深圳大学学报理工版

过渡金属硫化物因具有很大的激子束缚能、较强的库仑相互作用以及自旋谷能耦合特性而备受关注,同时该类材料也为研究原子层厚半导体的性质以及开发其在光电器件方向应用的潜力提供机会,研究过渡金属硫化物被激发后的光响应很重要.利用泵浦探测瞬态吸收光谱系统研究单层WS2中光生载流子的动力学行为,发现激子以俄歇式激子激子湮灭的方式进行无辐射复合,寿命约为27 ps.通过分析不同泵浦光(波长分别为590 nm、580 nm及570 nm)激发条件下位于613 nm的光致漂白信号,证实亚皮秒的衰减组分为激子的形成过程.通过分析A激子共振的漂白和线宽展宽随时间变化,研究导致激子跃迁能发生蓝移和红移的物理过程,结果表明,导致单层WS2被激发后光响应发生变化的原因有2个,分别是光生载流子导致的多体相互作用以及材料通过声子将热量传递给基底的冷却过程.

The transition metal dichalcogenides(TMDs)have received much attention because of their large exciton binding energy, strong Coulomb interactions and spin-valley coupling. TMDs materials also provide an excellent opportunity to probe properties of atomic-thick semiconductors and develop their potential applications in photoelectronic devices. Therefore, it is important to explore the optical response of TMDs after excitation. In this paper, we study the dynamical behavior of photo-excited carriers in monolayer WS2 via pump-probe transient absorption spectroscopy. We find that the excitons are recombined in the form of Auger exciton-exciton annihilation, and the lifetime of exciton is about 27 ps. By analyzing the photobleaching signals at 613 nm exited by different pumping wavelengths(590 nm, 580 nm and 570 nm, respectively), we conform the formation process of excitons in the sub-picosecond decay component. By analyzing the time-dependent bleaching and broadening of the A-exciton resonance and discussing the physical processes leading to blue-shift and red-shift of the exciton transition energy, it is shown that there are two reasons for the change of the light response after excitation of the monolayer WS2, which are the multi-body interaction of the photo-excited carriers and the cooling process of material through the heat transfer to substrate by phonon.

引言
1 实验
2 结果与讨论
3 结语

图1 单层WS2样品的光致发光谱图<br/>Fig.1 Photoluminescence of the monolayer WS2 sample

图1 单层WS2样品的光致发光谱图
Fig.1 Photoluminescence of the monolayer WS2 sample

图2 单层WS2的瞬态吸收信号<br/>Fig.2 Transient absorption signal of monolayer WS2 sample

图2 单层WS2的瞬态吸收信号
Fig.2 Transient absorption signal of monolayer WS2 sample

图3 单层WS2在不同波长泵浦光激发下的归一化的瞬态吸收信号<br/>Fig.3 The normalized transient absorption signals of monolayer WS2 sample with different pump pulses

图3 单层WS2在不同波长泵浦光激发下的归一化的瞬态吸收信号
Fig.3 The normalized transient absorption signals of monolayer WS2 sample with different pump pulses

图4 单层WS2激发后同时随探测光波长及时间延迟变化的瞬态吸收谱图<br/>Fig.4 (Color online)The transient absorption map of monolayer WS2 sample after pump excitation as the function of both wavelength and delay time of the probe light

图4 单层WS2激发后同时随探测光波长及时间延迟变化的瞬态吸收谱图
Fig.4 (Color online)The transient absorption map of monolayer WS2 sample after pump excitation as the function of both wavelength and delay time of the probe light

图5 在不同时间范围内的瞬态吸收光谱<br/>Fig.5 (Color online)The transient absorption spectrain different time ranges

图5 在不同时间范围内的瞬态吸收光谱
Fig.5 (Color online)The transient absorption spectrain different time ranges

[1] RUPPERT C, CHERNIKOV A, HILL H M, et al. The role of electronic and phononic excitation in the optical response of monolayer WS2 after ultrafast excitation[J]. Nano Letters, 2017, 17(2): 644- 651.
[2] SPLENDIANI A, SUN Liang, ZHANG Yuanbo, et al. Emerging photoluminescence in monolayer MoS2[J]. Nano Letters, 2010, 10(4): 1271-1275.
[3] DE FAZIO D, GOYKHMAN I, YOON D, et al. High responsivity, large-area graphene/MoS2 flexible photodetectors[J]. ACS Nano, 2016, 10(9): 8252-8262.
[4] ROY K, PADMANABHAN M, GOSWAMI S, et al. Graphene-MoS2 hybrid structures for multifunctional photoresponsive memory devices[J]. Nature Nanotechnology, 2013, 8(11): 826-830.
[5] SHANMUGAM M, JACOBS-GEDRIM R, SONG E S, et al. Two-dimensional layered semiconductor/graphene heterostructures for solar photovoltaic applications[J]. Nanoscale, 2014, 6(21): 12682-12689.
[6] YU W J, LI Zheng, ZHOU Hailong, et al. Vertically stacked multi-heterostructures of layered materials for logic transistors and complementary inverters[J]. Nature Materials, 2013, 12(3): 246-252.
[7] WANG Haining, ZHANG Changjiang, RANA F. Surface recombination limited lifetimes of photoexcited carriers in few-layer transition metal dichalcogenide MoS2[J]. Nano Letters, 2015, 15(12): 8204-8210.
[8] SUN Dezheng, RAO Yi, REIDER G A, et al. Observation of rapid exciton-exciton annihilation in monolayer molybdenum disulfide[J]. Nano Letters, 2014, 14(10): 5625-5629.
[9] CHERNIKOV A, RUPPERT C, HILL H M, et al. Population inversion and giant bandgap renormalization in atomically thin WS2 layers[J]. Nature Photonics, 2015, 9(7): 466- 470.
[10] CHERNIKOV A, BERKELBACH T C, HILL H M, et al. Exciton binding energy and nonhydrogenic Rydberg series in monolayer WS2[J]. Physical Review Letters, 2014, 113(7): 76802.
[11] GUTIÉRREZ H R, PEREA-LPEZ N, ELÍAS A L, et al. Extraordinary room-temperature photoluminescence in triangular WS2 monolayers[J]. Nano Letters, 2013, 13(8): 3447-3454.
[12] HE Jiaqi, KUMAR N, BELLUS M Z, et al. Electron transfer and coupling in graphene-tungsten disulfide Van der Waals heterostructures[J]. Nature Communications, 2014, 5: 5622.
[13] CEBALLOS F, CUI Qiannan, BELLUS M Z, et al. Exciton formation in monolayer transition metal dichalcogenides[J]. Nanoscale, 2016, 8(22): 11681-11688.
[14] WANG Haining, ZHANG Changjian, CHAN Weimin, et al. Radiative lifetimes of excitons and trions in monolayers of the metal dichalcogenide MoS2[J]. Physical Review B, 2016, 93(4): 045407.
[15] CUNNINGHAM P D, MCCREARY K M, JONKER B T. Auger recombination in chemical vapor deposition-grown monolayer WS2[J]. Journal of Physical Chemistry Letters, 2016, 7(24): 5242-5246.
[16] CUNNINGHAM P D, HANBICKI A T, MCCREARY K M, et al. Photoinduced bandgap renormalization and exciton binding energy reduction in WS2[J]. ACS Nano, 2017, 11(12): 12601-12608.
[17] JIANG Tian, CHEN Runze, ZHENG Xin, et al. Photo-induced excitonic structure renormalization and broadband absorption in monolayer tungsten disulphide[J]. Optics Express, 2018, 26(2): 859-869.
[18] SUN Q C, YADGAROV L, ROSENTSVEIG R, et al. Observation of a Burstein-Moss shift in rhenium-doped MoS2 nanoparticles[J]. ACS Nano, 2013, 7(4): 3506-3511.
[19] POGNA E A, MARSILI M, DE FAZIO D, et al. Photo-induced bandgap renormalization governs the ultrafast response of single-layer MoS2[J]. ACS Nano, 2016, 10(1): 1182-1188.

备注

引言

1 实验

2 结果与讨论

3 结语

期刊信息

备注

引言

1 实 验

2 结果与讨论

3 结 语

期刊信息

1 实验

3 结语