We operate four setups for studying correlated electron materials by spectroscopic imaging STM. 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. Each instrument has its own operating range:
- our STM1 is mounted in a liquid helium bath cryostat with a 14/16T 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).
- STM2 is based on a dilution refrigerator 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!
- STM3 operates at temperatures down to 1.6K in a vector magnet (built by American Magnetics), 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).
- STM4 is designed for in-vacuo transfer of thin film samples from the growth facilities of the Centre for Designer Quantum Materials and the ultra-low vibration laboratory. It enables topographic and spectroscopic characterisation at temperatures down to 1.8K.
Our capabilities for atomic-scale imaging and spectroscopy are closely interlinked with the facilities of the Centre for Designer Quantum Materials, including a molecular beam epitaxy system for transition metal oxide and chalcogenide materials with in-vacuo sample transfer to the STMs, thin film X-ray diffraction, and physical and magnetic property measurement systems.