Search

Functional oxides exhibit diverse useful properties, opening attractive prospects for electronic, magnetic, and optoelectronic devices. However, the chemical instability of these oxides with some microfabrication processes, especially when dealing with thin films (<40 nm) or micrometer-scale lateral dimensions, can pose a considerable challenge. Here, we describe the fabrication process of a Hall bar device used as a test structure for thin functional oxide films. This process employs photolithography and dry etching, utilizing standard clean-room materials and methods. The device layout and fabrication process are described in detail, including conclusions and lessons gained from several failed attempts during process development. A key lesson is the advantage of employing an ultrathin protective layer to protect the oxide film surface. In addition, we encountered two additional fabrication challenges: photoresist hardening during dry etching and edge accumulation of photoresist during spin-coating. Effective solutions to these issues are described. We hope that our lessons and conclusions, not limited to functional oxides, will help to shorten the process development for other materials and devices. [ABSTRACT FROM AUTHOR]

The magneto-optic Kerr effect can probe the process of magnetization reversal in ferromagnetic thin films and can, thus, be used as an alternative to magnetometry. The Kerr effect is wavelength-dependent and the Kerr rotation can reverse sign, vanishing at particular wavelengths. We investigate the epitaxial heterostructures of ferromagnetic manganite, La0.7Sr0.3Mn0.9Ru0.1O3, by using the polar Kerr effect and magnetometry. The manganite layers are separated by or interfaced with a layer of nickelate, NdNiO3. The Kerr rotation hysteresis loops of trilayers, with two manganite layers of different thicknesses separated by a nickelate layer, have intriguing humplike features when measured with light of 400 nm wavelength. By investigating additional reference samples, we disentangle the contributions of the individual layers to the loops: we show that the humps originate from the opposite sense of the Kerr rotation of the two different ferromagnetic layers, combined with the additive behavior of the Kerr signal. The change of sign of the Kerr rotation for the thinner manganite layer is most likely caused by optical interference. [ABSTRACT FROM AUTHOR]