Strongly correlated systems exhibits a large variety of exotic and interesting properties such as high temperature superconductivity, half metallicity and metal insulator transitions. Transition metal oxides (TMO) are typically correlated systems and one of the most studied system is the vanadium dioxide (VO2). Because of the interplay between electrons and lattice, it undergoes a hysteretic metal insulator transition (MIT) around room temperature (~340 K) with a change in resistivity of different orders of magnitude , paired to a complex structural phase transition (SPT) starting from an insulating monoclinic phase at low temperature to a final stable metallic phase at high temperature with the rutile symmetry.
The VO2 is also extremely sensitive to chemical and physical perturbations such as stress and strain  that slightly tune the MIT temperature. Moreover, as other TMOs, it is characterized by a phase separation, intermediate phases at the nanoscale with different micro- and nano-domains having different electrical, structural and optical properties [3-5]. All these phenomena make VO2 an extremely interesting case-study with a wide range of potential applications in optics, sensors and novel memory devices [6-7].
Actually, the occurrence of an extremely fast reversible electronics and structural transitions is unusual and the nature and the driving mechanism of the VO2 MIT are still under debate despite decades of efforts since its first observation in 1959 [8-9]. Because of the strong interplay between lattice and electronics properties, to investigate the MIT transition it is necessary to use a fast technique, which have also the sensitivity to probe local structural and electronics properties simultaneously. XANES spectroscopy is a suitable method capable to probe the local electronic properties and the local structure changes induced by the MIT in this complex system.
We present here some preliminary XANES spectra measured with the Auger yield technique and ResPes measurements on thin films of VO2 from 8 nm to 32 nm, in order to monitor changes induced from the MIT to electronics and structural properties and the possible presence of metastable phases during the transitions in these films. Finally, we will discuss the results and experimental perspectives based on the synthesis and characterization of VO2 nanoclusters of 5-10 nm using a Pulsed Microplasma Cluster Source (PMCS) under installation at Elettra.
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