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Optical properties of HfO <sub/>x</sub> ( <i>x</i> < 2) films grown by ion beam sputtering-deposition method
摘要： The optical properties of the HfOx films of different chemical composition (x < 2) deposited by ion beam sputtering-deposition (IBSD) method were studied. Spectral dependencies of refractive index n(λ) and extinction coefficient k(λ) were determined with ellipsometry in λ = 250–1100 nm wavelength region. The x values (i.e. [O]/[Hf] ratio) for the films were derived from x-ray photoelectron spectroscopy (XPS) data. The spectral dependences of optical constants n(λ) and k(λ) were found to undergo radical changes with x = 1.78–1.82. The films with x < 1.78 demonstrated high extinction coefficient k > 1 with the metallic-like behavior of optical constants spectral dependences. The films with x > 1.82 were found to be transparent, with k = 0 and n(λ) being well approximated by a Cauchy polynomial dependence for dielectrics. Using a sample with a gradient of x, it was established that the transition from the metallic to the dielectric-like behavior of the optical constants occurs not smoothly, but is discontinuous. A sharp jump in the optical constants is observed at x ≈ 1.8. According to XPS data, the transparent films were found to consist of two components only: HfO2 and Hf4O7 suboxide. Cauchy polynomial coefficients for Hf4O7 suboxide and HfO2 were found by using the Bruggeman effective medium approximation.
关键词： IBSD,ReRAM,spectroscopic ellipsometry,HfOx
更新于2025-09-23 15:21:01
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Recovery of cycling-induced endurance failed HfO <sub/><i>x</i> </sub> based memristive devices by utilizing oxygen plasma treatment
摘要： The oxygen ion (O2(cid:2)) loss effect during resistive switching (RS) cycles will inevitably lead to endurance degradation or even failure in oxide-based memristive devices. In this Letter, we propose an effective way to recover the cycling-induced endurance failed HfOx based memristive devices by utilizing oxygen plasma treatment (OPT). In the as-fabricated Pt/HfOx/Pt devices, a negative SET event is observed after consecutive normal RS cycles and eventually triggers endurance failure. The appearance of the intermediate resistance state at the initial stage of the negative SET cycle indicates a prominent reduction of the migration barrier of O2(cid:2), which accounts for the occurrence of negative SET after increasing cycles. Then, we recover the devices from endurance failure by moderate OPT, which can supply the available O2(cid:2) in RS cycles. More importantly, the first recovered devices after endurance failure can be recovered again through OPT, which better proves the validity of the recovery method. This study could provide an effective approach for understanding and addressing the cycling-induced endurance failure issue in oxide-based memristive devices.
关键词： oxygen plasma treatment,HfOx,endurance failure,memristive devices,resistive switching
更新于2025-09-12 10:27:22