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Defect induced changes on the excitation transfer dynamics in ZnS/Mn nanowires.

Kaiser U, Chen L, Geburt S, Ronning C, Heimbrodt W - Nanoscale Res Lett (2011)

Bottom Line: The transients of the Mn-related luminescence can be quantitatively described on the basis of a modified Förster model accounting for reduced dimensionality.Here, we confirm this modified Förster model by varying the number of killer centers systematically.The temporal behavior of the internal Mn2+ (3d5) luminescence is recorded on a time scale covering almost four orders of magnitude.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics and Material Sciences Center, Philipps-University of Marburg, Renthof 5, 35032 Marburg, Germany. limei.klar@physik.uni-marburg.de.

ABSTRACT
Transients of Mn internal 3d5 luminescence in ZnS/Mn nanowires are strongly non-exponential. This non-exponential decay arises from an excitation transfer from the Mn ions to so-called killer centers, i.e., non-radiative defects in the nanostructures and is strongly related to the interplay of the characteristic length scales of the sample such as the spatial extensions, the distance between killer centers, and the distance between Mn ions. The transients of the Mn-related luminescence can be quantitatively described on the basis of a modified Förster model accounting for reduced dimensionality. Here, we confirm this modified Förster model by varying the number of killer centers systematically. Additional defects were introduced into the ZnS/Mn nanowire samples by irradiation with neon ions and by varying the Mn implantation or the annealing temperature. The temporal behavior of the internal Mn2+ (3d5) luminescence is recorded on a time scale covering almost four orders of magnitude. A correlation between defect concentration and decay behavior of the internal Mn2+ (3d5) luminescence is established and the energy transfer processes in the system of localized Mn ions and the killer centers within ZnS/Mn nanostructures is confirmed. If the excitation transfer between Mn ions and killer centers as well as migration effects between Mn ions are accounted for, and the correct effective dimensionality of the system is used in the model, one is able to describe the decay curves of ZnS/Mn nanostructures in the entire time window.

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SEM image of the Mn-implanted ZnS wires. ZnS wires with diameters of 100-300 nm and lengths of several 10 μm.
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Figure 1: SEM image of the Mn-implanted ZnS wires. ZnS wires with diameters of 100-300 nm and lengths of several 10 μm.

Mentions: ZnS nanowire samples were synthesized by the vapor-liquid-solid method [7]. In the center of a three-zone tube furnace, ZnS powder (99.9% purity) was evaporated, and the vapor was carried by an argon gas flow to silicon (100) substrates coated with 5 nm Au at the lower temperature end of the furnace. The Au film decomposes into liquid Au dots at elevated temperatures which serve as a catalyst for the nanowire growth. The synthesized ZnS wires had a typical length of several micrometers and were about 100 to 300 nm in diameter (see Figure 1). After transferring a thin layer of ZnS nanowires on top of clean Si substrates, the ZnS nanowires were ion-beam implanted with 55Mn. A homogeneous Mn distribution over a depth of 300 nm was achieved by using multiple ion energies ranging from 20 to 380 keV and with two different total ion fluences resulting in Mn concentrations of 2.8·10-3 at.% and 0.28 at.%, respectively. There are three different approaches used in order to control the density of killer centers.


Defect induced changes on the excitation transfer dynamics in ZnS/Mn nanowires.

Kaiser U, Chen L, Geburt S, Ronning C, Heimbrodt W - Nanoscale Res Lett (2011)

SEM image of the Mn-implanted ZnS wires. ZnS wires with diameters of 100-300 nm and lengths of several 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211286&req=5

Figure 1: SEM image of the Mn-implanted ZnS wires. ZnS wires with diameters of 100-300 nm and lengths of several 10 μm.
Mentions: ZnS nanowire samples were synthesized by the vapor-liquid-solid method [7]. In the center of a three-zone tube furnace, ZnS powder (99.9% purity) was evaporated, and the vapor was carried by an argon gas flow to silicon (100) substrates coated with 5 nm Au at the lower temperature end of the furnace. The Au film decomposes into liquid Au dots at elevated temperatures which serve as a catalyst for the nanowire growth. The synthesized ZnS wires had a typical length of several micrometers and were about 100 to 300 nm in diameter (see Figure 1). After transferring a thin layer of ZnS nanowires on top of clean Si substrates, the ZnS nanowires were ion-beam implanted with 55Mn. A homogeneous Mn distribution over a depth of 300 nm was achieved by using multiple ion energies ranging from 20 to 380 keV and with two different total ion fluences resulting in Mn concentrations of 2.8·10-3 at.% and 0.28 at.%, respectively. There are three different approaches used in order to control the density of killer centers.

Bottom Line: The transients of the Mn-related luminescence can be quantitatively described on the basis of a modified Förster model accounting for reduced dimensionality.Here, we confirm this modified Förster model by varying the number of killer centers systematically.The temporal behavior of the internal Mn2+ (3d5) luminescence is recorded on a time scale covering almost four orders of magnitude.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics and Material Sciences Center, Philipps-University of Marburg, Renthof 5, 35032 Marburg, Germany. limei.klar@physik.uni-marburg.de.

ABSTRACT
Transients of Mn internal 3d5 luminescence in ZnS/Mn nanowires are strongly non-exponential. This non-exponential decay arises from an excitation transfer from the Mn ions to so-called killer centers, i.e., non-radiative defects in the nanostructures and is strongly related to the interplay of the characteristic length scales of the sample such as the spatial extensions, the distance between killer centers, and the distance between Mn ions. The transients of the Mn-related luminescence can be quantitatively described on the basis of a modified Förster model accounting for reduced dimensionality. Here, we confirm this modified Förster model by varying the number of killer centers systematically. Additional defects were introduced into the ZnS/Mn nanowire samples by irradiation with neon ions and by varying the Mn implantation or the annealing temperature. The temporal behavior of the internal Mn2+ (3d5) luminescence is recorded on a time scale covering almost four orders of magnitude. A correlation between defect concentration and decay behavior of the internal Mn2+ (3d5) luminescence is established and the energy transfer processes in the system of localized Mn ions and the killer centers within ZnS/Mn nanostructures is confirmed. If the excitation transfer between Mn ions and killer centers as well as migration effects between Mn ions are accounted for, and the correct effective dimensionality of the system is used in the model, one is able to describe the decay curves of ZnS/Mn nanostructures in the entire time window.

No MeSH data available.


Related in: MedlinePlus