Michael Goryll

Electroluminescence of strained SiGe/Si selectively grown above the critical thickness for plastic relaxation

Electroluminescence of strained Si0.80Ge0.20/Si(001) pin diodes has been investigated experimentally and by quantitative modeling. The key aspect of this investigation was that by selective epitaxial growth the experimental critical thickness for plastic relaxation (80 nm at Tepi=700 °C and large areas) could be increased in finite pads. SiGe layers with thickness of 60, 72 or 370 nm have been grown within the intrinsic i region of pin structures. Samples free of misfit dislocations revealed electroluminescence with the SiGe no-phonon peak and its transversal optical–phonon replica corresponding to interband transitions. It was found that by increasing the thickness of the SiGe layer the drop in the electroluminescence with increasing temperature could be shifted to higher temperature, so that for the 370 nm thick SiGe sample the emission was observed to persist still at 300 K. Modeling based on drift-diffusion and carrier recombination equations was used to simulate the current–voltage characteristics of...

Field effect modulation of ionic conductance of cylindrical silicon-on-insulator nanopore array

Results demonstrating the field effect modulation of ionic transport through an array of cylindrical nanopores fabricated in silicon-on-insulator substrates are presented. Pronounced modulation of the conductance is observed at low electrolyte concentrations when the electric double layers within the nanopores are overlapping. A numerical model based on Brownian dynamics reproduces the measured data.

Teflon™-coated silicon apertures for supported lipid bilayer membranes

We present a method for microfabricating apertures in a silicon substrate using well-known cleanroom technologies resulting in highly reproducible giga-seal resistance bilayer formations. Using a plasma etcher, 150μm apertures have been etched through a silicon wafer. Teflon™ has been chemically vapor deposited so that the surface resembles bulk Teflon and is hydrophobic. After fabrication, reproducible high resistance bilayers were formed and characteristic measurements of a self-inserted single OmpF porin ion channel protein were made.

Flexible ISFET Biosensor Using IGZO Metal Oxide TFTs and an ITO Sensing Layer

This letter presents the fabrication details and measured performance of a prototype flexible extended-gate ion-sensitive field effect transistor (ISFET) biosensor, manufactured using a metal oxide indium-gallium-zinc oxide thin film transistor and an indium-tin oxide sensing layer on a 125- μm thick flexible plastic substrate. ISFET drain current was shown to respond correctly to the pH buffer concentration with repeatable pH sensitivity observed over multiple cycles. These results demonstrate the initial viability of directly extending flexible plastic substrate organic light emitting diode display technology to the production of low-cost, plastic ISFET biosensors.

Structural and optical properties of Ge islands grown in an industrial chemical vapor deposition reactor

The use of Si based materials for optoelectronic applications is hampered by the indirect nature of the band gap. One possible solution by which to improve the radiative light emission is three-dimensional Stranski–Krastanow growth of Si1−xGex or pure Ge on top of Si. In this article we give a detailed overview about the growth kinetics observed for Ge growth in a standard production oriented chemical vapor deposition system. With increasing deposition time, we observed the usual changeover from monomodal to bimodal island distribution. The island morphology and density can be controlled by varying the growth conditions or by applying a thermal anneal after island growth. Island densities up to 2.3×1010 cm−2 have been obtained for depositions at 650 °C. A Si cap layer is needed for photoluminescence measurements as well as for some device structures. However, Si capping at 700 °C leads to nearly total dissolution of small islands and truncation of bigger dome-shaped islands. This can be prevented by reduc...

Study of dopant activation in biaxially compressively strained SiGe layers using excimer laser annealing

Excimer Laser Annealing (ELA) with a wavelength of 248 nm is used to study doping of biaxialy compressively strained Si1−xGex/Si heterostructures. The challenge is to achieve a high activation of As in SiGe, while conserving the elastic strain and suppressing dopant diffusion. Doping of 20 nm Si0.64Ge0.36 layers by ion implantation of 1 × 1015 As+/cm2 and subsequent laser annealing using single 20 ns pulse with an energy density of 0.6 J/cm2 leads to an As activation of about 20% and a sheet resistance of 650 Ω/sq. At this laser energy density, the entire SiGe layer melts and the subsequent fast recrystallization on a nanosecond time scale allows high As incorporation into the lattice. Moreover, using these annealing parameters, the SiGe layer exhibits epitaxial regrowth with negligible strain relaxation. ELA at energy densities greater than 0.6 J/cm2 resembles Pulsed Lased Induced Epitaxy, leading to an intermixing of the SiGe layer with the Si substrate, thus to thicker single-crystalline strained SiGe ...

Transform domain features for ion-channel signal classification

The study of the behavior of ion-channels can provide significant information to detect metal ions and small organic molecules in solution. Discrimination of different analytes can be performed by extracting appropriate features from the ion-channel signals and using them for classification. In this paper, we consider features extracted from the Fourier, Wavelet and Walsh-Hadamard domain representations of the ion-channel signals. The proposed approach uses the power distribution information in the transform domains as features for discrimination. We compare the performance of all the three sets of features using support vector machines for classification of analytes and present the results. Results obtained show that the transform domain features achieve high classification rates in addition to high sensitivity and specificity rates.

Optimization of Flexible Ag-Chalcogenide Glass Sensors for Radiation Detection

We demonstrate how the radiation response and performance of Ag-chalcogenide glass radiation sensors fabricated on a flexible substrate can be optimized by modifications of spacing between electrodes.

Ion channel sensor on a silicon support

We are building a biosensor based on ion channels inserted into lipid bilayers that are suspended across an aperture in silicon. The process flow only involves conventional optical lithography and deep Si reactive ion etching to create micromachined apertures in a silicon wafer. In order to provide surface properties for lipid bilayer attachment that are similar to those of the fluorocarbon films that are currently used, we coated the silicon surface with a fluoropolymer using plasma-assisted chemical vapor deposition. When compared with the surface treatment methods using self-assembled monolayers of fluorocarbon chemicals, this novel approach towards modifying the wettability of a silicon dioxide surface provides an easy and fast method for subsequent lipid bilayer formation. Current-Voltage measurements on OmpF ion channels incorporated into these membranes show the voltage dependent gating action expected from a working porin ion channel.

Investigation into Pseudo-Capacitance Behavior of Glycoside-Containing Hydrogels

Electrochemical pseudocapacitors are an attractive choice for energy storage applications because they offer higher energy densities than electrostatic or electric double layer capacitors. They also offer higher power densities in shorter durations of time, as compared to batteries. Recent efforts on pseudocapacitors include biocompatible hydrogel electrolytes and transition metal electrodes for implantable energy storage applications. Pseudocapacitive behavior in these devices has been attributed to the redox reactions that occur within the electric double layer, which is formed at the electrode-electrolyte interface. In the present study, we describe a detailed investigation on redox reactions responsible for pseudocapacitive behavior in glycoside-containing hydrogel formulations. Pseudocapacitive behavior was compared among various combinations of biocompatible hydrogel electrolytes, using carbon tape electrodes and transition metal electrodes based on fluorine-doped tin oxide. The hydrogels demonstrated a pseudocapacitive response only in the presence of transition metal electrodes but not in the presence of carbon electrodes. Hydrogels containing amine moieties showed greater energy storage than gels based purely on hydroxyl functional groups. Furthermore, energy storage increased with greater amine content in these hydrogels. We claim that the redox reactions in hydrogels are largely based on Lewis acid-base interactions, facilitated by amine and hydroxyl side groups along the electrolyte chain backbones, as well as hydroxylation of electrode surfaces. Water plays an important role in these reactions, not only in terms of providing ionic radicals but also in assisting ion transport. This understanding of redox reactions will help determine the choice of transition metal electrodes, Lewis acid-base pairs in electrolytes, and medium for ionic transport in future biocompatible pseudocapacitors.