Oxford cryostat with variable temperature insert (between 1.5 K and 300 K) and superconducting magnet with a maximum field of 11 Tesla equipped with:
1. Complete system for measurements of the I-V characteristics of point contacts as well as tunnel and Josephson junctions between 1.5 K and 300 K (Cryogenic insert picture).
Uses: tunnel and point-contact spectroscopy, study of the density of states as a function of the energy, extraction of the Eliashberg function (spectral density of the electron-phonon interaction) from the experimental conductance curves. Determination of the gap amplitude in superconducting materials and of its dependence on magnetic field, temperature and doping. Measurements of the critical field(s) of the material under study by means of non-resistive measurements.
2. Complete equipment for measurements of the DC and AC resistivity and of the Hall coefficient at temperatures down to 1.5 K and magnetic fields up to 11 Tesla.
Uses: study of the transport properties of materials; determination of the Debye temperature, and of the transport electron-phonon coupling constant; evaluation of the density of free carriers and of the mean free path. In superconducting samples, determination of the critical temperature, of the critical current density and of their dependence on the magnetic field. Possibility to evaluate the upper critical field of the material.
3. Equipment for dynamical measurements of the AC susceptibility also in very small-sized samples (sub-mm scale)
Uses: measurements of the real and imaginary part of the susceptibility at thermal equilibrium or during thermal drift, also in samples with very small mass and size (e.g., single crystals of sub-mm size). In superconducting samples, measurement of the critical temperature and of the transition width. Evaluation of the approximate superconducting fraction and evidence of the existence of different phases.
Scanning tunnel microscope (STM) and Atomic Force Microscope (AFM) at room temperature and in air .
Uses: morphological characterization of the surfaces of films, polycrystalline samples and single crystals both of insulators and of conductors, up to the atomic resolution. Spectroscopic analysis with the possibility to map the tunnelling current, the conductivity and the density of states at a given energy.