Para-ferroelectric phase transition driven by swift heavy-ion irradiation in KTN crystal

We report a novel approach of using swift O5+ ion irradiation to implement para-ferroelectric phase transition in a relaxor ferroelectric KTa0.62Nb0.38O3 (KTN) single crystal. With 15-MeV swift O5+ ion irradiation, a well-defined two-layer structure has been formed in the KTN sample due to the interaction between the O ions and KTN via electronic stopping and the nuclear stopping, respectively. The microstructures in these two layers are characterized by using a micro-Raman (μ-Raman) spectral technique. The significant changes of both spectral intensities and locations in three characteristic Raman peaks suggest that the top layer of the KTN sample due to electronic stopping exists a single-domain-ferroelectric state with a uniform and enhanced polarization orientation along [0 0 1]c direction. More importantly, we observe the irradiated region can effectively confine the light propagation in the ferroelectric layer, which can be further controlled by external fields. The results are promising for designing new integrated photonic devices.