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Photoluminescence response of colloidal quantum dots on VO2 film across metal to insulator transition.

Kuznetsov SN, Cheremisin AB, Stefanovich GB - Nanoscale Res Lett (2014)

Bottom Line: The supporting reflectance data point out that photoluminescence response mimics a reflectance change in VO2 across metal to insulator transition.Time-resolved photoluminescence study did not reveal any significant change of luminescence lifetime of deposited quantum dots under metal to insulator transition.It is a strong argument in favor of the proposed explanation based on the reflectance data. 71.30. + h; 73.21.La; 78.47.jd.

View Article: PubMed Central - HTML - PubMed

Affiliation: Physico-Technical Department, Petrozavodsk State University, Lenin av. 33, 185910 Petrozavodsk, Russian Federation.

ABSTRACT

Unlabelled: We have proposed a method to probe metal to insulator transition in VO2 measuring photoluminescence response of colloidal quantum dots deposited on the VO2 film. In addition to linear luminescence intensity decrease with temperature that is well known for quantum dots, temperature ranges with enhanced photoluminescence changes have been found during phase transition in the oxide. Corresponding temperature derived from luminescence dependence on temperature closely correlates with that from resistance measurement during heating. The supporting reflectance data point out that photoluminescence response mimics a reflectance change in VO2 across metal to insulator transition. Time-resolved photoluminescence study did not reveal any significant change of luminescence lifetime of deposited quantum dots under metal to insulator transition. It is a strong argument in favor of the proposed explanation based on the reflectance data.

Pacs: 71.30. + h; 73.21.La; 78.47.jd.

No MeSH data available.


Related in: MedlinePlus

Normalized PL decay curves for QDs deposited on different substrates. Vanadium dioxide film, curves 1 and 2; dielectric (sitall), curves 3 and 4. PL transients were measured at room temperature (curves 1 and 3) and at ≥75°C (curves 2 and 4).
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Figure 6: Normalized PL decay curves for QDs deposited on different substrates. Vanadium dioxide film, curves 1 and 2; dielectric (sitall), curves 3 and 4. PL transients were measured at room temperature (curves 1 and 3) and at ≥75°C (curves 2 and 4).

Mentions: This optical consideration meets a support in our measurements of time-resolved PL of QDs on the VO2 film. Time-resolved PL spectroscopy is a sensitive method to study an influence of surroundings on radiative processes in QDs. In our case, it is of interest to reveal whether strong change of free electron concentration in VO2 across MIT affects PL dynamics in deposited QDs. Figure 6 displays normalized PL decay curves in semi-logarithmic scale obtained with the use of apparatus impulse response function. Two sets of decay curves are shown for QDs deposited on the dielectric and VO2 film. Both sets are taken at RT and increased temperature above MIT. To quantify PL lifetimes in the case of nonexponential relaxation, biexponential deconvolution analysis was used. Then, average lifetimes were calculated taking into account the deconvolution parameters for each exponent. For the dielectric substrate, we found mean lifetimes of 14.95 and 14.43 ns at RT and 75°C, correspondently. For the VO2 film, they were 10.56 and 10.86 ns at RT and 77°C, correspondently. We see that no noticeable change of PL lifetime of QDs on VO2 is recorded in the course of metal to insulator transition when a carrier concentration is changed more than 2 orders of magnitude according our resistance data. Taking into account the direct relation between PL lifetime and steady-state PL intensity in QDs, we can exclude the role of intrinsic interaction between QDs and VO2 in the abovementioned PL features during MIT. Two such intrinsic mechanisms are known for QDs in literature: energy and charge transfer from/to excited QDs. The above time-resolved PL data may be an evidence against significant contribution of these mechanisms to PL response of our hybrid structure. This could be expected taking into account the i) out-of-resonance condition between QD's emission energy of approximately 2 eV and plasmon energy lower than 1 eV in metallic phase of VO2 (negligible energy overlap) and the ii) QD's thick shell (approximately 2 nm) that is blocking charge carrier exchange.


Photoluminescence response of colloidal quantum dots on VO2 film across metal to insulator transition.

Kuznetsov SN, Cheremisin AB, Stefanovich GB - Nanoscale Res Lett (2014)

Normalized PL decay curves for QDs deposited on different substrates. Vanadium dioxide film, curves 1 and 2; dielectric (sitall), curves 3 and 4. PL transients were measured at room temperature (curves 1 and 3) and at ≥75°C (curves 2 and 4).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4232974&req=5

Figure 6: Normalized PL decay curves for QDs deposited on different substrates. Vanadium dioxide film, curves 1 and 2; dielectric (sitall), curves 3 and 4. PL transients were measured at room temperature (curves 1 and 3) and at ≥75°C (curves 2 and 4).
Mentions: This optical consideration meets a support in our measurements of time-resolved PL of QDs on the VO2 film. Time-resolved PL spectroscopy is a sensitive method to study an influence of surroundings on radiative processes in QDs. In our case, it is of interest to reveal whether strong change of free electron concentration in VO2 across MIT affects PL dynamics in deposited QDs. Figure 6 displays normalized PL decay curves in semi-logarithmic scale obtained with the use of apparatus impulse response function. Two sets of decay curves are shown for QDs deposited on the dielectric and VO2 film. Both sets are taken at RT and increased temperature above MIT. To quantify PL lifetimes in the case of nonexponential relaxation, biexponential deconvolution analysis was used. Then, average lifetimes were calculated taking into account the deconvolution parameters for each exponent. For the dielectric substrate, we found mean lifetimes of 14.95 and 14.43 ns at RT and 75°C, correspondently. For the VO2 film, they were 10.56 and 10.86 ns at RT and 77°C, correspondently. We see that no noticeable change of PL lifetime of QDs on VO2 is recorded in the course of metal to insulator transition when a carrier concentration is changed more than 2 orders of magnitude according our resistance data. Taking into account the direct relation between PL lifetime and steady-state PL intensity in QDs, we can exclude the role of intrinsic interaction between QDs and VO2 in the abovementioned PL features during MIT. Two such intrinsic mechanisms are known for QDs in literature: energy and charge transfer from/to excited QDs. The above time-resolved PL data may be an evidence against significant contribution of these mechanisms to PL response of our hybrid structure. This could be expected taking into account the i) out-of-resonance condition between QD's emission energy of approximately 2 eV and plasmon energy lower than 1 eV in metallic phase of VO2 (negligible energy overlap) and the ii) QD's thick shell (approximately 2 nm) that is blocking charge carrier exchange.

Bottom Line: The supporting reflectance data point out that photoluminescence response mimics a reflectance change in VO2 across metal to insulator transition.Time-resolved photoluminescence study did not reveal any significant change of luminescence lifetime of deposited quantum dots under metal to insulator transition.It is a strong argument in favor of the proposed explanation based on the reflectance data. 71.30. + h; 73.21.La; 78.47.jd.

View Article: PubMed Central - HTML - PubMed

Affiliation: Physico-Technical Department, Petrozavodsk State University, Lenin av. 33, 185910 Petrozavodsk, Russian Federation.

ABSTRACT

Unlabelled: We have proposed a method to probe metal to insulator transition in VO2 measuring photoluminescence response of colloidal quantum dots deposited on the VO2 film. In addition to linear luminescence intensity decrease with temperature that is well known for quantum dots, temperature ranges with enhanced photoluminescence changes have been found during phase transition in the oxide. Corresponding temperature derived from luminescence dependence on temperature closely correlates with that from resistance measurement during heating. The supporting reflectance data point out that photoluminescence response mimics a reflectance change in VO2 across metal to insulator transition. Time-resolved photoluminescence study did not reveal any significant change of luminescence lifetime of deposited quantum dots under metal to insulator transition. It is a strong argument in favor of the proposed explanation based on the reflectance data.

Pacs: 71.30. + h; 73.21.La; 78.47.jd.

No MeSH data available.


Related in: MedlinePlus