NER: Silicide Quantum Dots for Nanoelectronics

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

This proposal was received in response to the Nanoscale Science and Engineering Initiative, Program Solicitation NSF 01-157, in the NER category. The proposal focuses on the fabrication of nanoscale silicide quantum dots. Silicide dots are potentially useful for fabrication of quantum cellular automata and other quantum dot devices. Quantum cellular automata are assemblies of quantum dots which can perform the basic information-processing functions of interconnect, digital logic, and memory. A major motivation for the exploration of silicide quantum dots in particular is the fact that they will be compatible with silicon devices which will probably remain useful as an interface between nanoelectronics and the outside world. This research will explore novel nanoscale fabrication processes and will develop improved understanding of surface chemical reactions and phase transitions on the nanoscale. We wish to demonstrate the integration of in situ lithography, selective deposition of metals, silicide formation, and epitaxial layer overgrowth. In particular, lithography will be performed by exposing thin silicon dioxide layers with an electron beam, thereby enhancing thermal desorption of oxide from the exposed regions. Subsequently the quantum dots will be formed by chemical vapor deposition and reaction to form a metallic silicide. One particularly attractive approach is selective deposition of the silicide-forming metal from an organometallic source, although other approaches may also be explored. This research will be performed using a recently constructed apparatus which combines electron beam patterning with the deposition and characterization of quantum dots. All process steps, including epitaxial overgrowth of the quantum dots, can be performed without exposing the substrates to atmosphere. Characterization tools to be used in the work include reflection high energy electron diffraction, thermal desorption mass spectrometry, and atomic force microscopy. Within this one-year exploratory program, we expect to fabricate patterned silicide quantum dots in the 20-40 nm size range. We will also obtain improved scientific understanding of selective growth which will be broadly useful in the fabrication of nanoscale devices.