Controlled direct growth of vertical and highly-ordered ’carbon nanotube - silicon’ heterojunction array

Abstract

AbstractCarbon nanotubes (CNT) have been studied intensively for its unique electrical and mechanic properties and numerous applications. However, electronical integration of carbon nanotubes with silicon to form an electronically functional entity or device, though highly desirable, has remained a great challenge. Whereas vertical aligned bundles of nanotubes have been grown directly on silicon, the integration is mechanical, rather than electronical, in nature. In the present work, we report on Controlled growth of vertical and highly-ordered array of ’carbon nanotube silicon’ (CNS) heterojunction diodes of uniform diameter, length, and alignment. The as grown CNS heterojunction structure is not only electronically functional but also strongly rectifying with an on off ratio as high as five orders of magnitude in current voltage characteristics measured at room temperature. The controlled direct growth of the CNS hetero junction array of such high uniformity is enabled by the formation of a highly ordered nanopore array alumina matrix directly on the silicon, following a precisely controlled anodization of an aluminum thin film evaporated on silicon. Iterations of development and optimization of the anodization process conditions and real time monitoring and control of the anodization process were required for the formation and adhesion of the alumina growth matrix directly on silicon. Under carefully controlled and optimized conditions developed in this work, we are able to obtain an abrupt heterointerface between a terminal end of the carbon nanotube and the silicon substrate, without an intermediate barrier layer, as required for an electronically functional CNS hetero junction. The growth process is applicable to silicon doped in either type, enabling access to another critical parameter of the electronic function.