Laser ablation of manganite thin films monitored by in situ RHEED

Reflection high-energy electron diffraction (RHEED) during crystal growth has become a standard analytical tool in the fabrication of semiconducting materials by molecular-beam epitaxy in an ultrahigh vacuum environment. For the fabrication of high-quality epitaxial and heteroepitaxial thin film structures of oxide materials such as perovskite manganites or high-temperature superconductors, it is also highly desirable to use RHEED technique during epitaxial growth. However, the complex oxide materials are commonly fabricated by pulsed laser deposition (PLD) at high oxygen pressure above 10 Pa preventing the use of standard RHEED systems. A two-stage differential pumping system can serve to circumvent this problem. In this way, the electron path in the high-pressure oxygen atmosphere within the deposition chamber can be reduced considerably. Then the specular beam intensity of the RHEED system is sufficiently high to allow the observation of intensity oscillations during the growth of oxide materials. We have used high-pressure RHEED and in situ atomic force microscopy (AFM) for the investigation of the surface morphology of oxide thin films prepared by PLD.