surfaces prepared by HCl etching*

In molecular beam epitaxy synthesis of crystalline heterostructures, the quality of the substrate surface is crucial. The substrate not only provides a structural template for the deposited film, but for many new materials which are just a few atomic layers thick, the interaction with the substrate determines the emergent electronic properties. SrTiO₃ substrates are widely used for growth of complex oxides and superconducting FeSe, but reproducible surface preparation remains challenging. The standard recipe employs a buffered hydrofluoric acid etch, but it has been shown that this step results in significant fluorine replacement of oxygen near the surface of SrTiO₃ [1]. Here we characterize halogen doping from use of an alternative etchant, hydrochloric acid.

[1] S.A. Chambers, T.C. Droubay, C. Capan, and G.Y. Sun, Surface Science 606, 554-558 (2012).