Modelización compacta de las características de conducción de dispositivos de conmutación resistiva

Abstract

The research area where this Ph. D thesis is framed is situated around a compact model for the conduction characteristics of metal-insulator-metal (MIM) structures in which resistive switching (RS) phenomena is observed. Titanium Oxide (TiO2) and Hafnium Oxide (HfO2) have been mainly the selected materials. In the case of TiO2, activities have been developed in collaboration with Physics Materials Group of CNEA, Buenos Aires, Argentina. In the case of HfO2, collaboration with the Institute of Electrical Engineering, SAS, Bratislava, Slovakia, has been performed. Moreover, other materials have been used in collaboration with other research groups (University College London, Universidad de Valladolid, University of Helsinki, etc.). The model proposed consists in an equivalent circuit representation based on diodes and series or parallel resistances. The resulting circuit equation is solved using the W Lambert function. To include this function in a compact model special approximations are required. The memory effect is represented as a recursive relation for an internal variable of the device, as is considered in memristive systems. Furthermore, tools to include the memory effect (hysteresis behavior) in the model have been developed, but in a more general from. It consists in a Preisach-like approximation. This is new in the field of the resistive switching compact modeling. On the other hand, the doctorate activity has also focused on the nanoscale MIM structure fabrication that shows resistive switching, structures defined with crossbar-like electrodes. The samples are fabricated at ICMAB-CNM under supervision of Dr. Francesca Campabadal and Dr. Mireia González. As compendium of works thesis, the presented results will refer to the published works done written as first author. The subjects to develop in the chapters are the following:_x000D_ _x000D_ • In chapter 1, resistive switching associated phenomenology is introduced: switching (bipolar, unipolar, filamentary, interfacial, soft or hard state transitions, etc.), used materials, technology associated (arrays, crossbar, etc.) and future applications._x000D_ _x000D_ • In chapter 2, resistive switching modeling types are collected. The estate of the art in memristive description models is presented before presenting the compact model developed as part of the thesis._x000D_ _x000D_ • Chapter 3 describes from its origins the circuit model used to represent the resistive switching: Quantum Point Contact model (QPC). The evolution of the considered sigmoid function, essential function to simulate low (HRS) and high (LRS) conduction of the hysteretic cycle, is also described. _x000D_ _x000D_ • The models described in chapter 4 add to the ability of simulating full state transitions of the past chapter the ability of simulating partial transitions._x000D_ _x000D_ • Chapter 5 is focused on the MIM structures fabrication developed at CNM-ICMAB, Barcelona. The fabricated structure is described, the electric characterization results are shown and the experimental data is represented using some of the reported models of the past chapters. _x000D_ _x000D_ • Finally the chapter 6 presents the conclusions obtained as a result of the developed research within the thesis.

Date of Award	19 Jun 2017
Original language	Spanish
Supervisor	Enrique Alberto Miranda Castellano (Director)