Homoepitaxial Growth of Vertical Si Nanowires on Si(100) Substrate using Anodic Aluminum Oxide Template
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1058-JJ03-01
Homoepitaxial Growth of Vertical Si Nanowires on Si(100) Substrate using Anodic Aluminum Oxide Template Tomohiro Shimizu1, Tian Xie1, Volker Schmidt1, Jo Nishikawa2, Shoso Shingubara2, Stephan Senz1, and Ulrich Goesele1 1 Max Planck Institute of Microstructure Physics, Halle, 06120, Germany 2 Graduate School of Engineering, Kansai University, Osaka, 564-8680, Japan ABSTRACT Homo-epitaxial growth of Si nanowires on Si (100) substrate was accomplished using a combination of anodic aluminum oxide (AAO) template and Vapor-Liquid-Solid (VLS) growth. We prepared two types of AAO templates for epitaxial growth of Si nanowires. We observed vertically grown epitaxial Si (100) nanowires in the AAO template. In addition, after leaving filled pores, Si nanowires changed their growth direction from [100] to . This result shows that the walls of the pores forced the growth direction of Si nanowires parallel to the direction of the pores, and after complete filling, the growth direction changes to that of the Si nanowires on a bare Si substrate. INTRODUCTION In order to combine epitaxial Si nanowires grown via a bottom-up process such as the VLS technique with conventional Si micro/nanoelectronics, the control of the growth direction of the nanowires is one of the most important issues. Usually, homo-epitaxial Si nanowires on bare Si (100) substrates are grown along , , and directions, depending on the diameter of the nanowires [1]. However, nanowires, which would be important to combine vertical nanowire transistors with conventional microelectronics on (100) substrates, have been reported only in few cases for non-epitaxial growth. On the other hand, Anodic Aluminum Oxide (AAO) is known to have ordered honeycomb nanopore arrays, perpendicular to the substrate, the diameter of which can be controlled from a few nanometers to several hundred nanometers depending on the anodic voltage and acid species used for anodic oxidation [2]. AAO has been used as a template for fabrication of various nanostructures since it has many advantages, such as small nanopore diameter, high packing density and much lower cost compared with conventional lithographic techniques. Generally, it is difficult to realize epitaxial growth of materials buried in AAO nanopores because AAO has an amorphous layer called the barrier layer at each nanopore bottom. Removal of the barrier layer, however, was possible on several conductive films and single crystalline substrates in particular ITO, Au, and Si etc. [3-5]. This allows obtaining a direct contact between materials grown inside the AAO nanopores and conductive layers or substrates. Hence, AAO can be expected to control the growth direction of epitaxial Si nanowire arrays. In the present study, we tried to combine AAO template and VLS growth aiming to grow epitaxial Si [100] nanowires. We prepared two types of AAO, in particular AAO/Si and AAO/Au/Si, to grow Si nanowires, shown in fig. 1.
In the case of AAO/Si, Au is deposited by electroless plating for each nanopore bottom, which works as ca
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