1. CENTRE FOR QUANTUM COMPUTER TECHNOLOGY 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 Microanalytical Research Centre M A R C

2. 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 *

3. 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

4. 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 31 P ion implantation Spin measurement by SETs or magnetic resonance force microscopy Major collaboration with Los Alamos National Laboratory, funded through US National Security Agency

5. 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

6. 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

7. CENTRE FOR QUANTUM COMPUTER TECHNOLOGY Nuclear microprobe essential components Aperture collimators Beam steerer & Object collimators Probe forming lens Microscope x-ray detector SSB s Ion pumps Sample stage goniometer Low vibration mounting From accelerator 1 m Scanner

8. CENTRE FOR QUANTUM COMPUTER TECHNOLOGY Chamber inside 30 mm 2 Si(Li) x- ray detector 25 and 100 msr PIPS particle detectors at 150 o 75 msr annular detector Re-entrant microscope port & light SiLi port Specimen SSB detectors

9. 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

10. 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

11. 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

12. 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 silica surface 2 MeV H + 20  m laser light emerging The work of Mark von Bibra

13. CENTRE FOR QUANTUM COMPUTER TECHNOLOGY MeV ion beam micromachining: Layered Waveguides Ion energy ---- waveguide depth The work of Mark von Bibra

14. CENTRE FOR QUANTUM COMPUTER TECHNOLOGY Single Ion Implantation Fabrication Strategy Resist layer Si substrate MeV 31 P implant Etch latent damage & metallise Read-out state of “qubits”

15. 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

16. 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 (Bi 2 Sr 2 CaCuO x ) Beam: 230 MeV Au Lighter ions produce narrower tracks ! 3 nm

17. 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.

18. CENTRE FOR QUANTUM COMPUTER TECHNOLOGY Spin array test structure Aim: Create a spin array for test imaging with MRAFM Implant 31 P through mask of 1 micron period grid 300 nm deep (220 keV 31 P + ) Grid Resulting array of 1 micron islands of spins Number of spins in each island is 1x10 -8  D, D is 31 P dose in P/cm 2