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Electric Field Driven Conductance Switching in Single Molecules We study single molecule conductance switching using the electric field between an scanning tunneling microscope (STM) tip and a gold substrate. Thus far, we have shown that conductance switching can be observed in vertically aligned tunnel junctions formed by porphyrin molecules ligating a zinc atom. Typically, conductance switching has been observed in porphyrin molecules, which adopted a configuration parallel to the substrate. Realizing how one can manipulate the electrical properties of such molecules can be essential in controlling the overall functionality of a molecular device when it is wired in a circuit. To this extent, such molecular junctions can be exploited in simple circuits to act as molecular switches or memory elements. Additional research topics include investigating reversible switching in porphyrin molecules and alternative methods to power and control conductance switching in molecular circuits through the use of external stimuli. Design and Characterization of a Multifunctional Chemiresistor Sensor Array We are designing a multifunctional chemiresistor sensor array which integrates a variety of preselected functionalized gold (Au) nanoparticles and supersensitive electrometers. This device will enable simultaneous detection of different volatile organic compounds (VOCs) on a single chip. In this device the nanoparticle acts as a transducer by converting the sorption of the organic vapor into an electrical signal. Currently, we are characterizing more than 50 devices, which have been fabricated from GaN/AlN system. A computer program is currently being written to control the number and placement of the gold nanoparticles (i.e. the sensing element) on each device. Future steps include a home-build vapor testing system and the use of atomic force microscopy to characterize the chemiresistor sensor array. This work is funded by the National Science Foundation as a part of the American Recovery & Reinvestment Act (AARA) of 2009. Find out more information at www.recovery.gov.
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