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THE ION BEAM PROGRAM FOR QUANTUM COMPUTING

 

Program Manager
Prof David Jamieson - University of Melbourne

Ion Beam Researchers
Staff

Prof Steven Prawer
Dr Changyi Yang
Dr Sergey Rubanov
Dr Chris Pakes
Dr Paul Spizzirri
Dr Grigori Tamanyan
Dr Sean Hearne
Mr Robert Short
Mr Roland Szymanski

Students
Mr Toby Hopf (PhD)

Collaborating Centre Researchers
Prof Andrew Dzurak - University of New South Wales
Dr Eric Gauja - University of New South Wales
Dr Fay Hudson - University of New South Wales
Mr Victor Chan - University of New South Wales
Mr Mladen Mitic - University of New South Wales

Program Description
This program is focussed on the development of ion implantation techniques for the construction of an array of single phosphorous atoms in a silicon matrix for fabrication of the solid state Kane quantum computer (B.E. Kane, Nature, 393 (1998) 133-7).

We propose to create this array using ion implantation as part of the top-down approach now under development in collaboration with other Centre personnel. An essential technology is the registration of single ion impacts. We are working on two strategies for the registration.

The first strategy involves the broad beam implantation of low dose phosphorous ions. In this strategy the implantation of ions is essentially randomly positioned, so the yield of usefully-spaced atoms is low. This problem can be reduced if the passage of a single ion can be registered so that usefully positioned ions can be identified. This can be accomplished by implantation of the ions through a thin surface layer consisting of resist. Changes to the chemical and/or electrical properties of the resist will be used to mark the site of the buried ion. For chemical changes, the latent damage can be developed and the atomic force microscope (AFM) used to image the changes in topography. Alternatively, changes in electrical properties (which obviate the need for post irradiation chemical etching) can be used to register the passage of the ion using scanning tunneling microscopy (STM) the surface current imaging mode of the AFM.

 

Cen Res Prog - Ion beam program

 

The second strategy involves low dose rate ion implantation through a precision mask that can be positioned at the desired locations on the silicon substrate. In this "step-and-repeat" process, the arrival of a single ion is registered by the electronic transient induced in the sample itself. This method draws on our extensive experience with the analytical technique of Ion Beam Induced Charge (IBIC) which is used with a scanned, focused MeV ion beam for measurement of the electrical characteristics of electronic devices such as integrated circuits, poly-silicon solar cells and other electronic materials. The figure below shows the formation of the charge transient from an implanted ion (red arrow) in a silicon substrate where a Schottky barrier has been used to form a surface depletion region.

 

Cen Res Prog - Ion Beam

 

In early 2001 a 10 keV P ion implanter will be commissioned for pilot studies of the technology of the two strategies. A novel feature of this implanter will be its installation on the preparation chamber of our existing Joel atomic force microscope. This will allow atomic resolution imaging of the implanted ions without having to transfer the specimens to a separate instrument.

 

 


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