Resistive switching characteristics and theoretical simulation of a Pt/a-Ta2O5/TiN synaptic device for neuromorphic applications

Highlights: • We propose Pt/a-Ta₂O₅/TiN memristor device for hardware driven neuromorphic. • Increased and decreased conductivity can be observed by potentiation and depression. • Theoretical confirmation of this interfacial layer is also provided by charge transportation phenomena. • Design the single layer neural network for MINIST handwritten pattern recognition. • Integrated charge density plots depicted charge transfer mechanism. -- Abstract: Internet of things and big data demand the development of new techniques for memory devices going beyond conventional ways of memorizing and computing. In this work, we fabricated a Pt/a-Ta₂O₅/TiN resistive switching memory device and demonstrated its resistive and synaptic characteristics. Firstly, X-ray photoelectron spectroscopy (XPS) of a-Ta₂O₅/TiN analysis was conducted to determine elemental compositions of a-Ta₂O₅/TiN and TiON interfacial layer between a-Ta₂O₅ and TiN layer. Repetitive bipolar resistive switching was achieved by a set at a negative bias and a reset at a positive bias. Moreover, its biological potentiation and depression behaviors were well emulated by applying a repetitive pulse on the device. For deep understanding of this device's properties based on materials, oxygen vacancies, and stack engineering, theoretical calculations were performed employing Vienna ab-initio simulation Package (VASP) code. All calculations were carried out using PBE and GGA+U method to obtain accurate results. Work function difference between electrodes provided a localized path for forming a V_o based conducting filament in a-Ta₂O₅. Iso-surface charge density plots confirmed the formation of intrinsic V_o based conducting filaments in a-Ta₂O₅. These conducting filaments became stronger with increasing concentration of V_os in a-Ta₂O₅. Integrated charge density, density of states (DOS), and potential line ups also confirmed that V_o was responsible for charge transportation in a-Ta₂O₅ based RRAM devices. Experimental and theoretical results confirmed the formation of TiON layer between a-Ta₂O₅ and active electrode (TiN), suggesting that the bipolar resistive switching phenomenon of the proposed device was based on oxygen vacancy (V_o).