Details of Grant 

EPSRC Reference:	GR/H05258/01
Title:	ULTIMATE LIMITS OF NANOFABRICATION IN SEMICONDUCTORS
Principal Investigator:	Humphreys, Professor Sir C
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Department:	Materials Science & Metallurgy
Organisation:	University of Cambridge
Scheme:	Standard Research (Pre-FEC)
Starts:	01 November 1991	Ends:	31 July 1995	Value (£):	225,926
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Summary on Grant Application Form
To perform electron-beam enhanced nanometre-scale patterning of SiO2.To perform direct electron-beam nanofabrication in silicon and to explore the fabrication of Si quantum wires.To fabricate directly quantum wires and dots.Progress: We have developed a novel way of making nanometre diameter silicon columns in a controlled manner. We have found that if silicon dioxide (SiO2) is irradiated with a high intensity 100 keV electron beam of nanometre diameter then a silicon column is formed as small as 2nm in diameter. If the beam is moved in a pattern and switched on and off then a controlled pattern of 2nm diameter silicon columns is formed. We have a world lead in the fabrication of a controlled array of silicon quantum columns of diameter only 2nm. This is significantly smaller than achieved anywhere else in the world. If the electron-beam is moved across the specimen in a straight line then a quantum wire of silicon is formed. These nanometre silicon structures are formed directly under intense electron irradiation and no resists or chemical development are required. It is extremely difficult to study and characterise such very small structures and the mechanism of their formation. We have performed electron energy loss spectroscopy (EELS) of the electrons transmitted by the specimen during irradiation. This shows that under electron irradiation of SiO2 both silicon and oxygen are lost from the irradiated volume, with oxygen being lost faster, to leave behind a quantum column of silicon. The EELS spectra show this to be silicon with no detectable oxygen. Images of the silicon nanostructures were formed using silicon plasmon loss energy-filtered images. This reveals the silicon nanostructures with high contrast. The silicon quantum structures formed in this way are amorphous. The next step will be to crystallise these by annealing and see if they emit light due to quantum confinement effects. This is a critical experiment to perform which is highly relevant to the potential of silicon to be an optoelectronic material if it is sufficiently small.
Key Findings
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Organisation Website:	http://www.cam.ac.uk