Structural and Surface Characterization
Contact person: Rossi Francesca

This research activity (AdR) is devoted to the characterization of solid materials – inorganics, organics and hybrids – and involves surface and interface analysis, structural and chemical analysis, optical spectroscopy and imaging. Single and hetero-structured systems, either in their bulk, thin film or low-dimensional state, i.e. 2D (quantum wells; flakes), 1D (nanowires; nanotubes), 0D (quantum dots; nanoparticles), are analysed. This approach allows a complete characterisation of materials and devices, aimed at growth optimisation, device performance improvement, reverse engineering and problem solving.

The CSS AdR combines several studies, concerning: 

A. Morphology, topography and size statistics. Activities include: Atomic Force Microscopy (AFM); Low Temperature Scanning Tunnelling Microscopy (LT-STM); Scanning Electron Microscopy, combined with Focused Ion Beam (FIB, with Ga ions) to cut selected sample regions and study the internal structure of hetero-structured and porous materials; Transmission Electron Microscopy (TEM) enabling 3D tomographycal reconstruction.

B. Crystal structure: crystallinity, phase and orientation, defects. Activities include: X-Ray Diffraction (XRD) techniques; Transmission Electron Microscopy (TEM) imaging and Electron Diffraction, carried out when required on FIB-prepared lamellas; Low Energy Electron Diffraction (LEED) for surface order analysis.

C. Composition and chemistry (e.g. coordination, chemical environment, valence state). Activities include: Energy Dispersive X-Ray spectroscopy and mapping (EDX), either SEM-EDX or TEM-EDX; Electron Energy Loss Spectroscopy (EELS), either TEM-EELS or UHV-EELS, and high resolution EELS (HREELS); Scanning Transmission Electron Microscopy with High Angle Annular Dark Field (STEM-HAADF) imaging.

D. Electronic properties. Activities include: X-Ray Photoelectron Spectroscopy (XPS), carried out either with laboratory facilities or at the synchrotron beamline; Ultraviolet Photoelectron Spectroscopy (UPS); Scanning Tunnelling Spectroscopy (STS) with LT-STM; X-Ray Absorption Spectroscopy (XAS) at the synchrotron beamline.

E. Optical properties. Activities include: Ellipsometry; Photoluminescence (PL) spectroscopy; Cathodoluminescence (i.e. luminescence excited by the electron beam of an SEM, SEM-CL) spectroscopy and imaging; X-Ray Excited Optical Luminescence (XEOL) spectroscopy, carried out either with laboratory facilities or at the synchrotron beamline.