Study of electronic properties and mechanical dissipation in epitaxially grown La_2-xSr_xCuO₄ thin films using scanning probe microscopy

Understanding interplay between the superconducting dome and adjacent phases is important to better design and manipulate superconductors with high critical temperatures. Here we use the techniques of non-contact atomic force microscopy (nc-AFM) and scanning tunneling spectroscopy (STS) in ultrahigh vacuum to characterize thin films of La_2-xSr_xCuO₄ (LSCO). We grow the LSCO with molecular beam epitaxy and an oxygen plasma source. We produce high quality LSCO (001) samples with precise control over Sr doping level and choose the level of epitaxial strain our films experience by using different substrates (e.g., SrTiO₃ or LaSrAlO₄). We use nc-AFM to measure excitation and frequency shift as a function of tip distance from the surface and applied voltage bias. These measurements give us insight into the electronic nature of our films, as well as information about how energy dissipates into the sample.