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Thursday, September 24, 2009
3pm (2:45pm refreshments)
RLE Conference Room, 36-428
Nanoscale Semiconductor Materials: Challenges & Opportunities
Prof. Ali Javey, University of California, Berkeley
ABSTRACT
In this talk, I will present large-scale assembly of highly ordered, dense, and regular arrays of nanowires (NWs) with high uniformity and reproducibility through a simple contact printing process. This printing approach enables large-scale integration of NW arrays for various device and sensor structures on both rigid and mechanically flexible substrates. The potency and versatility of the method is further demonstrated by large-scale, heterogeneous integration of NWs for image sensor circuitry by utilizing optically active NW sensors and high mobility NW transistors. The NW sensors and electronic devices are interfaced to enable an all-NW circuitry with on-chip integration, capable of detecting and amplifying an optical signal with high sensitivity and precision. The ability to interface NW sensors with integrated electronics on large scales and with high uniformity presents an important advance toward the integration of nanomaterials for sensor applications. Additionally, I will present strategies for controlled nanoscale doping of semiconductors by utilizing surface chemistry and monolayer formation. I will also present a new connector technology based on hybrid NW structures that enables self-selective binding of connector mates with high robustness and strong adhesion. This work may have important implications toward realization of programmable materials that can change shape and functionality on command. Finally, I will discuss the use of 3D structures for efficient and cost effective PVs. In this regard, we have recently reported the direct growth of highly regular, single-crystalline nanopillar (NPL) arrays of optically active semiconductors on aluminum substrates which are then configured as solar cell modules. As an example, we have demonstrated a PV structure that incorporates 3D, single crystalline n-CdS NPLs, embedded in poly-crystalline thin films of p-CdTe, to enable high absorption of light and efficient collection of the carriers. Through experiments and modeling, we demonstrate the potency of this approach for enabling highly versatile solar modules on both rigid and flexible substrates with enhanced carrier collection efficiency arising from the geometric configuration of the NPLs.
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