Solid State Physics
The He3/He4 Cryogen Free Dilution Fridge in the Nanoelectronics Research Lab
Solid state physics in the department focuses on the physics of modern nano materials in both fundamental and applied physics research. The department is home to the “Coldest Place in Africa” a Cryogen Free He3/He4 Dilution Fridge which is housed in the Nanoelectronics Research Lab in the RW James Building. The dilution fridge with a base temperature less than 8mK is equipped with an 80mm bore, 10T superconducting magnet and has semi rigid coaxial cabling allowing for RF measurements up to 18GHz. The fridge has a cooling power of up to 1400 μW at 120 mK making it one of the most powerful fridges on the market. The mixing chamber plate which is kept at the base temperature of the fridge is 408 mm in diameter and offers a very large sample space of 70 liters when the magnet is not in place.
A 3D rendered image of a double dot electron pump and barrier gates on an etched Ahronov Bohm ring
There are three other sample spaces ranging in temperature from 50mK up to 4K where experiments can be setup. The high mass of the system provides for a very stable and low vibrational environment.
A fully integrated data acquisition system has been developed which allows for both DC and AC measurements. The department is equipped with lock-in amplifiers, source measure units capable of measuring current to a few fA as well as high frequency RF signal generators. The entire system is computer controlled and allows for remote operation from anywhere in the world.
The department is also equipped with a chemical vapor deposition system (CVD) for the production of nanowires such a silicon and carbon nanotubes. An Electro chemical deposition system is also in place to fabricate semiconductor and metallic nanorods using templated assisted growth.
A CdSe nano forest using templated assisted electro chemical deposition (Each wire is approx. 200nm is diameter)
Research areas of interest include low dimensional electron gas systems which incorporates single electron transport, electron pumping, quantum dots, quantum Hall effect, the Ahronov Bohm effect, and electron spin entanglement.
Applied research areas included the photocatalytic production of hydrogen, nanowire fabrication using chemical vapor deposition (CVD), fabrication of graphene, electrical metrology, and the production of polarized helium and Bose Einstein Condensates.