NUCLEAR ACCELERATOR FACILITIES
The Melbourne Node of the Centre for Quantum Computer Technology (CQCT) is co-located with the Microanalytical Research Centre (MARC) in the School of Physics at the University of Melbourne. It is home to six major research laboratories: Nuclear Accelerator, CQCT Cleanrooms, Scanning Probe Microscopy, Advanced Micro-Spectroscopy, Advanced Materials and Pulsed Laser Deposition laboratories. The Centre is of the largest research groups in the School of Physics and is involved with a diverse range of research projects funded by the Australian Research Council, government laboratories (CSIRO) and the ARO of the USA.
One of the groups areas of expertise lies in applications using the Nuclear Microprobe technique which exploits the unique properties of focused beams of high energy ions interacting with matter. Nuclear microscopy is applied to a wide range of specimens to probe fundamental questions about the structure of materials. The three nuclear accelerators located in the Centre are: the Pelletron, the Colutron and a JEOL/Orsay focussed ion beam (FIB). The NEC 5U Pelletron is a high energy accelerator (0.5-5MeV) manufactured by the National Electrostatics Corporation and was originally commissioned in 1975. It is a high brightness source of protons or alpha particles and is routinely used for both ion implantation and analysis (RBS, PIXE, CCM, IBIC and STIM).
Figure 1: Ion source (left) and beam lines within the Pelletron Laboratory
The Colutron is a low energy phosphorus ion implanter (0.01-15keV) commissioned in 2001 specifically for Quantum device fabrication, a role it continues to perform. Located in the CQCT cleanroom (from 2003), it is equipped with a G2 ion gun, beam imaging system, computer controlled mass selection, beam on demand and single ion detection capabilities.
The focussed ion beam system, a JEOL/Orsay Physics cross beam SEM/FIB, was installed in 2003. Fitted with gas injection and eutectic sources, the system is able to process (machine) materials with nanometer resolution while simutaneously imaging in either SEM or FIB modes. This instrument has also been designed to perform single ion implantation with a variety of sources. In addition to the electron microscopy facilties provided by the FIB, a JEOL 4000CX TEM is used for subnanometer analysis of materials.
Figure 2: (Above Left)Colutron phosphorus ion implanter with single ion detection syste
Figure 3: (Above Right)Cross beam FIB/SEM located in the CQCT Cleanrooms. The inner chamber is shown (right) where the scanning electron and focussed ion beam columns can be seen.
Figure 4: JEOL 4000CX TEM located adjacent to the CQCT cleanrooms
SCANNING PROBE MICROSCOPY FACILITIES
The group is also home to a range of scanning probe microscopy resources which are distributed between the CQCT cleanroom, general laboratories and an undergraduate teaching laboratory. One of these systems, the JEOL JAFM 4500 UHV AFM is capable of CITS, lateral force, scanning Kelvin and modulation imaging modes. It also features the following in-situ surface treatment facilities: an argon ion gun, thermal evaporator, e-beam evaporator, cleaver and atomic hydrogen source. In 2002, this system was further updated with a surface spectroscopy package from STAIB Instruments. This includes: a microfocus electron gun and scintillating detector (SEM), cylindrical mirror analyser (CMA) with integral electron gun for Auger spectroscopy and scanning Auger mapping (SAM) and an X-ray source for XPS analysis.
Figure 5: JEOL ultrahigh vacuum AFM with surface spectroscopy facility
A second JEOL AFM, a JSTM 4200A ambient/high vacuum system, is used for routine analysis. This system is equipped with the same imaging modes as the 4500 system and is also capable of atomic resolution. The two JEOL systems are complimented by a Nanonics NSOM/AFM and an NT-MDT SMENA handheld AFM. The Nanonics system provides 50nm lateral resolution operating in contact or non-contact mode using an optical fibre cantilever probe. It can also operate as a Near-field Scanning Optical Microscope (NSOM) and can be coupled to a micro-Raman spectrometer such as the Renishaw system located in the CQCT cleanroom. The SMENA AFM is located in the School undergraduate teaching laboratories where it can cater for both teaching and research activites.
ADVANCED MICRO-SPECTROSCOPY FACILITIES
Two micro-Raman spectrometers are located within the Centre for conducting visible (VIS) and ultraviolet (UV) studies on various materials including silicon and diamond. Commissioned in 1991, the Dilor XY triple grating, confocal visible micro-spectrometer provides micro-photoluminescence and Raman imaging capabilities. It incorporates an argon ion laser, a dye laser and a CW Nd:YAG laser for optical trapping. The second, a Renishaw 1000 UV/Vis confocal micro-Raman spectrometer is located is located in the CQCT cleanroom. Designed as a wide spectrum, high resolution imaging spectrometer, the system has 5 interchangeable gratings and three optics sets to support 244, 325 and 514.5nm excitation with detection capabilities from 244nm to >1000nm.
Figure 6: Dilor (lhs) and new Renishaw (rhs) micro-Raman spectrometers
MATERIALS FABRICATION AND CHARACTERISATION FACILITIES
Thin film deposition facilities are located in the Advanced Materials, Pulsed Laser Deposition (PLD) and Pelletron laboratories. The PLD laboratory, constructed in 2000, provides two state-of-the-art deposition systems (APX Scientific Instruments) which allow the deposition of new and varied material layers and multilayers under UHV conditions. The systems are equipped with very high temperature stages (>700°C and >1000°C), spectroscopy ports and a Lambda Physik LPX 305I excimer laser (KrF, 248nm). The laboratory is equipped with a Class 350 cleanroom, class 35 laminar flow cabinet, laminar flow fumecupboard and Type II deionised water system.
Figure 7: Ultra-high vacuum pulsed laser deposition chamber
The deposition facilities in the Advanced Materials Laboratory include: a hot filament chemical vapour and copper vapour laser based PLD. In 2003, these facilities were upgraded following the installation of an Astex microwave HPMD/ECR system. Suited to diamond and diamond like material coatings, the system incorporates: a multigas delivery system, full computer control of the deposition process, inductively coupled heating stage (>800°C) and reactive plasma etching capabilities. Supplementary deposition facilities are located in the Pelletron Laboratory. These include: a thermal/e-beam evaporator and a gold sputter coater.
Figure 8: Astex microwave HPMD/ECR deposition system
Materials preparation and analysis facilities, located in the Pelletron and Advanced Materials Laboratories include: wet chemical cleaning/etching, inert gas furnace annealing, electrical characterisation, time-resolved reflectivity, spin coater for polymer resists and optical microscopy suite. Future upgrades of these facilities will see a deep level transient spectroscopy system (DLTS) and a rapid thermal annealer (RTA) installed in 2004. The DLTS system will be located in the Schools undergraduate teaching laboratory where it will service the needs of both teaching and research.
CENTRE FOR QUANTUM COMPUTER TECHNOLOGY CLEANROOMS
Completed in October 2002, the Centre's cleanrooms span more than 200m2 of the basement of the Physics building and are home to the Colutron implanter, JEOL/Orsay cross beam SEM/FIB, wet chemical processing laboratory, JEOL JAFM 4500XT UHV AFM and Renishaw micro-Raman spectrometer. Equipped with two laminar flow fumecupboards, reticulated processing gases and a two-stage changeroom, the facility has been designed to cater for the various requirements of the Centre. Constructed to cleanroom standards, initial commissioning yielded an "as built" classification of Class 350.
Figure 9: Class 350 cleanroom