Speaker
Description
Plasmas are a (strongly) non-equilibrium medium and an efficient source of radicals, ions, and electrons. As such, they can strongly impact the structure and chemical composition of solid surfaces. Plasma sources are widely utilized to deposit new types of coatings using techniques like magnetron sputtering, plasma torches or pulsed laser deposition. In particular, magnetron sputtering is a flexible and powerful method for thin films deposition of various types including perovskites and ferroelectric materials. It is moreover easily scalable for treating large areas and it is relatively unexpensive. In this presentation we will present results for deposition of various materials and more particularly HfZrO and SrTiO3 which are considered for fabricating memory devices. By controlling the plasma parameters, it is possible to obtain epitaxial growth of ultra-thin films on vicinal surfaces. SrTiO3 is of particular interest as, at room temperature it is a dielectric, while under strain, or with doping, it can become ferroelectric. Due to lattice mismatch between MgO and SrTiO3, homo- and heterogeneous strain will be present in ultra-thin SrTiO3 films. In this presentation, it is shown that, to get insight and control of the plasma deposition process, specific care needs also to be taken about the preparation of the samples. Our results indicate that the MgO single crystal miscut angle, dislocations as well as impurities diffusion from the crystal bulk influence the MgO surface morphology after annealing. All these are thus critical for controlling the deposited thin films. The relation between the morphology of the MgO surface after preparation (i.e. cleaning and annealing) and the stability of the deposited SrTiO3 thin films is highlighted. Plasma parameters influencing the film properties such as the amount of oxygen need moreover to be taken into account.
