本研究以伽凡尼法製備奈米銀線，探討不同製程參數（如銀離子濃度、反應溫度、銀離子來源及反應金屬種類等）對形貌之影響，根據實驗結果，當使用1 mM硝酸銀溶液並以釩作為反應金屬，在25 ℃下可合成出大量的奈米銀線。實驗過程分別以SEM及XRD鑑定產物之表面形貌及相結構，並以TEM及STEM進一步瞭解奈米銀線之微結構及缺陷狀況。
成功合成出大量銀線後，以滴塗法製備奈米銀線電極陣列，當奈米銀線塗佈濃度為248 mg·m-2時，其對550 nm之光穿透度可達90%。本研究進一步將之與同樣對光具有穿透度且擁有可撓性之二硫化鉬薄膜結合製作出大面積可撓式透明元件，由於使用多層的二硫化鉬薄膜，元件整體之穿透度下降至60%。
除了穿透度分析，本研究在元件受力彎曲之情況下進行電性量測，以理解元件陣列在不同彎曲程度及次數下之操作穩定性，結果顯示當對元件施予大應變量為0.5%的情況下，元件電流值變化量小於5%，另外當元件經過50000次0.33%應變量之彎曲循環後，電流值僅衰退約13%，展現了以伽凡尼法合成之奈米銀線作為可撓式透明電極之應用潛力。

Silver nanowires (AgNWs) were synthesized by Galvanic replacement method in this study. The influences of experimental parameters, e.g., Ag+ concentration, reaction temperature, species of Ag+ source and donor metals, on the morphological changes of Ag nanostructures were investigated. As a result, large quantity of AgNWs is grown in 1 mM AgNO3 solution at room temperature with V foil, V foil serves as donor metal during the reaction, while Ag nanoparticles or dendrites were obtained in other cases.
AgNWs film were prepared by photolithography and drop-coating, the transmittance of which reaches up to approximately 90% at the wavelength of 550 nm as deposition density of AgNWs is 248 mg·m-2. To fabricate flexible transparent devices, multilayer MoS2 film was integrated with AgNWs electrodes, meanwhile the transmittance dropped to 60%.
The electrical measurements under bending were conducted to examine stability and durability of flexible transparent devices. The currents change less than 5% as 0.5% strain is applied onto the device. Furthermore, after bearing 50000 bending cycles under a strain of 0.33%, devices functioned normally with the attenuation of electrical current of merely about 13%, demonstrating the potential of AgNWs for the application of transparent flexible conducting film.

摘要 i
Abstract ii
致謝 iii
目錄 iv
圖目錄 vii
表目錄 x
壹、 緒論與文獻回顧 1
一、 科技發展趨勢 1
二、 奈米銀線基本性質 3
（一） 形貌定義 3
（二） 導電度 5
（三） 穿透度 7
（四） 可撓度 8
三、 奈米銀線製備方法 9
（一） 多元醇法 9
（二） 模板合成法（Hard Template Method） 11
（三） 伽凡尼法（Galvanic Displacement Method） 13
（四） 合成方法比較 14
（五） 成長機制 15
四、 奈米銀線應用領域 16
（一） 透明導電薄膜 16
（二） 溫度計（Thermometer） 18
（三） 表面增強拉曼散射（Surface-enhanced Raman Scattering, SERS） 19
五、 研究動機 20
貳、 實驗步驟 21
一、 實驗流程介紹 21
（一） 奈米銀線合成 21
（二） 二硫化鉬薄膜成長 22
（三） 二硫化鉬薄膜轉移 23
（四） 透明電極陣列製備 24
二、 實驗儀器介紹 25
（一）旋轉塗佈機（Spin Coater） 25
（二）單區加熱爐管（Single Zone Furnace） 26
（三）對準曝光機（Mask Aligner） 27
（四）光學顯微鏡（Optical Microscope, OM） 28
（五）掃描式電子顯微鏡（Scanning Electron Microscope, SEM） 29
（六）X射線繞射分析（X-ray diffractometer, XRD） 30
（七）穿透式電子顯微鏡（Transmission Electron Microscope, TEM） 31
（八）紫外/可見分光光譜儀（Ultraviolet-visible Spectroscopy, UV-Vis） 32
（九）原子力顯微鏡（Atomic Force Microscope, AFM） 33
（十）拉曼（Raman Spectrometer）/光致螢光（Photoluminescence）光譜儀 34
（十一）X射線光電子能譜儀（X-ray Photoelectron Spectroscopy, XPS） 35
（十二）電動線性平移台（Motorized Linear Stage） 36
（十三）電性量測系統 37
參、 結果與討論 38
一、 奈米銀線外觀 38
二、 銀離子濃度之影響 39
三、 反應溫度之影響 42
四、 銀離子來源之影響 44
五、 反應金屬之影響 47
六、 穿透式電子顯微鏡分析 50
七、 奈米銀線之電性及穿透度分析 53
八、 透明導電薄膜之應用 56
（一） 二硫化鉬薄膜之材料分析 56
（二） 二硫化鉬合成參數調控之影響 59
（三） 透明元件之穿透度分析 61
（四） 可撓式透明元件之電性分析 63
肆、 結論 65
伍、 未來展望 66
陸、 參考文獻 67

[1]Feynman, R. P. There's plenty of room at the bottom. Engineering and Science 23, 22-36 (1960).
[2]Binnig, G., Rohrer, H., Gerber, C., and Weibel, E. Tunneling through a controllable vacuum gap. Applied Physics Letters 40, 178-180 (1982).
[3]Novoselov, K. S., Geim, A. K., Morozov, S. V., Jiang, D., Zhang, Y., Dubonos, S. V., I. V. Grigorieva, and Firsov, A. A. Electric field effect in atomically thin carbon films. Science 306, 666-669 (2004).
[4]Yeh, Y. C., Creran, B., and Rotello, V. M. Gold nanoparticles: preparation, properties, and applications in bionanotechnology. Nanoscale 4, 1871-1880 (2012).
[5]Skrabalak, S. E., Au, L., Li, X., and Xia, Y. Facile synthesis of Ag nanocubes and Au nanocages. Nature Protocols 2, 2181-2190 (2007).
[6]Li, Z. H. and Ren, D. Y. Preparation of ITO transparent conductive film by sol-gel method. Transactions of Nonferrous Metals Society of China 16, 1358-1361 (2006).
[7]Ma, H. L., Zhang, D. H., Ma, P., Win, S. Z., and Li, S. Y. Preparation and properties of transparent conducting indium tin oxide films deposited by reactive evaporation. Thin Solid Films 263, 105-110 (1995).
[8]Kim, J. H. and Park, J. W. Improving the flexibility of large-area transparent conductive oxide electrodes on polymer substrates for flexible organic light emitting diodes by introducing surface roughness. Organic Electronics 14, 3444-3452 (2013).
[9]Minami, T., Ida, S., and Miyata, T. High rate deposition of transparent conducting oxide thin films by vacuum arc plasma evaporation. Thin Solid Films 416, 92-96 (2002).
[10]Yang, W., Broski, A., Wu, J., Fan, Q. H., and Li, W. Characteristics of transparent, PEDOT: PSS-coated indium-tin-oxide (ITO) microelectrodes. IEEE Transactions on Nanotechnology 17, 701-704 (2017).
[11]Furukawa, T. and Koden, M. Novel roll-to-roll deposition and patterning of ITO on ultra-thin glass for flexible OLEDs. IEICE Transactions on Electronics 100, 949-954 (2017).
[12]Wu, W. Inorganic nanomaterials for printed electronics: a review. Nanoscale 9, 7342-7372 (2017).
[13]Liu, J., Yi, Y., Zhou, Y., and Cai, H. Highly stretchable and flexible graphene/ITO hybrid transparent electrode. Nanoscale Research Letters 11, 108 (2016).
[14]Hssein, M., Tuo, S., Benayoun, S., Cattin, L., Morsli, M., Mouchaal, Y., Addou M., Khelil A., and Bernède, J. C. Cu-Ag bi-layer films in dielectric/metal/dielectric transparent electrodes as ITO free electrode in organic photovoltaic devices. Organic Electronics 42, 173-180 (2017).
[15]Wang, Y., Xu, M., Li, J., Ma, J., Wang, X., Wei, Z., Chu, X., Fang, X., and Jin, F. Sol-combustion synthesis of Al-doped ZnO transparent conductive film at low temperature. Surface and Coatings Technology 330, 255-259 (2017).
[16]Nasiri, M. and Rozati, S. M. Muscovite mica as a flexible substrate for transparent conductive AZO thin films deposited by spray pyrolysis. Materials Science in Semiconductor Processing 81, 38-43 (2018).
[17]Yu, X., Yu, X., Zhang, J., Zhang, D., Ni, J., Cai, H., Zhang D., and Zhao, Y. Efficient inverted polymer solar cells based on surface modified FTO transparent electrodes. Solar Energy Materials and Solar Cells 136, 142-147 (2015).
[18]Xia, Y., Sun, K., and Ouyang, J. Highly conductive poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) films treated with an amphiphilic fluoro compound as the transparent electrode of polymer solar cells. Energy & Environmental Science 5, 5325-5332 (2012).
[19]Xia, Y., Sun, K., and Ouyang, J. Solution-processed metallic conducting polymer films as transparent electrode of optoelectronic devices. Advanced Materials 24, 2436-2440 (2012).
[20]De, S., Lyons, P. E., Sorel, S., Doherty, E. M., King, P. J., Blau, W. J., Nirmalraj, P. N., Boland, J. J., Scardaci, V., Joimel, J, Coleman, J. N. Transparent, flexible, and highly conductive thin films based on polymer-nanotube composites. Acs Nano 3, 714-720 (2009).
[21]Gaynor, W., Burkhard, G. F., McGehee, M. D., and Peumans, P. Smooth nanowire/polymer composite transparent electrodes. Advanced Materials 23, 2905-2910 (2011).
[22]Liu, C. H. and Yu, X. Silver nanowire-based transparent, flexible, and conductive thin film. Nanoscale Research Letters 6, 75 (2011).
[23]Kang, S. B., Kwon, K. C., Choi, K. S., Lee, R., Hong, K., Suh, J. M., Im, M. J., Sanger A., Choi, I. Y., Kim, S. Y., Shin, J. C., Jang, H.W., and Shin, J. C. Transfer of ultrathin molybdenum disulfide and transparent nanomesh electrode onto silicon for efficient heterojunction solar cells. Nano energy 50, 649-658 (2018).
[24]Van De Groep, J., Spinelli, P., and Polman, A. Transparent conducting silver nanowire networks. Nano Letters 12, 3138-3144 (2012).
[25]Lee, J. Y., Connor, S. T., Cui, Y., and Peumans, P. Solution-processed metal nanowire mesh transparent electrodes. Nano Letters 8, 689-692 (2008).
[26]Cheng, Y., Wang, S., Wang, R., Sun, J., and Gao, L. Copper nanowire based transparent conductive films with high stability and superior stretchability. Journal of Materials Chemistry C 2, 5309-5316 (2014).
[27]Kou, P., Yang, L., Chi, K., and He, S. Large-area and uniform transparent electrodes fabricated by polymethylmethacrylate-assisted spin-coating of silver nanowires on rigid and flexible substrates. Optical Materials Express 5, 2347-2358 (2015).
[28]Tokuno, T., Nogi, M., Jiu, J., Sugahara, T., and Suganuma, K. Transparent electrodes fabricated via the self-assembly of silver nanowires using a bubble template. Langmuir 28, 9298-9302 (2012).
[29]Zhang, P., Wyman, I., Hu, J., Lin, S., Zhong, Z., Tu, Y., Huang, Z., and Wei, Y. Silver nanowires: Synthesis technologies, growth mechanism and multifunctional applications. Materials Science and Engineering: B 223, 1-23 (2017).
[30]Coskun, S., Aksoy, B., and Unalan, H. E. Polyol synthesis of silver nanowires: an extensive parametric study. Crystal Growth & Design 11, 4963-4969 (2011).
[31]Manepalli, R., Stepniak, F., Bidstrup-Allen, S. A., and Kohl, P. A. Silver metallization for advanced interconnects. IEEE Transactions on Advanced Packaging 22, 4-8 (1999).
[32]Gao, L., Härter, P., Linsmeier, C., Wiltner, A., Emling, R., and Schmitt-Landsiedel, D. Silver metal organic chemical vapor deposition for advanced silver metallization. Microelectronic Engineering 82, 296-300 (2005).
[33]Zhang, Z., Zhang, X., Xin, Z., Deng, M., Wen, Y., and Song, Y. Controlled inkjetting of a conductive pattern of silver nanoparticles based on the coffee‐ring effect. Advanced Materials 25, 6714-6718 (2013).
[34]He, G. C., Lu, H., Dong, X. Z., Zhang, Y. L., Liu, J., Xie, C. Q., and Zhao, Z. S. Electrical and thermal properties of silver nanowire fabricated on a flexible substrate by two-beam laser direct writing for designing a thermometer. RSC Advances 8, 24893-24899 (2018).
[35]Cheng, Z., Liu, L., Xu, S., Lu, M., and Wang, X. Temperature dependence of electrical and thermal conduction in single silver nanowire. Scientific Reports 5, 10718 (2015).
[36]Tokuno, T., Nogi, M., Karakawa, M., Jiu, J., Nge, T. T., Aso, Y., and Suganuma, K. Fabrication of silver nanowire transparent electrodes at room temperature. Nano Research 4, 1215-1222 (2011).
[37]Yan, X., Ma, J., Xu, H., Wang, C., and Liu, Y. Fabrication of silver nanowires and metal oxide composite transparent electrodes and their application in UV light-emitting diodes. Journal of Physics D: Applied Physics 49, 325103 (2016).
[38]Gebeyehu, M. B., Chala, T. F., Chang, S. Y., Wu, C. M., and Lee, J. Y. Synthesis and highly effective purification of silver nanowires to enhance transmittance at low sheet resistance with simple polyol and scalable selective precipitation method. RSC Advances 7, 16139-16148 (2017).
[39]Lee, J., Lee, P., Lee, H., Lee, D., Lee, S. S., and Ko, S. H. Very long Ag nanowire synthesis and its application in a highly transparent, conductive and flexible metal electrode touch panel. Nanoscale 4, 6408-6414 (2012).
[40]Li, B., Ye, S., Stewart, I. E., Alvarez, S., and Wiley, B. J. Synthesis and purification of silver nanowires to make conducting films with a transmittance of 99%. Nano Letters 15, 6722-6726 (2015).
[41]Anh Dinh, D., Nam Hui, K., San Hui, K., Singh, J., Kumar, P., and Zhou, W. Silver nanowires: a promising transparent conducting electrode material for optoelectronic and electronic applications. Reviews in Advanced Sciences and Engineering 2, 324-345 (2013).
[42]Xu, F., Xu, W., Mao, B., Shen, W., Yu, Y., Tan, R., and Song, W. Preparation and cold welding of silver nanowire based transparent electrodes with optical transmittances > 90% and sheet resistances < 10 ohm/sq. Journal of Colloid and Interface Science 512, 208-218 (2018).
[43]Xue, Q., Yao, W., Liu, J., Tian, Q., Liu, L., Li, M., Lu, Q., Peng, R., and Wu, W. Facile synthesis of silver nanowires with different aspect ratios and used as high-performance flexible transparent electrodes. Nanoscale Research Letters 12, 480 (2017).
[44]Jiu, J., Araki, T., Wang, J., Nogi, M., Sugahara, T., Nagao, S., Koga, H., Suganuma, H., Nakazawa, E., Hara, M., Uchida, H., and Shinozaki, K. Facile synthesis of very-long silver nanowires for transparent electrodes. Journal of Materials Chemistry A 2, 6326-6330 (2014).
[45]Sun, Y., Yin, Y., Mayers, B. T., Herricks, T., and Xia, Y. Uniform silver nanowires synthesis by reducing AgNO3 with ethylene glycol in the presence of seeds and poly (vinyl pyrrolidone). Chemistry of Materials 14, 4736-4745 (2002).
[46]Jiu, J., Murai, K., Kim, D., Kim, K., and Suganuma, K. Preparation of Ag nanorods with high yield by polyol process. Materials Chemistry and Physics 114, 333-338 (2009).
[47]Huang, Q. and Zhu, Y. Gravure printing of water-based silver nanowire ink on plastic substrate for flexible electronics. Scientific Reports 8, 15167 (2018).
[48]Zhang, K., Du, Y., and Chen, S. Sub 30 nm silver nanowire synthesized using KBr as co-nucleant through one-pot polyol method for optoelectronic applications. Organic Electronics 26, 380-385 (2015).
[49]Ran, Y., He, W., Wang, K., Ji, S., and Ye, C. A one-step route to Ag nanowires with a diameter below 40 nm and an aspect ratio above 1000. Chemical Communications 50, 14877-14880 (2014).
[50]Zhang, Q., Li, Y. A. N., Xu, D., and Gu, Z. Preparation of silver nanowire arrays in anodic aluminum oxide templates. Journal of Materials Science Letters 20, 925-927 (2001).
[51]Huang, M. H., Choudrey, A., and Yang, P. Ag nanowire formation within mesoporous silica. Chemical Communications 36, 1063-1064 (2000).
[52]Kazeminezhad, I., Barnes, A. C., Holbrey, J. D., Seddon, K. R., and Schwarzacher, W. Templated electrodeposition of silver nanowires in a nanoporous polycarbonate membrane from a nonaqueous ionic liquid electrolyte. Applied Physics A 86, 373-375 (2007).
[53]Feng, Y., Kim, K. D., Nemitz, C. A., Kim, P., Pfadler, T., Gerigk, M., Polarz, S., Dorman, J. A., Weickert, J., and Schmidt-Mende, L. Uniform large-area free-standing silver nanowire arrays on transparent conducting substrates. Journal of The Electrochemical Society 163, 447-452 (2016).
[54]Yang, S. and Liu, Q. Guided growth of Ag nanowires by galvanic replacement on a flexible substrate. Langmuir 33, 11851-11856 (2017).
[55]Wang, S. C., Chang, C. S., and Chen, L. J. Electromigration behaviors of Ag nanowires and complete replacement of ZnO nanowires via atomic diffusion. Department of Materials Science and Engineering, National Tsing Hua University (2014).
[56]Liu, R. and Sen, A. Unified synthetic approach to silver nanostructures by galvanic displacement reaction on copper: from nanobelts to nanoshells. Chemistry of Materials 24, 48-54 (2011).
[57]Avizienis, A. V., Martin-Olmos, C., Sillin, H. O., Aono, M., Gimzewski, J. K., and Stieg, A. Z. Morphological transitions from dendrites to nanowires in the electroless deposition of silver. Crystal Growth & Design 13, 465-469 (2013).
[58]Sun, Y. Growth of silver nanowires on GaAs wafers. Nanoscale, 3, 2247-2255 (2011).
[59]Alami, A. H., Rajab, B., and Aokal, K. Assessment of silver nanowires infused with zinc oxide as a transparent electrode for dye-sensitized solar cell applications. Energy 139, 1231-1236 (2017).
[60]Wang, D., Zhou, W., Liu, H., Ma, Y., and Zhang, H. Performance improvement in flexible polymer solar cells based on modified silver nanowire electrode. Nanotechnology 27, 335203 (2016).
[61]Kim, J. Y., Jeon, J. H., and Kwon, M. K. Indium tin oxide-free transparent conductive electrode for gan-based ultraviolet light-emitting diodes. ACS Applied Materials & Interfaces 7, 7945-7950 (2015).
[62]Sun, J. G., Yang, T. N., Wang, C. Y., and Chen, L. J. A flexible transparent one-structure tribo-piezo-pyroelectric hybrid energy generator based on bio-inspired silver nanowires network for biomechanical energy harvesting and physiological monitoring. Nano Energy 48, 383-390 (2018).
[63]Tseng, J. Y., Lee, L., Huang, Y. C., Chang, J. H., Su, T. Y., Shih, Y. C., Lin, H. W., and Chueh, Y. L. Pressure welding of silver nanowires networks at room temperature as transparent electrodes for efficient organic light‐emitting diodes. Small 14, 1800541 (2018).
[64]Kim, D., Ko, Y., Kwon, G., Kim, U. J., and You, J. Micropatterning silver nanowire networks on cellulose nanopaper for transparent paper electronics. ACS Applied Materials & Interfaces 10, 38517-38525 (2018).
[65]Zhang, L., Wang, B., Zhu, G., and Zhou, X. Synthesis of silver nanowires as a SERS substrate for the detection of pesticide thiram. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 133, 411-416 (2014).
[66]Cui, Y., Chen, J., Di, Y., Zhang, X., and Lei, W. High performance field emission of silicon carbide nanowires and their applications in flexible field emission displays. AIP Advances 7, 125219 (2017).
[67]Wang, D. H., Xu, D., Wang, Q., Hao, Y. J., Jin, G. Q., Guo, X. Y., and Tu, K. N. Periodically twinned SiC nanowires. Nanotechnology 19, 215602 (2008).
[68]Sunde, T. O. L., Garskaite, E., Otter, B., Fossheim, H. E., Sæterli, R., Holmestad, R., Einarsrud, M. A., and Grande, T. Transparent and conducting ITO thin films by spin coating of an aqueous precursor solution. Journal of Materials Chemistry 22, 15740-15749 (2012).
[69]Sun, J., Chen, Z., Yuan, L., Chen, Y., Ning, J., Liu, S., Ma, D., Song, S., Priydarshi, M. K., Bachmatiuk, A., Rümmeli, M. H., Ma, T., Zhi, L., Huang, L., Zhang, Y., and Liu, Z. Direct chemical-vapor-deposition-fabricated, large-scale graphene glass with high carrier mobility and uniformity for touch panel applications. ACS nano 10, 11136-11144 (2016)
[70]Dhakal, K. P., Duong, D. L., Lee, J., Nam, H., Kim, M., Kan, M., Lee, Y. H., and Kim, J. Confocal absorption spectral imaging of MoS2: optical transitions depending on the atomic thickness of intrinsic and chemically doped MoS2. Nanoscale 6, 13028-13035 (2014).
[71]Splendiani, A., Sun, L., Zhang, Y., Li, T., Kim, J., Chim, C. Y., Galli, G., and Wang, F. Emerging photoluminescence in monolayer MoS2. Nano letters 10, 1271-1275 (2010).
[72]George, A. S., Mutlu, Z., Ionescu, R., Wu, R. J., Jeong, J. S., Bay, H. H., Chai, Y., Mkhoyan, A., Ozkan M., and Ozkan, C. S. Wafer scale synthesis and high resolution structural characterization of atomically thin MoS2 layers. Advanced Functional Materials 24 7461-7466 (2014).
[73]Kim, K. S., Kim, K. H., Nam, Y., Jeon, J., Yim, S., Singh, E., Lee, J. Y., Lee, S. J., Jung, Y. S., Yeom, G. Y., and Kim, D. W. Atomic layer etching mechanism of MoS2 for nanodevices. ACS Applied Materials & Interfaces 9, 11967-11976 (2017).
[74]Wang, H. W., Skeldon, P., and Thompson, G. E. XPS studies of MoS2 formation from ammonium tetrathiomolybdate solutions. Surface and Coatings Technology 91, 200-207 (1997).
[75]Tan, L. K., Liu, B., Teng, J. H., Guo, S., Low, H. Y., and Loh, K. P. Atomic layer deposition of a MoS2 film. Nanoscale 6, 10584-10588 (2014).
[76]Liu, K. K., Zhang, W., Lee, Y. H., Lin, Y. C., Chang, M. T., Su, C. Y., Chang, C. S., Li, H., Shi, Y., Zhang, H., Lai, C. S., and Li, L. J. Growth of large-area and highly crystalline MoS2 thin layers on insulating substrates. Nano Letters 12, 1538-1544 (2012).
[77]Dhakal, K. P., Duong, D. L., Lee, J., Nam, H., Kim, M., Kan, M., Lee, Y. H., and Kim, J. Confocal absorption spectral imaging of MoS2: optical transitions depending on the atomic thickness of intrinsic and chemically doped MoS2. Nanoscale 6, 13028-13035 (2014).
[78]Kozawa, D., Kumar, R., Carvalho, A., Amara, K. K., Zhao, W., Wang, S., Toh, M., Ribeiro, R. M., Neto, A. C., Matsuda, K., and Eda, G. Photocarrier relaxation pathway in two-dimensional semiconducting transition metal dichalcogenides. Nature Communications 5, 4543 (2014).
[79]Qiu, D. Y., Felipe, H., and Louie, S. G. Optical spectrum of MoS2: many-body effects and diversity of exciton states. Physical Review Letters 111, 216805 (2013).
[80]Frisenda, R., Niu, Y., Gant, P., Molina-Mendoza, A. J., Schmidt, R., Bratschitsch, R., Liu, J., Fu, L., Dumcenco, D., Kis, A., De Lara, D. P., and Castellanos-Gomez, A. Micro-reflectance and transmittance spectroscopy: a versatile and powerful tool to characterize 2D materials. Journal of Physics D: Applied Physics 50, 074002 (2017).