Spectroscopic investigation of defects in two-dimensional materials

Wu, Zhangting; Ni, Zhenhua

doi:10.1515/nanoph-2016-0151

Cited by 125 publications

(119 citation statements)

References 123 publications

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“…The power law dependence seen in Fig. 3b is consistent with results of calculations 54 and experimental observations 20,26,55 .…”

Section: Defect-related Exciton Analysissupporting

confidence: 90%

“…Binding energies [5][6][7] , formation and dissociation mechanisms 8,9 , coherence effects 10 , and spin-valley effects [11][12][13][14][15][16][17] of these excitons have been identified. In addition to neutral and charged excitonic peaks, a feature that is often attributed to localized, rather than free excitons appears in photoluminescence (PL) spectra of many TMDC devices at low temperatures [18][19][20][21][22][23][24][25][26] . While it is widely assumed that this feature is related to defects in TMDCs, multiple questions remain unanswered.…”

Section: Introductionmentioning

confidence: 99%

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Intrinsic and Extrinsic Defect-Related Excitons in TMDCs

et al. 2020

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We investigate an excitonic peak appearing in low-temperature photoluminescence of monolayer transition metal dichalcogenides (TMDCs), which is commonly associated with defects and disorder. First, to uncover the intrinsic origin of defect-related excitons, we study their dependence on gate voltage, excitation power, and temperature in a prototypical TMDC monolayer, MoS2. We show that the entire range of behaviors of defect-related excitons can be understood in terms of a simple model, where neutral excitons are bound to ionized donor levels, likely related to sulphur vacancies, with a density of 7×10 11 cm -2 . Second, to study the extrinsic origin of defect-related excitons, we controllably deposit oxygen molecules in-situ onto the surface of MoS2 kept at cryogenic temperature. We find that in addition to trivial pdoping of 3×10 12 cm -2 , oxygen affects the formation of defect-related excitons by functionalizing the vacancy. Combined, our results uncover the origin of defect-related excitons, suggest a simple and conclusive approach to track the functionalization of TMDCs, benchmark device quality, and pave the way towards exciton engineering in hybrid organicinorganic TMDC devices.

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“…The power law dependence seen in Fig. 3b is consistent with results of calculations 54 and experimental observations 20,26,55 .…”

Section: Defect-related Exciton Analysissupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Intrinsic and Extrinsic Defect-Related Excitons in TMDCs

et al. 2020

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“…The Raman spectra of graphene and graphite can be found in the Supporting Information, along with a further discussion of the observations of the Raman spectra. The results indicate that the source material used is primarily many‐layer graphene/graphite with non‐oxidative defects …”

Section: Resultsmentioning

confidence: 99%

Dynamics of pristine graphite and graphene at an air‐water interface

Goggin

Samaniuk

2018

AIChE Journal

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We examine the dynamics and morphology of graphitic films at an air-water interface in a Langmuir trough by varying interfacial surface coverage, by observing in situ interfacial structure, and by characterizing interfacial structure of depositions on mica substrates. In situ interfacial structure is visualized with Brewster angle microscopy and depositions of the interface are characterized with atomic force microscopy and field-emission scanning electron microscopy. Compression/expansion curves exhibit a monotonically decreasing surface pressure between consecutive compressions, but demonstrate a "rebound" of hysteretic behavior when the interface is allowed to relax between consecutive compressions. This dynamic results from a competition between consolidation of the interface via agglomeration of particles or the stacking of graphene sheets, and a thermally-driven relaxation where nanometer-thick particles are able to overcome capillary interactions. These results are especially relevant to applications where functional films with controlled conductivity and transparency may be produced via liquid-phase deposition methods. V C 2018 American Institute of Chemical Engineers AIChE J, 00: 000-000, 2018 Figure 3. Different microscopy methods used to characterize interfaces at different length scales. From left to right, BAM image at 11 mN/m, AFM image at 3 mN/m, FESEM image at 13 mN/m. [Color figure can be viewed at wileyonlinelibrary.com] AFM images taken from an interface deposited at 3 mN/m after a 15 h relaxation time. Mono-and few-layer graphene sheets are present between large islands of graphitic material. (b) AFM image (left) that reveals few-and mono-layer graphene sheets present at the interface at a surface pressure of 20 mN/m. A corresponding height trace (right) follows the red path indicated in image on the left.Figure 5. Compression curves for graphene interfaces. The upper left plot shows pre-relaxation and post-relaxation compression curves for a 2.5 h relaxation period, and the upper right plot shows the pre-relaxation and postrelaxation compression curves for a 15 h relaxation period. Pre-relaxation curves are plotted with red dashes, post-relaxation curves are plotted with blue dots. The bottom two plots contain the same data, but the postrelaxation curves have been shifted along both axes. The shift factors were obtained "by eye" to overlap the first compressions of the pre-relaxation and post-relaxation curve sets. The inset FESEM images (scale bars: 10 μm) were obtained fromdepositions at low Π (indicated by the black boxes). The images reveal that aggregates are present at all times and are surrounded to different degrees by micron and sub-micron particles. [Color figure can be viewed at wileyonlinelibrary.com] Figure 7. BAM images taken during each of the three compression cycles for both the pre-relaxation and postrelaxation interfaces.White areas indicate graphitic material. All images were taken with the barriers in a fully open state and show the evolution of the interface between cons...

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“…Since high irradiation-dose gives rise to more sulfur vacancies, the p-doping concentration induced by sulfur vacancies increases. 27 As a result, the FWHM of the A 1g and (Γ) peaks becomes broader. It is well-1 2…”

Section: Please Do Not Adjust Marginsmentioning

confidence: 99%