Identifying Excitation and Emission Rate Contributions to Plasmon

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Identifying excitation and emission rate contributions to plasmon-enhanced photoluminescence from monolayer MoS2 using a tapered gold nanoantenna Edgar Palacios, Spencer Park, Lincoln Lauhon, and Koray Aydin ACS Photonics, Just Accepted Manuscript • Publication Date (Web): 09 Jun 2017 Downloaded from http://pubs.acs.org on June 9, 2017

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Identifying excitation and emission rate contributions to plasmon-enhanced photoluminescence from monolayer MoS2 using a tapered gold nanoantenna Edgar Palacios, Spencer Park, Lincoln Lauhon, Koray Aydin

E. Palacios, K. Aydin Department of Electrical Engineering and Computer Science Northwestern University Evanston, IL [email protected], [email protected]

S. Park, L. Lauhon Department of Material Science and Engineering Northwestern University Evanston, IL

Abstract Single element and periodic arrays of plasmonic nanoantennas have be used to enhance light-matter interactions in 2D materials to improve their suitability for optoelectronic devices. However, single nanoantennas with discrete resonances do not readily enable separation of enhancements in excitation and emission, each of which influence total Raman and photoluminescence (PL) enhancement.

Here we use a single Au tapered

plasmonic nanoantenna with optical resonances that extend above and below the bandgap to observe a broad enhancement in PL of MoS2. The largest peak enhancement of ~3.2 is observed at an antenna position between the position of maximum excitation-field enhancement and the position of maximum Purcell factor (PF), indicating a contribution of both excitation and emission rate enhancements.

In contrast, the peak Raman

enhancement occurs at the position of the excitation-field maximum because it is only dependent on the enhancement of the electric field. This independent determination of

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excitation and emission rate enhancements via spatial separation provides a more comprehensive picture of light-matter interactions in MoS2 monolayers interfaced with plasmonic materials. Keywords: ((MoS2, optical antenna, plasmonics, photoluminescence, raman))

The recent surge in two-dimensional transition metal dichalcogenide (2D-TMDC) research is driven in part by the unique electrical and optical properties that emerge when they are thinned down to several monolayers. It is the direct electronic band gap of some TMDCs, however, that has attracted researchers to explore this newly emerging class of materials for use in optoelectronic devices. Interest was stimulated by the demonstration of photoluminescence (PL) enhancement 1-3 and has led to their incorporation in ultra-thin emitters4 and photodetectors5-8. However, poor light absorption and emission resulting from their atomic thickness has been a major drawback for optoelectronic applications. Efforts to improve light absorption and emission include placing resonant antennas or cavities near 2D-TMDCs that enhance the excitation and radiative emission rates. Conventionally, the highest PL enhancement is achieved by engineering the spectral response of the resonator so excitation rates are increased. In particular, periodic nanoparticle arrays9-11, isolated nanoparticles12-15, sub20nm gap plasmonic structures 12, 16, photonic crystals17-19 and optical microcavities20-21 have been shown to enhance light-matter interactions in 2D-TMDCs that govern light absorption and emission. Although significant PL enhancements have been observed, many of these studies focus on the correlation of the electric field (EF) enhancement but do not address the contribution from the Purcell factor enhancement. In this study, we identify the separate contributions from excitation and emission field enhancements in MoS2 via spatially resolved photoluminescence(PL) and Raman measurements. Using a tapered Au nanoantenna on MoS2 to


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access a broad range of dipolar resonances in the visible spectrum, we achieve a maximum PL enhancement of ~3.2 located at a width of 121nm which lies between the simulated EF enhancement and Purcell factor (PF) maxima, indicating a contribution of both excitation and emission rate enhancements. Raman line scans of the same antenna were found to exhibit the peak enhancement at a smaller width corresponding to the theoretical EF maxima for the excitation source. From these results, we can spatially resolve the modification of PL and Raman signal along the antenna allowing us to separate the contributions of excitation and emission field enhancements in MoS2. This approach provides new insights into light-matter interactions of 2D materials interfaced with plasmonic nanoantennae that will inform the design of photon management and enhancing light-matter interactions. MoS2 monolayers were grown by chemical vapor deposition on 300 nm of thermally grown SiO2 on a Si wafer (Fig. S1). Monolayer regions of interest were identified by atomic force microscopy (AFM) and PL measurements showing a step height of 0.8 nm and PL peak at 675 nm, respectively, agreeing well with reported values22. A single 40 nm thick Au tapered nanoantenna was fabricated directly on MoS2 using electron-beam lithography on a monolayer MoS2 region of at least 20x20µm. As shown in the scanning electron microscopy (SEM) image (Fig. 1a), the trapezoidal antenna is 5 µm long and its width increases from 74 to 244 nm. The variable width antenna is an enabling platform to systematically investigate distinct contributions to PL enhancement at various resonant wavelengths. Results and discussion The plasmonic nanoantenna couples incident light to transverse dipolar resonances under polarized illumination at visible frequencies (Fig. 1b). The color gradient along the nanoantenna spanning from blue to yellow indicates a broad resonance range. Differential reflection


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measurements show the spectral response of the nanoantenna as shown in Fig. S2. PL emission mapping was carried out over a 4x8 µm2 region around the nanoantenna using a polarized 633 nm HeNe laser source to gain a clearer picture of where and how much the different resonances modify the PL emission. The measurements are conducted by spatially filtering a region of interest smaller than the beam diameter. This is accomplished by adjusting a physical slit before the spectrometer entrance and utilizing CCD pixel binning to capture emission from a selected region of the nanoantenna equivalent to ~200x200nm2. Measured PL intensities were integrated between 650 and 750 nm and enhancement factors were calculated by normalizing the integrated PL from the nanoantenna region to the integrated PL from a nearby region of MoS2 on the same flake. When the polarization is parallel to the long axis of the antenna (Fig. 1c), the antenna is not on resonance and no PL enhancement is observed. The maximum variation in this emission is calculated to be less than 10% of the maximum in enhanced PL, as can be seen by comparing figures 1c and 1d. Upon polarizing the laser perpendicular to the long axis of the antenna, the transverse dipolar resonances of the antenna are excited. This excitation enhances the spectrally integrated PL along the entire length of the nanoantenna with a maximum enhancement of 7.2 at an antenna width of 121 nm, just below the middle of the antenna (Fig. 1d). The maximum results from a combination of absorption and emission enhancement due to transverse dipolar resonances, as explained below. Analysis of the dependence of PL and Raman emission on wavelength and width reveals the physical mechanisms responsible for the enhancement. PL line scans along the nanoantenna for different wavelengths were used to calculate an enhancement factor as a function of antenna width and emission wavelength (Fig. 2a). The PL enhancement is calculated as the ratio of the


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PL intensity along the nanoantenna to the PL intensity of “blank” MoS2 away from the antenna. The PL enhancement is larger on the narrow end of the antenna starting from 74 nm, increases with increased width, and peaks at a width of 121 nm. It then decays as the width continues to increase. Raman spectra of the same nanoantenna at different widths were also generated using a 633 nm laser. The Raman intensity shows a similar variation along the length of the antenna as the PL intensity (Fig. 2b), but it peaks at a slightly narrower width (108 nm). This observation of distinct peak positions along the antenna for Raman and PL spectra indicates that incident electric field enhancements and emission enhancements contribute differently to both signals and will be explained via the simulations results that follow. To identify the physical mechanisms responsible for emission enhancement, we conducted two different full-wave electromagnetic simulations. The first simulation established the resonant wavelengths as a function of antenna width by calculating the electric-field (EF) enhancement within the MoS2 monolayer using the finite-difference time-domain (FDTD) method (Fig. 3a). The field monitor was placed 4 nm away from the edge of the nanoantenna and 0.5 nm deep inside the 1 nm thick MoS2, whose dielectric function was fitted to previous experimental work23. For excitation at 633 nm, an antenna width of 101 nm creates the highest electric field enhancement. Even larger field enhancements are observed at longer wavelengths, with the resonance shifting to larger widths, due to the sharp decrease in the imaginary refractive index of MoS2 below the band gap. From the dips in differential reflection spectra (Fig. S2) we verify the existence and position of the resonant modes along the nanoantenna which correlate well with simulated results. In the second simulation, the emission rate enhancement was calculated by determining the spatially averaged Purcell factor for an array of dipoles extending away from the Au antenna


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for different widths (Fig. 3b). These 2D simulations were set up with an array of fifteen dipoles starting 4 nm away from the Au. The starting position of the array was chosen to minimize numerical error associated with dipole power calculations near a dispersive media. The effective Purcell factor for each width was calculated by taking the ratio of power emitted in the far field to the power emitted by the dipole in vacuum, averaged over the entire array. As the plasmon resonance wavelength redshifts, the peak Purcell factor shifts accordingly which is indicative of strong coupling between the radiative emission and Au surface plasmon. The comparison of simulations with the measured PL enhancement enables the identification of two distinct mechanisms of PL enhancement that dominate in different regimes. For smallest antenna widths, the dipolar resonance occurs below 633 nm, so the excitation source is slightly off-resonance, resulting in small degree of field enhancement and a modest PL enhancement. As the antenna width increases, the dipolar resonance wavelength approaches the laser source wavelength, and the PL enhancement is dominated by the enhancement of the excitation field, i.e. absorption enhancement. The maximum field enhancement occurs at a width of 101 nm, at which point the Purcell effect also contributes to emission enhancement. For smaller widths, excitation rate enhancement dominates, but as we continue to move to larger widths the emission rate enhancement starts to play a larger role. The maximum PL enhancement (observed at 121 nm) occurs just beyond a width of 101 nm because the Purcell factor is rising faster than the field enhancement is decaying. A further increase in the antenna width results in reduction of the PL enhancement as the field enhancement begins to fall off rapidly. Here, the resonance lies below the bandedge so the PL enhancement mostly only occurs due to the increased emission rate.


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To illustrate this effect more clearly, we present two measurements and two simulations in a single plot in Fig. 4, where we take slices from the theoretical electric field enhancement of the laser at 633 nm, the Purcell factor at 675 nm, and linescans of the Raman at 408 cm-1 and PL at 680nm. In both of these measurements, the finite beam width illuminates a range of antenna widths of ∆w~34 nm, but we only collect data from a smaller region that covers a range of ∆w~7 nm as explained in the experimental methods section. Because we are measuring a finite range of widths, it is important to note that this can cause a slight broadening in the measured spectra so when comparing linescans we focus on the peak positions. The incident electric field enhancement peak is observed for a Au nanoantenna width of 101 nm whereas the peak Purcell factor is achieved for 130 nm width. The measured Raman-shift has a peak at 105 nm which is close to that of the EF plot. While Raman enhancement depends on product of the squares of both the incident and scattered electric field24, they are close in frequency, and therefore wavelength. The red-shift in overall Raman enhancement relative to incident field enhancement is consistent with the measurement of Stokes scattering. For PL, the emission enhancement occurs at a longer wavelength, and is described by the Purcell effect. Our measurements for PL show that the maximum PL enhancement occurs at an antenna width of 120 nm, which is in between the simulated EF and the Purcell factor peaks, suggesting that the PL enhancement is achieved due to both excitation and emission rate enhancements enabled by the two distinct mechanisms as discussed above. To conclude, we have identified and quantified the contributions of excitation and emission enhancements to photoluminescence enhancement from a 2D MoS2 film using a single Au optical nanoantenna platform. We observed an experimental PL enhancement of ~3.2 along a broad range of antenna widths. We find that enhanced radiative emission is not just a result of


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excitation enhancement at the laser wavelength, but is also due to emission rate enhancement due to the increased Purcell factor at different positions along the nanoantenna. Furthermore, we showed that the highest Raman enhancement occurs for a narrower range of nanoantenna widths because incident and outgoing fields are very similar in frequency (or wavelength). Hence, the greatest PL emission enhancement from 2D-TMDCs does not simply occur where the excitation field is highest, but instead where the combined effects of the incident electric field enhancement and Purcell factor are maximized. Identification and quantification of the contributions of different physical mechanisms to emission enhancement provides essential understanding for controlling radiative emission using plasmonic optical antennas in 2D TMDCs, supporting the better design and optimization of photonic nanostructures with improved light-matter interactions and enhanced performance in optoelectronic applications.


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Figure 1. (a) False colored SEM perspective micrograph of the Au tapered nanoantenna on monolayer MoS2. Inset shows a topdown view with the scale bar measuring 2µm. (b) Optical microscopy image of tapered antenna. Spatially resolved photoluminescence maps integrated between 650-750nm for incident 633nm laser polarized (c) parallel to antenna (d) perpendicular to antenna.


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Figure 2. Experimental PL enhancement (a) and Raman (b) linescans along the Au nanoantenna measured using a polarized 633 nm laser source.


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Figure 3. Theoretical simulations of electric field enhancement in MoS2 2nm away from the Au antenna edge (a) and average Purcell factor of dipole emitter arrays along the edge (b). The red and blue dashed lines indicate the location of the excitation wavelength and peak MoS2 emission line.

Figure 4. Experimental PL enhancement (red dashed) and Raman signal (blue dashed) as a function of nanoantenna width. Calculated electric field enhancements at 633 nm within MoS2 are shown as the blue filled curve and Purcell factor at 675 nm as the red filled curve.


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Methods Fabrication MoS2 was grown using chemical vapor deposition (CVD) methods on top of 300 nm thick thermally grown SiO2 on Si substrates. The tapered Au nanoantenna was fabricated using ebeam lithography. The patterns were exposed in a bi-layer PMMA resist using a JEOL 9300 100kV e-beam tool. Development was completed using a cold development in a solution of IPA/DI water(7:3) at 5°C then rinsed in IPA at room temperature. 40nm of Au was e-beam evaporation followed by lift off in 1165 Microchem resist remover at 70°C and an IPA rinse. Measurements Photoluminescence measurements were conducted using a homemade setup with a polarized 633 nm HeNe laser source filtered through a 632.8nm filter and focused to a 1.2µm beam diameter. The spectrometer is equipped with a physical slit which can close below 100µm and CCD binning which allows us to capture data from a region below 1µm using a 100x objective. In the final measurements, the slit and binning was adjusted to acquire a signal from a ~200x200nm2 region. The maps and linescans were then constructed by taking data at discrete 100nm steps using a computer controlled x-y piezo stage coupled to a Nikon inverted microscope. The


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emitted power was filtered through a 650 nm longpass filter and sent to a 303-mm-focal-length spectrometer containing an Andor Newton electron multiplication charge-coupled device (EMCCD) detector. Raman measurements were done using a Acton TriVista CRS system with a polarized 633 nm HeNe laser source focused to 1.2µm in diameter. We determine widths at which a measurement was taken by starting line scans from the edge of the nanoantenna, choosing the step size, and calculating the width at each point. By knowing the step size, length of the antenna, and range of widths we can calculate the width for each measurement point. To ensure that both Raman and PL linescans start from the same point of the nanoantenna, we align the center of the beamspot to the edge of the antenna for each measurement. The calculated error in width is < 3.4nm.

Simulations 2D-electromagnetic wave numerical calculations were performed using the finite-difference time-domain simulation software package Lumerical™ . The first simulation aimed to understand the amount of excitation enhancement for the 633nm laser within the MoS2. Here, a total-field scattered-field source was chosen as the source with electric field polarized along the gap of the nanoantennas. In the second simulation, we aimed to understand the Purcell enhancements when an array of dipoles is near the antenna. The array was made up of fifteen dipoles perpendicularly polarized starting 4nm away from the Au with a 2nm spacing and embedded 0.5nm below the Au (Fig. S3). The simulation region was 500 x 1400 nm2 in xz using perfectly matched layers (PML) and anti-symmetric boundary conditions perpendicular to the electric field polarization. Then PML and symmetric boundary conditions were set parallel to


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the electric field polarization. The mesh size was set to 0.5 nm in both x and y in the 1 nm MoS2 region and 1 nm everywhere else. Au nanoantenna refractive index data was taken from the work of Johnston and Christy25 while the MoS2 index data is taken from Yim et al23.

Associated Content Supporting info Design, differential reflection spectra and dipolar emitter arrangement in simulations. This information is available free of charge via the Internet at http://pubs.acs.org.

Author Information Corresponding Author Email: [email protected]

Notes The authors declare no competing financial interest.

Acknowledgements


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This material is based upon work supported by the Materials Research Science and Engineering Center (NSF-MRSEC) (DMR-1121262) of Northwestern University. K.A. also acknowledges support from the AFOSR under Award No. FA9550-12-1-0280. Work performed in the group of K.A. is also partially supported by the Institute for Sustainability and Energy at Northwestern (ISEN) through ISEN Booster Award. This work made use of NUFAB of Northwestern University’s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205); the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. Also, Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

References 1. Ganatra, R.; Zhang, Q. Few-layer MoS2: a promising layered semiconductor. ACS Nano. 2014, 8, 4074-4099. 2. Eda, G.; Yamaguchi, H.; Voiry, D.; Fujita, T.; Chen, M.; Chhowalla, M. Photoluminescence from chemically exfoliated MoS2. Nano Lett. 2011, 11, 5111-5116. 3. Splendiani, A.; Sun, L.; Zhang, Y.; Li, T.; Kim, J.; Chim, C. Y.; Galli, G.; Wang, F. Emerging photoluminescence in monolayer MoS2. Nano Lett. 2010, 10, 1271-1275. 4. Sundaram, R. S.; Engel, M.; Lombardo, A.; Krupke, R.; Ferrari, A. C.; Avouris, P.; Steiner, M. Electroluminescence in single layer MoS2. Nano Lett. 2013, 13, 1416-1421. 5. Cheng, R.; Li, D.; Zhou, H.; Wang, C.; Yin, A.; Jiang, S.; Liu, Y.; Chen, Y.; Huang, Y.; Duan, X. Electroluminescence and photocurrent generation from atomically sharp WSe2/MoS2 heterojunction p-n diodes. Nano Lett. 2014, 14, 5590-5597. 6. Sobhani, A.; Lauchner, A.; Najmaei, S.; Ayala-Orozco, C.; Wen, F.; Lou, J.; Halas, N. J. Enhancing the photocurrent and photoluminescence of single crystal monolayer MoS2 with resonant plasmonic nanoshells. Appl Phys Lett. 2014, 104, 031112. 7. Yin, Z.; Li, H.; Li, H.; Jiang, L.; Shi, Y.; Sun, Y.; Lu, G.; Zhang, Q.; Chen, X.; Zhang, H. Single-layer MoS2 phototransistors. ACS Nano. 2012, 6, 74-80. 8. Lopez-Sanchez, O.; Lembke, D.; Kayci, M.; Radenovic, A.; Kis, A. Ultrasensitive photodetectors based on monolayer MoS2. Nat Nanotechnol. 2013, 8, 497-501.


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9. Bahauddin, S. M.; Robatjazi, H.; Thomann, I. Broadband Absorption Engineering to Enhance Light Absorption in Monolayer MoS2. ACS Photonics. 2016, 3, 853-862. 10. Butun, S.; Tongay, S.; Aydin, K. Enhanced light emission from large-area monolayer MoS2 using plasmonic nanodisc arrays. Nano Lett. 2015, 15, 2700-2704. 11. Najmaei, S., Mlayah, A., Arbouet, A., Girard, C., Leotin, J., Lou, J. Plasmonic Pumping of Exitonic Photoluminescence in Hybrid MoS2 - Au Nanostructures. ACS Nano. 2014, 8, 12682-12689. 12. Akselrod, G. M.; Ming, T.; Argyropoulos, C.; Hoang, T. B.; Lin, Y.; Ling, X.; Smith, D. R.; Kong, J.; Mikkelsen, M. H. Leveraging Nanocavity Harmonics for Control of Optical Processes in 2D Semiconductors. Nano Lett. 2015, 15, 3578-3584. 13. Gao, W.; Lee, Y. H.; Jiang, R.; Wang, J.; Liu, T.; Ling, X. Y. Localized and Continuous Tuning of Monolayer MoS2 Photoluminescence Using a Single Shape-Controlled Ag Nanoantenna. Adv Mater. 2016, 28, 701-706. 14. Kang, Y.; Najmaei, S.; Liu, Z.; Bao, Y.; Wang, Y.; Zhu, X.; Halas, N. J.; Nordlander, P.; Ajayan, P. M.; Lou, J.; Fang, Z. Plasmonic hot electron induced structural phase transition in a MoS2 monolayer. Adv Mater. 2014, 26, 6467-6471. 15. Shi, Y.; Huang, J. K.; Jin, L.; Hsu, Y. T.; Yu, S. F.; Li, L. J.; Yang, H. Y. Selective decoration of Au nanoparticles on monolayer MoS2 single crystals. Sci Rep. 2013, 3, 1839. 16. Wang, Z.; Dong, Z.; Gu, Y.; Chang, Y. H.; Zhang, L.; Li, L. J.; Zhao, W.; Eda, G.; Zhang, W.; Grinblat, G.; Maier, S. A.; Yang, J. K.; Qiu, C. W.; Wee, A. T. Giant photoluminescence enhancement in tungsten-diselenide-gold plasmonic hybrid structures. Nat Commun. 2016, 7, 11283. 17. Gan, X.; Gao, Y.; Fai Mak, K.; Yao, X.; Shiue, R. J.; van der Zande, A.; Trusheim, M. E.; Hatami, F.; Heinz, T. F.; Hone, J.; Englund, D. Controlling the spontaneous emission rate of monolayer MoS2 in a photonic crystal nanocavity. Appl Phys Lett. 2013, 103, 181119. 18. Wu, S.; Buckley, S.; Jones, A. M.; Ross, J. S.; Ghimire, N. J.; Yan, J.; Mandrus, D. G.; Yao, W.; Hatami, F.; Vučković, J.; Majumdar, A.; Xu, X. Control of two-dimensional excitonic light emission via photonic crystal. 2D Mater. 2014, 1, 011001. 19. Noori, Y. J.; Cao, Y.; Roberts, J.; Woodhead, C.; Bernardo-Gavito, R.; Tovee, P.; Young, R. J. Photonic Crystals for Enhanced Light Extraction from 2D Materials. ACS Photonics. 2016. 2515-2520. 20. Dufferwiel, S.; Schwarz, S.; Withers, F.; Trichet, A. A.; Li, F.; Sich, M.; Del PozoZamudio, O.; Clark, C.; Nalitov, A.; Solnyshkov, D. D.; Malpuech, G.; Novoselov, K. S.; Smith, J. M.; Skolnick, M. S.; Krizhanovskii, D. N.; Tartakovskii, A. I. Exciton-polaritons in van der Waals heterostructures embedded in tunable microcavities. Nat Commun. 2015, 6, 8579. 21. Schwarz, S.; Dufferwiel, S.; Walker, P. M.; Withers, F.; Trichet, A. A.; Sich, M.; Li, F.; Chekhovich, E. A.; Borisenko, D. N.; Kolesnikov, N. N.; Novoselov, K. S.; Skolnick, M. S.; Smith, J. M.; Krizhanovskii, D. N.; Tartakovskii, A. I. Two-dimensional metal-chalcogenide films in tunable optical microcavities. Nano Lett. 2014, 14, 7003-7008. 22. Li, H.; Zhang, Q.; Yap, C. C. R.; Tay, B. K.; Edwin, T. H. T.; Olivier, A.; Baillargeat, D. From Bulk to Monolayer MoS2: Evolution of Raman Scattering. Adv Funct Mater. 2012, 22, 1385-1390. 23. Yim, C.; O'Brien, M.; McEvoy, N.; Winters, S.; Mirza, I.; Lunney, J. G.; Duesberg, G. S. Investigation of the optical properties of MoS2 thin films using spectroscopic ellipsometry. Appl Phys Lett. 2014, 104, 103114.


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24. Chew, H.; Wang, D. S. Double Resonance in Fluorescent and Raman Scattering by Molecules in Small Particles. Phys Rev Lett. 1982, 49, 490-492. 25. Johnson, P. B.; Christy, R. W. Optical Constants of the Noble Metals. Phys Rev B. 1972, 6, 4370-4379.

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Identifying Excitation and Emission Rate Contributions to Plasmon

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