Energy Mater. More by Ye Liu. KG, Tatzberg 47, Dresden, Germany. More by Vyacheslav Khavrus. More by Thomas Lehmann. More by Hong-liu Yang. More by Lukas Stepien. More by Moritz Greifzu. IFW Dresden, P. Box , D Dresden, Germany. More by Steffen Oswald. We ascribe these levels to the localized excitons and trions. Together with absorption and PL data, this finding indicates that the trions do not form via the direct optical excitation from the ground energy state in SWNTs noncovalently doped by HCl.
Doping of the nanotubes was achieved by adding HCl to this suspension. The three peaks labelled E 1 6,5 , E 1 7,5 and E 1 7,6 in the spectrum of a non-doped sample black line correspond to the excitation of the first bright excitonic states in nanotubes with the indicated chiral indexes.
With increasing concentration of HCl, one can observe a gradual suppression of all three excitonic peaks. In the rest of this paper, we omit chiral indices n,m in E 1 n,m , as we only discuss 6,5 nanotubes. Inset: zoomed D-mode spectral region. The colour map in Fig. The differential absorption spectra taken at different delay times between pump and probe pulses horizontal cuts in Fig. The time evolution of E 1 and X energy levels are obtained as vertical cuts in Fig.
Thin noisy lines are experimental data, while the solid lines refer to bi-exponential fitting curves. Measured dynamics of E blue lines , X red lines and T energy level green line.
The black line shows the difference between X and E 1 dynamics. Although the T spectral feature is clearly observable at delay times exceeding 1 picosecond green line in Fig.
Therefore, the time evolution of the T -associated energy level cannot be obtained simply from a vertical cut of Fig. Applying such a procedure, we obtain dynamics of the T -associated energy level as shown by green line in Fig.
This finding signifies that the T spectral feature does not correspond to either X or E 1 energy levels, but is associated with another energy level see Fig. Similar dynamics of the ordinary exciton and the doping-induced states was recently observed by Bai et al. The black line in Fig.
The difference in relaxation dynamics of these two levels black line in Fig. This original finding strongly supports the appearance of additional ultrafast energy relaxation channel of X states through the doping-induced energetically lower lying states, namely, the formation of the T states.
Thus, in our experimental conditions, the T states are formed via a nonradiative relaxation from the X energy level, but not via the direct optical transition from the ground energy level of nanotubes see crossed-out arrow in Fig. We further speculate on the physical nature of X and T energy levels see Fig. The authors who attributed the X energy level to trion 5 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , did not observed a second doping-induced level T , as we do in this work.
In contrast, in works where two different doping-induced levels were observed 24 , 25 , 26 , and also in several other works 15 , 16 , 17 , 18 , 19 , 20 , the X energy level is ascribed either to a defect-localized exciton or to a hole-polaron-dressed exciton. However, both theoretical 21 and experimental 22 studies have shown that excitons may localize due to the impact of ions adsorbed on the surface of SWNTs, even without covalent bonds.
Due to the theoretical support, we are inclined to favour the latter hypothesis, although further experimental studies, such as Fourier-transform infrared spectroscopy and x-ray photoelectron spectroscopy measurement, should be done to clearly specify the physical nature of the X energy level.
Regarding interpretation of the second doping-induced level T , located energetically below the X level, we follow previous works and ascribe it to the trion energy level 24 , 25 , However, in contradiction to some other works 24 , 25 , but in consonance with Bai et al.
This discrepancy might be caused by specific doping techniques and environmental circumstances. Following Bai et al. Such an interpretation is in agreement with theoretical work 31 , claiming that not only one but rather a set of trion levels exist in SWNTs. To summarize, we provide new physical insight on the energy structure of SWNTs doped with hydrochloric acid and on the physical nature and behaviour of the corresponding many-particle excitations in such modified nanomaterial.
We present an original finding showing that the dynamics of the trion states matches the difference between the dynamics of the ordinary exciton E 1 and the exciton X , localized on the physisorbed ion. Thus, our results strongly suggest that the SWNT trion energy level T in HCl-doped 6,5 -SWNTs is occupied via relaxation from the X energy level, but not via a direct optical excitation from the ground energy level of nanotube. These findings significantly contribute to understanding the energy structure of doped SWNTs and many-body interactions in low-dimensional materials, although further studies should be aimed at the accurate attribution of energy levels in SWNTs, doped by different methods.
The linear optical absorption measurements were done using a two-channel PerkinElmer Lambda spectrophotometer. The installation has already been used in our previous studies 32 , A detailed description of the method and setup we reported previously and can be found elsewhere 34 , The femtosecond pulses with a central wavelength tunable in the — nm range and a femtosecond continuum were employed as pump and probe, respectively.
The visible part of the continuum generated in the sapphire crystal was removed from the probe channel using a long-pass filter. The pump and probe beams were polarized collinearly. The time delay between the probe and the pump pulses was controlled by a rapid motorized delay line.
All measurements were performed at room temperature. Wang, F. Science Miyauchi, Y. Photoluminescence studies on exciton photophysics in carbon nanotubes. C 1 , — Dresselhaus, M. Exciton Photophysics of Carbon Nanotubes. With this, record incorporation of B substitutional atoms was achieved reaching up to 13 and 6 at.
This is almost an order of magnitude larger of everything reported so far for materials alike. In a wider context, we have been able to master the production of CBx-SWNT, control their degree of purity, and to understand the B incorporation profile. Although single-walled carbon nanotube SWCNT films are the most promising candidates for flexible TCFs, they still do not meet optoelectronic requirements demanded for their successful industrial integration.
The strong p-doping was examined by open-circuit potential OCP measurements and confirmed by ab initio calculations demonstrating a downshift of the Fermi level of around 1 eV for the case of bilateral doping. Goldt, O. Zaremba, M. Bulavskiy, F. Fedorov, K. Larionov, A. Tsapenko, Z. Popov, P. Sorokin, A. Anisimov, H.
Inani, J. Kotakoski, K. Mustonen and A. Nasibulin, J. C , , 9 , DOI:
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