Electrodeposited Light-EmittingNanojunctions.

Electroluminescent (EL) metal-semiconductor-metal nanojunctionsare prepared by electrodepositing nanocrystalline cadmium selenide(nc-CdSe) within ∼250 nm gold (Au) nanogapsprepared by focused ion beam milling. The electrodeposition of nc-CdSe is carried out at two temperatures: 20 °C (“cold”)and 75 °C (“hot”), producing mean grain diametersof 6 ± 1 nm and 11 ± 2 nm, respectively, for the nc-CdSe. Light-emitting nanojunctions (LEnJs) prepared atboth temperatures show a low threshold voltage for light emissionof <2 V; just above the 1.74 eV bandgap of CdSe. The EL intensityincreases with the injection current and hot-deposited LEnJs produceda maximum EL intensity that is an order of magnitude higher than thecold-deposited LEnJs. Emitted photons are bimodal in energy with emissionnear the band gap of CdSe, and also at energies 200 meV below it;consistent with a mechanism of light emission involving the radiativerecombination of injected holes with electrons at both band-edge anddefect states. The quantum yield for “hot” electrodeposited nc-CdSe LEnJs is comparable to devices constructed fromsingle crystalline nanowires of CdSe, and the threshold voltage of1.9 (±0.1) V (cold) and 1.5 (±0.2) V (hot) is at the lowend of the range reported for CdSe nanowire based devices. [ABSTRACT FROM AUTHOR]