Fabrication of organic semiconductor crystalline thin films and crystals from solution by confined crystallization

Highly crystalline thin films of organic semiconductors processed from solution for electronic devices are difficult to achieve due to a slow and preferential three-dimensional growth of the crystals. Here we describe the development of a processing technique to induce a preferential two-dimensional crystalline growth of organic semiconductors by means of minimizing one dimension and confining the solution in two dimensions into a thin layer. The versatility of the process is demonstrated by processing small molecules (TIPS-pentacene and C₆₀) and a polymer (P3HT), all from solvents with a relatively low boiling point, to obtain crystalline thin films. The thin films show an improved in-plane packing of the molecules compared to films processed under similar conditions by spin coating, which is beneficial for the use in organic field-effect transistors.     

A Universal VLSI Architecture for Reed–Solomon Error-and-Erasure Decoders

This paper presents a universal architecture for Reed-Solomon (RS) error-and-erasure decoder. In comparison with other reconfigurable RS decoders, our universal approach based on Montgomery multiplication algorithm can support not only arbitrary block length but various finite-field degree within different irreducible polynomials. Moreover, the decoder design also features the constant multipliers in the universal syndrome calculator and Chien search block, as well as an on-the-fly inversion table for calculating error or errata values. After implemented with 0.18-mum 1P6M technology, the proposed universal RS decoder correcting up to 16 errors can be measured to reach a maximum 1.28 Gb/s data rate at 160 MHz. The total gates count is around 46.4 K with 1.21 mm² silicon area, and the average core power consumption is 68.1 mW.     

Miniband properties of superlattice quantum dot arrays fabricated by the edge-defined nanowires

A new scheme to fabricate quantum dot arrays using the edge-defined nanowires is proposed. The three-dimensional quantum size effect due to the nanowire crossing was analyzed by using the finite-difference method taking into account the periodic nature of the superlattices. The quantum dot modes were graphically verified, and the miniband gap between quantum dot and quantum wire modes was quantitatively analyzed.     

Investigation of Sn Whisker Growth in Electroplated Sn and Sn-Ag as a Function of Plating Variables and Storage Conditions

Sn whiskers are becoming a serious reliability issue in Pb-free electronic packaging applications. Among the numerous Sn whisker mitigation strategies, minor alloying additions to Sn have been proven effective. In this study, several commercial Sn and Sn-Ag baths of low-whisker formulations are evaluated to develop optimum mitigation strategies for electroplated Sn and Sn-Ag. The effects of plating variables and storage conditions, including plating thickness and current density, on Sn whisker growth are investigated for matte Sn, matte Sn-Ag, and bright Sn-Ag electroplated on a Si substrate. Two different storage conditions are applied: an ambient condition (30°C, dry air) and a high-temperature/high-humidity condition (55°C, 85% relative humidity). Scanning electron microscopy is employed to record the Sn whisker growth history of each sample up to 4000 h. Transmission electron microscopy, x-ray diffraction, and focused ion beam techniques are used to understand the microstructure, the formation of intermetallic compounds (IMCs), oxidation, the Sn whisker growth mechanism, and other features. In this study, it is found that whiskers are observed only under ambient conditions for both thin and thick samples regardless of the current density variations for matte Sn. However, whiskers are not observed on Sn-Ag-plated surfaces due to the equiaxed grains and fine Ag₃Sn IMCs located at grain boundaries. In addition, Sn whiskers can be suppressed under the high-temperature/high-humidity conditions due to the random growth of IMCs and the formation of thick oxide layers.     

Slot-fed higher order mode Fabry-Perot filters

Low-loss bandpass filters consisting of Fabry-Perot resonators excited by waveguide-fed slots coupling to higher-order resonator modes are demonstrated. For close reflector spacings, the waveguide couples efficiently through the slots to the TEM₄₀₀ and TEM₃₀₀ modes. The characteristics of both rectangular and circular waveguide feeds with various slot lengths and widths are presented. At X-band the filters have unloaded Q values which range from 1000 to 7000 with insertion losses less than 1 dB. The filters which have the rectangular waveguide feeds are mechanically tunable over a 20% bandwidth     

Increased linear dynamic range by low biasing the Mach-Zehndermodulator

Operating a Mach-Zehnder modulator at an optical bias below the conventional 50% (quadrature) bias is investigated. Theoretical distortion curves as a function of bias have been calculated and experimentally verified. These curves show that (single octave) linear dynamic range increases as the bias is lowered, so long as optical power at the detector can be maintained just below the saturation level or laser noise limit. This method thus provides a way for very large optical power to be used to benefit linear dynamic range. Theoretically, 20 dB of excess optical power, attenuated through low biasing, can result in an increase in linear dynamic range of 15 dB     

Partial adaptive nulling on a monopulse phased array antenna system

A partial phase-only nulling (PPON) algorithm has been developed and evaluated on a 496-element monopulse phased array antenna system which employs five-bit phase shifters. Using this PPON algorithm allows nulls in the far-field pattern to be steered to the desired directions for a phased array equipped with low-resolution phase shifters to perform simultaneous nulling in the sum and two difference patterns in the environment of multiple jammers. Simulated and experimental patterns are illustrated     

Fiber transmission for sub-500-fs pulses using adispersion-compensating fiber

We report transmission of ~60-fs and ~245-fs pulses, respectively, over 42-m and 2.5-km fiber links which consist of standard single-mode fibers (SMF) concatenated with dispersion-compensating fibers (DCF). The experiments using very short pulses (~60 fs) over a short fiber length (~42 m) demonstrate the ability to achieve simultaneous dispersion and dispersion slope compensation using this technique. Femtosecond spectral interferometry measurements of this 42-m link show that its residual dispersion slope is approximately six times lower than that of the dispersion-shifted fiber. Finally, to demonstrate that the dispersion-limited propagation distance is proportional to the cube of the pulsewidth, we transmit ~245-fs pulses over a 2.5-km SMF-DCF link and achieve comparable pulse restoration as with the shorter fiber experiments