III-V Nitride Based Micro and Nanoscale Sensors

Dr. Goutam Koley, an Associate Professor from the University of South Carolina, presented a lecture at the Nano@Tech Meeting on March 8, 2011 at 12 noon in room 1116 of the Marcus Nanotechnology Building.Dr. Goutam Koley received his B. Tech. degree from the Indian Institute of Technology, Kharagpur, in 1998, and M.S. degree from the University of Massachusetts, Lowell, in 1999, and Ph.D. degree from Cornell University, Ithaca, New York in 2003. He then joined the department of Electrical Engineering at the University of South Carolina where he is currently an Associate Professor. His current research interests include MEMS and NEMS based sensors, bio-implantable sensors, nanoelectronic devices, and scanning probe microscopy. Dr. Koley won the prestigious National Science Foundation CAREER Award in 2009, and he has been nominated as a Rising Star of the University of South Carolina System for 2011. He has authored or co-authored more than 53 journal articles and conference proceedings, 40 conference presentations, and one book chapter. His research has resulted in 4 invention disclosures and 2 pending patents. He is a co-founder and shareholder of 2 companies, Widetronix, Inc. and SENS4, Inc. He is a senior member of the IEEE and a nominated member of the TMS.Runtime: 62:54 minutesStructural, mechanical, and sensing properties of InN nanowires (NWs) grown by chemical vapor deposition process have been investigated for their applications in nanoscale sensors. It has been observed that the NWs bend spontaneously or upon meeting an obstacle in their growth path at angles that are multiples of 30°. Lithographically patterned barriers served as guides for the NW growth, which depending on the angle of incidence of the NW, made them grow along the barrier or get deflected from it. Diameter dependent electrical properties of InN nanowires (NWs) grown by chemical vapor deposition were also investigated. InN NW based back-gated field effect transistors (FETs) showed excellent gate control and drain current saturation behaviors. Both NW conductance and carrier mobility calculated from the FET characteristics were found to increase regularly with decrease in NW diameter, with values of ~1000 cm²/Vs and ~1050 S/cm, observed respectively, for a 12 nm diameter NW. The observed mobility and conductivity variations have been modeled by considering NW surface and core conduction paths. InN NWs grown with thick In₂O₃ shell layer demonstrated NO₂ detection capability down to 45 ppb in a field effect transistor configuration. Overall, the structural and electrical properties of the NWs are found to be highly suitable for applications in nanoscale sensors and nanoelectromechanical systems. AlGaN/GaN heterostructure based microcantilever sensors on Si (111) substrate are also being developed at USC for harsh environment sensing applications. Initial fabrication and characterization results indicate very high sensitivity for these sensors