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Terahertz Nanoscopy for Non-Destructive Detection of Perovskite Films

  • Youngsoo Jang (장영수, KU-KIST융합대학원 NBIT융합전공)

초록/요약

In the semiconductor industry, a diverse range of analytical methods is employed to evaluate material defects or assess the degree of synthesis. However, many of these techniques involve sampling processes that require the target material or sample to be altered or prepared in specific ways to suit the measurement equipment. Unfortunately, these preparation processes often induce unintended physical or chemical changes in the sample, complicating efforts to obtain accurate measurements. As semiconductor devices shrink to the nanometer scale and their structures become thinner and more complex, traditional analysis methods encounter significant limitations. These include difficulties in maintaining the intrinsic properties of materials and achieving the precision needed for reliable evaluations. To address these challenges, non-destructive analysis techniques utilizing terahertz (THz) radiation have emerged as a promising alternative. THz waves are uniquely suited for material characterization due to their ability to deeply penetrate samples without causing physical damage. This feature enables the internal structures of materials to be analyzed while preserving their original states. Consequently, THz-based techniques are rapidly gaining traction in advanced material research, particularly in fields like semiconductors and photovoltaics. One material of particular interest is perovskite, renowned for its exceptional energy conversion efficiency in solar cells and its potential in next-generation optoelectronic devices. However, the precise analysis of perovskite materials remains a significant challenge due to their complex layered structures, sensitivity to external factors, and the need for non-destructive evaluation techniques. To overcome these obstacles, we propose a novel analytical approach termed "THz nanoscopy." This technique employs metamaterials to estimate Rabi splitting energy and enables detailed investigation of perovskite layer structures, including in thin-film configurations. The methodology of THz nanoscopy is centered around the phonon-polariton phenomenon, which occurs in the THz frequency range. Specifically, we utilized nanoslot metamaterials with 500 nm gaps to control resonance frequencies and induce polaritonic branch phenomena. This approach allows for the identification of dispersion curves exhibiting anticrossing behavior, which is a hallmark of strong light-matter interactions. The observed Rabi splitting energy serves as a quantitative indicator of the coupling strength between THz photons and the material's excitations. By leveraging the efficient mode volume and high field enhancement capabilities of nanoslot metamaterials, we achieved precise measurements of strong coupling (SC) between THz photons and perovskite materials. This research aims to advance the field of THz-based non-destructive analysis by demonstrating its potential to address critical challenges in the semiconductor and solar cell industries. By minimizing uncertainties arising from conventional sampling processes and enhancing the precision of material characterization, THz nanoscopy offers a powerful new tool for analyzing complex materials. Furthermore, the insights gained from this study contribute significantly to the broader understanding of strong light-matter interactions, with implications for fundamental science and applied technology.

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ABSTRACT
국문 초록
TABLE OF CONTENTS
LIST OF FIGURES
ABBREVIATION
CHAPTER 1. INTRODUCTION
1. 1. THz Frequency
1. 2. THz Time Domain Spectroscopy
1. 3. THz Metamaterials with Nano Slot Patterning
1. 4. Phonon Polariton between Light and Matter
CHAPTER 2. Phonon Polariton in THz regime
2. 1. Introduction
2. 2. Strong Coupling in PbBr2-combined Nanoslot Configuration
2. 3. Terahertz Nanoscopy for Perovskite Films
CHAPTER 3. CONCLUSION
REFERENCES

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