Transcript A NUCLEAR SPIN QUANTUM COMPUTER IN SILICON

M
A
Microanalytical
R
Research
C
Centre
A NUCLEAR SPIN
QUANTUM COMPUTER
IN SILICON
• National Nanofabrication Laboratory, School of Physics,
University of New South Wales
• Laser Physics Centre, Department of Physics, University
of Queensland
• Microanalytical Research Centre, School of Physics,
University of Melbourne
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Key Personnel
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Academic Staff
– David Jamieson
– Steven Prawer
– Lloyd Hollenberg
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Postdoctoral Fellows
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Jeff McCallum
Paul Spizzirri
Igor Adrienko
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Infrastructure
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Alberto Cimmino
Roland Szymanski
William Belcher
Eliecer Para
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Students
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Paul Otsuka
MatthewNorman
Elizabeth Trajkov
Brett Johnson
– Amelia Liu*
– Leigh Morpheth
– David Hoxley*
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Andrew Bettiol
Deborah Beckman
Jacinta Den Besten
Kristie Kerr
Louie Kostidis
Poo Fun Lai
Jamie Laird
Kin Kiong Lee
– Geoff Leech*
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DeborahLouGreig
Ming Sheng Liu
Glenn Moloney
Julius Orwa
Arthur Sakalleiou
Russell Walker
– Cameron Wellard*
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
The Quantum Computer:
Melbourne Node
Node Team Leader:
Steven Prawer
Test structures
created by single
ion implantation
Atom Lithography
and AFM
measurement of test
structures
Theory of
Coherence and
Decoherence
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Fabrication Pathways
Fabrication strategies:
• (1) Nano-scale lithography:
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Atom-scale lithography using STM H-resist
MBE growth
EBL patterning of A, J-Gates
EBL patterning of SETs
• (2) Direct 31P ion implantation
• Spin measurement by SETs or magnetic resonance force
microscopy
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Major collaboration with Los Alamos National Laboratory, funded through US National
Security Agency
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
keV electrons and MeV ions interact with
matter
30 keV e
60 keV e
2 MeV He
5 m
• Restricted to 10
m depth, large
straggling
• Low beam
damage
10 m
0.5 m
• Deep probe
• Large damage at
end of range
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
The Melbourne Pelletron Accelerator
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Installed in 1975 for nuclear
physics experiments.
National Electrostatics Corp. 5U
Pelletron.
Now full time for nuclear
microprobe operation.
Will be state-of-the-art following
RIEFP upgrade
Inside
Outside
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Nuclear microprobe essential
components
1m
x-ray detector
From
accelerator
Beam steerer &
Object collimators
Low
vibration
mounting
Scanner
Aperture
Probe
collimators forming lens
Microscope
SSB
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Sample
stage
goniometer
Ion pumps
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Chamber inside
SSB detectors
• 30 mm2 Si(Li) xray detector
• 25 and 100 msr
PIPS particle
detectors at 150o
• 75 msr annular
detector
Re-entrant microscope
port & light
SiLi port
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
MeV ions interact with matter
3 MeV H+
• MeV ions penetrate
deeply without
scattering except at
end of range.
PMMA substrate
(side view)
• Energy loss is first by
electronic stopping
surface
• Then nuclear
interactions at end of
range
100 m
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Micomachining
Protons
• Example
• Proton beam lithography
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PolyMethyl MethAcrylate (PMMA)
exposure followed by development
2 MeV protons
clearly shows lateral straggling
10 m
Side view
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
The work of Frank Watt
MeV ion beam micromachining:
High aspect ratio structures in PMMA
Work done at the Nuclear Microscopy Unit at the National University of Singapore
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2.3 MeV protons on PMMA
This work dates from 1996, much more
interesting structures are now available
See review by Prof F. Watt, ICNMTA6 - Cape
Town, October 1998
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
The work of Mark von Bibra
MeV ion beam micromachining:
Optical Materials
• Fused Silica
– Increase in density at end of range
– Increase in refractive index (up to 2%) at end of range
2 MeV H+
Proton
beam
Enhanced
index
region
silica surface
laser light
emerging
Substrate
20m
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
The work of Mark von Bibra
MeV ion beam micromachining:
Layered Waveguides
• Ion energy ---- waveguide depth
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Single Ion Implantation Fabrication
Strategy
MeV 31P implant
Etch latent damage
&
metallise
Read-out state of
“qubits”
Resist layer
Si substrate
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
MeV ion etch pits in track detector
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Single MeV heavy ions are used to produce latent
damage in plastic
Etching in NaOH develops this damage to
produce pits
Light ions produce smaller pits
Light ion etch pits
Heavy ion etch pit
1. Irradiate
2. Latent
damage
3. Etch
Scale bars: 1 m intervals
From: B.E. Fischer, Nucl. Instr. Meth. B54 (1991) 401.
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Single ion tracks
Depth
• Latent damage from
single-ion irradiation of
a crystal (Bi2Sr2CaCuOx)
• Beam: 230 MeV Au
• Lighter ions produce
narrower tracks!
1 m
3 m
5 m
7.5 m
3 nm
From Huang and Sasaki, “Influence of ion velocity on damage efficiency in the single ion target irradiation
system” Au-Bi2Sr2CaCu2Ox Phys Rev B 59, p3862
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
High energy single-ion tracks in silicon: direct
imaging with scanning probe microscopy
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Nanofabrication by the implantation of MeV single-ions offers a novel method
for the construction of small devices which we call atomic-lithography. A
leading contender for the first nano-device constructed by this method is an
array of spins for a quantum computer. For the first time, we propose the use
of high resolution scanning probe microscopy (SPM) to directly image
irradiation-induced machining along the ion track and lattice location of the
implanted ion in silicon on an atomic scale. This will allow us to measure the
spatial distribution of defects and donors along the tracks to analyse the
atom-scale electronic properties of the irradiated materials.
STM/AFM tip
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Spin array test structure
• Aim: Create a spin array for test imaging with MRAFM
Grid
<Si>
Implant 31P through mask of
1 micron period grid
Resulting array of 1 micron
islands of spins
300 nm deep (220 keV 31P+)
Number of spins in each
island is 1x10-8D, D is 31P
dose in P/cm2
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY