Studies of ferroelectric heterostructure thin films, interfaces, and device-related processes via in situ analytical techniques

The science and technology of ferroelectric thin films has experienced an explosive development during the last ten years. Low-density non-volatile ferroelectric random access memories (NVFRAMs) are now incorporated in commercial products such as 'smart cards', while high permittivity capacitors are incorporated in cellular phones. However, substantial work is still needed to develop materials integration strategies for high-density memories. We have demonstrated that the implementation of complementary in situ characterization techniques is critical to understand film growth and device processes relevant to device development. We are using uniquely integrated time of flight ion scattering and recoil spectroscopy (TOF-ISARS) and spectroscopic ellipsometry (SE) techniques to perform in situ, real-time studies of film growth processes in the high background gas pressure required to growth ferroelectric thin films. TOF-ISARS provides information on surface processes, while SE permits the investigation of buried interfaces as they are being formed. Recent studies on SrBi2Ta2O9 (SBT) and BaxSr1-xTiO3 (BST) film growth and interface processes are discussed. Direct imaging of ferroelectric domains under applied electric fields can provide valuable information to understand domain dynamics in ferroelectric films. We discuss results of piezoresponse scanning force microscopy (SFM) imaging for nanoscale studies of polarization reversal and retention loss in Pb(ZrxTi1-x)O3 (PZT)-based capacitors. Another powerful technique suitable for in situ, real-time characterization of film growth processes and ferroelectric film-based device operation is based on synchrotron X-ray scattering, which is currently being implemented at Argonne National Laboratory.