We have three experimental setups for studying correlated electron materials by spectroscopic imaging STM, a fourth one is currently under construction. The instruments operate in cryogenic ultra-high vacuum and are optimized for high stability and a long continuous measurement time. They provide sample transfer without the need to warm the systems up and in-situ sample cleavage.
- The first STM is mounted in a liquid helium bath cryostat with a 16T superconducting magnet. The STM is attached to a home-built insert which allows for operation of the STM at temperatures from 1.6K to ~50K. Hold time of the cryostat is ~100h. Details of the design are discussed in Rev. Sci. Instr. 82, 113708 (2011).
- The second machine is based on a dilution fridge mounted in a 14T superconducting magnet and can operate at temperatures down to below 20mK. The cryostat has been built by Oxford Instruments with modifications to allow for sample transfer and continuous operation for more than 100h. For details of the setup see Rev. Sci. Instrum. 84, 013708 (2013). To the best of our knowledge, this is the coldest STM in the UK!
- The third instrument operates at temperatures down to 1.6K in a vector magnet, allowing for fields of up to 5T being applied in any direction with respect to the sample as well as up to 9T normal to the sample surface. The instrument is prepared for a combined STM/AFM head to allow also for studies of poorly conducting and insulating materials, as well as for multiple sample contacts. The setup is described in Rev. Sci. Instrum. 88, 093705 (2017).
All instruments are controlled by the Open Source STM software project GXSM and with home-built electronics.
Furthermore, as part of the Centre for Designer Quantum Materials, we operate a molecular beam epitaxy system for transition metal oxide and chalcogenide materials with in-vacuo sample transfer to the STMs.