Abstract-Study of A-site substituted quantum paraelectric strontium titanate crystals by terahertz time-domain spectroscopic ellipsometry

Seiji Kojima, Toshiyuki Iwamoto,  Yukinori Satou

https://iopscience.iop.org/article/10.35848/1347-4065/aba2c1/pdf

The dielectric properties of the terahertz frequency range were studied in A-site substituted quantum paraelectric strontium titanate SrTiO3 (STO) crystals with the perovskite structure. The complex dielectric constants were determined accurately by the terahertz time-domain spectroscopic ellipsometry.The soft optic mode of STO has T1u symmetry in a cubic phase. The hardening of a soft mode frequency of pure STO at 2.7 THz was observed with increasing the La content of the A-site of the perovskite structure up to 3.8 THz of a La 5.0 at% doped STO crystal. However, the softening of a soft mode frequency was observed in a Ca doped STO crystal reflecting the enhancement of ferroelectric instability.

Abstract-Characterization of the electrical properties of an InN epilayer using terahertz time-domain spectroscopic ellipsometry

Kenta Morino, Shingo Arakawa, Takashi Fujii, Shinichiro Mouri, Tsutomu Araki and Yasushi Nanishi

https://iopscience.iop.org/article/10.7567/1347-4065/ab1394/meta

We demonstrate the measurement of electrical properties of InN layers grown by RF-MBE using terahertz time-domain spectroscopic ellipsometry (THz-TDSE). Dependences of carrier density and mobility on InN film thickness are characterized using THz-TDSE. It is found that these electrical properties of the InN films are improved with the increase in the film thickness. Although the results obtained by Hall effect measurement also show the same tendency, the electrical properties of InN obtained by THz-TDSE is superior to those by Hall effect measurement. In addition, we also apply a two-layer model for THz-TDSE measurement to analyze the electrical properties of the bulk InN region and the surface electron accumulation layer independently. The mobility ranging from 50 to 140 cm2 V−1 s−1 are obtained for the surface electron accumulation layer of InN.