ATOMIC-SCALE STRUCTURAL CHARACTERIZATION OF OXIDES
Senior investigator: Dr. Matteo Ferroni
The investigation of the chemical composition and crystalline arrangement of the nanostructured materials is carried out by advanced imaging techniques:
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Electron microscopy
Scanning (SEM) and transmission (TEM) electron microscopy feature the highest attainable spatial resolution and the associated imaging/analytical techniques are capable to provide structural and chemical information at the atomic scale. The research activity is based on the high-resolution SEM put into operation in 2004 at SENSOR and the TEM at the characterization facility of the IMM CNR Bologna. The SEM is capable of detection of transmitted electrons, thus providing compositional imaging at the nanoscale associated to semi-quantitative EDX elemental analysis. The SEM was also equipped in 2006 with two-independently operated piezo-actuators for manipulation of nanowires and in-situ probing of the electrical conductance of nanostructures.
TEM measurements are carried out within the SENSOR scientific collaboration with IMM CNR Bologna.
The conventional imaging methods (high resolution and diffraction contrast imaging, electron diffraction, nanoprobe diffraction and EDX analysis) are used for morphological and micro-structural investigation of the materials.
The TEM is also equipped with High-Angle-Annular-Dark-Field (HAADF) detector and electrostatic bi-prism for Z-contrast imaging and holography.
HAADF allows atomically-resolved imaging of the crystalline lattice and the determination of dopants and impurities; in addition electron holography will provide an accurate measurement of the spatial distribution of electrically-active dopants and their effect on the electrical properties in nanostructures.
Structural characterization facilities available at Ferrara include clean rooms for technological processes, physico-chemical characterizations (BET and chemisorption with mass spectrometer) optical characterizations (in particular photoluminescence measurements at operating conditions), electrical characterization (AC and DC measurements, work function and Hall effect at operating conditions), thermal characterization as DTA/TG; the Electron Microscopy Centre (SEM, TEM, AFM) is available, too.
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Scanning probe microscopy
Scanning probe microscopy, namely scanning tunnelling microscopy (STM) and atomic force microscopy (AFM), allow characterization and modification of surfaces at the nanoscale. The activity at SENSOR is mainly focused on AFM-based techniques. The microscope works in different AFM-modes including phase imaging and Kelvin probe force microscopy (KPFM), which permit to map different samples properties together with surface morphology. The microscope is also equipped to work with nanolithography techniques such as local anodic oxidation (LAO) and dip-pen nanolithography (DPN).