  For over 70 years, ferroelectric materials have been remaining one of the
central research topics for condensed matter physics and material science, the
interest driven both by fundamental science and applications. However,
ferroelectric surfaces, the key component of ferroelectric films and
nanostructures, still present a significant theoretical and even conceptual
challenge. Indeed, stability of ferroelectric phase per se necessitates
screening of polarization charge. At surfaces, this can lead to coupling
between ferroelectric and semiconducting properties of material, or with
surface (electro) chemistry, going well beyond classical models applicable for
ferroelectric interfaces. In this review, we summarize recent studies of
surface screening phenomena in ferroelectrics. We provide a brief overview of
the historical understanding of physics of ferroelectric surfaces, and existing
theoretical models that both introduce screening mechanisms and explore the
relationship between screening and relevant aspects of ferroelectric
functionalities starting from phase stability itself. Given that majority of
ferroelectrics exist in multiple-domain states, we focus on local studies of
screening phenomena using scanning probe microscopy techniques. We discuss
recent studies of static and dynamic phenomena on ferroelectric surfaces, as
well as phenomena observed under lateral transport, light, chemical, and
pressure stimuli. We also note that the need for ionic screening renders
polarization switching a coupled physical-electrochemical process, and discuss
the non-trivial phenomena such as chaotic behavior during domain switching that
stem from this.
