The evolution of the optical phonon spectra of colloidal core/shell CdSe/ZnS quantum dots with an increase of the shell thickness from 0.5 to 3.4 monolayers has been studied by resonant Raman spectroscopy. The results obtained suggest that the ZnS shell changes its structure from amorphous to partly crystalline as the thickness increases. Simultaneously, an increase in Raman scattering by surface ͑core/shell interface͒ phonons and the redshift of the corresponding phonon band have been observed and assigned to variations in the shell structure. The disorder present in the shell provides a major contribution to the line shape of the Raman spectra at higher ZnS coverage. A method to control the quality of quantum dots based on Raman spectroscopy is proposed.

For the first time highly efficient photon energy up-conversion (anti-Stokes photoluminescence) has been observed in colloids of CdTe nanocrystals (NCs) and CdSe NCs covered by ZnS shell. The maximum magnitude of the up-converted blue shift DE max UC = 335 meV was obtained for CdSe/ ZnS NCs under excitation by a low-power He-Ne laser. The maximum efficiency for energy conversion was estimated to be about h max = 2.7 Â 10 --2 % at room temperature. The intensity of the anti-Stokes photoluminescence increases with temperature and shows a linear dependence on the excitation intensity. We suggest that subgap surface states are involved as intermediate states in the up-conversion process rather than nonlinear two-photon absorption or Auger processes.Anti-Stokes photoluminescence (ASPL), or photon energy up-conversion (UC), in semiconductor compounds --the observation of an emission at energies higher than that of the excitation energy --has attracted much attention recently [1][2][3][4][5][6]. Previously it has been observed in bulk semiconductors [1,7,8], heterostructures [2] and selfassembled quantum dots [3,4] at low temperatures. Recently, ASPL has been observed in InP and CdSe colloidal nanocrystals (NCs) [5].In this work we report the observation of well resolved ASPL bands at room temperature and very low excitation intensity in colloidal CdTe and CdSe/ZnS nanocrystals.CdTe NCs stabilized by thioglycolic acid were synthesized in aqueous solution by reaction of cadmium perchlorate with H 2 Te gas following the method of Ref. [9]. A fraction of CdTe NCs with size of 2.5 nm and PL quantum yield (QY) of %15% was isolated from the crude solution by size-selective precipitation [9] and used for spectroscopic measurements. CdSe NCs capped with a shell of ZnS (CdSe/ZnS) were prepared by an organometallic approach in a three-component hexadecylamine-trioctylphosphine-oxide-trioctylphosphine mixture [10]. A sample with CdSe core size of 4.5 nm and a thickness of the ZnS shell %0.3 nm (PL QY % 55%) was used for spectroscopic measurements. Absorption, the normal (Stokes shifted) PL and PL excitation (PLE) spectra of the samples are presented in Fig. 1.Absorption spectra were measured using a Shimadzu UV-3101 PC spectrometer. The PL spectra were recorded using a Spex Fluorolog spectrometer (1680-B monochromators with a dispersion of 1.70 nm/mm) equipped with a R943 Hamamatsu photomulti-1 ) Corresponding author;

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If thermoplasmonic applications such as heat-assisted magnetic recording are to be commercially viable, it is necessary to optimize both thermal stability and plasmonic performance of the devices involved. In this work, a variety of different adhesion layers were investigated for their ability to reduce dewetting of sputtered 50 nm Au films on SiO2 substrates. Traditional adhesion layer metals Ti and Cr were compared with alternative materials of Al, Ta, and W. Film dewetting was shown to increase when the adhesion material diffuses through the Au layer. An adhesion layer thickness of 0.5 nm resulted in superior thermomechanical stability for all adhesion metals, with an enhancement factor of up to 200× over 5 nm thick analogues. The metals were ranked by their effectiveness in inhibiting dewetting, starting with the most effective, in the order Ta > Ti > W > Cr > Al. Finally, the Au surface-plasmon polariton response was compared for each adhesion layer, and it was found that 0.5 nm adhesion layers produced the best response, with W being the optimal adhesion layer material for plasmonic performance.