, and transmit/receive efficiency of the array elements. The annular array elements, designed for imaging applications in the 20 MHz range, had a resonance frequency of 13.5 MHz in air. The immersion pulse-echo data collected from a plane reflector showed that the devices operate in the 5-26 MHz range with a fractional bandwidth of 135%. The output pressure at the surface of the transducer was measured to be 24 kPa/V. These values translate into a dynamic range of 131.5 dB for 1-V excitation in 1-Hz bandwidth with a commercial low noise receiving circuitry. The designed, forward-viewing annular CMUT array is suitable for mounting on the front surface of a cylindrical catheter probe and can provide Doppler information for measurement of blood flow and guiding information for navigation through blood vessels in intravascular ultrasound imaging.     

Fabrication of Flexible MoS2 Thin‐Film Transistor Arrays for Practical Gas‐Sensing Applications

By combining two kinds of solution‐processable two‐dimensional materials, a flexible transistor array is fabricated in which MoS₂ thin film is used as the active channel and reduced graphene oxide (rGO) film is used as the drain and source electrodes. The simple device configuration and the 1.5 mm‐long MoS₂ channel ensure highly reproducible device fabrication and operation. This flexible transistor array can be used as a highly sensitive gas sensor with excellent reproducibility. Compared to using rGO thin film as the active channel, this new gas sensor exhibits much higher sensitivity. Moreover, functionalization of the MoS₂ thin film with Pt nanoparticles further increases the sensitivity by up to ～3 times. The successful incorporation of a MoS₂ thin‐film into the electronic sensor promises its potential application in various electronic devices.     

Vertical nanowire array-based light emitting diodes

Electroluminescence from a nanowire array-based light emitting diode is reported. The junction consists of a p-type GaN thin film grown by metal organic chemical vapor deposition (MOCVD) and a vertical n-type ZnO nanowire array grown epitaxially from the thin film through a simple low temperature solution method. The fabricated devices exhibit diode like current voltage behavior. Electroluminescence is visible to the human eye at a forward bias of 10 V and spectroscopy reveals that emission is dominated by acceptor to band transitions in the p-GaN thin film. It is suggested that the vertical nanowire architecture of the device leads to waveguided emission from the thin film through the nanowire array.     

薄膜场发射阴极中纳米线密度的理论优化

现在人们正在研究各种纳米线薄膜 ,因为它们很有可能成为新一代的场发射阴极而被应用于平面显示器等器件中。研究表明 ,除了纳米线的物理特性 ,薄膜的场发射特性也强烈地依赖于纳米线阵列的几何构造。一方面 ,薄膜阴极的纳米线阵列密度要足够大 ,使得大量的场发射源能够产生。另一方面 ,过大的密度带来的屏蔽效应将严重削弱纳米线尖端的局域电场。在本文的参数下 ,利用Ansys软件计算出了纳米线的最佳间距———使得纳米线之间的屏蔽效应可以忽略的最小距离———为纳米线高度的两倍     

Pure magnetooptic diffraction and Kerr microscopy of periodic domain structures

The fabrication of a periodic domain structure in a ferromagnetic thin film is reported. This periodic domain structure is formed in a thin continuous magnetic film by coupling it to a periodic array of magnetic elements grown on top. When the array and the continuous film are exchange decoupled, magnetostatic interactions produce in the continuous layer a domain structure replica of the topographic pattern at selected field values. The present work reports a direct confirmation of this periodic domain structure in the flat continuous film by Kerr microscopy, which is responsible for the pure magnetooptic diffraction. The effect on the magnetization processes of oneand two-dimensional structures with different periodicities and dimensions is studied in detail and compared with micromagnetic simulations, for Co and Fe films.     

Implementation of a redox microarray: an experimental model for future nanoscale biomolecular computing using integrated circuits

The possibility of constructing high-density parallel computing architectures using molecular electronics technology is explored. By employing molecular computing devices, new circuitsystem integration could be realised. To clarify the proposed concept, an experimental model of a redox microarray is presented. A first experimental system for a redox microarray consists of a two-dimensional array of platinum microelectrodes to catalyse reversible reactions of redox-active molecules. Experimental results of active wave propagation in the redox microarray are presented to demonstrate the potential of molecular computing devices for creating artificially programmable reaction-diffusion dynamics for specific target applications.     

2.27 1/f noise voltage in a thin film structure

1/f noise in current carrying thin film devices is caused by fluctuation of the electrical conductivity of the film material. Describing its effect on the voltage distribution in a device requires a two-dimensional analysis. This may be done by means of a theory, presented in this article, where the fluctuation is treated as current dipoles.The geometrical dependence of the noise intensity across electrodes on Hall generator structures, made from InSb thin films, is measured. This is in fair agreement with predictions based on the theory.     

The design of SAW RAC's using arrays of thin metal dots

Many successful dot array SAW devices including RAC's, resonators and band-pass filters have been reported, but the wide range of dot parameters, including dot dimensions, spacing and pattern, which allows flexibility in design, has not previously been utilized. This paper reports on the design of an RAC (reflecting array compressor) with a TB product of 1000, the emphasis being to exploit some of this flexibility. The design has been implemented using YZ LiNbO₃ with thin metal dots as the reflectors. It makes use of the wide range of reflectivities available from electrical effects in a novel weighting scheme based on dot size. The dots have been designed so that the sensitivity to over-etch is minimal. The array, which is sparse and near-periodic, has been designed to reduce unwanted reflections. This is least successful in the case of SAW to bulk wave reflection and the consequent loss due to this cause is accounted for in the design. The design approach is quite general and should be of use for other devices     

High‐Resolution Spin‐on‐Patterning of Perovskite Thin Films for a Multiplexed Image Sensor Array

Inorganic–organic hybrid perovskite thin films have attracted significant attention as an alternative to silicon in photon‐absorbing devices mainly because of their superb optoelectronic properties. However, high‐definition patterning of perovskite thin films, which is important for fabrication of the image sensor array, is hardly accomplished owing to their extreme instability in general photolithographic solvents. Here, a novel patterning process for perovskite thin films is described: the high‐resolution spin‐on‐patterning (SoP) process. This fast and facile process is compatible with a variety of spin‐coated perovskite materials and perovskite deposition techniques. The SoP process is successfully applied to develop a high‐performance, ultrathin, and deformable perovskite‐on‐silicon multiplexed image sensor array, paving the road toward next‐generation image sensor arrays.     

Fabrication of large area flexible and highly transparent film by a simple Ag nanowire alignment

This article describes the fabrication of a flexible polymer thin film incorporating a highly aligned Ag nanowire array, resulting in high transparency and polarisation that are useful for potential applications to optical filters, electronic and optical devices and negative refractive index materials.     

Fabrication of thin-film micropolarizer arrays for visible imaging polarimetry

We describe a microfabrication process for fabricating micropolarizer devices with polarization thin film. The polarization film is less than a 0.5 mum thick and can have a polarization extinction ratio of ~330 in the visible wavelength range. A single-state micropolarizer array with polarizing pixels as small as 5 mum x 5 mum has been fabricated. A multilayer spatially multiplexed three-state micropolarizer line array with a 14.4-mum resolution has also been fabricated for visible imaging polarimetry application.     

Novel transmit protection scheme for ultrasound systems

The problem of protecting or isolating extremely sensitive receive circuitry from high-voltage transmit circuitry is commonly addressed through the use of diode bridges, transformers, or high-voltage switches, which prove to be prohibitively expensive, bulky, and power consuming for use in portable, low-cost, battery-powered systems. These approaches also compound the interconnect difficulties associated with two-dimensional (2-D) transducer arrays. In this paper we present a novel transmit protection scheme that allows compact MOSFET shunting devices to be brought on-chip within each receive channel implemented in a standard CMOS integrated circuit process. During transmit, the high voltage transmit pulse is driven onto the common connection of the transducer array and the on-chip MOSFET devices shunt the current to ground. During receive, these devices are turned off, the common connection of the transducer array is shunted to ground, and the received echo can be detected as usual. The transmit protection scheme was experimentally shown to shunt a 16 mA peak current resulting from the equivalent of a 100-V, 25-ns-risetime transmit pulse through a 4 pF transducer element. The scheme was also incorporated into a prototype 1024-channel, low-cost, ultrasound system successfully used to form pulse echo images.     

Large array of sub-10-nm single-grain Au nanodots for use in nanotechnology

A uniform array of single-grain Au nanodots, as small as 5-8 nm, can be formed on silicon using e-beam lithography. The as-fabricated nanodots are amorphous, and thermal annealing converts them to pure Au single crystals covered with a thin SiO(2) layer. These findings are based on physical measurements, such as atomic force microscopy (AFM), atomic-resolution scanning transmission electron microscopy, and chemical techniques using energy dispersive X-ray spectroscopy. A self-assembled organic monolayer is grafted on the nanodots and characterized chemically with nanometric lateral resolution. The extended uniform array of nanodots is used as a new test-bed for molecular electronic devices.     

Development and calibration of field-effect transistor-based sensor array for measurement of hydrogen and ammonia gas mixtures in humid air

A sensor array for analyzing hydrogen and ammonia gas mixtures in humid air has been developed, built into a rugged system, and calibrated for laboratory testing. The sensor array is comprised of four chemically sensitive field-effect transistors (CHEMFETs). Chemically sensitive layers for the sensors were developed and tested using a Kelvin probe. A combination of catalytic and noncatalytic thin layers (palladium and polyaniline) was selected for the four-sensor array. The work function responses of the CHEMFET sensor array to mixtures of hydrogen, ammonia, and humid air were measured. Chemometric multivariate methods, linear and nonlinear partial least squares, were used for the calibration of the sensor array using gas mixtures in the concentration range from 0 to 10?000 ppm hydrogen and ammonia in humid air. The sensor array for ammonia showed good sensitivity, selectivity, response time, and stability and is recommended for field deployment. In contrast, the sensor array for hydrogen, though highly sensitive to hydrogen, demonstrated inadequate stability, requiring further development before deployment is recommended.