Si Nanowire Location and Growth Direction Control Enabling Both Nanowire MOSFET Fabrication and Resonant Chemical Sensing

ChEMS Seminar

Featuring Nate Quitoriano, Ph.D.
Hewlett-Packard Laboratory

Location: 1300 Donald Bren Hall
Free and open to the public

Abstract:
Semiconducting nanowires (NWs) have promising properties suggesting future use in electronic, optical, and sensing applications.  Despite these promising properties, significant problems in controlling NW location and growth direction to integrate NWs into practical devices limit their potential.  Because of these problems, most work demonstrating promising NW properties has focused on growing NWs on one substrate, removing them and then placing them on another device substrate.  Alternatively, the NWs can be grown in-place, in a pre-defined location, enabling future device fabrication and integration.  For some applications, like integration with logic or other devices, we believe this latter method is preferred and we report progress in controlling the location and growth direction of NWs. 

In this talk we present results on guiding NW growth by growing VLS NWs against the buried-oxide layer of a silicon-on-insulator (SOI) substrate.  Using a (001) SOI substrate, we can grow NWs in <110> directions against the substrate surface.  Growth against the substrate surface enabled straightforward subsequent top-gated, metal-oxide-semiconductor, field-effect transistor (MOSFET) fabrication to demonstrate NW FETs exhibiting an Ion/Ioff ratio ~10,000 and a subthreshold slope of ~150 mV/decade.  Using this structure, NWs grown in a predefined location in contact with the surface were more robust to further processing and could be integrated with other NW or logic devices.  In addition to the device results, we also discuss the structure and mechanism of this type of growth and how these surface NWs could be used as a chemical sensor in a micro-fluidic channels.  We also discuss exciting results using NWs as differential-mass, resonant sensors.  Using NWs as resonant sensors, we functionalized the NWs by binding biotin to them and used these biotinilated NWs to detect the presence of streptavidin.

About the Speaker:
In 2000, Nate Quitoriano received his bachelor's degrees in electrical engineering and computer science and materials science engineering from the University of California, Berkeley, and did research with Professor Tim Sands on an ohmic, transient-liquid-phase bond for semiconductors.  Quitoriano received his Ph.D. in materials science engineering at the Massachusetts Institute of Technology under the supervision of Gene Fitzgerald and worked on III-V, lattice-mismatched semiconductors.  After that, he worked in Stan William's group at Hewlett-Packard Laboratories under the direction of Ted Kamins, where he studied Si and Ge nanowires for use as sensors and electrical devices.