本論文利用化學氣相傳導法成功生長出含碘化合物半導體碘化銅 (CuI) 和碘化鉛 (PbI2)，藉由能量色散 X 射線譜 (Energy dispersive X-ray spectroscopy, EDS)，X 射線晶體繞射儀 (X-ray Diffraction, XRD) 和拉曼量測 (Raman) 分析，可以確定成長的碘化銅與碘化鉛符合預期的原子比例生成，並且碘化銅以 α 相立方晶系 (空間群 Fm-3m) 形成，碘化鉛則以六方 2H 堆疊相 (空間群P3m-1) 生成。由於碘容易揮發的特性，碘化物容易形成碘空缺的特徵，因此雖然兩者具備的結構不同，但在光電特性上還是有一定程度的相似。本論文使用 X 射線光電子能譜儀 (X-ray photoelectron spectroscopy, XPS)，測量碘化銅與碘化鉛的鍵結結構，透過價電帶、費米能階分析以及熱探針實驗，量測出碘化銅及碘化鉛均屬於 P 型的半導體，再利用穿透光譜以及光激發螢光等一系列實驗測出碘化銅的能隙位於3.012 eV 處，碘化鉛的能隙位於2.43 eV 處，二者均為寬能隙直接能隙半導體。在低溫時，碘化銅的光激發螢光會有自由激子以及多根的束縛激子態訊號的出現，並伴隨著能隙藍移的現象，由於碘化銅具備高強度的螢光訊號，本論文亦進行了一系列的螢光實驗，包含改良穿透光路的光激螢光吸收 (Photoluminescence excitation, PLE) 系統的架設與量測，以及時間相關的光激螢光映射實驗等。碘化鉛受到其二維層狀堆疊的特性影響，在不同波長雷射 (532、633 nm) 照射下，產生4種不同方向的拉曼震動模態 (72, 111,167,213 cm-1) 會出現明顯的消長行為，另外熱調制反射光譜中碘化鉛亦觀察到位於能隙峰值前的缺陷複製峰值，本論文亦使用厚度和溫度相依的實驗方式解析此現象，未來寬能隙半導體的發展日漸重要，本論文的研究將有助於此等材料的了解與發展。

The Iodine-containing compound semiconductors, copper iodide (CuI) and lead iodide (PbI2) are successfully grown by chemical vapor transport. Energy dispersive X-ray spectroscopy (EDS) is carried out to verify the stoichiometry of the compound. The X-ray Diffraction (XRD) and Raman measurement analysis confirm that as-grown crystals are crystallized in α phase (space group Fm-3m) for CuI and two layer hexagonal (2H) stacking phase (space group P3m-1) for PbI2. Due to the easy volatilization of iodine, CuI and PbI2 have the characteristics of easy-to-form iodine vacancies. Here, we use XPS to analyze bonding structure and valence band of CuI and PbI2.
The band edge transitions are characterized by optical absorption measurement, photoluminescence, and thermoreflectance. The experimental results confirm that both CuI and PbI2 are direct band gap semiconductors with band gaps is about 3.02 eV and 2.34 eV, respectively. The temperature dependent photoluminescence of CuI was also carried out and the result shows blue shift behavior as the temperature decreases. For CuI, the PL results show free exciton and multiple bound exciton states at 20K. Several fluorescence experiments, such as TRPL (time-resolved photoluminescence) and PLE (photoluminescence excitation), have also been carried out owing to the high intensity fluorescent signal of CuI. In terms of PbI2, due to the characteristics of its two-dimensional layered stack, it show its uniqueness in many aspects, such as the relation between the strength and weakness of four different vibration modes in Raman measurement under different laser illuminations. The thermoreflectance results also shows PbI2 has high-intensity replica peak before the band-edge transition, so we used thickness and temperature-dependent experiments to analyze this phenomenon. The hot probe measurement is carried out and indicates that both crystals are P-type semiconductors. Since the development of wide energy gap semiconductors is gradually increasing, this work will contribute to the future development and application of wide band gap iodides.

[1] B. Ozpineci and L. M. Tolbert, "Comparison of wide-bandgap semiconductors for power electronics applications," U.S. Department of Energy, USA, New York, 2004.
[2] A. C. Nkele, U. K. Chimea, A. C. Nwanya, R. U. Osujia, R. Bucherb, P. M. Ejikemed, M. Maazab and F. I. Ezema, "Role of metallic dopants on the properties of copper iodide nanopod-like structures," Vacuum, vol. 161, pp. 306-313, 2019.
[3] Y. Shan, G. Li, G. Tiana, J. Hana, C. Wanga, S. Liua, H. Dua and Y. Yang, "Description of the phase transitions of cuprous iodide," Journal of alloys and compounds, vol. 477, no. 1-2, pp. 403-406, 2009.
[4] J. Wang, J. Li and S. S. Li, "Native p-type transparent conductive CuI via intrinsic defects," Journal of Applied Physics, vol. 110, no. 5, p. 054907, 2011.
[5] S. L. Dhere, S. S. Latthe, C. Kappenstein, S. Mukherjee and A. V. Rao, "Comparative studies on p-type CuI grown on glass and copper substrate by SILAR method," Applied surface science, vol. 256, no. 12, pp. 3967-3971, 2010.
[6] G. K. Kasi, N. R. Dollahon and T. S. Ahmadi, "Fabrication and characterization of solid PbI2 nanocrystals," Journal of Physics D: Applied Physics, vol. 40, no. 6, p. 1778, 2007.
 
[7] E. Salje, B. Palosz and B. Wruck, "In situ observation of the polytypic phase transition 2H-12R in PbI2: investigations of the thermodynamic structural and dielectric properties," Journal of Physics C: Solid State Physics, vol. 20, no. 26, p. 4077, 1987.
[8] S. S. Jamil, A. M. Mousa, M. A. Mohammad and K. M. Thajeel, "Structural and optical properties of lead iodide thin films prepared by vacuum evaporation method," Eng. & Tech. Journal, vol. 29, no. 3, pp. 531-543, 2011.
[9] M. Binnewies, R. Glaum, M. Schmidt and P. Schmidt, "Chemical vapor transport reactions–A historical review," Zeitschrift für anorganische und allgemeine Chemie, vol. 639, no. 2, pp. 219-229, 2013.
[10] D. Y. Lin, B. C. Guo, Z. Y. Dai, C. F. Lin and H. P. Hsu, "PbI2 single crystal growth and its optical property study," Crystals, vol. 9, no. 11, p. 589, 2019.
[11] K. Vernon Parry, "Scanning electron microscopy: an introduction," III-Vs Review, vol. 13, no. 4, pp. 40-44, 2000.
[12] C. M. Becchi and M. D'Elia, "Introduction to the basic concepts of modern physics," Springer, USA, New York, 2007.
[13] D. Cherns, A. Howie, and M. Jacobs, "Characteristic X-ray production in thin crystals," Zeitschrift für Naturforschung A, vol. 28, no. 5, pp. 565-576, 1973.
[14] L. Elton and D. F. Jackson, "X-ray diffraction and the Bragg law," American Journal of Physics, vol. 34, no. 11, pp. 1036-1038, 1966.
 
[15] M. Moram and M. Vickers, "X-ray diffraction of III-nitrides," Reports on progress in physics, vol. 72, no. 3, p. 036502, 2009.
[16] L. A. Giannuzzi and F. A. Stevie, "A review of focused ion beam milling techniques for TEM specimen preparation," Micron, vol. 30, no. 3, pp. 197-204, 1999.
[17] C. V. Raman and K. S. Krishnan, "A new type of secondary radiation," Nature, vol. 121, no. 3048, pp. 501-502, 1928.
[18] P. Graves and D. Gardiner, "Practical raman spectroscopy," Springer, USA, New York, 1989.
[19] C. H. Ho, M. C. Chiou and T. M. Herninda, "Nanowire grid polarization and polarized excitonic emission observed in multilayer GaTe," The Journal of Physical Chemistry Letters, vol. 11, no. 3, pp. 608-617, 2020.
[20] F. H. Pollak and H. Shen, "Modulation spectroscopy of semiconductors: bulk/thin film, microstructures, surfaces/interfaces and devices," Materials Science and Engineering: R: Reports, vol. 10, no. 7-8, pp. xv-374, 1993.
[21] M. Farzaneh, K. Maize, D. Luerßen, J. A. Summers, P. M. Mayer, P. E. Raad, K. Pipe, A. Shakouri, R. J. Ram and J. A. Hudgings, "CCD-based thermoreflectance microscopy: principles and applications," Journal of Physics D: Applied Physics, vol. 42, no. 14, p. 143001, 2009.
[22] T. Haas, J. Grant and G. Dooley Iii, "Chemical effects in Auger electron spectroscopy," Journal of Applied Physics, vol. 43, no. 4, pp. 1853-1860, 1972.
 
[23] J. Chastain and R. C. King Jr, "Handbook of X-ray photoelectron spectroscopy," Perkin-Elmer Corporation, USA, Minnesota, vol. 40, p. 221, 1992.
[24] J. Zhang, T. Song, Z. Zhang, K. Ding, F. Huang and B. Sun, "Layered ultrathin PbI2 single crystals for high sensitivity flexible photodetectors," Journal of Materials Chemistry C, vol. 3, no. 17, pp. 4402-4406, 2015.
[25] A. Axelevitch and G. Golan, "Hot-probe method for evaluation of majority charged carriers concentration in semiconductor thin films," Facta universitatis-series: Electronics and Energetics, vol. 26, no. 3, pp. 187-195, 2013.
[26] F. D. G. Burns, M. Shafer and R. Alben, "The Raman spectra of the superionic conductor CuI in its three phases," Solid State Communications, vol. 24, no. 11, pp. 753-757, 1977.
[27] D. K. Kaushik, M. Selvaraj, S. Ramu and A. Subrahmanyam, "Thermal evaporated copper iodide (CuI) thin films: a note on the disorder evaluated through the temperature dependent electrical properties," Solar Energy Materials and Solar Cells, vol. 165, pp. 52-58, 2017.
[28] C. C. Li, M. Gong, X. D. Chen, S. Li, B. W. Zhao, Y Dong, G. C. Guo and F.W. Sun, "Temperature dependent energy gap shifts of single color center in diamond based on modified Varshni equation," Diamond and Related Materials, vol. 74, pp. 119-124, 2017.
[29] 陳鑫封、張文豪，「利用低溫光激螢光光譜偵測半導體微量雜質濃度」，國立交通大學電子物理學系碩士論文，2013.
 
[30] C. Ho, P. Liao, Y. Huang and K. K. Tiong, "Temperature dependence of energies and broadening parameters of the band-edge excitons of ReS2 and ReSe2," Physical Review B, vol. 55, no. 23, p. 15608, 1997
[31] Y. Chen and A. Periasamy, "Characterization of two‐photon excitation fluorescence lifetime imaging microscopy for protein localization," Microscopy research and technique, vol. 63, no. 1, pp. 72-80, 2004.
[32] M. R. Eftink and C. A. Ghiron, "Fluorescence quenching studies with proteins," Analytical biochemistry, vol. 114, no. 2, pp. 199-227, 1981.
[33] M. Y. Berezin and S. Achilefu, "Fluorescence lifetime measurements and biological imaging," Chemical reviews, vol. 110, no. 5, pp. 2641-2684, 2010.
[34] 朱韻儒，「硒化銦系列半導體之晶體成長與特性研究」，國立台灣科技大學，國立台灣科技大學電子工程系碩士論文，2015.
[35] C. C. Lin, K. D. Yang, M. C. Shih, S. K. Huang, T. P. Chen, H. C. Hsu, C. A. Chuang, C. Y. Huang, L. Wang, C. C. Chen, C. H. Ho, Y. P. Chiu and C. W. Chen, "Internal Built-In Electric Fields at Organic–Inorganic Interfaces of Two-Dimensional Ruddlesden–Popper Perovskite Single Crystals," ACS Applied Materials & Interfaces, vol. 14, no. 17, pp. 19818-19825, 2022.