Ali Javey (Advisor)

Research Advised by Professor Ali Javey

BPN525: Hybrid Core-Multishell Nanowire Forests for Electrical Connector Applications

Rehan Kapadia
2010

Electrical connectors based on hybrid core-multishell nanowire forests that require low engagement forces are demonstrated. The physical binding and electrical connectivity of the nanowire electrical connectors arise from the van der Waals interactions between the conductive metallic shells of the engaged nanowire forests. Specifically, the nanofibrillar structure of the connectors causes an amplification of the contact area between the interpenetrating nanowire arrays, resulting in strong adhesion with relatively low interfacial resistance. The nanowire electrical connectors may...

BPN526: Semiconducting Nanopillars for Photodiodes

Rehan R. Kapadia
Zhiyong Fan
Daniel Ruebusch
2010

The ability to grow high-quality, vertically oriented, single-crystalline nanopillar arrays non-epitaxially enables the fabrication of novel and potentially highly-efficient opto-electronic devices on arbitrary substrates. This project aims to exploit the optical and electronic properties of these structures to fabricate highly sensitive photodiodes on low-cost substrates. In addition, photodiodes will be fabricated from multiple semiconductor materials to explore devices sensitive to different wavelength ranges.

Project end date: 08/09/10

BPN532: Sub-5 nm-wide Junction Formation by Monolayer Doping

Hui Fang
Kuniharu Takei
Johnny Ho
2010

We have previously created a new doping method of semiconductor-monolayer doping (MLD). This method can fulfill the need of the shrinking size of devices by making ultra shallow junctions. More importantly, it causes much less lattice damage in the crystal than conventional ion-implantation technique. In this project, we are going to apply MLD to sub-5 nm-wide patterned lines (by the e-beam lithography), which is very essential to achieve future nanoscale VLSI. The doping profile will be characterized by C-V measurement.

Project end date: 08/10/10

BPN527: Materials Development for Nanopillar Array Photovoltaics

Daniel J. Ruebusch
Rehan R. Kapadia
Zhiyong Fan
Xiaobo Zhang
2010

We have previously demonstrated a first generation solar cell employing an array of vertically oriented and spatially ordered n-CdS nanopillars (NPLs) embedded in a p-CdTe film. The single crystal NPLs are grown by a Au catalyzed vapor-liquid-solid (VLS) process that is compatible with a wide range of materials systems. We seek to expand the design space of our solar cells by developing and integrating promising NPL materials. Successfully grown NPLs will be characterized and ultimately integrated into complete solar cells.

Project end date: 08/11/10

BPN601: Strain Engineering of Epitaxially Transferred, Ultrathin Layers of III-V Semiconductor on Insulator

Hui Fang
Morten Madsen
Kuniharu Takei
Ha Sul Kim
2011

Strain state of ultrathin InAs-on-insulator layers obtained from an epitaxial transfer process is studied. The as-grown InAs epilayer (10¨C20 nm thick) on the GaSb/AlGaSb source wafer has the expected ~0.62% tensile strain. The strain is found to fully release during the epitaxial transfer of the InAs layer onto a Si/SiO2 substrate. In order to engineer the strain of the transferred InAs layers, a ZrOx cap was used during the transfer process to effectively preserve the strain. The work presents an important advance toward the control of materials properties of III-V on insulator...

BPN588: Direct Bonding of Ultra-Thin InAs on SiO2 for High Performance Transistors

Morten Madsen
Kuniharu Takei
Hui Fang
2010

In the past years, integration of III-V materials on Si have been thoroughly investigated, in order to combine the well establish, low cost, processing of the Si technology with the high mobility of III-V semiconductors for high performance electron devices. In this work, direct bonding of InAs nanoribbons on Si/SiO2 (XOI) is proposed as a method for obtaining high performance nanoscale transistors with clean and purely inorganic interfaces between InAs and SiO2.

Project end date: 02/03/11

BPN531: Gigahertz Operation of Flexible Transistors Using InAs Nanomaterial Arrays

Toshitake Takahashi
Kuniharu Takei
2011

In this project, we present NW-based high frequency flexible transistors operating in gigahertz regime. InAs NWs are printed on polyimide (PI) substrate with contact printing method, in which semiconducting NWs on the growth chip can be directly transferred to and aligned on the receiver substrate. Thus fabricated NW-based devices have ft = 1.04 GHz (unit transit frequency of the current gain) and fmax = 1.8 GHz (maximum frequency of oscillation). These results promise the potential of NW-based flexible TFT for future microwave applications.

Project end date: 08/...

BPN462: Programmable Matter

Xiaobo Zhang
Bryan Schubert
2011

Poly NIPAM (N-isopropylacrylamide) is a kind of thermal responsive polymer that can be synthesized by polymerize NIPAM monomer from its water solution by UV radiation or other synthetic methods. The main impetus to study this material is due to its novel thermal behaviors such as "squeezing out" water from inside, switching from hydrophilic to hydrophobic and changing from transparent to opaque when heating up to its phase transition temperature. Numerous poly NIPAM co- polymers and composites were made to utilize these properties for drug delivery, chemical connectors, and optical...

BPN583: Development of Functional Nanowire Devices

Min Hyung Lee
2011

Semiconductor nanowires have been widely studied for applications such as sensors, photovoltaics, field-effect transistors, and lasers due to their unique physical properties. However, controlling the density and alignment of nanowires over large-area is still challenging for commercial applications. In this project, we plan to design programmable nanowire integration and actuation methods using soft matters. Field-effect transistors and sensing devices will be tested.

Project end date: 08/17/11

BPN581: Shape-Controlled Synthesis of Single-Crystalline Nanopillar Arrays by Template-Assisted Vapor-Liquid-Solid Process

Onur Ergen
Daniel J. Ruebusch
Hui Fang
2011

In this work highly regular, single-crystalline nanopillar arrays with tunable shapes and geometry are synthesized by the template-assisted vapor-liquid-solid growth mechanism. The grown nanopillars faithfully reproduce the shape of the pores because during the growth the liquid catalyst seeds fill the space available, thereby conforming to the pore geometry. The process is highly generic for various material systems, and as an example, CdS and Ge nanopillar arrays with square, rectangular, and circular cross- sections are demonstrated. This technique has great potential im many...