ZnO nanorods, heterostructures, and nanodevices
Date : November 9, 2005 16:00 ~
Speaker : 이규철 교수(포항공대 재료공학과)
Professor :
Location : 56동106호
National CRI Center for Semiconductor Nanorods and Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea; gcyi@postech.ac.kr
One-dimensional (1D) semiconductor nanowires and nanorods have attracted increasing interest due to their novel physical properties and diversity for potential electronic and photonic device applications [1]. For 1D nanostructure 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 1D semiconductor nanostructures including Si, GaAs, ZnO, and GaN nanowires. However, the catalytic method has several problems in fabrication of high quality nanostructures, due to the use of metal catalysts. At first, the catalyst impurity might be incorporated into nanowires during growth and these unintentionally doped impurities make it difficult to control the intrinsic properties of these materials and are detrimental to device fabr! ication. In addition, due to the re-alloying of alternating reactants in the metal catalyst during the condensation-precipitation process, compositionally modulated 1D structures with well defined interfaces might be difficult to obtain. In this talk, I introduce an alternating approach, catalyst-free metalorganic vapor phase epitaxy (MOVPE) as a ZnO nanorod growth method, which minimizes 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 [2]. With precise thickness control down to the monolayer level, compositionally modulated nanorod quantum structures can be readily designed within individual nanorods [3]. 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 a! nd 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.
[1] G.-C. Yi, C. Wang, and W. I. Park, Semicond. Sci. Technol. 20, S22 (2005).
[2] W. I. Park, D. H. Kim, S.-W. Jung, and G.-C. Yi, Appl. Phys. Lett. 80, 4232 (2002).
[3] W. I. Park, G.-C. Yi, M. Kim, and S. J. Pennycook, Adv. Mater. 15, 526 (2003).
One-dimensional (1D) semiconductor nanowires and nanorods have attracted increasing interest due to their novel physical properties and diversity for potential electronic and photonic device applications [1]. For 1D nanostructure 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 1D semiconductor nanostructures including Si, GaAs, ZnO, and GaN nanowires. However, the catalytic method has several problems in fabrication of high quality nanostructures, due to the use of metal catalysts. At first, the catalyst impurity might be incorporated into nanowires during growth and these unintentionally doped impurities make it difficult to control the intrinsic properties of these materials and are detrimental to device fabr! ication. In addition, due to the re-alloying of alternating reactants in the metal catalyst during the condensation-precipitation process, compositionally modulated 1D structures with well defined interfaces might be difficult to obtain. In this talk, I introduce an alternating approach, catalyst-free metalorganic vapor phase epitaxy (MOVPE) as a ZnO nanorod growth method, which minimizes 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 [2]. With precise thickness control down to the monolayer level, compositionally modulated nanorod quantum structures can be readily designed within individual nanorods [3]. 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 a! nd 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.
[1] G.-C. Yi, C. Wang, and W. I. Park, Semicond. Sci. Technol. 20, S22 (2005).
[2] W. I. Park, D. H. Kim, S.-W. Jung, and G.-C. Yi, Appl. Phys. Lett. 80, 4232 (2002).
[3] W. I. Park, G.-C. Yi, M. Kim, and S. J. Pennycook, Adv. Mater. 15, 526 (2003).