A resistive switching random access memory (RRAM) has occupied great scientific and industrial interest for next-generation data storage technology because of its advantages of nonvolatile behavior, low power consumption, high density, rapid writing/erasing speed, and simple operating system. In this work, the wide spectrum with self-colored ZnO layers on the Ti foil is obtained by varying the sputtering time, and the colors of these ZnO films can be tuned by a MoS 2 layer covering. Further, an existence of resistive switching (RS) memory and negative differential resistance (NDR) state in MoS 2 /ZnO heterojunction devices was demonstrated, in which the bright yellow Ag/MoS 2 /ZnO/Ti device shows the best performance with long time endurance. This work opens up an opportunity for exploration of the multifunctional components in future electronic applications.

We have theoretically and experimentally studied exciton properties of three normal Nb 2 O 5 polymorphs, including pseudo-hexagonal (TT-), orthorhombic (T-), and monoclinic (H-) phases. Theoretical work shows that the exciton binding energy for H-Nb 2 O 5 is 73.553 meV, much higher than that for TT-Nb 2 O 5 (3.515 meV) and T-Nb 2 O 5 (24.071 meV). The H-Nb 2 O 5 material, as characterized by field-induced surface photovoltage spectroscopy, uniquely presents bound exciton states near the bottom of the conduction band. Thermogravimetric analysis and photoluminescence (PL) lifetime demonstrate that the bound exciton states in H-Nb 2 O 5 originate from interactions between the exciton pairs and oxygen vacancy sites. Such excitons in H-Nb 2 O 5 can be effectively dissociated into free electrons and holes with the incorporation of the oxygen vacancies, leading to the longer PL lifetime. This work allows one to find correlations between material structures and exciton properties, which will provide some basic knowledge to optimize materials for optoelectronic and photonic performance.

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In this study, large-area ZnO nanorod arrays covering a Zn foil substrate were produced by a low-cost and low temperature approach. In this approach, oxidation of zinc metal was achieved in a formamide/water mixture. Taking advantage of the product, a sandwiched structure, Ag/ZnO/Zn, was fabricated in which Ag acts as the top electrode, ZnO as the active layer and Zn foil as the bottom electrode. Resistive switching memory behavior (with an HRS/LRS resistance ratio of ∼10) along with a negative differential resistance effect (the largest slope being −3.85) was synchronously observed for this device at room temperature. This device opens up possibilities for multifunctional components in future electronic applications.

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