Phonon Mode Transformation across the Orthohombic-Tetragonal Phase Transition in a Lead-Iodide Perovskite CH$_{3}$NH$_{3}$PbI$_{3}$: a Terahertz Time-Domain Spectroscopy Approach
ORAL
Abstract
Using terahertz time-domain spectroscopy (THz-TDS), we study the temperature-dependent phonon modes of the organometallic lead iodide perovskite CH$_{3}$NH$_{3}$PbI$_{3}$ thin film across the terahertz (0.5-3 THz) and temperature (20-300 K) ranges. These modes are related to the vibration of the Pb-I bonds. We found that two phonon modes in the tetragonal phase at room temperature split into four modes in the low-temperature orthorhombic phase. By use of the Lorentz model fitting, we analyze the critical behavior of this phase transition.
*King Mongkut’s University of Technology Thonburi (Grant No. SCI58-003), Singapore MOE Tier 1 (RG13/12, RG123/14), ONR, ARO, NTU Biophysics Center, LANL LDRD, LANL CINT.
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