Abstract
Emerging memory technologies have sparked great interest in studying a variety of materials that can be employed in metal–insulator–metal topologies to support resistive switching. While the majority of reports focus on identifying appropriate materials that can be used as active core layers, the selection of electrodes also impacts the performance of such memory devices. Here, both the top and the bottom interfaces of symmetric Metal–Al:TiO $_{x}$ –Metal structures have been investigated by the analysis of their current versus voltage characteristics in the temperature range of 300–350 K. Three different metals were utilized as electrodes, Nb, Au, and Pt, for covering a wide range of work function and electronegativity values. Despite their symmetric structure, the devices were found to exhibit asymmetric performance with respect to the applied bias polarity. Clear signature plots indicating thermionic emission over the interface Schottky barriers have been obtained. The asymmetry between the top and the bottom interfaces was further evaluated by the values of the potential barrier heights and by the barrier lowering factors, both calculated from the experimental data. This study highlights the importance of the interface effects and proves that in addition to film doping, proper (top/bottom) metal selection, and interface engineering should also be exploited for developing thin film metal oxide based devices with tailored electrical characteristics.
Highlights
T HIN metal oxide (MO) films have attracted great attention over the last decade, mainly due to their promising exploitation in a variety of applications, including memristive devices/Resistive Random Access Memories (RRAMs) [1], [2], neuromorphic systems [3], [4], semiconductor devices [5] and sensing [6]
Our results present an asymmetric electrical behavior with respect to the applied bias polarity
In order to confirm that this asymmetry does not arise by any substrate induced effect (the substrate Metal-Oxide-Semiconductor (MOS) formed capacitor has been reported to affect Capacitance-Voltage (C– V) measurements [25] along with the interface states that induce losses on RF performance [26]), preliminary measurements performed with the substrate both floating and grounded revealed absolutely any differences
Summary
T HIN metal oxide (MO) films have attracted great attention over the last decade, mainly due to their promising exploitation in a variety of applications, including memristive devices/Resistive Random Access Memories (RRAMs) [1], [2], neuromorphic systems [3], [4], semiconductor devices [5] and sensing [6]. A common approach on the aforementioned studies is the implementation of distinct metal contacts formed at the top of the TiO2 films and are benchmarked via the room temperature assessment of their current-voltage characteristic. Considering these aspects, the paper aims to present a quantitative experimental study on the characteristics of both the top and the bottom electrode interfaces on Metal-Al:TiOx -Metal structures, linking the timely research fields of the film doping and interface characterization. This way clear field and temperature dependent signature plots of the dominant conduction mechanism were obtained, allowing quantitative interpretation of the experimental data
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