14 research outputs found
MgyNi1-y(Hx) thin films deposited by magnetron co-sputtering
In this work we have synthesised thin films of MgyNi1-y(Hx) metal and metal
hydride with y between 0 and 1. The films are deposited by magnetron
co-sputtering of metallic targets of Mg and Ni. Metallic MgyNi1-y films were
deposited with pure Ar plasma while MgyNi1-yHx hydride films were deposited
reactively with 30% H2 in the Ar plasma. The depositions were done with a fixed
substrate carrier, producing films with a spatial gradient in the Mg and Ni
composition. The combinatorial method of co-sputtering gives an insight into
the phase diagram of MgyNi1-y and MgyNi1-yHx, and allows us to investigate
structural, optical and electrical properties of the resulting alloys. Our
results show that reactive sputtering gives direct deposition of metal hydride
films, with high purity in the case of Mg~2NiH~4. We have observed limited
oxidation after several months of exposure to ambient conditions. MgyNi1-y and
MgyNi1-yHx films might be applied for optical control in smart windows, optical
sensors and as a semiconducting material for photovoltaic solar cells
Optical properties of MgH2 measured in situ in a novel gas cell for ellipsometry/spectrophotometry
The dielectric properties of alpha-MgH2 are investigated in the photon energy
range between 1 and 6.5 eV. For this purpose, a novel sample configuration and
experimental setup are developed that allow both optical transmission and
ellipsometric measurements of a transparent thin film in equilibrium with
hydrogen. We show that alpha-MgH2 is a transparent, colour neutral insulator
with a band gap of 5.6 +/- 0.1 eV. It has an intrinsic transparency of about
80% over the whole visible spectrum. The dielectric function found in this work
confirms very recent band structure calculations using the GW approximation by
Alford and Chou [J.A. Alford and M.Y. Chou (unpublished)]. As Pd is used as a
cap layer we report also the optical properties of PdHx thin films.Comment: REVTeX4, 15 pages, 12 figures, 5 table