STSM of Matteo Salvato at Chalmers University of Technology Quantum Device Physics Laboratory
The main purpose of the STSM between September and December 2018 was to fabricate Topological Insulator (TI) nanowires and nanobelts by CVD vapor-solid deposition method. During the first period, the experimental facility was set-up, calibrated and tested and nanobelts of Bi2Se3 were grown on different substrates. EDS, SEM and x-ray diffraction analyses confirmed the achievement of the correct phase within 2% and the expected shape and lattice structure. At optimal growth conditions, jungle of nanowires with average length of the order of 30 microns and width as large as 100 nm were observed. Their density was of more than 100 nanowires in areas of 50×50 square microns. Some nanowires were transferred on SiO2 substrates and contacted in Hall bar geometry for transport measurements. They show room temperature sheet resistance of the order of 100 Ohm in agreement with the data reported in literature for the same material. Oscillation of the longitudinal resistance as a function of the external magnetic field up to 14 T at T=4 K demonstrated the topological properties of the obtained samples. Some results are the object of recent scientific publications (10.1103/PhysRevApplied.16.024038; doi: 10.1063/5.0022126).
As a result of the stay, a strong and a fruitful collaboration started with the Chalmers group. We elaborated a new fabrication method for TI thin film deposition, which was the object of a further scientific publication (DOI: 10.1039/d0nr02725a). Furthermore, thanks to the experience acquired at Chalmers, Matteo Salvato is now active as growers of TI and other 2-dimensional thin films for optoelectronic applications and opened a new research line in his Department at University of Rome “Tor Vergata” participating at several national and international research projects.