Dissertation/Thesis Abstract

Semiconductor nanowires for nanoelectronics and optoelectronics
by Dong, Yajie, Ph.D., Harvard University, 2010, 104; 3415413
Abstract (Summary)

Nanowires (NWs) have been acting as exciting platforms for nanoscience and nanotechnology research. This thesis presents study of semiconductor nanowires as platforms for exploring fundamental electronic properties and realizing novel device concepts of nanoelectronics and optoelectronics, with potential applications in information and energy technologies.

First, we focus on the discovery of high performance nonvolatile switch effect in crystalline silicon/amorphous silicon core/shell NWs X metal NW (Si/a-Si X M) crossbar devices. Room-temperature electrical measurements on single device exhibit bistable switching between high (off) and low (on) resistance states with well-defined switching threshold voltages, on/off ratios greater than 104, and current rectification in the on state. Contact area dependence and temperature-dependent characterization reveal the physical origin of the switch. Nonvolatile memory performance tests show that (i) the bit size can be at least as small as 20 nm X 20 nm, (ii) the writing time is <100 ns, (iii) the retention time is >2 weeks, and (iv) devices can be switched >104 times without degradation in performance. The scalability and flexibility of the switch have been demonstrated by fabricating working dense one-dimensional and two-dimensional Si/a-Si X Ag NW device arrays on both crystalline Si and plastic substrates.

Next, we discuss the experimental realizations of photovoltaic (PV) and microwave electronics devices using coaxial III-nitride nanowires with either n-GaN/i-InxGa1-xN/p-GaN or GaN/AlN/AlGaN core/shell/shell structures. Dark current-voltage (I-V) characterization of the former devices shows clear diode characteristics with tunable composition. Light I-V under simulated white light and UV light yields promising PV performance and demonstrates them as a powerful platform for exploring nano-enabled PVs. Promising microwave performances have been obtained with the later devices.

Furthermore, we describe a universal strategy for compound semiconductor nanostructures epitaxial growth which could find potential applications for energy conversion. The epitaxy mechanism has been discussed within a simple thermodynamics versus kinetics physical picture and ordered vertical and oriented nanowire arrays of a variety of II-VI, IV-VI and III-nitride compound semiconductors have been grown out to demonstrate the concept.

Lastly, we present our work on single nanowire batteries with a simple design. These smallest electrical energy storage devices have been taken as a platform to push the fundamental limits of the nanowire materials for battery applications and meanwhile explore their potential as power sources for nanoelectronics devices.

Indexing (document details)
Advisor: Lieber, Charles M.
School: Harvard University
School Location: United States -- Massachusetts
Source: DAI-B 71/07, Dissertation Abstracts International
Subjects: Physical chemistry, Nanotechnology, Materials science
Keywords: Nanoelectronics, Nanowires, Optoelectronics, Photovoltaics, Semiconductors
Publication Number: 3415413
ISBN: 9781124090931
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