Current Optics and Photonics

Optical Society of Korea (한국광학회)
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Development of a Microspot Spectroscopic Ellipsometer Using Reflective Objectives, and the Ellipsometric Characterization of Monolayer MoS2

  • Received : 2020.02.04
  • Accepted : 2020.05.11
  • Published : 2020.08.25
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Abstract

Adopting an elaborately designed reflective objective consisting of four mirrors, we have developed a rotating-polarizer-type microspot spectroscopic ellipsometer (SE) with an ultra-small spot size. The diameter of the focused beam, whether evaluated using a direct-image method or a knife-edge method, is less than 8.4 ㎛. After proper correction for the polarizing effect of the mirrors in the reflective objective, we unambiguously determine the dispersion of the complex refractive index and the thickness of monolayer MoS2 using the measured microspot-spectroellipsometric data. The measured ellipsometric spectra are sensitive enough to identify small variations in thickness of MoS2 flakes, which ranged from 0.48 nm to 0.67 nm.

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References

  1. A. R. Beal and H. P. Hughes, "Kramer-Kronig analysis of the reflectivity spectra of 2H-$MoS_2$, 2H-$MoSe_2$ and 2H-$MoTe_2$," J. Phys. C: Solid State Phys. 12, 881 (1979). https://doi.org/10.1088/0022-3719/12/5/017
  2. Y. Li, A. Chernikov, X. Zhang, A. Rigosi, H. M. Hill, A. M. van der Zande, D. A. Chenet, E.-M. Shih, J. Hone, and T. F. Heinz, "Measurement of the optical dielectric function of monolayer transition-metal dichalcogenides: $MoS_2$, $MoSe_2$, $WS_2$, and $WSe_2$," Phys. Rev. B 90, 205422 (2014). https://doi.org/10.1103/PhysRevB.90.205422
  3. Y. V. Morozov and M. Kuno, "Optical constants and dynamic conductivities of single layer $MoS_2$, $MoSe_2$, and $WSe_2$," Appl. Phys. Lett. 107, 083103 (2015). https://doi.org/10.1063/1.4929700
  4. A. Castellanos-Gomez, J. Quereda, H. P. van der Meulen, N. Agrait, and G. Rubio-Bollinger, "Spatially resolved optical absorption spectroscopy of single- and few-layer $MoS_2$ by hyperspectral imaging," Nanotechnology 27, 115705 (2016). https://doi.org/10.1088/0957-4484/27/11/115705
  5. C. Hsu, R. Frisenda, R. Schmidt, A. Arora, S. M. de Vasconcellos, R. Bratschitsch, H. S. J. van der Zant, and A. Castellanos-Gomez, "Thickness-dependent refractive index of 1L, 2L, and 3L $MoS_2$, $MoSe_2$, $WS_2$, and $WSe_2$," Adv. Opt. Mater. 7, 1900239 (2019). https://doi.org/10.1002/adom.201900239
  6. H. S. Lee, S.-W. Min, Y.-G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, "$MoS_2$ nanosheet phototransistors with thickness-modulated optical energy gap," Nano. Lett. 12, 3695-3700 (2012). https://doi.org/10.1021/nl301485q
  7. H. Zhang, Y. Ma, Y. Wan, X. Rong, Z. Xie, W. Wang, and L. Dai, "Measuring the refractive index of highly crystalline monolayer $MoS_2$ with high confidence," Sci. Rep. 5, 8440 (2015). https://doi.org/10.1038/srep08440
  8. T. Han, H. Liu, S. Wang, S. Chen, W. Li, X. Yang, M. Cai, and K. Yang, "Probing the optical properties of $MoS_2$ on $SiO_2$/Si and sapphire substrates," Nanomaterials 9, 740 (2019). https://doi.org/10.3390/nano9050740
  9. M. M. Benameur, B. Radisavljevic, J. S. Heron, S. Sahoo, H. Berger, and A. Kis, "Visibility of dichalcogenide nanolayers," Nanotechnology 22, 125706 (2011). https://doi.org/10.1088/0957-4484/22/12/125706
  10. B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, "Single-layer $MoS_2$ transistors," Nat. Nanotechnol. 6, 147-150 (2011). https://doi.org/10.1038/nnano.2010.279
  11. Y.-H. Lee, X.-Q. Zhang, W. Zhang, M.-T. Chang, C.-T. Lin, K.-D. Chang, Y.-C. Yu, J. T.-W. Wang, C.-S. Chang, L.-J. Li, and T.-W. Lin, "Synthesis of large-area $MoS_2$ atomic layers with chemical vapor deposition," Adv. Mater. 24, 2320-2325 (2012). https://doi.org/10.1002/adma.201104798
  12. Y. Yu, Y. Yu, Y. Cai, W. Li, A. Gurarslan, H. Peelaers, D. E. Aspnes, C. G. Van de Walle, N. V. Nguyen, Y.-W. Zhang, and L. Cao, "Exciton-dominated dielectric function of atomically thin $MoS_2$ films," Sci. Rep. 5, 16996 (2015). https://doi.org/10.1038/srep16996
  13. S. K. Kang and H. S. Lee, "Study on growth parameters for monolayer $MoS_2$ synthesized by CVD using solutionbased metal precursors," Appl. Sci. Converg. Technol. 28, 159-163 (2019). https://doi.org/10.5757/ASCT.2019.28.5.159
  14. R. M. A. Azzam and N. M. Bashara, Ellipsometry and Polarized Light (North-Holland Publishing, Amsterdam, 1987).
  15. S. Y. Kim, Ellipsometry (Ajou University, Suwon, 2000), Chapter 3-4.
  16. V. G. Kravets, V. V. Prorok, L. V. Poperenko, and I. A. Shaykevich, "Ellipsometry and optical spectroscopy of lowdimensional family TMDs," Semicond. Phys. Quantum Electron. Optoelectron. 20, 284-296 (2017). https://doi.org/10.15407/spqeo20.03.284
  17. C. Yim, M. O'Brien, N. McEvoy, S. Winters, I. Mirza, J. G. Lunney, and G. S. Duesberg, "Investigation of the optical properties of $MoS_2$ thin films using spectroscopic ellipsometry," Appl. Phys. Lett. 104, 103114 (2014). https://doi.org/10.1063/1.4868108
  18. H.-L. Liu, C.-C. Shen, S.-H. Su, C.-L. Hsu, M.-Y. Li, and L.-J. Li, "Optical properties of monolayer transition metal dichalcogenides probed by spectroscopic ellipsometry," Appl. Phys. Lett. 105, 201905 (2014). https://doi.org/10.1063/1.4901836
  19. T. R. Piwonka-Corle, K. F. Scoffone, X. Chen, L. J. Lacomb, Jr., J.-L. Stehle, D. Zahorski, and J.-P. Rey, "Focused beam spectroscopic ellipsometry method and system," U.S. Patent 5608526A (1997).
  20. J. A. Woollam Co., RC2 Ellipsometer Brochure (2017). Accessed: April 4, 2020 [Online]. Available: https://www.jawoollam.com/download/pdfs/rc2-brochure.pdf.
  21. S. J. K im a nd M . H. L ee, "Microsp ot sp ectroscopic ellip someter with 4-reflectors," Korean Patent 10-1922973 (2018).
  22. Y. Xiong, Y. Dai, S. Chen, and G. Tie, "Design and experimental demonstration of coaxially folded all-reflective imaging system," Curr. Opt. Photon. 3, 227-235 (2019). https://doi.org/10.3807/copp.2019.3.3.227
  23. L. Beiser and R. B. Johnson, "Scanners," in Handbook of Optics, 2nd ed., M. Bass, ed. (McGraw-Hill, NY, 1995), Chapter 19.
  24. S. J. Kim, H. K. Yoon, M. H. Lee, S. J. Ii, S. Y. Cho, Y. H. Kwon, B. K. Kim, D. H. Bae, J. H. Shin, and S. Y. Kim, "Development and evaluation of micro spot spectroscopic ellipsometer," in Proc. 8th International Conference on Spectroscopic Ellipsometry (Barcelona, Spain, May 2019), p. 152.