Cryogenic Quantum Microscope Facility
The University of Melbourne 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 532 nm 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 4 K. 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.
Advanced Spectroscopy and Modeling
A suite of electrical measurement tools is also housed within the Melbourne node 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 University supercomputer ‘Spartan’ for NEMO3D simulations.
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 60 GHz) 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 characterization of superconducting boron doped diamond samples, and hydrogen-terminated surface conducting diamond devices. This fridge cools a mixing chamber plate of 30 cm diameter to a base temperature of 20 mK, 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 36 DC 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. The capabilities of this laboratory were extended in 2019 with the addition of a small-scale closed circuit fridge from Janis Research which will be used for electrically detected magnetic resonance (EDMR) experiments.
Optical Quantum Measurement System
The quantum sensing lab was established in 2010 and 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.