Abstract
ZnMgO is a wide band gap material and its band gap can be tuned from 3.37 eV to 7.8 eV. It has promising applications in ultraviolet optoelectronic devices, particularly in ultraviolet detectors and laser diodes. ZnMgO thin films at different oxygen partial pressure were prepared by pulsed laser deposition. Effect of oxygen partial pressure on structural and optical properties of ZnMgO thin films were investigated. Phase separation of ZnMgO into cubic and hexagonal was observed at high PO2 of 1.5 pa. Zn, Mg contents were also influenced by PO2, which results a decrease in band gap from 5.78 eV to 4.04 eV as the PO2 increased from 0 pa to 2 pa.
A Transparent ZnMgO/ZnO:Ga/c-sapphire hetero-structure with an optical transmittance of 73% in the visible region was fabricated by pulsed laser deposition technique. A simple contact approach, (i.e. across a W pin on top of the ZnMgO surface and another connected to the ZnO:Ga which acts as the transparent electrode) was used to observe the bipolar resistive switching in this structure. IV measurements were performed to determine the Conduction mechanisms. It was found that for low resistance state (LRS) conduction is explained by Ohmic behavior, but for high resistance state (HRS) Schottky emission model was used to explain for the conduction behavior. Moreover, the memory effect, good retention and endurance characteristics of the fabricated ZnMgO/GaZnO/c-sapphire device suggest its prospective application for the transparent resistive random-access memory devices.
Magnetic measurements on un-doped ZnO thin films grown at different PO2 were performed to expose the room temperature (RT) ferromagnetism (FM). An increase in magnetic moment with the increase in PO2 was observed. Coupling of un-pair electrons at O sites surrounding the Zn-vacancies is considered to arise the observed ferromagnetism in ZnO. Change in tensile stress along c axis and grain boundary area to volume ratio (sGB) may lead to increase in ferromagnetism with the increase in PO2. Temperature dependent magnetic measurements depicts that the Curie temperature of ZnO samples is well above the room temperature.
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