The PhD thesis of Dr. Antônio Cláudio Michejevs Padilha, entitled “Computational simulation of TiO2-based memristive systems: from the raw material to the device”, won the CAPES Award for best PhD thesis of the year 2015. The PPG-NMA congratulates the author as well as his supervisor Gustavo M. Dalpian.
Dr. Padilha developed his work with a FAPESP scholarship, and a short-term internship at Yokohama University, Japan. The main theme of his research focused on memristive devices, also called memristors. These are devices that possess the property of changing their state of resistance when a current passes through them. The memoristor is a two-terminal device capable of storing information through its resistance, consisting of a metal / insulator / metal structure. This device can revolutionize the memory industry since they have fast switching times and long retention times, as well as high densities. However, its working principle is not fully understood at the atomic level, so its application is prevented.
The purpose of the doctoral thesis was to study these types of devices, trying to clarify their working mechanism. The student developed initial studies on the materials inherent to the devices, that is, oxygen deficient phases of TiO2; studied in detail the interface properties between materials within these devices; developed a theoretical model, purely electronic, for the switching of these devices; studied the load/storage properties inherent to the oxygen deficient phases observed in these devices. To develop his work, Dr. Padilha used theoretical methods based on the Density Functional Theory, but also made use of simpler models, solving the Poisson Equation for a metal-insulator-metal interface. Finally, he developed computational codes to estimate the current that would be observed in these devices.
At the end of the work, there was a perfect marriage of multiscale techniques, starting with atomic and electronic methods, and using macroscopic theoretical techniques for the simulation of devices. The resulting papers have been published in major journals, including Physical Review B, Physical Review Applied, and Scientific Reports.
More information and full work here.