We investigate a series of Ag-Al thin films containing up to 12 at% Al with the purpose of discovering whether these alloys would be a better choice for nanophotonic applications than pure Ag. Variable angle spectroscopic ellipsometry, AFM, x-ray diffraction and density functional theory are applied to explore and characterize the materials. Electromagnetic simulations of optical properties are used to place the results into a theoretical framework. We find that the increase in electron-to-atom ratio associated with the Al additions changes the optical properties: additions of the order of 1-2 at% Al are beneficial as they are associated with favorable changes in the dielectric function, but for greater additions of Al there is a flattening of the absorption edge and an increase in optical loss. In addition, contents of more than about 2 at% Al are associated with the onset of time-dependent intergranular oxidation, which causes a pronounced dip in the reflectance spectrum at about 2.3-2.4 eV (∼500-540 nm).

The effects of graphene oxide (GO) addition on the dispersion of nanosilver (Ag) in an MgB2 matrix were studied using bulk samples prepared through a diffusion process. The influence of the dispersion of Ag and Ag/GO particles on the critical current density ( Jc) of MgB2 was also investigated. GO has emerged as an excellent dopant which can significantly improve both the low-and high-field performance of MgB2 due to its capability to improve intergrain connectivity (GO) and inter-and intragrain pinning (GO and AgMg). The addition of nanosize Ag particles also results in an improvement of vortex pinning, and at the same time, it offers the advantage of preventing the loss of Mg during the sintering process. It is found that the dispersion of nanosilver in the presence of GO results in significant improvements in the critical current density in MgB2, particularly at high magnetic fields, due to improved intergrain connectivity and flux pinning. The use of the GO net as a platform for doping MgB2 in our case with Ag yielded a 10-fold-better critical current density ( Jc) than standard Ag doping at 9 T and 5 K. Even without sophisticated processes, we obtained a Jc result of 10 4 A/cm 2 at 9 T and 5 K, which is one of the best ever achieved. Corresponding author: mislav@uow.edu.au ABSTRACT:The effects of graphene oxide (GO) addition on the dispersion of nano-silver (Ag) in an MgB 2 matrix were studied using bulk samples prepared through a diffusion process. The influence of the dispersion of Ag and Ag/GO particles on the critical current density (J C ) of MgB 2 was also investigated. GO has emerged as an excellent dopant which can significantly improve both low-and high-field performance of MgB 2 due to its capability to improve inter-grain connectivity (GO), and inter-and intra-grain pinning (GO and AgMg). The addition of nano-size Ag particles also results in improvement of vortex pinning, and at the same time, it offers the advantage of preventing the loss of Mg during the sintering process. It is found that dispersion of nano-silver in the presence of GO results in significant improvements to the critical current density in MgB 2 , particularly at high magnetic fields, due to improved inter-grain connectivity and flux pinning. The use of the GO net as a platform for doping MgB 2 in our case with Ag, yielded a 10 times better critical current density (J C ) than standard Ag doping at 9 T and 5 K. Even without sophisticated processes, we obtained J C result of 10 4 A/cm 2 at 9 T and 5 K, which is one of the best ever achieved.

The unexpected growth of highly aligned and optically polarizing metallic fins during physical vapor deposition under modestly oblique conditions is investigated. The fins exhibit nanoscale dimensions and are formed when Al is co-sputtered with any of V, Cr, Nb, Mo, Ta, W, Ru, Fe, Ni, Pt, Zr, Mg, and Ti. It is proposed that the phenomenon is caused by anomalously low atomic mobility in the alloys and intermetallic compounds formed by co-depositing with Al. In contrast, when Cu, Ag, and Au (which diffuse more rapidly in Al) are deposited, no fins form. There is a sharp visible transition in optical properties as the ratio of Al to other element is decreased: the color of the sample changes from black to silver-white for compositions containing less than about 55 atom % Al. The region over which the color change occurs is associated with a very strongly polarized reflectance. Cross-sectional elemental mapping and Monte Carlo simulations suggest that growth of the fins may be nucleated by Al hillocks and enhanced by shadowing effects. The diversity of suitable metals makes this a versatile technique for producing nanoscale polarizing surfaces suitable for high-flux and high-temperature applications.