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Silicon dioxide memristors possess multiple resistance states and can be used as a key component of memory devices and neuromorphic systems. However, their conductive mechanisms are incompletely understood, and their resistance switching (RS) variability is a major challenge for commercialization of memristors. In this work, by combining the desirable properties of silicon dioxide with those of a two-dimensional MXene material (Ti3C2), a memristor based on an MXene/SiO2 structure is fabricated. The Cu/MXene/SiO2/W memristive devices exhibit excellent switching performance compared with traditional Cu/SiO2/W devices under the same conditions. Furthermore, the role of the MXene/SiO2 structure in the SiO2-based memristors is revealed by the physical characterization of the MXene and first-principles calculation of the MXene/SiO2 structure. The results indicate that the conductive filaments (CFs) are more likely to grow along the locations of MXene nanostructures, which reduces the randomness of CFs in the Cu/MXene/SiO2/W memristors and further improves the device performance. Meanwhile, the MXene/SiO2 structure appears to greatly reduce the mobility of Cu ions in the entire RS region, as well as improve the performance of the SiO2-based memristors while maintaining the operating voltages low.

Optical properties and thermal stability of the solar selective absorber based on the metal/dielectric four-layer film structure were investigated in the variable temperature region. Numerical calculations were performed to simulate the spectral properties of multilayer stacks with different metal materials and film thickness. The typical four-layer film structure using the transition metal Cr as the thin solar absorbing layer [SiO 2 (90nm)/Cr(10nm)/SiO 2 (80nm)/Al (≥100nm)] was fabricated on the Si or K9 glass substrate by using the magnetron sputtering method. The results indicate that the metal/dielectric film structure has a good spectral selective property suitable for solar thermal applications with solar absorption efficiency higher than 95% in the 400-1200nm wavelength range and a very low thermal emittance in the infrared region. The solar selective absorber with the thin Cr layer has shown a good thermal stability up to the temperature of 873K under vacuum atmosphere. The experimental results are in good agreement with the calculated spectral results. KeywordsSolar Energy, Thermo-optical materials, Multilayers, Thin films, optical properties Abstract: Optical properties and thermal stability of the solar selective absorber based on the metal/dielectric four-layer film structure were investigated in the variable temperature region. Numerical calculations were performed to simulate the spectral properties of multilayer stacks with different metal materials and film thickness. The typical four-layer film structure using the transition metal Cr as the thin solar absorbing layer [SiO 2 (90nm)/Cr(10nm)/SiO 2 (80nm)/Al (≥100nm)] was fabricated on the Si or K9 glass substrate by using the magnetron sputtering method. The results indicate that the metal/dielectric film structure has a good spectral selective property suitable for solar thermal applications with solar absorption efficiency higher than 95% in the 400-1200nm wavelength range and a very low thermal emittance in the infrared region. The solar selective absorber with the thin Cr layer has shown a good thermal stability up to the temperature of 873K under vacuum atmosphere. The experimental results are in good agreement with the calculated spectral results.

A solar selective absorber with a multilayered SiO2 (87.0 nm)/Cr (8.3 nm)/SiO2 (96.3 nm) film structure was designed and fabricated by magnetron sputtering on a surface-roughened copper (Cu) substrate. The proposed structure can enhance solar absorption by combining both the typical solar absorption designs of the textured surface and metal–dielectric multilayer film structure. The measured solar absorptance is about 94%, which yields an enhancement of about 2% accompanied by a slightly higher thermal emittance than that observed for the surface-smoothed structure. The increasing thermal emittance of the surface-roughened film structure is expected to markedly cancel the advantage of absorptance enhancement as the temperature increases to 600 K, implying that the proposed film structure functions more efficiently at low or intermediate temperatures (<600 K).