我們量測摻雜釤離子氧化鋅薄膜的拉曼散射光譜、穿透光譜及橢圓偏振光譜，研究不同摻雜濃度對氧化鋅薄膜光譜性質的影響。另外，我們量測單層過渡金屬二硫屬化合物薄膜(MoS2、MoSe2、WS2及WSe2)的變溫橢圓偏振光譜，探討單層過渡金屬二硫屬化合物薄膜的光譜性質。
未摻雜氧化鋅薄膜的拉曼散射光譜顯示兩個拉曼特徵峰，頻率位置為99.1 cm-1和437.9 cm-1，分別為E2(low)及E2(high)振動模，隨釤離子濃度上升，E2(low)藍移，E2(high)紅移，強度逐漸下降，並於釤離子濃度3%以上消失。穿透光譜顯示隨著釤離子濃度增加，紫外光區的透光率增加。吸收光譜展現隨著釤離子濃度增加，能隙逐漸藍移，我們分別以柏斯坦-莫斯位移理論(Burstein-Moss effect)及Zn1-xSmxO合金能帶結構解釋低濃度(≤5%)與高濃度(≥8%)摻雜樣品能隙之變化。
藉由分析變溫橢圓偏振光譜數據，我們取得單層過渡金屬二硫屬化合物薄膜之變溫折射率與消光係數能譜圖，隨著溫度上升，整體折射率與消光係數強度逐漸下降，結構紅移。我們觀察到所有樣品於近紅外與可見光區域皆有兩個明顯的吸收峰值，標記為A，B激子，為自由激子於布里淵區K(K´)點之躍遷。緊接在自由激子後的數個結構為電子於布里淵區Λ與M點之躍遷。所有樣品之光學能隙皆隨著溫度上升而紅移，A，B激子紅移，半高寬增寬。A，B激子之能量差為自旋耦合分裂能量，其不隨溫度變化而改變。

We investigated the samarium (Sm) doping effects on the optical properties of ZnO thin films and reported the temperature dependence spectroscopic ellipsometry studies of monolayer transition metal dichalcogenides thin films such as MoS2, MoSe2, WS2, and WSe2.

Room temperature Raman scattering spectrum of undoped ZnO thin film shows two phonon modes at approximately 99.1 cm-1 and 437.9 cm-1, displaying symmetries of E2(low) and E2(high). With increasing Sm doping, E2(low) mode shows a blueshift. By contrast, E2(high) mode shows a redshift. Furthermore, the intensities of these two phonon modes decrease and become completely diminished for the 3% Sm doped sample. The intensities of optical transmission spectra show an increase in the ultraviolet region and the band gap energy shows a blueshift as the Sm contents increases. We attributed this feature to the Burstein-Moss effect for 3% and 5% doped samples and the band characteristics of ternary Zn1-xSmxO alloys for 8% and 10% doped samples.

The temperature dependent refractive index and extinction coefficient spectra of monolayer transition metal dichalcogenides thin films were extracted from the ellipsometry parameters. Room temperature optical absorption spectra of these materials show two excitonic transitions (denoted as A and B excitons). They originate from the spin-split direct gap transitions at the K points of the Brillouin zone. Several high energy absorptions are associated with the electronic transitions at the Λ and M points. With increasing temperature, the intensity of refractive index decreases and the absorption structures show a redshift. Notably, the valence spin-orbit coupling is temperature independent.

參考文獻
[1] Ü. Özgür, Y. Alivov, C. Liu, A. Teke, M. Reshchikov, S. Dogan, V. Avrutin, S. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices”, J. Appl. Phys. 98, 041301 (2005).
[2] K. Keis, E. Magnusson, H. Lindström, S. Lindquist, and A. Hagfeldt, “A 5% efficient photoeletrochemical solar cell based on nanostructured ZnO electroes”, Solar Energy Materials & Solar Cells 73, 51 (2002).
[3] S. Ko, D. Lee, H. Kang, K. Nam, J. Yeo, S. Hong, C. Grigoropoulos, and H. Sung, “ Nanoforest of hydrothermally grown hierarchical ZnO nanowires for a high efficiency dye-sensitized solar cell”, Nano Lett. 11, 666 (2011).
[4] A. Mitra and R. Thareja, “Photoluminescence and ultraviolet laser emission from nanocrystalline ZnO thin films”, J. Appl. Phys. 89, 2025 (2001).
[5] A. Tsukazaki, A. Ohtomo, T. Onuma, M. Ohtani, T. Makino, M. Sumiya, K. Ohtani, S Chichibu, S. Fuke, Y. Segawa, H. Ohno, H. Koinuma, and M. Kawasaki, “Repeated temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO”, Nature Materials 4, 42 (2005).
[6] H. Liang, S. Yu, and H. Yang, “ZnO random laser diode arrays for stable single-mode operation at high power”, Appl. Phys. Lett. 97, 241107 (2010).
[7] J. Guo, J. Zhang, M. Zhu, D. Ju, H. Xu, and B. Cao, “High-performance gas sensor based on ZnO nanowires functionalized by Au nanoparticales”, Sensor and Actuators B: Chemical 199, 339 (2014).
[8] J. Yoo, T. Ahmed, W. Tang, Y. Kim, Y. Hong, C. Lee, and G. Yi, “Single crystalline ZnO radial homojunction light-emitting diodes fabricated by metalorganic chemical vapour deposition”, Nanotechnology 28, 394001 (2017).
[9] K. Kittilstved, N. Norberg, and D. Gamelin, “Chemical manipulation of High-TC ferromagnetism in ZnO diluted magnetic semiconductors”, Phys. Rev. Lett. 94, 147209 (2005).
[10] J. Yi, C. Lin, G. Xing, H. Fan, L. Van, S. Huang, K. Yang, X. Huang, X. Qin, B. Wang, T. Wu, L. Wang, H. Zhang, X. Gao, T. Liu, A. Wee, Y. Feng, and J. Ding, “Ferromagnetism in dilute magnetic semiconductors through defect engineering: Li-doped ZnO”, Phys. Rev. Lett. 104, 137201 (2010).
[11] K. Novoselov, A. Geim, S. Morozov, D. Jiang, Y. Zhang, S. Dubonos, I. Grigorieva, and A. Firsov, “Electric field effect in atomically thin carbon films”, Science 306, 666 (2004).
[12] Q. Wang, K. Kalantar-Zadeh, A. Kis, J. Coleman, and M. Strano, “Electronics and optoelectronics of two-dimensional transition metal duchalcogenides”, Nature Nanotechnology 7, 699 (2012).
[13] Y. Li, A. Chernikov, X. Zhang, A. Rigosi, H. Hill, A. van der Zande, D. Chenet, E. Shih, J. Hone, and T. Heinz, “Measurement of the optical dielectric function of monolayer transition-metal dichalcogenides: MoS2, MoSe2, WS2, and WSe2”, Phys. Rev. B 90, 205422 (2014).
[14] K. Matsuda, “Optical properties of atomically thin layered transition metal dichalchogenide”, J. Phys. Soc. Jpn. 84, 121009 (2015).
[15] Y. Morozov and M. Kuno, “Optical constants and dynamic conductivities of single layer MoS2, MoSe2, and WSe2” Appl. Phys. Lett. 107, 083103 (2015).
[16] H. Park, T. Kim, H. Kim, C. Yoo, N. Barange, V. Le, H. Kim, V. Senthilkumar, C. Le, Y. Kim, M. Seong, and Y. Kim, “Temperature dependence of the critical points of monolayer MoS2 by ellipsometry”, Applied Spectroscopy Review 51, 621 (2016).
[17] B. Jin, S. Im, and S. Lee, “Violet and UV luminescence emitted from ZnO thin films grown on sapphire by pulsed laser deposition”, Thin Solid Films 366, 107 (2000).
[18] G. Martaza Rai, M. Iqbal, Y. Xu, and I. Will, Z. Huang, “Study of Sm-doped ZnO samples sintered in a nitrogen atmosphere and deposited on n-Si(100) by evaporation technique”, Journal of Magnetism and Magnetic Materials 323, 3239 (2011).
[19] T. Prasada Rao, S. Gokul Raj, and M. C. Santhosh Kumar, “Optical properties of Samarium doped ZnO thin films”, ICDCS 2, 1 (2014).
[20] H. He, J. Fei, and J. Lu, “Sm-doping effect on optical and electrical properties of ZnO films”, J. Nanostruct. Chem. 5, 169 (2015).
[21] A. Kuc, N. Zibouche, and T. Heine, “Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2”, Phys. Rev. B 83, 245213 (2011).
[22] W. Huang, X. Luo, C. Gan, S. Quek, and G. Liang, “Theoretical study of thermoelectric properties of few-layer MoS2 and WSe2”, Phys. Chem. Chem. Phys. 16, 10866 (2014).
[23] S. Tongay, J. Zhou, C. Ataca, K. Lo, T. Matthews, J. Li, J. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2”, Nano Lett. 12, 5576 (2012).
[24] K. Mak, C. Lee, J. Hone, J. Shan, and T. Heinz, “Atomically Thin MoS2: A new direct-gap semiconductor” Phys. Rev. Lett. 105, 136805 (2010).
[25] W. Zhao, Z. Ghorannevis, L. Chu, M. Toh, C. Kloc, P. Tan, and G. Eda, “Evolution of electronic structure in atomically thin sheets of WS2 and WSe2”, ACS Nano 7, 791 (2013).
[26] C. Zhang, A. Johnson, C. Hsu, L. Li, and C. Shih, “Direct imaging of band profile in single layer MoS2 on graphite: quasiparticle energy gap, metallic edge states, and edge band bending”, Nano Lett. 14, 2443 (2014).
[27] M. Ugeda, A. Bradley, S. Shi, F. Jornada, Y. Zhang, D. Qiu, W. Ruan, S. Mo, Z. Hussain, Z. Shen, F. Wang, S. Louie, and M. Crommie, “Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor”, Nature Materials 13, 1091 (2014).
[28] H. Liu, L. Jiao, L. Xie, F. Yang, J. Chen, W. Ho, C. Gao, J. Jia, X. Cui, and M. Xie, “Molecular-beam epitaxy of monolayer and bilayer WSe2: a scanning tunneling microscopy/spectroscopy study and deduction of exciton binding energy”, 2D Mater. 2, 034004 (2015).
[29] A. Arora, M. Koperski, K. Nogajewski, J. Marcus, C. Faugeras, and M. Potemski, “Excitonic resonances in thin films of WSe2: from monolayer to bulk material”, Nanoscale 7, 10421 (2015).
[30] A. Arora, K. Nogajewski, M. Molas, M. Koperski, and M. Potemski, “Exciton band structure in layered MoSe2: from a monolayer to the bulk limit”, Nanoscale 7, 20769 (2015).
[31] S. Eichfeld, C. Eichfeld, Y. Lin, L. Hossain, and J. Robinson, “Rapid, non-destructive evaluation of ultrathin WSe2 using spectroscopic ellipsometry”, APL Materials 2, 092508 (2014).
[32] W. Zhao, R. Ribeiro, M. Toh, A. Carvallo, C. Kloc, A. Castro Neto, and G. Eda, “Origin of indirect optical transitions in few-layer MoS2, WS2, and WSe2”, Nano Lett. 13, 5627 (2013).
[33] C. Yim, M. O’Brien, N. McEcoy, S. Winters, I. Mirza, J. Lunney, and G. Duesberg, “Investigation of the optical properties of MoS2 thin films using spectroscopic ellipsometry”, Appl. Phys. Lett. 104, 103114 (2014).
[34] 林宜霖，以拉曼散射光譜研究 Sr2Y(Ru1-xCux)O6 與 Fe(Se, Te) 超導材料之晶格-電荷-自旋多重耦合效應，國立臺灣師範大學物理研究所碩士論文，101年6月。
[35] 黃俊儒，新穎材料 Cs2Nb4O11 與 MexMn1-xS (Me = Co, Gd) 之光譜性質研究，國立臺灣師範大學物理研究所碩士論文，99年6月。
[36] Y. Lee, X. Zhang, W. Zhang, M. Chang, C. Lin, K. Chang, Y. Yu, J. Wang, C. Chang, L. Li, and T. Lin, “Synthesis of large-area MoS2 atomic layers with chemical vapor deposition”, Adv. Mater. 24, 2320 (2012).
[37] Y. Chang, W. Zhang, Y. Zhu, Y. Han, J. Pu, J. Chang, W. Hsu, J. Huang, C. Hsu, M. Chiu, T. Takenobu, H. Li, C. Wu, W. Chang, A. Wee, and L. Li, “Monolayer MoSe2 grown by chemical vapor deposition for fast photodetection”, ACS Nano 8, 8582 (2014).
[38] Y. Lee, L. Yu, H. Wang, W. Fang, X. Ling, Y. Shi, C. Lin, J. Huang, M. Chang, C. Chang, M. Dresselhaus, T. Palacios, L. Li, and J. Kong, “Synthesis and transfer of single-layer transition metal disulfides on diverse surfaces”, Nano Lett. 13, 1852 (2013).
[39] J. Huang, J. Pu, C. Hsu, M. Chiu, Z. Juang, Y. Chang, W. Chang, Y. Iwasa, T. Takenobu, and L. Li, “Large-area synthesis of highly crystalline WSe2 monolayers and device applications”, ACS Nano 8, 923 (2014).
[40] C. A. Arguello, D. L. Rousseau, and S. P. S. Porto, “First-order Raman effect in wurtzite-type crystals”, Phys. Rev. 181, 1351 (1969).
[41] J. M. Calleja and Manuel Cardona, “Resonant Raman scattering ZnO”, Phys. Rev. B 16, 3753 (1977).
[42] N. Ashkenov, B. N. Mbenkum, C. Bundesmann, V. Riede, M. Lorenz, D. Spemann, E. M. Kaidashev, A. Kasic, M. Schubert, and M. Grundmann, “Infrard dielectric functions and phonon modes of high-quality ZnO films”, J. Appl. Phys. 93, 126 (2003).
[43] M. Schumm, M. Koerdel, S. Müller, H. Zutz, C. Ronning, J. Stehr, D. M. Hofmann, and J. Geurts, “Structure impact of Mn implantation on ZnO”, New J. Phys. 10, 043004 (2008).
[44] K. A. Alim, V. A. Fonoberov, M. Shamsa, and A. A. Balandin, “Micro-Raman investigation of optical phonons in ZnO nanocrystals”, J. Appl. Phys. 97, 124313 (2005).
[45] F. Decremps, J. Pellicer-Porres, A. M. Saitta, J. Chervin, and A. Polian, “High-pressur Raman spectroscopy study of wurtzite ZnO”, Phys. Rev. B 65, 092101 (2002).
[46] Y. J. Lin, C. L, Tsai, Y. M. Lu, and C. J. Liu, “Optical and electrical properties of undoped ZnO films”, J. Appl. Phys. 99, 093501 (2006).
[47] R.C. Rai, M. Guminiak, S Wilser, B. Cai, and M. L. Nakarmi, “Elevated temperature dependence of energy band gap of ZnO thin films grown by e-beam deposition”, J. Appl. Phys. 111, 073511 (2012).
[48] A. A. Toropov, O. V. Nekrutkina, and T. V. Shubina, “Temperature-dependent exciton polariton photoluminescence in ZnO films”, Phys. Rev. B 69, 165205 (2004).
[49] Jacques I. Pankove: Optical Processes in Semiconductors, Page 36 ~ 40 (1st edition, 1975).
[50] S. J. Pearton, D. J. Norton, K. Ip, Y. W. Heo, and T. Steiner, “Recent progress in processing and properties of ZnO.”, Prog. Mater. Sci. 50, 293 (2005).
[51] Chennupati Jagadish and Stephen J. Pearton: Zinc Oxide Bulk, Thin Films and Nanostructures Processing, Properties and Applications, Page 1 ~ 20 (1st edition, 2006).
[52] J. Mass, P. Bhattacharya, and R. S. Katiyar, “Effect of high substrate temperature on Al-doped ZnO thin films grown by pulsed laser deposition”, Materials Science and Engineering B 103, 9 (2003).
[53] H. Huang, Y. Ou, S. Xu, G. Fang, M. Li, and X. Z. Zhao, “Properties of Dy-doped ZnO nanocrystalline thin films prepared by pulsed laser deposition”, Applied Surface Science 254, 2013 (2008).
[54] J. H. Kim, H. Kim, D. Kim, S. G. Yoon, and W. K. Choo, “Optical and magnetic properties of laser-deposited Co-doped ZnO thin films”, Solid State Commun 131, 677 (2004).
[55] B. C. Mohanty, Y. H. Jo, D. H. Yeon, and Y. S. Cho, “Stress-induced anomalous shift of optical band gap in ZnO:Al thin films”, Appl. Phys. Lett. 95, 062103 (2009).
[56] B. E. Sernelius, K. F. Berggren, Z. C. Jin, and C. G. Granqvist, “Band-gap tailoring of Zno by means of heavy Al doping”, Phys. Rev. B 37, 10244 (1988).
[57] F. Lo, Y. Ting, K. Chou, T. Hsieh, C. Ye, Y. Hsu, M. Chern and H. Liu, “Paramagnetic dysprosium-doped znic oxide thin films grown by pulsed-laser deposition”, J. Appl. Phys. 117, 213911 (2015).
[58] A. Atta, M. El-nahass, K. Elsabawy, M. El-raheem, A. Hassanien, A. Alhuthali, A. Badawi, and A. Merazga, “Optical characteristics of transparent samarium oxide thin films deposition by the radio-frequency sputtering technique”, Pramana-J. Phys. 87, 72 (2016).
[59] H. Fujiwara: Spectroscopic Ellipsometry Principles and Applications (John Wiley & Sons, Ltd, 2003).
[60] G. A. Niklasson, O. G. Granqvist, and O. Hunderi, “Effective medium models for the optical properties of inhomogeneous materials”, Appl. Opt. 20, 26 (1981).
[61] 葉秦維，摻雜鑭系元素(鏑, 釓)氧化鋅與單層二(硫, 硒)化鎢薄膜的光譜性質研究，國立臺灣師範大學物理研究所碩士論文，104年6月。
[62] X. Zhang, X. Qiao, W. Shi, J. Wu, D. Jiang, and P. Tan, “Phonon and Raman scattering of two-dimensional transition metal dichalcogenides from monolayer, multilayer to bulk material”, Chem. Soc. Rev. 44, 2757 (2015).
[63] D. Guzman and A. Strachan “Role of strain on electronic and mechanical response of semiconducting transition-metal dichalcogenide monolayer: An ab-initio study”, J. Appl. Phys. 115, 243701 (2014).
[64] A. Pawbake, M. Pawar, S. Jadkar, and D. Late, “Large area chemical vapor deposition of monolayer transition metal dichalcogenides and their temperature dependent Raman spectroscopy studies”, Nanoscale 8, 3008 (2016).
[65] X. Huang, Y. Gao, T. Yang, W. Ren, H. Cheng, and T. Lai, “Quantitative analysis of temperature dependence of Raman shift of monolayer WS2”, Sci. Rep. 6, 32236 (2016).
[66] H. Terrones, E. Corro, S. Feng, J. Poumirol, D. Rhodes, D. Smirnov, N. Pradhan, and Z. Lin, “New first order Raman-active modes in few layered transition metal dichalcogenides”, Sci. Rep. 4, 4215 (2014).
[67] 張雅婷，單層二(硫, 硒)化(鉬, 鎢)薄膜的光譜性質研究，國立臺灣師範大學物理研究所碩士論文，105年7月。
[68] A. Ramasubramaniam, “Large excitonic effects in monolayers of molybdenum and tungsten dichalcogenides”, Phys. Rev. B 86, 115409 (2012).
[69] J. Li, Y. Zhong and D. Zhang, “Exciton in monolayer transition metal dichalcogenides”, J. Phys.: Condens. Matter 27, 315301 (2015).
[70] M. Chhowalla, H. Shin, G. Eda, L. Li, K. Loh, and H. Zhang, “The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets”, Nature Chemistry 5, 263 (2013).
[71] G. Shim, K. Yoo, S. Seo, J. Shin, D. Jung, I. Kang, C. Ahn, B. Cho, and S. Choi, “Large-area single-layer MoSe2 and its van der Waals Heterostructures”, ACS Nano 8, 6655 (2014).
[72] B. Zhu, X. Chen, and X. Cui, “Exciton binding energy of monolayer WS2”, Sci. Rep. 5, 9218 (2015).
[73] K. He, N. Kumar, L. Zhang, Z. Wang, K. Mak, H. Zhao, and J. Shan, “Tightly bound excitons in monolayer WSe2”, Phys. Rev. Lett. 113, 026803 (2014).
[74] Y. Tastumi, K. Ghalamkari, and R. Saito, “Laser energy dependence of valley polarization in transition-metal dichalcogenides”, Phys. Rev. B 94, 235408 (2016).
[75] R. Bromley, R. Murray, and A. Yoffe, “The band structures of some transition metal dichalcogenides: III. Group VI A: trigonal prism materials”, J. Phys. C: Solid State Phys. 5, 759 (1972).
[76] A. Carvalho, R. Ribeiro, and A. Castro Neto, “Band nesting and the optical response of two-dimensional semiconducting transition metal dichalcogenides”, Phy. Rev. B 88, 115205 (2013).
[77] A. Kormányos, G. Burkard, M. Gmitra, J. Fabian, V. Zólyomi, N. Drummond, and V. Fal’ko, “k‧p theory for two-dimenional transition metal dichalcogenide semiconductors”, 2D Matt. 2, 022001 (2015).
[78] L. Viña, S. Logothetidis, and M. Cardona, “Temperature dependence of the dielectric function of germanium”, Phys. Rev. B 30, 1979 (1984).
[79] D. Kozawa, R. Kumar, A. Carvalho, K. Amara, W. Zhao, S. Wang, M. Toh, R. Ribeiro, A. Castro Neto, K. Mastuda, and G. Eda, “Photocarrier relaxation pathway in two-dimensional semiconducting transition metal dichalcogenides”, Nature Communications 5, 4543 (2014).
[80] K. O’Donnell and X. Chen, “Temperature dependence of semiconductor band gaps”, Appl. Phys. Lett. 58, 2924 (1991).
[81] Y. Varshni, “Temperature dependence of the energy gap in semiconductors”, Physica 34, 149 (1967).
[82] G. Plechinger, P. Nagler, J. Kraus, N. Paradiso, C. Strunk, C. Schüller, and T. Korn, “Identification of exciton, trions, and biexcitons in single-layer WS2”, Phys. Status Solidi RRL 9, 457 (2015).
[83] T. Korn, S. Heydrich, M. Hirmer, J. Schmutzler, and C. Schüller, “Low-temperature photocarrier dynamics in monolayer MoS2”, Appl. Phys. Lett. 99, 102109 (2011).
[84] Z. He, Y. Sheng, Y. Rong, G. Lee, and J. Warner, “Layer-dependent modulation of tungsten disulfide photoluminescence by lateral electric fields”, ACS Nano 9, 2740 (2015).
[85] A. Mitioglu, K. Galkowski, A. Surrente, L. Klopotowski, A. Kis, D. Maude, and P. Plochocka, “Magnetoexcitons in large area CVD-grown monolayer MoS2 and MoSe2 on sapphire”, Phys. Rev. B 93, 165412 (2016).
[86] B. Peng, H. Zhang, H. Shao, Y. Xu, X. Zhang, and H. Zhu, “Thermal conductivity of monolayer MoS2, MoSe2, andWS2: interplay of mass effect, interatomic bonding and anharmonicity”, RSC Adv. 6, 5767 (2016).
[87] P. Norouzzadeh and D. Singh, “Thermal conductivity of single-layer WSe2 by a Stillinger-Weber potential”, Nanotechnology 28, 075708 (2017).