Unveiling the dual role of chemically synthesized copper doped zinc oxide for resistive switching applications

• Main Authors: Gollu, Sankara Rao, Roy, Sounak, Banerjee, Souri, Kundu, Souvik, Boppidi, Pavan Kumar Reddy, Raj, P. Michael Preetam, Challagulla, Swapna
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2019
• Subjects: Ferroelectric Devices; DRNTU::Engineering::Electrical and electronic engineering; Polarization
• Online Access: https://hdl.handle.net/10356/82966; http://hdl.handle.net/10220/47526
• Institution: Nanyang Technological University

In this study, efforts were devoted to unveiling the dual role of single crystalline Cu (5%) doped ZnO (Cu:ZnO) synthesized by a simple and low-cost chemical process and to investigate its efficacy on resistive switching (RS) applications. It was found that when Cu:ZnO was annealed at a lower temperature of 450 °C and integrated onto ITO/glass for RS applications, only oxygen mediated vacancies were responsible for its resistive switching. However, ferroelectric properties have been observed when the same Cu:ZnO was annealed at a higher temperature of 800 °C and integrated onto Nb doped SrTiO3. X-ray diffraction, high resolution transmission electron microscope, x-ray photoelectron spectroscopy, UV-VIS-near infrared spectrometer, and piezoelectric force microscopy (PFM) were employed to study the crystallinity, interfaces, chemical compositions, bandgap, and domains in Cu:ZnO thin films, respectively. The bandgap of Cu:ZnO was found to be 3.20 eV. PFM study exhibits the domain inversion with 180° polarization inversion by applying an external bias, evidencing its effectiveness for memory applications. When the electrical characteristics were concerned, the RS device based on this ferroelectric Cu:ZnO offers better performance, such as lower SET/RESET voltages (∼1.40 V), higher retention (up to 106 s) without distortion, and higher ON/OFF ratio (2.20 × 103), as compared to the former lower temperature annealed Cu:ZnO devices. A band-diagram was proposed, and transport studies were developed to understand the operational mechanism of these devices. This study explains both the limits and scopes of Cu:ZnO RS devices and formulates an idea which may accelerate the design of future generation devices.