ZnO Nanorods, Heterostructures, and Nanodevices
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Date: 01-18-2006
Start Time:
4:00pm
End Time: 5:00pm
Speaker: Gyu-Chul Yi
From:
Pohang University of Science and Technology, Korea
Location: Interschool Lab, 7th floor, Schapiro/CEPSR
Hosted by:
Center for Integrated Science
Abstract:
Semiconductor nanowires and nanorods have attracted increasing interest due to their novel physical properties and diversity for potential electronic and photonic device applications. For the nanomaterials preparation, a catalyst-assisted vapor-liquid-solid (VLS) method has widely been used since this technique offers an easy and simple method for the synthesis of many kinds of semiconductor nanowires including Si, GaAs, ZnO, and GaN. Alternatively, our group developed catalyst-free metal-organic chemical vapor deposition of ZnO nanorods in order to minimize both incorporation of unintentional impurity and formation of a mixed interfacial layer, i.e., by utilizing direct adsorption of atoms on the top surface of nanorods. In this presentation, I will discuss characteristics of ZnO nanorods grown by catalyst-free metal-organic chemical vapor deposition, and their nanorod heterostructures and device applications. First of all, the catalyst-free method excludes possible incorporation of metal impurities which may occur in the catalyst-assisted VLS methods, which enables to minimize unintentional impurity incorporation and offer high purity nanorods. As evidence of the high purity ZnO nanorod growth using the catalyst-free method, free exciton emission peaks was observed in PL spectra of ZnO nanorods measured even at low temperatures below 15 K. With precise thickness control down to the monolayer level, compositionally modulated nanorod quantum structures can be readily designed within individual nanorods. Moreover, ZnO nanorods grown by this method are aligned vertically and exhibit uniform thickness and length distributions, highly appropriate for a direct integration of incorporating 1D nanorod on a device platform to fabricate a unique vertical devices and device arrays. Finally, I briefly describe our recent activities on ZnO nanorod device fabrication and evaluation, including nanorod light emitting devices, field-effect transistors (FETs), Schottky diodes, and logic circuits.