Cleanrooms

The cleanroom complex comprises a dual class (350/3500) change-room (23m2), services area (32m2), wet chemical processing (40m2), scanning electron microscopy (SEM)/electron beam lithography (EBL) laboratory (19m2), general measurement area (41m2), advanced spectroscopy (27m2) and Ion Implantation facility (23m2). The cleanroom is equipped with two turbulently ventilated (HEPA) fume-cupboards, chemical storage and decontamination stations.

Nanometer-Depth Ion Implanter

The University of Melbourne node has a specialised low energy (0.01-15keV) Colutron ion implanter, located in the cleanroom complex. This implanter provides deterministic single ion implantation directed with sub-20nm precision with an Atomic Force Microscope nanostencil. The system can implant silicon donor dopant atoms, P and Sb, as well as molecular ions including PFx. The system is optimised for sub-20nm depths in silicon quantum devices. Nitrogen implants for the formation of shallow N-V centres in diamond samples is also possible as is a range of other species for specialized quantum devices. This unique facility can produce large-scale single-donor arrays in silicon.

Mev Ion Beam Facilities

UM is home to the NEC 5U Pelletron Accelerator in the Microanalytical Research Laboratory located in the basement of the Physics South Building. This machine has a high brightness source of light ions operating at charging potentials up to 5MV. It is routinely used to perform ion beam analysis, nuclear microprobe analysis, ion beam modification of materials, high-energy ion beam lithography and high-energy ion implantation. The IBA applications with and without micro-beam options include measurements with Rutherford Backscattering and Ion Beam Induced Charge suitable for analysis of a variety of materials. This system provides high precision analysis of the on-chip detector devices developed for the directed ion implantation program and analysis for the development of the in-house silicon enrichment process.

Dilution Refrigerator

The low temperature laboratory is equipped with a closed-cycle, cryogen-free dilution refrigerator from Leiden Cryogenics. It was commissioned and installed in 2011. The instrumentation includes a broadband Agilent microwave source and several lock-in amplifiers for low-noise electrical measurements. The dilution fridge is fitted with high frequency (up to 60GHz) coaxial lines.

This dedicated characterization facility is used for low temperature electrical measurements and spin spectroscopy studies involving defects in semiconductors such as silicon, III-V nanowires, quantum dots and NV- diamond devices.

More recently the system has been used for the characterisation of superconducting boron doped diamond samples, and hydrogen-terminated surface conducting diamond devices. This fridge cools a mixing chamber plate of 30cm diameter to a base temperature of 20mK, which provides a versatile surface for measuring a number of devices simultaneously and in one cool-down cycle.

The system is also equipped with a cold-insertable probe to rapidly characterise electronic devices at low temperatures without having to first bring the fridge to room temperature. The probe positions the samples directly into the centre of a superconducting 3D vector magnet (9-1-1 Tesla) for magneto-transport and/or anisotropy studies, and is fitted with 36dc lines, two semi-rigid microwave coaxial cables, and four optical fibres. Optical windows can also be fitted in the outer and inner vacuum cans of the dilution refrigerator to illuminate devices mounted on the probe with external light sources. Cryogenic low-pass filters and breakout boxes have been constructed for signal optimisation and interfacing the wiring of the probe to room temperature low-noise electronics.

Janis 4k Optical Cryostat

In addition to the dilution refrigerator, there is also a Janis Model SHI-950 closed cycle cryogenic refrigerator system designed to operate from below 4K to room temperature. Similar to the Leiden, the Janis system is equipped with a cold-insertable sample probe suspended within an exchange gas sample tube, which is in turn connected by copper straps to the 4K stage of the Gifford-McMahon cryocooler. Helium exchange gas forms a thermal link between the refrigerator and the sample; the exchange gas transfers heat from the sample to the refrigerator, cooling the sample in the process.

The sample probe is fitted with both dc and ac coaxial lines connected to breakout boxes for room temperature interfacing with low-noise electronics. A low-noise source meter unit is used for zero-field, low temperature resistance measurements (4K to RT) for characterizing superconducting devices. On the other hand, low-noise filters, lock-in amplifiers, and pulsed RF/MW electronics are used for low-field (LF) pulsed-EDMR measurements for investigating the physics of paramagnetic spin centers in group V donor implanted silicon. Furthermore, the sample chamber is fitted with four optical windows, allowing illumination of the sample from outside the chamber, while in house-built Helmholtz coils provide low magnetic fields (< 80G), as required for electrically detected magnetic resonance experiments.

Optical Quantum Measurement Systems

The Quantum Sensing Laboratory, operated in collaboration with other groups in the School, hosts three custom-built confocal microscopes as well as four wide-field microscopes, dedicated to quantum sensing and imaging based on spin defects in diamond. All microscopes are equipped with green excitation lasers, single photon counting detectors (Excelitas) or sCMOS cameras (Andor), microwave generators, static magnetic field alignment stages, and advanced electronic instrumentation for quantum control and time-resolved measurements. A custom-built interface allows the user to implement a variety of quantum measurements on single or multiple spins, which is used for various applications such as detecting ions in solution, performing magnetic resonance spectroscopy of nanoscale volumes, or imaging two-dimensional materials. In addition, one of the wide-field microscopes is fitted with an environmental control system that allows adjustment of temperature (from room temperature up to 37 ̊C), humidity and CO2 level (Clear state solutions). This system is used to image the magnetic properties of biological samples in their native environment (in-vitro), with a sub-micrometre diffraction-limited resolution. Finally, one of the confocal systems is combined with an atomic force microscope (Asylum Research), allowing scanning spin experiments to be performed with nanometer scale resolution.

Cryogenic Quantum Microscope Facility

The cryogenic quantum microscope facility, installed in 2018, combines a closed-cycle pulsed-tube cryostat from Attocube Systems with a wide-field optical microscope equipped with a 532nm laser and a sCMOS camera. The cryostat also comprises a superconducting 3D vector magnet (1-1-1 Tesla). This facility enables quantum sensing/microscopy based on diamond NV centres from room temperature down to 4K. It will be used to perform spin spectroscopy and image magnetism or charge transport in various low-dimensional systems, for instance to characterize silicon quantum processors or develop single molecule MRI.

Materials Fabrication

The micro- and nano-fabrication facilities are primarily located within the CQC2T Cleanroom laboratories and systems for electron beam lithography and photolithographic processing. A UV front side mask aligner (Neutronix Quintel Q4000-6 UV) has an extendible size vacuum chuck system for handling wafers (2”) and smaller pieces with a sub-micron feature resolution, contact/non-contact/vacuum/proximity exposure modalities, and the ability to process both thin and thick photoresists.

A customised Thermionics physical vapour deposition system includes both electron beam and resistive element heating sources with a quartz crystal monitor for thickness control.

The cleanroom also houses a Bruker 3D surface measurement optical profilometer, a Kurt J. Lesker Physical Vapor Deposition indium thin film deposition system, with an associated bump bonder, a Diener plasma cleaner and a wire bonder.

The advanced materials laboratories include a diamond synthesis capability, in the form of a pair of microwave plasma chemical vapour deposition systems (Astex and Iplas), and a 532nm laser cutter (Oxford Laser). In 2022 the laboratory was equipped with a 4Pico PM-100 Laser Lithography System that is shared with external users. This new facility is used to make devices at the micrometer scale for electrical measurements of materials developed for the quantum computer programs.

Advanced Spectroscopy and Modeling

A suite of electrical measurement tools is housed on the UM campus including a SULA Technologies Deep Level Transient Spectroscopy (DLTS) and high-energy-resolution Laplace DLTS systems for measuring bulk and interface traps in silicon devices. Further charge pumping, impedance spectroscopy and electrically detected magnetic resonance stations compliment these measurement set-ups. A Hall system complete with a cryostat for measurements in the range 77-300 K to measure carrier transport is also included. Facilities elsewhere on the campus are also employed for Centre research including the microscopy facilities in the Bio21 laboratories and the School of Chemistry. Extensive use is also made of the UM’s supercomputer ‘Spartan’ for NEMO3D simulations.