Mixed anodic oxides for forming-free memristors revealed by combinatorial screening of hafnium-tantalum system. (March 2022)

• Record Type: Journal Article
• Authors: Zrinski, Ivana; Minenkov, Alexey; Cancellieri, Claudia; Hauert, Roland; Mardare, Cezarina Cela; Kollender, Jan Philipp; Jeurgens, Lars P.H.; Groiss, Heiko; Hassel, Achim Walter; Mardare, Andrei Ionut
• Is Part Of: Applied materials today. Volume 26(2022)
• Publication Date: 2022-03
• Subjects: Metallic thin films -- Combinatorial libraries -- Anodic memristors -- Anodic oxides -- Valve metals; random access memories (ReRAMs) -- complementary metal-oxide-semiconductor (CMOS) -- conductive filaments (CF) -- high resistance state (HRS) -- low resistance state (LRS) -- metal-insulator-metal (MIM) -- valence change memory (VCM) -- electrochemical metallization memory (ECM) -- energy-dispersive x-ray spectroscopy (EDX) -- scanning edx (SEDX) -- standard hydrogen electrode (SHE) -- citrate buffer (CB) -- scanning electron microscopy (SEM) -- pulsed voltage stress (PVS) -- high-resolution transmission electron microscopy (HRTEM) -- focused ion beam (FIB) -- X-ray photoelectron spectroscopy (XPS) -- hard X-ray photoelectron spectroscopy (HAXPES) -- inelastic mean free path (IMFP) -- phosphate buffer (PB) -- Auger parameter (AP) -- fast Fourier transform (FFT) -- nanoparticles (NPs); Materials science -- Periodicals; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1016/j.apmt.2021.101270
• Languages: English
• ISSNs: 2352-9407

Abstract

Highlights: A combinatorial approach identifies enhanced forming-free Hf-Ta anodic memristors. Alloys with Hf < 50at% produce oxides memristors similar to anodic Ta2 O5 . Between 50 and 70at%Hf, the memristors exhibit threshold and non-volatile behavior. High resistance state ratios are found for anodic Hf-Ta unipolar memristors. Crystallites embedded into an amorphous oxide matrix are identified by TEM. Abstract: A combinatorial screening approach has been designed for identification of Hf-Ta anodic memristors with enhanced properties. Three distinct compositional zones with similar characteristics have been identified, two of which are relevant for memristive applications. In a Hf-poor zone, (< 50 at.% Hf), the memristive behavior is similar to that of anodic Ta2 O5 . A second compositional zone (Hf content between 50 and 70 at.%) produced anodic memristors which dramatically differ. Devices in this region resemble forming-free unipolar behavior and show resistive states ratios of more than 8 orders of magnitude while retaining and enduring more than one million switching cycles. Photoelectron spectroscopy with soft and hard X-rays has been applied for understanding the chemistry of these special anodic structures and enrichment of Hf species close to the surface of anodic oxides has been evidenced. Unlike bipolar memristors from the first zone, the newly identified unipolar memristors show an in-depth homogeneous local chemical state of Hf and lower electronic polarizabilities for both O and Hf. High-resolution transmission electron microscopy reveals HfO2 crystallites embedded into an amorphous oxide matrix. These entities formed during the anodization process are considered to be responsible for the coexistence of threshold and non-volatile memristive characteristics. Abstract : Image, graphical abstract