Thickness Dependence of Dielectric Characteristics of SrTiO₃ Thin Films on MgAl₂O₄ Substrates

Ryuhei Kinjo, Iwao Kawayama, Hironaru Murakami, Masayoshi Tonouchi

Institute of Laser Engineering, Osaka University, Osaka, Japan..

DOI: 10.4236/ampc.2013.31009                

Abstract

SrTiO₃ (STO) thin films of different thicknesses were deposited on MgAl₂O₄ (MAO) substrates to investigate the in-plane strain effect on the soft-mode frequency of the STO films. X-ray reciprocal space mapping (X-RSM) results indicate that there was no relaxation of the in-plane lattice strain of the STO films on MAO. Shifts in the soft-mode frequencies with a decrease in the film thickness were observed using terahertz time-domain spectroscopy (THz-TDS). However, despite the larger lattice mismatch between STO and MAO than that between STO and DyScO₃ (DSO), the shifts in the soft-mode frequencies of the STO films on MAO were smaller than those on DSO. The results indicate that the soft-mode frequencies of the STO films on MAO are affected by the c-axis (out-of-plane) lengths.

Keywords

Strontium Titanate; Ferroelectric; Soft Mode; Thin Film; Strain Effect

Conflicts of Interest

The authors declare no conflicts of interest.

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