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STM-induced light emission from thin films of perylene derivatives on the HOPG and Au substrates.

Fujiki A, Miyake Y, Oshikane Y, Akai-Kasaya M, Saito A, Kuwahara Y - Nanoscale Res Lett (2011)

Bottom Line: A fluorescence peak with vibronic progressions with large Stokes shifts was observed on both highly ordered pyrolytic graphite (HOPG) and Au substrates, indicating that the emission was derived from the isolated-molecule-like film condition with sufficient π-π interaction of the perylene rings of perylenetetracarboxylic diimide molecules.The upconversion emission mechanism of the tunneling-electron-induced emission was discussed in terms of inelastic tunneling including multiexcitation processes.The wavelength-selective enhanced emission due to a localized tip-induced surface plasmon on the Au substrate was also obtained.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Precision Science & Technology, Graduate school of Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan. fujiki@ss.prec.eng.osaka-u.ac.jp.

ABSTRACT
We have investigated the emission properties of N,N'-diheptyl-3,4,9,10-perylenetetracarboxylic diimide thin films by the tunneling-electron-induced light emission technique. A fluorescence peak with vibronic progressions with large Stokes shifts was observed on both highly ordered pyrolytic graphite (HOPG) and Au substrates, indicating that the emission was derived from the isolated-molecule-like film condition with sufficient π-π interaction of the perylene rings of perylenetetracarboxylic diimide molecules. The upconversion emission mechanism of the tunneling-electron-induced emission was discussed in terms of inelastic tunneling including multiexcitation processes. The wavelength-selective enhanced emission due to a localized tip-induced surface plasmon on the Au substrate was also obtained.

No MeSH data available.


Related in: MedlinePlus

Photoluminescence spectrum excited by an Ar-Ne laser at 514 nm (green line) and STM-LE spectrum (blue line) of PTCDI-C7 thin film on HOPG substrate (Vs = +2.2 V, It = 20 nA, acquisition time = 15 min).
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Figure 4: Photoluminescence spectrum excited by an Ar-Ne laser at 514 nm (green line) and STM-LE spectrum (blue line) of PTCDI-C7 thin film on HOPG substrate (Vs = +2.2 V, It = 20 nA, acquisition time = 15 min).

Mentions: Figure 4 shows the PL spectrum of the PTCDI-C7 thin film on the HOPG substrate (green line). The STM-LE spectrum of the PTCDI-C7 thin film on the HOPG substrate is shown in blue in the figure. It was found that the PL spectrum had a pronounced peak at 680 nm and shoulders at 625 and 750 nm. The obtained peaks of the PL spectrum were ascribed to the vibronic progressions related to the S1(0-0) transition at 520 nm, as shown in the absorption spectra in Figure 3, because the energy intervals of the observed PL peaks were approximately 0.17 eV corresponding to the stretching energy of perylene rings, as mentioned earlier. The peaks at 625, 680, and 750 nm were assigned to the S1(0-2), S1(0-3), and S1(0-4) transitions with respect to the S1 state, respectively. The PL spectrum included a large Stokes shift of approximately 100 nm compared with the absorption spectra. Note that the PL spectra of the PTCDI-C7 thin films on the ITO and HOPG substrates almost coincided with each other in terms of peak shape and position (data not shown), indicating that the electronic configurations, which are related to the optical properties of the PTCDI-C7 thin films on the ITO and HOPG substrates, were similar to each other. In the STM-LE spectrum of the PTCDI-C7 thin film, some pronounced peaks were observed at 550-950 nm. The peaks of STM-LE were explained by the vibronic progressions related to the S1 transition because the peak positions in the PL and STM-LE spectra almost coincided with each other. One can see that the STM-LE spectrum has a broad band up to 900 nm and that the peaks including higher indexes of progressions (up to the S1(0-5) transition at 860 nm) are more discriminable than those of the PL spectrum. This result would be derived from our STM-LE condition, e.g., with a local electric field between the STM tip and the substrate surface or with structural deformation of the molecules scratched by a scanning STM tip, which affects the transition probability of electronic excitation or radiation.


STM-induced light emission from thin films of perylene derivatives on the HOPG and Au substrates.

Fujiki A, Miyake Y, Oshikane Y, Akai-Kasaya M, Saito A, Kuwahara Y - Nanoscale Res Lett (2011)

Photoluminescence spectrum excited by an Ar-Ne laser at 514 nm (green line) and STM-LE spectrum (blue line) of PTCDI-C7 thin film on HOPG substrate (Vs = +2.2 V, It = 20 nA, acquisition time = 15 min).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211436&req=5

Figure 4: Photoluminescence spectrum excited by an Ar-Ne laser at 514 nm (green line) and STM-LE spectrum (blue line) of PTCDI-C7 thin film on HOPG substrate (Vs = +2.2 V, It = 20 nA, acquisition time = 15 min).
Mentions: Figure 4 shows the PL spectrum of the PTCDI-C7 thin film on the HOPG substrate (green line). The STM-LE spectrum of the PTCDI-C7 thin film on the HOPG substrate is shown in blue in the figure. It was found that the PL spectrum had a pronounced peak at 680 nm and shoulders at 625 and 750 nm. The obtained peaks of the PL spectrum were ascribed to the vibronic progressions related to the S1(0-0) transition at 520 nm, as shown in the absorption spectra in Figure 3, because the energy intervals of the observed PL peaks were approximately 0.17 eV corresponding to the stretching energy of perylene rings, as mentioned earlier. The peaks at 625, 680, and 750 nm were assigned to the S1(0-2), S1(0-3), and S1(0-4) transitions with respect to the S1 state, respectively. The PL spectrum included a large Stokes shift of approximately 100 nm compared with the absorption spectra. Note that the PL spectra of the PTCDI-C7 thin films on the ITO and HOPG substrates almost coincided with each other in terms of peak shape and position (data not shown), indicating that the electronic configurations, which are related to the optical properties of the PTCDI-C7 thin films on the ITO and HOPG substrates, were similar to each other. In the STM-LE spectrum of the PTCDI-C7 thin film, some pronounced peaks were observed at 550-950 nm. The peaks of STM-LE were explained by the vibronic progressions related to the S1 transition because the peak positions in the PL and STM-LE spectra almost coincided with each other. One can see that the STM-LE spectrum has a broad band up to 900 nm and that the peaks including higher indexes of progressions (up to the S1(0-5) transition at 860 nm) are more discriminable than those of the PL spectrum. This result would be derived from our STM-LE condition, e.g., with a local electric field between the STM tip and the substrate surface or with structural deformation of the molecules scratched by a scanning STM tip, which affects the transition probability of electronic excitation or radiation.

Bottom Line: A fluorescence peak with vibronic progressions with large Stokes shifts was observed on both highly ordered pyrolytic graphite (HOPG) and Au substrates, indicating that the emission was derived from the isolated-molecule-like film condition with sufficient π-π interaction of the perylene rings of perylenetetracarboxylic diimide molecules.The upconversion emission mechanism of the tunneling-electron-induced emission was discussed in terms of inelastic tunneling including multiexcitation processes.The wavelength-selective enhanced emission due to a localized tip-induced surface plasmon on the Au substrate was also obtained.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Precision Science & Technology, Graduate school of Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan. fujiki@ss.prec.eng.osaka-u.ac.jp.

ABSTRACT
We have investigated the emission properties of N,N'-diheptyl-3,4,9,10-perylenetetracarboxylic diimide thin films by the tunneling-electron-induced light emission technique. A fluorescence peak with vibronic progressions with large Stokes shifts was observed on both highly ordered pyrolytic graphite (HOPG) and Au substrates, indicating that the emission was derived from the isolated-molecule-like film condition with sufficient π-π interaction of the perylene rings of perylenetetracarboxylic diimide molecules. The upconversion emission mechanism of the tunneling-electron-induced emission was discussed in terms of inelastic tunneling including multiexcitation processes. The wavelength-selective enhanced emission due to a localized tip-induced surface plasmon on the Au substrate was also obtained.

No MeSH data available.


Related in: MedlinePlus