Year: 2026
Type: article
Abstract: Piezoresponse force microscopy (PFM) techniques, which probe nanoscale electromechanical coupling, are often difficult to interpret. For ferroelectric mixed conductors useful for computation elements, this becomes more difficult due to non-piezoelectric electromechanical effects. The measured PFM signal can have tip-local and nonlocal contributions associated with multiple coupling mechanisms, and it is often unclear what material property is truly being probed. Here, using antimony sulfide (Sb2S3) as a model system, an emerging phase change material for optical and electrical memory and computation elements, we show that the PFM signal can be separated into a fast, capacitive contribution, and a slow, ionic contribution whose time-domain characteristics match well with diffusion-controlled kinetics. This ionic contribution, rather than ferroelectric switching, leads to electromechanical hysteresis in Sb2S3, with no clearly measurable ferroelectric switching effects. Uniquely, electromechanical behavior has a very clear spatial contrast that is decoupled from surface topography, showing that the signal arises from surface charging that reflects bulk-like properties and allowing a self-consistent interpretation in terms of dielectric behavior. This protocol establishes a clear interpretation of a non-piezoelectric signal, often mischaracterized as an indication of the ferroelectric state. Additionally, because all electromechanical experiments show a strong, low-frequency electric relaxation in crystalline Sb2S3 while the response of glassy Sb2S3 is static, we conclude that the crystalline phase of Sb2S3 is a mixed conductor, while the amorphous phase remains strictly insulating.
Institutions: Lehigh University, Oak Ridge National Laboratory
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
Award: G1128355560
OpenAlex ID: W7224552977