M.K. Rabinal

Simple setup to measure electrical properties of polymeric films

A simple method to measure electrical conductivity of conducting organic films has been described. A setup, based on four-probe technique, is specifically designed and fabricated for nondestructive electrical conductivity measurements of freestanding thin films. The current-voltage and temperature dependent characteristics of thin films of polyethylenedioxythiophene and polypyrrole and thick wafers of germanium have been used to test the setup. The results obtained are highly reproducible and are in good agreement with the reported values in the literature, employing different techniques.

Electrical characterization of a phenylacetylene-modified silicon surface via mercury probe

The influence of phenylacetylene molecules on a silicon (100) surface has been investigated by formation of metal–molecule–semiconductor junctions with soft mercury contacts. Molecules are bonded covalently to the semiconductor surface via Si–C bonds by thermochemical reaction. The chemical bonding of these molecules is confirmed by XPS measurements. Current–voltage and capacitance–voltage curves were recorded under dark and light on these junctions to understand the role of the organic molecules. Junctions with phenylacetylene molecules are more ideal, with an extra density of surface states which are responsible for quenching photoconductivity. The presence of surface states is reflected as well-defined peaks in low frequency photocapacitance curves.

A Simple and Portable Setup for Thermopower Measurements.

Thermoelectric energy conversion technology has received significant attention because of its promising applications and environmentally clean nature. The innovative design of efficient thermoelectric materials is assisted by simple and reliable techniques for fast and accurate testing. Here, a simple approach for rapid measurement of the Seebeck coefficient is described using commonly available materials based on hot and cold probes; both probes are heated by built-in microheaters. A spring-loaded sample mounting arrangement provides easy sample loading/unloading. The setup is suitable for measurements on a wide range of materials, such as pellets, films, and even soft surfaces without damage. Several known thermoelectric materials, such as alumel, bismuth, and silicon, yielded values close to reported ones. The setup is very compact, simple, fast, low cost, and reliable to develop as a laboratory characterization tool.

Large-scale synthesis of copper sulfide by using elemental sources via simple chemical route

Copper sulfide is a low-cost and non-toxic material which is very attractive and promising for various applications. There is a need of a large-scale production of this material by simple methods. Here, a simple and ambient method is proposed for a large-scale preparation of copper sulfide. The synthesis is carried out at room temperature by using ultrasonication method where the elemental precursors, copper and sulfur are directly used. The present method gives gram scale synthesis with high yield in a short period of time. The materials are characterized by different techniques, their electrical conductivity and Seebeck coefficient are also measured and analyzed. The present method is one of the simple ways of producing copper sulfide just at room temperature.

Soft electrical contacts for conductivity measurements of molecularly modified surfaces

A portable conductivity setup, using soft electrical contacts, is proposed to measure the charge transport properties of molecularly modified solid surfaces. The present technique facilitates the conductivity measurements of both single and back-to-back metal?semiconductor junctions formed on soft matter using liquid mercury columns as electrical contacts. The utility of the above setup is demonstrated for back-to-back junctions using bare and chemically modified silicon surfaces with organic molecules belonging to ethynylbenzene (EBZ) series. The measured conductivity is found to be very sensitive to the dipole moment of bonded organic molecules.

A simple dip coat patterning of aluminum oxide to constitute a bistable memristor

Charge transport studies on a bipolar resistive random access memory device based on aluminum oxide were successfully undertaken. The device was designed in a simple metal–insulator–metal format, which was characterized in detail for structural, morphological and electrical measurements. A low cost technique has been adopted for the formation of the memristive element, exhibiting three orders of magnitude change between its two states of conductivity. The obtained memristive behavior is explained based on evidence obtained from charge transport characteristics. Formation/rupture of the conducting filament by external electric field is found to be the main mechanism behind resistive switching.

A facile synthesis of metal nanoparticle - graphene composites for better absorption of solar radiation

Herein, a facile chemical approach has been adopted to prepare silver nanoparticles (AgNPs)- graphene (G) composite to study photothermal effect. Sodium borohydride (SBH), a strong reducing agent has been selected for this work. Effect of SBH concentrations on optical behavior of AgNPs-G composite was also investigated. Resultant materials were characterized by various techniques including X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), optical absorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM micrographs confirm wrapping of AgNPs into graphene whereas XRD analysis reveals their particle size variation between 47 nm to 69 nm. Optical studies throw a light on their strong absorption behavior towards solar radiation.