This study investigates the impact of narrow-band terahertz pulses on the ferroelectric order parameter in Ba_0.8Sr_0.2TiO₃ films on various substrates. THz radiation in the range of 1–2 THz with the pulse width of about 0.15 THz was separated from a broadband pulse with the interference technique. The 375 nm thick BST film on a MgO (001) substrate exhibits enhanced THz-induced second harmonic generation when excited by THz pulses with a central frequency of 1.6 THz, due to the resonant excitation of the soft phonon mode. Conversely, the BST film on a Si (001) substrate shows no enhancement, due to its polycrystalline state. The 800 nm thick BST film on a MgO (111) substrate demonstrates the maximum of a second harmonic generation signal when excited by THz pulses at 1.8 THz, which is close to the soft mode frequency for the (111) orientation. Notably, the frequency spectrum of the BST/MgO (111) film reveals peaks at both the fundamental and doubled frequencies, and their intensities depend, respectively, linearly and quadratically on the THz pulse electric field strength.

The ability to grow the interfacial defect-poor Sr0.5Ba0.5Nb2O6 + Ba0.2Sr0.8TiO3 and Ba0.8Sr0.2TiO3 + Ba0.4Sr0.6TiO3ferroelectric films onto the doped silicon substrates is discussed. A study of...

The structural properties of one- and two-layer heterostructures based on the barium–strontium titanate of various compositions deposited by the Frank–Van der Merve on a magnesium oxide substrate have

Single-crystal Bi₄Ti₃O₁₂ films deposited on a 4-nm-thick Ba_0.4Sr_0.6TiO₃ sublayer covering an MgO(001) substrate have been investigated. It has been found that the unit cells of Bi₄Ti₃O₁₂ films in the resulting heterostructures are turned by 45° relative to the cells of the MgO substrate in the interface plane. In addition, the unit cells of the films are strained, the amount of strain depending on the Bi₄Ti₃O₁₂ film thickness. When the films become about 40 nm thick, strain changes sign. It has been shown that reversible spontaneous polarization in Bi₄Ti₃O₁₂ films with a 180° domain structure in the interface plane arises at a thickness of 10 nm and grows with thickness to 54 μC/cm². The anisotropy of the film’s properties in the interface plane and the influence of unit cell distortion on the properties of the heterostructures have been confirmed by studying the dielectric performance of the films.

The authors consider the polarization behavior and controllability of thin ferroelectric barium strontium titanate films in a wide range of temperatures for two groups that differ by the conditions of fabrication. An indirect connection between the coefficient of film capacitor controllability and the polarization of films is noted.