Transparent metal oxides for low power neuromorphic devices

Thesis submitted in the fulfillment of the requirement for the degree of Doctor of Philosophy by Darshika Sanjay Khone Under the supervision of Dr. Abhimanyu Singh Rana and Dr. Suchitra Rajput Chauhan Doctor of Philosophy 2024

The motivation for this thesis was to study the resistive switching and memristive properties of metal insulator metal structure neuromorphic device due to the increasing demand of computing power consumption where neuromorphic electronics can pay a vital role. Therefore, we have fabricated the transparent thin films like a- tantalum oxide (Ta2O5) and a- hafnium oxide (HfO2) was grown using electron beam evaporation technique. The increasing demand for transparent and flexible electronic devices in a range of applications, including wearable electronics, augmented reality displays, and transparent smart windows and circuits, has motivated significant research efforts to develop T-RRAM (Transparent- Resistive Random-Access Memory) and F-RRAM (Flexible- Resistive Random-Access Memory) devices. These devices have a capacitor like Metal-Insulator-Metal (MIM) architecture. We have fabricated the device based on different optimized coatings on transparent glass substrate and flexible substrate. We have successfully developed transparent smart materials thin film for neuromorphic devices which exhibit more than 85% transparency. We have found that it shows a clear hysteresis and RS behavior and, in some case, also memristive behavior. After that a comprehensive examination of the RS characteristics demonstrated by the fabricated transparent resistance memory device. A thorough analysis is conducted to study the RS behavior, aiming to clarify the filamentary mechanisms. Experimental results containing voltage-current characteristics, retention, endurance tests, and cumulative probability distributions are presented and discussed. These findings aim to provide valuable insights into the performance and reliability of the device. Additionally, we explored the RS phenomena in more detail by examining how it depends on different operational characteristics. This includes the impact of altering the thickness of insulating switching materials, employing different top electrodes, and analyzing the effects of external perturbations such as temperature variations and gamma irradiation.