CENTRE FOR QUANTUM COMPUTER TECHNOLOGY A NUCLEAR SPIN QUANTUM COMPUTER IN SILICON National...

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


• 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*


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


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


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


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


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


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


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


Micomachining

• Example• Proton beam lithography

– PolyMethyl MethAcrylate (PMMA)

– exposure followed by development

– 2 MeV protons

– clearly shows lateral straggling

Protons

Side view

10 m


• 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


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


MeV ion beam micromachining:Layered Waveguides

• Ion energy ---- waveguide depth

The work of Mark von Bibra


Single Ion Implantation Fabrication Strategy

Resist layer

Si substrate

MeV 31P implant Etch latent damage&

metallise

Read-out state of “qubits”


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


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


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.


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

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CENTRE FOR QUANTUM COMPUTER TECHNOLOGY A NUCLEAR SPIN QUANTUM COMPUTER IN SILICON National...

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