Description: |
[DCS seminar] Daniel Rich (Department of Physics, Ben-Gurion University of the Negev, Beersheva, Israel) -- Probing plasmonic effects in metal-covered semiconductor nanowires, quantum wells, and nanocrystals with time-resolved cathodoluminescence |
Date: |
Wednesday, Oct 28, 2015 |
Time: |
3 p.m. - 4 p.m. |
Venue: |
G08, Lecture Hall Complex |
Details: |
The enhancement of the spontaneous emission rate (SER) for silver, gold, and aluminum films deposited on three different quantum heterostructures and nanostructures was probed with time-resolved cathodoluminescence (CL). We show that such metal films on (i) GaAs/AlAs core-shell nanowires, (ii) InGaN/GaN quantum wells and (iii) multilayer Si nanocrystals (SiNCs) lead to an increase in the SER which is attributed to the coupling of excitons and surface plasmon polaritons (SPPs). Exciton-SPP coupling for metal-coated nanostructures is investigated as a viable option to enhance the SER and to improve the internal quantum efficiency of light emitting devices. The CL technique is found to be an ideal method of excitation for metal-covered nanostructures which may be opaque to laser/light excitation. Electron-hole pairs were generated in the metal-covered samples by injecting a pulsed high-energy electron beam through the thin metal films. The enhancement of the SER was observed by direct measurements of the changes in the temperature-dependent excess carrier lifetime. The three chosen plasmonic metals of Ag, Au, and Al facilitate an interesting comparison of the exciton-SPP coupling for metal films that exhibit varying differences between the surface plasmon energy and the excitonic transition energy of the three foregoing material systems. A modeling of the temperature dependence of the Purcell enhancement factor (Fp) included the effects of ohmic losses of the metals and changes in the dielectric properties due to the temperature dependence of (i) the intraband behavior in the Drude model and (ii) the interband critical point transition energies which involve the d-bands of Au and Ag.
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Calendar: |
Seminar Calendar (entered by arun.ds) |