Enhancement of temperature-modulated NbO₂-based relaxation oscillator via interfacial and bulk treatments

Abstract

This work demonstrates oscillation frequency modulation in a NbO2-based relaxation oscillator device, in which the oscillation frequency increases with operating temperature and source voltage, and decreases with load resistance. An annealing-induced oxygen diffusion at 373 K was carried out to optimize the stoichiometry of the bulk NbO2 to achieve consistent oscillation frequency shift with device temperature. The device exhibits stable self-sustained oscillation in which the frequency can be modulated between 2 MHz and 33 MHz, and a wider operating voltage range can be obtained. An additional surface treatment step was employed during fabrication to reduce the surface roughness of the bottom electrode and to remove surface contaminants that affect the interfacial properties of the device. The device frequency tunability coupled with high oscillating frequency and high endurance capability of more than 1.5×108 cycles indicate that the Pt/NbO2/Pt device is particularly suitable for applications in oscillatory neural network.

Enhancement of NbO2-based oscillator neuron device performance via cryogenic operation

“…´´-f is the frequency, R s is the series resistance, and C is the capacitance [7]. Since we can obtain V th , V h , R s , and f through the oscillation data of figures 4(a) and (b), we can extract the capacitance at 300 K (80 pF) and 120 K (71 pF).…”

“…However, conventional silicon CMOS-based circuits occupy a large footprint, hindering the high-density array. Niobium dioxide (NbO 2 ), which has insulator-metal transition (IMT) characteristics, has attracted much attention for use as an oscillator neuron device owing to its simple metal-insulatormetal structure [1][2][3][4][5][6][7][8]. Nevertheless, the limited on/off resistance ratio of NbO 2 poses a challenge, narrowing the weighted sum range that meets the oscillation operation requirements and limiting the implementation of large-scale synapse arrays [1][2][3].…”

Effect of Interdiffusion and Crystallization on Threshold Switching Characteristics of Nb/Nb2O5/Pt Memristors

“…This process refers to the intricate interplay between the electrode and the metal oxide (e.g., HfO 2 , TaO 2 , and TiO 2 ), encompassing various redox processes and ionic migrations within the material. − Understanding and controlling these effects is critical for optimizing the performance, stability, and reliability of memristive devices. , Further, recent studies have shown that the specific nature of volatile resistive switching in oxide-based devices depends strongly on the choice of electrodes and their reaction with the functional oxide layer. , For example, threshold switching is observed in Nb 2 O 5 -based devices that employ a reactive electrode (e.g., Nb, Ti, Cr, and TiN), while low-endurance, bipolar resistive switching is observed in devices with inert (e.g., Pt) electrodes . It has also been shown that resistive switching characteristics depend on the structure of the oxide film, with polycrystalline films requiring lower electroforming voltages than amorphous films due to grain-boundary conduction. , Since devices can be subjected to elevated temperatures during processing and/or operation (e.g., electroforming), it is important to understand how metal/oxide interactions and crystallization depend on the temperature . While extreme temperatures can likely be avoided, even back-end of line (BEOL) processing will see devices subjected to temperatures in the range of 673–773 K. , …”

“…18 It has also been shown that resistive switching characteristics depend on the structure of the oxide film, with polycrystalline films requiring lower electroforming voltages than amorphous films due to grain-boundary conduction. 20,21 Since devices can be subjected to elevated temperatures during processing and/or operation (e.g., electroforming), it is important to understand how metal/oxide interactions and crystallization depend on the temperature. 22 While extreme temperatures can likely be avoided, even back-end of line (BEOL) processing will see devices subjected to temperatures in the range of 673−773 K. 23,24 In this study, we investigate the temperature dependence of oxygen interdiffusion and crystallization in Nb/Nb 2 O 5 heterostructures and how such processes affect the quasistatic current−voltage characteristics of Nb/Nb 2 O 5 -based devices.…”