Role of antimony sulfide buffer layers in the growth of ferroelectric antimony sulfo-iodide thin films

The growth and properties of ferroelectric antimony sulfo-iodide (SbSI) films on platinized silicon (Pt/Ta/SiO₂/Si) for various applications are reported here. Films were grown with and without antimony sulfide (Sb₂S₃) buffer layers using the physical vapor transport technique (PVT). The Sb₂S₃ buffer layers significantly improve the crystalline orientation and microstructure of the SbSI films. It is possible to control the crystalline orientation of the SbSI films to a large degree by annealing the buffer layers under optimized conditions of temperature and time. The films are chemically homogeneous, uniform in thickness, and ferroelectric in nature. The PVT method is effective for the growth of device quality ferroelectric SbSI films with preferred orientation along the c-axis either perpendicular or parallel to the substrate surface. The former configuration is particularly suited for the fabrication of uncooled focal plane arrays, whereas the films with c-axis orientation parallel to the substrate are useful for the development of infrared imagers based on the pyro-optic effect. The peak dielectric constant of c-axis oriented films (perpendicular to the substrate) is determined to be 590 at the Curie point of 19 °C. This is the highest value of the dielectric constant ever reported for SbSI films.