Post on 13-Jan-2016
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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
A NUCLEAR SPINQUANTUM 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
Microanalytical Research CentreM A R C
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
• Students– Paul Otsuka– MatthewNorman– Elizabeth Trajkov– Brett Johnson
– Amelia Liu*
– Leigh Morpheth
– David Hoxley*
– Andrew Bettiol– Deborah Beckman– Jacinta Den Besten– Kristie Kerr– Louie Kostidis– Poo Fun Lai– Jamie Laird– Kin Kiong Lee
Key Personnel
• Academic Staff– David Jamieson– Steven Prawer– Lloyd Hollenberg
• Postdoctoral Fellows– Jeff McCallum – Paul Spizzirri– Igor Adrienko – +2
• Infrastructure– Alberto Cimmino– Roland Szymanski– William Belcher– Eliecer Para
– Geoff Leech* DeborahLouGreig
– Ming Sheng Liu– Glenn Moloney– Julius Orwa– Arthur Sakalleiou– Russell Walker
– Cameron Wellard*
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Test structures created by single ion implantation
Node Team Leader: Steven
Prawer
Atom Lithography and AFM
measurement of test structures
Theory of Coherence and Decoherence
The Quantum Computer: Melbourne Node
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Fabrication Pathways
Fabrication strategies:• (1) Nano-scale lithography:
– 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• 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
10 m
• Restricted to 10 m depth, large straggling
• Low beam damage
2 MeV He
5 m
0.5 m• Deep probe• Large damage at
end of range
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
The Melbourne Pelletron Accelerator
• 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
Aperture collimators
Beam steerer & Object collimators
Probe forming lens
Microscope
x-ray detector
SSBs
Ion pumps
Sample stage
goniometerLow
vibration mounting
From accelerator
1 m
Scanner
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Chamber inside
• 30 mm2 Si(Li) x-ray detector
• 25 and 100 msr PIPS particle detectors at 150o
• 75 msr annular detector
Re-entrant microscopeport & light
SiLi port
Specimen
SSB detectors
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
MeV ions interact with matter
PMMA substrate(side view)
100 m
surface
3 MeV H+• MeV ions penetrate
deeply without scattering except at end of range.
• Energy loss is first by electronic stopping
• Then nuclear interactions at end of range
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Micomachining
• Example• Proton beam lithography
– PolyMethyl MethAcrylate (PMMA)
– exposure followed by development
– 2 MeV protons
– clearly shows lateral straggling
Protons
Side view
10 m
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
• 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
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
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
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
Proton beam
Enhanced index region
Substrate
silica surface
2 MeV H+
20m
laser light emerging
The work of Mark von Bibra
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
MeV ion beam micromachining:Layered Waveguides
• Ion energy ---- waveguide depth
The work of Mark von Bibra
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Single Ion Implantation Fabrication Strategy
Resist layer
Si substrate
MeV 31P implant Etch latent damage&
metallise
Read-out state of “qubits”
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
MeV ion etch pits in track detector
• 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
1. Irradiate 2. Latent damage
3. Etch
From: B.E. Fischer, Nucl. Instr. Meth. B54 (1991) 401.
Scale bars: 1 m intervals
Heavy ion etch pit
Light ion etch pits
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
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
1 m
3 m
5 m
7.5 m
Depth
Single ion tracks
• Latent damage from single-ion irradiation of a crystal (Bi2Sr2CaCuOx)
• Beam: 230 MeV Au
• Lighter ions produce
narrower tracks!
3 nm
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
STM/AFM tip
High energy single-ion tracks in silicon: direct imaging with scanning probe microscopy
• 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.
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY
Spin array test structure
• Aim: Create a spin array for test imaging with MRAFM
Implant 31P through mask of 1 micron period grid
300 nm deep (220 keV 31P+)
<Si>
Grid
Resulting array of 1 micron islands of spins
Number of spins in each island is 1x10-8D, D is 31P
dose in P/cm2