Low-temperature luminescence of thin C60 films of different structures

Avdeenko, A. A.; Eremenko, V. V.; Zinoviev, P. V.; Silaeva, N. B.; Tiunov, Yu. A.; Gorbenko, N. I.; Pugachev, A. T.; Churakova, N. P.

doi:10.1063/1.593704

Cited by 5 publications

(3 citation statements)

References 20 publications

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“…Despite the large number of publications about the low-temperature luminescence spectra of C 60 , the mechanisms that form these spectra are still far from clear. As it was recently shown, the low-tem-perature photoluminescence spectrum of the fullerite C 60 is determined by a set of emission centers of different origin, such as Frenkel-Davydov excitons [3,4], charge transfer excitons [5], structural defects [3,4,6,7], as well as pairs or chains of molecules that play the role of deep exciton traps, typical of the fullerites C 60 and C 70 [3,[8][9][10].…”

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“…In the next stage of this work we studied effects of intercalation on low-temperature photoluminescence spectra of fullerite C 60 . The luminescence measurement technique, as well as the experimental setup have been reported elsewhere [7]. A minor modification consisted in using a FEU-62(S 1 ) photomultiplier which enabled us to record photoluminescence spectra down to energies around 1.2 eV.…”

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Structure and photoluminescence of helium-intercalated fullerite C60

Legchenkova

Prokhvatilov

Stetsenko

et al. 2002

Low Temperature Physics

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Intercalation of C 60 single crystals with helium was studied by powder x-ray diffractometry. It was established that the intercalation is a two-stage process, octahedral cavities are filled first and then tetrahedral ones, the chemical pressure being negative during both stages. For the first time low-temperature (5 K) photoluminescence spectra of helium-intercalated fullerite C 60 were studied. The presence of helium in lattice voids was shown to reduce that part of the luminescent intensity which is due to the emission of covalently bound pairs of C 60 molecules, the so-called «deep traps» with the 0-0 transition energy close to 1.69 eV. The mechanism of the effect of the intercalation with helium on the pair formation in fullerite C 60 is discussed.

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Structure and photoluminescence of helium-intercalated fullerite C60

Legchenkova

Prokhvatilov

Stetsenko

et al. 2002

Low Temperature Physics

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“…The photoluminescence spectrum of fullerite C 60 is determined by various emitting entities such as Frenkel excitons [22,23], charge-transfer excitons [24], and the so-called deep X-traps [22,23,25,26], most likely, associated with structure defects and impurities. Using luminescence data it has been demonstrated [20] that emission from X-traps and the variation of the integrated photoluminescence intensity can be a powerful instrument in studying effects of intercalation on the orientational ordering of fullerene molecules in the C 60 crystal lattice.…”

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Orientational glassification in fullerite C60 saturated with H2: Photoluminescence studies

Zinoviev

Zoryansky

Silaeva

et al. 2012

Low Temperature Physics

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Using one-photon excitation we studied photoluminescence of C 60 saturated with molecular hydrogen over a temperature range 10 to 230 K. Saturation of samples was done at a pressure of 30 atm and at temperatures low enough (T < 250 °C) to exclude chemical sorption. The samples were saturated during periods of varied duration τ to reach different occupancy levels. To check reliability of our luminescence results and interpretation, our spectra for pure C 60 were compared with data known in the art, demonstrating good compatibility. The luminescence spectra were attributed according to the approach of Akimoto and Kan , no by separating total spectra in two components of different origin. The A-type spectra, which are associated with exciton transport to deep traps, above 70 K become prevail over the B-type emission. Until saturation times did not exceed a certain value (for one, 50 h for a saturation temperature of 200 °C) the integrated intensity I as a function of the temperature T of luminescence measurements, I(T), remained at a constant level up to the orientational vitrification point of about 100 K and then went rather steeply down with increasing T. However, at longer τ the intensity I(Τ) persisted in constancy to higher T (the higher, the longer τ) and then dropped with increasing T. This finding made us to reexamine more closely the lattice parameter vs saturation time dependence for saturation temperatures 200 and 230 °C. As a result, additional evidence allowed us to infer that after completion of the single-molecule filling of O-voids (specifically, after roughly 50 h for T sat = 200 °C) a slower process of double filling sets in. Double filling entails an anisotropic deformation of the octahedral cage, which modifies rotational dynamics stronger than single filling. Further, we argue that singlet exciton transport to traps (which is responsible for the A-type emission) can be crucially hampered by rotational jumps of one of the molecules over which a travelling exciton is spread. Such jumps break coherence and the exciton stops thereby increasing the probability of emissionless deactivation. If so, then the temperature, at which the rotational jumps occur sufficiently frequently, may be by inference considered the unfreezing point for the orientational glass state (essentially coinciding with the inverse critical point T g where the rotational system freezes into the orientational glass). This treatment of T g differs from that existing in the art according to which the glass state is destroyed owing to the increased density of phonon states. Keeping to our reasoning, we conclude that the orientational glass state does not disappear but, instead, is conserved almost unchanged under one-molecule feeling and persists to appreciably higher temperatures in the case of double filling, which affects exciton dynamics stronger.

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