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High dielectric constant oxides for CMOS technology

Authors: Marco Curado Alberto

Supervisors: Rui César do Espírito Santo Vilão

MSc thesis, (2017)

Abstract: Hydrogen in the paramagnetic rare earth oxide Nd2O3 (neodymium sesquioxide) was investigated through muon spin spectroscopy measurements obtained at the EMU instrument of the ISIS Facility (Rutherford Appleton Laboratory, United Kingdom). Muonium, as a light pseudo-isotope of hydrogen, was used to mimic the electronic configurations of hydrogen. Both the donor-like configuration at an oxygen-bound site and the acceptor-like configuration at an interstitial site have been identified. A fast relaxing component is also observed, which is identified with a transition muonium state occurring during the formation. This fast component presents a negative frequency shift that we interpret as an effect of the paramagnetic magnetization at low-temperatures, in conjunction with ancillary magnetometry measurements performed at the TAIL Facility of the University of Coimbra. The temperature dependence of the fractions allows identifying the conversion barrier from the interstitial congfiuration to the oxygen-bound congfiuration with an activation energy of 0.5 eV, as well as the barrier height from the transition state to the oxygen-bound configuration at 0.15 eV. The diffusion of the positively charged species above room temperature is also identified as an activated process with an activation energy of 0.14 eV. This is the first attempt to characterize the hydrogen configurations at a paramagnetic oxide using the sensitive muon probe, and the results clearly show the feasibility of the method.