
- Chinese Optics Letters
- Vol. 20, Issue 10, 100002 (2022)
Abstract
1. Introduction
Transition metal dichalcogenides (TMDs) have attracted tremendous attention and played an important role in the development of two-dimensional (2D) semiconductor materials in the past decade due to their unique physical properties and outstanding photoelectric performance[
As one of the most studied materials in the family of TMDs, tungsten disulphide (
It is well known that, in the measurement of dynamic processes on ultrafast time scales, the reported methods include multi-shot methods[
Sign up for Chinese Optics Letters TOC. Get the latest issue of Chinese Optics Letters delivered right to you!Sign up now
2. Experiments
The
Figure 1.Characterization of the WS2 films with different layers used in this study. (a) Optical image of sample with size of 10 mm × 10 mm. The WS2 film was plated on a 0.3 mm sapphire substrate by the CVD method. (b) Raman spectra of the three-layer WS2 at different points. (c)–(e) Raman spectra of WS2 films with 1–5 layers. (f)–(h) The surface roughness of the 1L, 3L, and 5L samples characterized by AFM.
The schematic diagram of the proposed single pulse pump probe method is shown in Fig. 2(a), which is similar to the configuration in our previous work[
Figure 2.(a) Schematic diagram of the pump-probe-based optical configuration. (b) Schematic diagram of the marked area in (a). The probe light spot size is smaller than the pump light spot and falls in the center of the pump light spot on the sample. NPBS, non-polarized beam splitter; P, polarizer; F, neutral filter wheel; M, mirror; S, mechanical shutter; L, lens.
3. Results and Discussion
The experiment of the photoexcited free carrier dynamics of
Figure 3.(a) Static spectrum I0 (black line) and dynamic spectrum I1 (blue line). The time of pump excitation is marked. (b) Spectrum after differential processing. The open circles are the measured data, and the solid line represents the corresponding fitting result using a biexponential function. The spectra shown in this figure are the results of the three-layer WS2 sample.
In order to further reveal the layer dependency of the dynamic response of
Figure 4.Temporal evolution of the transmitted probe light intensity ΔI/I0 of the WS2 films with different layers (1L, 3L, and 5L). The open circles are extracted from the measured spectrum, and the solid lines are the results of fitting using a biexponential function.
Then, the layer dependency of the characteristic time for the three phases in the dynamic response of the carriers is discussed. First, the relationship between the fast carrier excitation time
Parameters | Layers | ||
---|---|---|---|
1L | 3L | 5L | |
20.9 | 8.4 | 3.9 | |
139.2 | 338.1 | 673.4 |
Table 1. The Characteristic Times
Figure 5.(a) Characteristic time of the carrier excitation process as a function of the material layers. (b) The layer dependence of the carrier fast decay characteristic time and (c) the slow decay characteristic time in the process of carrier decay. The corresponding solid lines in (b) and (c) are the fitting results using an exponential function.
It is worth noting that the characteristic time of the carrier dynamic response (the rise and decay) obtained in our experiment is longer than the results reported in Refs. [18,21], which may be attributed to the relatively high pump pulse fluence used in our work[
We now discuss the mechanism that contributes to the observed phenomenon. First, we can start with the fast photoexcitation phase with characteristic time
Further, we may try to explain the mechanism of the layer dependency of the characteristic time for the decay processes. It can be observed from Figs. 5(b) and 5(c) that the characteristic time of the fast decay phase
4. Conclusion
In summary, a pump probe method has been proposed to study the ultrafast carrier dynamics of monolayer and few-layer
References
[1] C. Cong, J. Shang, Y. Wang, T. Yu. Optical properties of 2D semiconductor WS2. Adv. Opt. Mater., 6, 1700767(2018).
[2] R. K. Chowdhury, S. Nandy, S. Bhattacharya, M. Karmakar, S. N. B. Bhaktha, P. K. Datta, A. Taraphder, S. K. Ray. Ultrafast time-resolved investigations of excitons and biexcitons at room temperature in layered WS2. 2D Mater., 6, 015011(2018).
[3] T. Zhu, J. M. Snaider, L. Yuan, L. Huang. Ultrafast dynamic microscopy of carrier and exciton transport. Annu. Rev. Phys. Chem., 70, 219(2019).
[4] K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, A. K. Geim. Two-dimensional atomic crystals. Proc. Natl. Acad. Sci. USA, 102, 10451(2005).
[5] H. Gu, B. Song, M. Fang, Y. Hong, X. Chen, H. Jiang, W. Ren, S. Liu. Layer-dependent dielectric and optical properties of centimeter-scale 2D WSe2: evolution from a single layer to few layers. Nanoscale, 11, 22762(2019).
[6] B. Song, H. Gu, M. Fang, Y.-T. Ho, X. Chen, H. Jiang, S. Liu. Complex optical conductivity of 2D MoS2: a striking layer-dependency. J. Phys. Chem. Lett., 10, 6246(2019).
[7] K. F. Mak, C. Lee, J. Hone, J. Shan, T. F. Heinz. Atomically thin MoS2: a new direct-gap semiconductor. Phys. Rev. Lett., 105, 136805(2010).
[8] L. Gao. Flexible device applications of 2D semiconductors. Small, 13, 1603994(2017).
[9] D. Jariwala, V. K. Sangwa, L. J. Lauhon, T. J. Marks, M. C. Hersam. Emerging device applications for semiconducting two-dimensional transition metal dichalcogenides. ACS Nano, 8, 1102(2014).
[10] B. W. Baugher, H. O. Churchill, Y. Yang, P. Jarillo-Herrero. Optoelectronic devices based on electrically tunable p-n diodes in a monolayer dichalcogenide. Nat. Nanotechnol., 9, 262(2014).
[11] T. Yang, H. Lin, B. Jia. Ultrafast direct laser writing of 2D materials for multifunctional photonics devices [Invited]. Chin. Opt. Lett., 18, 023601(2020).
[12] T. Jiang, R. Chen, X. Zheng, Z. Xu, Y. Tang. Photo-induced excitonic structure renormalization and broadband absorption in monolayer tungsten disulphide. Opt. Express, 26, 859(2018).
[13] P. Schiettecatte, P. Geiregat, Z. Hens. Ultrafast carrier dynamics in few-layer colloidal molybdenum disulfide probed by broadband transient absorption spectroscopy. J. Phys. Chem. C, 123, 10571(2019).
[14] Y. Li, W. Liu, Y. Wang, Z. Xue, Y. C. Leng, A. Hu, H. Yang, P. H. Tan, Y. Liu, H. Misawa, Q. Sun, Y. Gao, X. Hu, Q. Gong. Ultrafast electron cooling and decay in monolayer WS2 revealed by time- and energy-resolved photoemission electron microscopy. Nano Lett., 20, 3747(2020).
[15] A. Hu, W. Liu, X. Li, S. Xu, Y. Li, Z. Xue, J. Tang, L. Ye, H. Yang, M. Li, Y. Ye, Q. Sun, Q. Gong, G. Lu. Spectromicroscopy and imaging of photoexcited electron dynamics at in-plane silicon pn junctions. Nanoscale, 13, 2626(2021).
[16] W. Zheng, P. Jiang, L. Zhang, Y. Wang, Q. Sun, Y. Liu, Q. Gong, C. Wu. Ultrafast extreme ultraviolet photoemission electron microscope. Rev. Sci. Instrum., 92, 043709(2021).
[17] L. Yuan, L. Huang. Exciton dynamics and annihilation in WS2 2D semiconductors. Nanoscale, 7, 7402(2015).
[18] X. Xing, L. Zhao, Z. Zhang, X. Liu, K. Zhang, Y. Yu, X. Lin, H. Y. Chen, J. Q. Chen, Z. Jin, J. Xu, G.-h. Ma. Role of photoinduced exciton in the transient terahertz conductivity of few-layer WS2 laminate. J. Phys. Chem. C, 121, 20451(2017).
[19] J. K. Gustafson, P. D. Cunningham, K. M. McCreary, B. T. Jonker, L. M. Hayden. Ultrafast carrier dynamics of monolayer WS2 via broad-band time-resolved terahertz spectroscopy. J. Phys. Chem. C, 123, 30676(2019).
[20] H. Wang, C. Zhang, F. Rana. Ultrafast dynamics of defect-assisted electron-hole recombination in monolayer MoS2. Nano Lett., 15, 339(2015).
[21] C. Ruppert, A. Chernikov, H. M. Hill, A. F. Rigosi, T. F. Heinz. The role of electronic and phononic excitation in the optical response of monolayer WS2 after ultrafast excitation. Nano Lett., 17, 644(2017).
[22] Z. Chi, H. Chen, Q. Zhao, Y. X. Weng. Observation of the hot-phonon effect in monolayer MoS2. Nanotechnology, 31, 235712(2020).
[23] Z. Nie, R. Long, L. Sun, C. C. Huang, J. Zhang, Q. Xiong, D. W. Hewak, Z. Shen, O. V. Prezhdo, Z. H. Loh. Ultrafast carrier thermalization and cooling dynamics in few-layer MoS2. ACS Nano, 8, 10931(2014).
[24] V. Vega-Mayoral, D. Vella, T. Borzda, M. Prijatelj, I. Tempra, E. A. Pogna, S. Dal Conte, P. Topolovsek, N. Vujicic, G. Cerullo, D. Mihailovic, C. Gadermaier. Exciton and charge carrier dynamics in few-layer WS2. Nanoscale, 8, 5428(2016).
[25] Z. E. Eroglu, O. Comegys, L. S. Quintanar, N. Azam, S. Elafandi, M. Mahjouri-Samani, A. Boulesbaa. Ultrafast dynamics of exciton formation and decay in two-dimensional tungsten disulfide (2D-WS2) monolayers. Phys. Chem. Chem. Phys., 22, 17385(2020).
[26] A. Brasington, D. Golla, A. Dave, B. Chen, S. Tongay, J. Schaibley, B. J. LeRoy, A. Sandhu. Role of defects and phonons in bandgap dynamics of monolayer WS2 at high carrier densities. J. Phys. Mater., 4, 015005(2021).
[27] P. D. Cunningham, K. M. McCreary, A. T. Hanbicki, M. Currie, B. T. Jonker, L. M. Hayden. Charge trapping and exciton dynamics in large-area CVD grown MoS2. J. Phys. Chem. C, 120, 5819(2016).
[28] Y. Zhao, Q. Huang, H. Cai, X. Lin, H. He, H. Cheng, T. Ma, Y. Lu. Ultrafast control of slow light in THz electromagnetically induced transparency metasurfaces. Chin. Opt. Lett., 19, 073602(2021).
[29] L. Zhang, J. Liu, W. Gong, H. Jiang, S. Liu. Diffraction based single pulse measurement of air ionization dynamics induced by femtosecond laser. Opt. Express, 29, 18601(2021).
[30] Q. Yue, Z. Cheng, L. Han, Y. Yang, C. Guo. One-shot time-resolved holographic polarization microscopy for imaging laser-induced ultrafast phenomena. Opt. Express, 25, 14182(2017).
[31] Z. Zhong, L. Zhang, H. Jiang, W. Gong, H. Gu, X. Chen, S. Liu. A Brewster incidence method for shocked dynamic metrology of transparent materials and its error evaluation. AIP Adv., 10, 105203(2020).
[32] H. Tsai, Y. Huang, P. Tsai, Y. Chen, H. Ahn, S. Lin, Y. Lu. Ultrafast exciton dynamics in scalable monolayer MoS2 synthesized by metal sulfurization. ACS Omega, 5, 10725(2020).
[33] Z. Zhong, W. Gong, H. Jiang, H. Gu, X. Chen, S. Liu. Investigation of spatial chirp induced by misalignments in a parallel grating pair pulse stretcher. Appl. Sci., 10, 103110(2020).
[34] M. Palummo, M. Bernardi, J. C. Grossman. Exciton radiative lifetimes in two-dimensional transition metal dichalcogenides. Nano Lett., 15, 2794(2015).
[35] H. Wang, C. Zhang, W. Chan, C. Manolatou, S. Tiwari, F. Rana. Radiative lifetimes of excitons and trions in monolayers of the metal dichalcogenide MoS2. Phys. Rev. B, 93, 045407(2016).

Set citation alerts for the article
Please enter your email address