Resistive switching in ZrO 2 based metal-oxide-metal structures

There is an increasing interest in resistive switching (RS) random-access memories (RRAM) for future electronics. A popular class of materials nowadays investigated for redox based resistive switches is transition metal oxides. A great challenge for the RRAM production is to develop a well-performing RS device compatible with a highly scalable CMOS technology. Among the group IV metal oxides, ZrO2 is of interest for RRAM because of its chemical similarity to HfO2 (exploited for high-k gate and RRAM applications) and because it is a fast ion conducting material. The goal of this work is a deeper understanding of the influence of the (i) metal-oxide-metal (MOM) layer stacks configuration, (ii) the oxide films microstructure, (iii) and their defect structure on the appearance of different switching modes, i. e. unipolar (UP) and bipolar (BP). The thesis is based on the work which was supported by a European Marie Curie action and performed at the Research Center Jülich in collaboration with the Finnish ALD Center of Excellence in Helsinki. The first part deals with the fabrication of ZrO2 thin films by an industrial compatible atomic layer deposition (ALD) process, the chemical, structural and morphological characterization of the films, the growth of ZrO2/TiO2 bilayers, the integration of the layers into metal-oxide-metal (MOM) devices and the electrical characterization with focus on the RS behavior. In the second part the effect of the device structure, in particular the thickness of the electrochemical active electrode (EAE) and the ZrO2 film morphology, on the RS switching polarity of Pt/ZrO2/(EAE) cells is discussed.