Fabrication and performance of MMW and SMMW platelet horn arrays

Future spaceborne millimeter and sub-millimeter wave sensing systems will require the sensitivity and resolution only achievable with large focal plane array receiving systems. A technique has been developed for the low cost fabrication of large arrays of millimeter and sub-millimeter wave corrugated feed horns. These arrayed horns exhibit high efficiency and symmetrical receiving patterns and are compatible with integrated receivers. W-band test results of a 3×3 array are presented.     

Fabrication and performance of color filter arrays for solid-state imagers

A technique has been developed for the fabrication of a color filter array (CFA) to be used in conjunction with a solid-state area sensor to provide three-color image information from a single sensor. The fabrication technique employs sublimable dyes which are heat-transferred through photoresist windows onto a polymer receiving layer. Good edge sharpness and a low dye penetration depth into the polymer have been achieved. The predicted and measured spectral response of the color channels of the composite device are in good agreement. The pattern noise associated with CFA transmittance fluctuations from element to element is on the order of 10 percent.     

Fabrication and electrical performance of high-density arrays of nanometric silicon tips

We propose and demonstrate a simple and low cost process for the fabrication of large area arrays of nanometric silicon tips, for use as Field Emission Devices (FEDs). The process combines Interference Lithography (IL) with isotropic Reactive Ion Etching (RIE). Si tips with typical curvature radius of 20 nm and height of 900 nm were recorded with a periodicity of 1 μm (density of 10⁶ tips/mm²) covering a Silicon wafer of 2 in. The measurement of the electrical performance of the arrays demonstrates the feasibility of the association of these two techniques for recording Field Emission Tips.     

Fe纳米线的制备及其磁性能研究

采用电化学沉积法封装阳极氧化铝(AAO)模板,制备出不同直径的Fe纳米线阵列。Fe纳米线阵列的形貌、组成、晶型、磁学性能分别通过场发射扫描电子显微镜(SEM)、X-射线能谱仪(EDS)、X-射线衍射仪(XRD)、震动样品磁强计(VSM)进行表征。结果表明:电化学沉积法可以制备出直径为33~95 nm的Fe纳米线;纳米线排列有序,粗细均匀,具有明显的[110]择优取向。VSM测试结果表明纳米线的直径对其磁性能影响很大。当纳米线直径为33~40 nm时,纳米线具有明显的磁各向异性,垂直模板表面的方向为易磁化方向,该方向上矫顽力达112 745.4 A/m以上,矩形比达0.43以上;当纳米纤维直径为75~95 nm时,纳米线的磁各向异性较弱,轴向上矫顽力和矩形比也较小。     

InGaN/GaN多量子阱纳米线发光二极管制备及研究

用SiO2纳米图形层作为模板在以蓝宝石为衬底的n-GaN单晶层上制备了InGaN/GaN多量子阱纳米线,并成功实现了其发光二极管器件(LED).场发射扫描电子显微镜(FESEM)的测量结果表明,InGaN/GaN多量子阱纳米线具有光滑的表面形貌和三角形的剖面结构.室温下阴极射线荧光谱(CL)的测试发现了位于461 nm...     

Fabrication and some applications of large-area silicon field emission arrays

A method of fabricating large-area arrays of sharply-pointed field emitters at densities up to 1·5 × 10⁵ per cm² from single crystal silicon wafers is described. The point emitters are formed by etch-undercutting a precision oxide pattern which is delineated on the silicon surface by projection photolithography. Observations indicate that emitters with very small tip dimensions in the 200Årange are formed. In the presence of an external electric field, such as produced by a voltage applied to a closely-spaced, planar anode, multiple-emitter arrays are shown to field-emit electrons uniformly over areas up to 3 cm dia. Two important applications currently being explored, are discussed: (1) High resistivity, p-Si has been utilized to develop experimental field emission photocathodes with which field emission imaging has been demonstrated. These photoemitters exhibit very high photo-sensitivities at visible and near i.r. wavelengths. For example, at 0·86 μm, the measured quantum efficiency is 25 per cent which is about five-times higher than the red-sensitive S-20 photocathode and comparable to the highest reported sensitivities of the III–V photosurfaces; (2) N-type emitter arrays show considerable promise as high current, cold cathodes and total emission currents of 1/4 A from 1 cm² areas of 100 Ω-cm n-type emitters have been obtained. Measurements were made under pulse conditions because of anode dissipation considerations.     

Characterization and performance evaluation of coupledmultiwaveguide arrays

A new and effective nonintrusive method for characterization of N coupled waveguides is presented. The method is able to furnish readily the coupling parameters of most significance, and furnishes in addition, a way of assessment of overall device quality and performance. The procedure is based on a semi-empirical implementation of coupled mode theory, by means of which different functions are defined for different input configurations. In a well-functioning device, all these function should attain a common single minimum, out of which the coupling coefficient and additional parameters of the device are deduced. Devices were fabricated on Z-cut LiNbO₃ crystals by in-diffusion of titanium. The method was applied in order to measure the wavelength and polarization dependence of the coupling coefficient     

Fabrication of arrays of carbon micro- and nanostructures via electrochemical etching

New methods to pattern and etch a variety of materials are proving to be extremely important owing to the broad impact of microfabrication technology on chemistry and biology. A method, for etching graphitic carbon materials that opens pathways for the creation of arrays of carbon structures, has been developed. The method involves standard photolithographic pattern transfers to a thin carbon film and anodisation of the exposed carbon substrate in basic electrolytes. Structures of various shapes can be fabricated that range in size from tens of microns to submicrons. Arrays of these structures can be fabricated over areas encompassing hundreds of microns with low failure rates. The shape, size and distance between array objects are easily controlled by the fabrication procedure. Scanning electron microscopy is used to visualise the various structures fabricated. The authors show that this technology is useful for the fabrication of microelectrode arrays.     

Fabrication of ECL gate arrays on quick turn-around line

A quick turn-around line (QTL) technology, including a high-speed on-line data system, electron-beam direct writing, and dry process technologies are described in this paper. Electron-beam pattern data is converted by a VAX 11/780 and transmitted to the electron-beam exposure system (EBES) through a communication controller at the speeds of 1 Mbits/s. After various data manipulations, patterns are quickly written directly on wafers. The first metal layer using an Al-Si-Cu alloy is etched in a reactive ion beam etcher with carbon tetrachloride (CCl4). In order to avoid the charge-up phenomenon of the electron beam, the surface of the silicon nitride (SiN) interlevel insulation layer is coated with a thin conductive layer of TiW. TiW/SiN layers are successively etched by the reactive ion etching (RIE) with CF4+ O2(2%). The damage induced by electron-beam irradiation on the device is perfectly annealed out with a 450°C anneal. Bias-temperature tests have been performed on various logic circuits used in a main frame computer.     

Fabrication of periodic square arrays by angle-resolved nanosphere lithography

We investigate the fabrication of periodic square arrays of solid gold islands by angle-resolved nanosphere lithography (ARNSL) in conjunction with thermal evaporation and etching. By varying θ (the tilt angle between the direction of gold deposition beam and the substrate surface normal) and ? (the substrate rotation angle about the beam axis), adjacent islands on a deposited hexagonal gold array will have a constant and periodic difference in height. Upon etching, this height bias will result in the shorter structures being removed to produce an array with a different symmetry from the original hexagonal symmetry of the parent mask. By depositing at three directions of ? = 0°, 120° and −120° with a constant θ = 20°, experimental results show that deposited two-dimensional gold periodic arrays will have a measurable difference in height between adjacent islands. Etching of the resulting patterns produced periodic near-square arrays with triangular nanostructures. Thus the combination of ARNSL and etching can allow selective periodic nanostructures to be removed, increasing the diversity of array symmetries available through nanosphere lithography.     

Fabrication and characterization of Co-Pt nanodot arrays by nanoimprint lithography and electrodeposition

Co-Pt nanodot arrays of 50 nm in diameter and 100 nm pitch were fabricated by nanoimprint lithography and electrodeposition process. A polymer mold used was replicated from a Si master mold with nanopatterns which were fabricated by EBL and ICP-RIE, where hydrophobic surface of these was achieved by FOTS coating. UV-NIL was successfully performed under pressures of 5 MPa for 5 min with an UV exposure time of 30 s, where the substrate was Ru (30 nm)/NiFe (10 nm)/Ta (5 nm)/Si (1 0 0). The size of patterns was measured at 53 nm in diameter, 25 nm in height, 100 nm in pitch. Finally, Co-Pt nanodot arrays were galvanostatically electrodeposited and characterized. The size and the composition of these arrays were measured to be 50 nm in diameter and 100 nm in pitch and Co-23.6 at.% Pt, respectively. According to MFM analysis, these arrays for the remnant states represent a single domain structure of perpendicular direction with a magnetic field, where a field of 15 kOe was applied perpendicular to the sample plane. These results show that for the Co-Pt dot arrays of 50 nm diameter perpendicular magnetic signal can be recorded and switched.     

Fabrication and performance of selectively oxidized vertical-cavitylasers

We report the high yield fabrication and reproducible performance of selectively oxidized vertical-cavity surface emitting lasers. We show that linear oxidation rates of AlGaAs without an induction period allows reproducible fabrication of buried oxide current apertures within monolithic distributed Bragg reflectors. The oxide layers do not induce obvious crystalline defects, and continuous wave operation in excess of 650 h has been obtained. The high yield fabrication enables relatively high laser performance over a wide wavelength span. We observe submilliamp threshold currents over a wavelength range of up to 75 nm, and power conversion efficiencies at 1 mW output power of greater than 20% over a 50-nm wavelength range     

Realization and performance of as-fabricated SGDBR multiwavelengthlaser arrays

For simplifying the fabrication and operation of multiwavelength laser arrays, sampled grating distributed Bragg reflector (SGDBR) lasers are utilized to form the arrays, where the two SGDBR mirrors of each laser are fabricated on waveguides of different thicknesses. Fabrication of such laser arrays requires a single step of holographic exposure to realize the gratings. The lasers in an array can output wavelength combs of narrow wavelength spacing without the necessity of coarse tuning to the mirrors. We demonstrate monolithically integrated 16-wavelength laser arrays of which the wavelengths are aligned to the International Telecommunication Union grid with single-electrode operation     

High performance SWIR HgCdTe detector arrays

Short wave infrared (SWIR) devices have been fabricated using Rockwell’s double layer planar heterostructure (DLPH) architecture with arsenic-ion implanted junctions. Molecular beam epitaxially grown HgCdTe/CdZnTe multilayer structures allowed the thin, tailored device geometries (typical active layer thickness was ∼3.5 μm and cap layer thickness was ∼0.4 μm) to be grown. A planar-mesa geometry that preserved the passivation advantages of the DLPH structure with enhanced optical collection improved the performance. Test detectors showed Band 7 detectors performing near the radiative limit (∼3-5X below theory). Band 5 detector performance was ∼4-50X lower than radiative limited performance, apparently due to Shockley-Hall-Read recombination. We have fabricated SWIR HgCdTe 256 × 12 × 2 arrays of 45 um × 45 μm detector on 45 μm × 60 μm centers and with cutoff wavelength which allows coverage of the Landsat Band 5 (1.5−1.75 μm) and Landsat Band 7 (2.08−2.35 μm) spectral regions. The hybridizable arrays have four subarrays, each having a different detector architecture. One of the Band 7 hybrids has demonstrated performance approaching the radiative theoretical limit for temperatures from 250 to 295K, consistent with test results. D* performance at 250K of the best subarray was high, with an operability of ∼99% at 10¹² cm Hz^1/2/W at a few mV bias. We have observed 1/f noise below 8E-17 AHz ^1/2 at 1 Hz. Also for Band 7 test structures, Ge thin film diffractive microlenses fabricated directly on the back side of the CdZnTe substrate showed the ability to increase the effective collection area of small (nominally <20 μm μm) planar-mesa diodes to the microlens size of 48 urn. Using microlenses allows array performance to exceed 1-D theory up to a factor of 5.     

Fabrication and noise performance of high-power GaAs IMPATTS

Schottky-barrier GaAs IMPATT diodes have been fabrirated in a double epitaxial layer structure on low-etch-pit density substrates. The resulting low defect density in the active region permits high power outputs and low noise measure. Mounted on copper studs and a 20°C heat sink, such diodes have given a maximum CW power output of 2.94 W at 6.1 GHz with 13.8 percent efficiency. The small-signal amplifier noise measure was 25dB. Operated as injection-locked oscillators, the noise measure was 32 dB at an output of 1 W. These results show that in a suitable structure, GaAs can surpass the efficiency and noise performance of other materials, and demonstrate the capability of high power output in this frequency band.     

Fabrication and performance of strip-centered microminiature coaxial cable

This letter presents a new design in flexible microminiature coaxial cable. A discussion of performance and method of fabrication is given, and experimental data are compared to a simple theoretical model.     

Fabrication of high-packing-density vertical cavity surface-emitting laser arrays using selective oxidation

We describe the nearly-planar processing of two-dimensional vertical cavity laser arrays based on the selective conversion of AlAs to Al/sub x/O/sub y/. The individual lasers of 8/spl times/8 and 2/spl times/2 arrays are defined by native Al/sub x/O/sub y/ to achieve 4-/spl mu/m square active regions on 12-/spl mu/m center-to-center spacings. Interelement thermal coupling is characterized along with the optical mode structure.     

Fabrication of microlens arrays using UV micro-stamping with soft roller and gas-pressurized platform

The conformal contact between the roller stamper and the thin flexible substrate is important for precisive replication of microstructures. In this study, we have proposed a novel mechanism which employs a soft roller stamper and a gas-pressurized platform to fabricate UV-cured polymeric microlens arrays on a continuous flexible substrate. The new facilities constructed in this study comprise a polydimethylsiloxane (PDMS) stamping roller, a gas-pressurized platform and an UV light source underneath the platform. The soft roller was made by casting a pre-polymer of PDMS in a plastic master of microlens array. During the rolling micro-stamping process, the microlens array cavity on the soft roller is first filled with liquid UV-curable resin. The roller stamper then rolls and stamps over the moving transparent thin polymeric substrate which is located on the gas-pressurized platform. At the same time, the UV light irradiates beneath the platform and cures the resin in the rolling zone. Thus, the microlens array patterns are successfully fabricated. The dimensions of the microlens are 115.5 μm in diameter, of, a sag height of 7.88 μm in sag height, and 200 μm in pitch size. This method developed in this work clearly demonstrates its potential of using the soft mold and the gas-pressurized platform for continuous mass production of films with microstructural patterns.     

Effects of electronic current overflow and inhomogeneous carrier distribution on InGaN quantum-well laser performance

Laser performance of several InGaN quantum-well (QW) lasers with an emission wavelength of 392-461 nm are numerically studied with a LASTIP simulation program. Specifically, the effects of electronic current overflow and inhomogeneous carrier distribution on the laser performance of InGaN QW lasers operating at different wavelengths are investigated. Simulation results indicate that the use of an AlGaN blocking layer can help reduce the electronic current overflow and, in addition to the dissociation of the InGaN well layer at a high growth temperature during crystal growth, the inhomogeneous carrier distribution in the QWs also plays an important role in the laser performance. From the simulation results, we conclude that the lowest threshold current density is obtained when the number of InGaN well layers is two if the emission wavelength is shorter than 427 nm and one if the emission wavelength is longer than 427 nm, which are in good agreement with the results observed by Nakamura et al. in their experiments.     

Exciton wavefunction coupled surface plasmon resonance for In-rich InGaN film with perforated aluminum cylindrical micropillar arrays

The optical characterization of excitons coupled with surface plasmon resonance (SPR) for InGaN/GaN heterostructures with perforated cylindrical micropillar arrays is investigated. We analyze the optical characteristics of excitons coupled with SPR for InGaN/GaN heterostructures with perforated cylindrical micropillars, as shown in measurements of the photoluminescence (PL) spectra over a broad range of temperatures between 20 and 300 K. From the temperature-dependent PL spectra, we observe the better SPR coupling effects, resulting in less carrier confinement in the InGaN energy band. The magnitude of the redshift of the emission peak shown by the sample with the coated aluminum (Al) pattern is larger than that shown by the sample with no metal film. This was due to the presence of more exciton coupling surface plasmons within the Al/InGaN interface. The enhancement of the PL intensity of the sample with the deposited Al pattern film can be attributed to a stronger SPR coupling interaction with the excitons. The experimental results indicate that a perforated Al cylindrical micropillar array can significantly affect carrier confinement, enhancing the quantum efficiency of Al/In-rich InGaN heterostructures due to the interaction of the SPR coupling effect between the InGaN quantum dot-like region and the Al film.