Electrochemical redox cycling in a new nanogap sensor:Design and simulation

We propose a new geometry for nanogap electrochemical sensing devices. These devices consist of two closely spaced side-by-side electrodes which work under redox cycling conditions. Using finite element simulations, we investigate the effects of different geometric parameters on the redox cycling signal amplification to gain insight into the electrochemical sensing performance of the device design. This will allow optimizing the sensor performance of devices to be fabricated in the future. (C) 2015 Elsevier B.V. All rights reserved

Si-C Linked Organic Monolayers on Crystalline Silicon Surfaces as Alternative Gate Insulators

Herein, the influence of silicon surface modification via Si-CnH2n+1 (n=10,12,16,22) monolayer-based devices on p-type (100) and n-type (100) silicon is studied by forming MIS (metal–insulator–semiconductor) diodes using a mercury probe. From current density–voltage (J–V) and capacitance–voltage (C–V) measurements, the relevant parameters describing the electrical behavior of these diodes are derived, such as the diode ideality factor, the effective barrier height, the flatband voltage, the barrier height, the monolayer dielectric constant, the tunneling attenuation factor, and the fixed charge density (Nf). It is shown that the J–V behavior of our MIS structures could be precisely tuned via the monolayer thickness. The use of n-type silicon resulted in lower diode ideality factors as compared to p-type silicon. A similar flatband voltage, independent of monolayer thickness, was found, indicating similar properties for all silicon–monolayer interfaces. An exception was the C10-based monolayer device on p-type silicon. Furthermore, low values of Nf were\ud found for monolayers on p-type silicon (=6A1011 cm-2). These results suggest that SiClinked monolayers on flat silicon may be a viable material for future electronic devices

Impedance spectroscopy and surface study of potassium-selective silicone rubber membranes

Impedance spectroscopy measurements of silicone rubber membranes containing potassium-selective neutral carriers are reported. Two types of silicone rubbers are studied viz. the commercially available Siloprene and a novel copolymer, that was synthesized for application on Ion-Sensitive Field Effect Transistors (ISFETs). Three different potassium-selective ionophores have been studied, the natural ionophore, valinomycin, and two hemispherand type ionophores. One of the hemispherands can be covalently bonded to the polysiloxane copolymer matrix. The bulk resistance of the valinomycin containing membranes was found to be dependent on the contacting electrolyte solution. The K+/Na+ selectivity of the membrane is reflected in the behavior of the bulk resistance. The presence of a surface film on Siloprene membranes reported in the literature is confirmed. A surface study revealed the presence of small droplets exuded by the Siloprene membrane. The copolymer seems not to suffer from the presence of a surface film