Energy consumption is a critical limitation for future devices. Semiconductor technologies have reached their intrinsic limitations and disruptive breakthroughs are required. Neuromorphic computing offers a new path towards devices with higher efficiency. Recent results of our collaborators in Sandia National Laboratories (USA) indicate that a device based upon a resistance switching mechanism using LixCoO2 offers a highly promising solution. LixCoO2 has been widely used as a charge storage material in batteries, but it may become soon critical for building a synaptic transistor. However, the physical mechanisms behind the operation of LixCoO2 are not yet understood. In particular, the electronic behavior of LixCoO2 is governed by a poorly understood metal-insulator transition that drives the compound from an insulating phase for LiCoO2 to a metal for the delithiated LixCoO2.
This project focuses on the electronic and structural properties of epitaxial thin films of LixCoO2, using photoelectron spectroscopy and microscopy, surface x-ray diffraction and scanning probe microscopies, both in our home laboratories in Madrid and in European synchrotron radiation laboratories. Epitaxial thin films of LixCoO2 grown ex-situ will be characterized,in order to understand their complex electronic behavior and the structural parameters determining it. The delithiation process, related to hole doping and relevant for operation, will be analyzed. Third, model systems suitable to understand the relevant physical processes in the metal-insulator transition will be studied. The goal of the project is to achieve a much better understanding of the physical processes governing the electronic behavior of LixCoO2, to improve its features and to find new materials with better characteristics.