ABSTRACT
2D materials with intriguing properties have been widely used in optoelectronics. However, electronic devices suffered from structural damage due to the ultrathin materials and uncontrolled defects at interfaces upon metallization, which hindered the development of reliable devices. Here, a damage-free Au/h-BN/Au memristor is reported using a clean, water-assisted metal transfer approach by physically assembling Au electrodes onto the layered h-BN which minimized the structural damage and undesired interfacial defects. The memristors demonstrate significantly improved performance with the coexistence of nonpolar and threshold switching as well as tunable current levels by controlling the compliance current, compared with devices with evaporated contacts. The devices integrated into an array show suppressed sneak path current and can work as both logic gates and latches to implement logic operations allowing in-memory computing. Cross-sectional scanning transmission electron microscopy analysis validates the feasibility of this nondestructive metal integration approach, the crucial role of high-quality atomically sharp interface in resistive switching, and a direct observation of percolation path. The underlying mechanism of boron vacancies-assisted transport is further supported experimentally by conductive atomic force microscopy free from process-induced damage, and theoretically by ab initio simulations.
ABSTRACT
Motivated from increasing demands of non-contact optical temperature sensing, the Yb3+-Er3+ and Eu3+ doped NaY9Si6O26 (NYS) oxide phosphors were designed by high-temperature solid-state reaction method. The phase purity of the as-prepared samples was checked from XRD patterns. For the upconversion luminescence in NYS:Yb3+,Er3+, the optimal Er3+ doping content was determined to be 1â¯mol%, and the characteristic emission peaks of Er3+ were observed in the region of 500-700â¯nm. In Eu3+ activated NYS phosphors, it has been found that the emissions originating in 5D1 and 5D0 levels demonstrate different change tendencies in intensity with Eu3+ doping concentration. By studying the temperature-dependent luminescent spectra, it was indicated that the emissions intensities from different excited states of Er3+ change differently with temperature. Two kinds of fluorescence intensity ratio (FIR) strategies were used in NYS:10%Yb3+,1%Er3+, containing thermally-coupled levels and non-thermally-coupled levels. In the NYS:3%Eu3+ phosphor, it was found that the FIR for 577 and 536â¯nm emissions follows a linear relation with temperature. The high sensitivities in the present phosphors indicate the potential application in optical temperature sensing.
ABSTRACT
In this paper, new upconversion (UC) phosphors for Yb3+-Er3+- and Yb3+-Ho3+-doped Gd9.33(SiO4)6O2 (GSO) were designed via a solid-state reaction method. The phase purity of the samples was examined using XRD patterns. In Yb3+-Er3+ -doped GSO, the characteristic emission peaks of Er3+ appear upon 980 nm excitation, and the optimum Er3+ concentration was found to be 1 mol%. Different changes in the intensity of green and red emissions with Er3+ concentration appeared, and were interpreted by cross-relaxation between Er3+ ions. In Yb3+-Ho3+-doped GSO, three emission peaks of Ho3+ were observed, and the power-dependent UC luminescence was studied. For studying the temperature-sensing properties, different strategies were employed, including thermally coupled levels and non-thermally coupled levels. High sensitivities were obtained in the phosphors, and GSO:Yb3+,Er3+ showed the highest sensitivities. The above investigation results indicated that the developed GSO:Yb3+-Er3+/Ho3+ phosphors could have potential applications in optical thermometry.
