Abstract
We have developed a mass-separated low-energy oxygen ion (O+) beam as an oxygen source for molecular beam epitaxy growth of oxide thin films in ultrahigh vacuum. As an application of this technique to oxide superconductors, Sr-Cu-O infinite-layer (IL) films were grown by alternate atomic-layer deposition of Sr and Cu. Sr- and Cu-terminated IL films exhibit different reconstruction patterns in reflection high-energy electron diffraction (RHEED), suggesting that the film growth proceeds by repetition of these two reconstructions at surfaces. The films have high crystallinity, which is demonstrated by Kikuchi lines in RHEED patterns and by X-ray diffraction rocking curves with a full width at half-maximum of 0.016°. Mass spectral analysis of residual gas during the growth showed that the films grow under an extremely low background partial pressure of molecular oxygen (<3×10-9 Pa).
