It was a long-term internship within the team "Oxydes in low dimension" under the supervision of Mr Rémi Lazzari Alain, the objective of this internship is the finalization of my PhD thesis and the work done was STM exploration of the growth of MgO thin films on Ag (100) crystals while learning ultra-high vacuum technologies and advanced surface characterization techniques such as LEED, XPS and STM.