Abstract
Electroluminescent (EL) metal-semiconductor-metal nanojunctions are prepared by electrodepositing nano crystalline cadmium selenide (nc-CdSe) within similar to 250 nm gold (Au) nanogaps prepared by focused ion beam milling. The electrodeposition of nc-CdSe is carried out at two temperatures: 20 degrees C ("cold") and 75 degrees C ("hot"), producing mean grain diameters of 6 +/- 1 nm and 11 +/- 2 nm, respectively, for the nc-CdSe. Light-emitting nanojunctions (LEnJs) prepared at both temperatures show a low threshold voltage for light emission of <2 V; just above the 1.74 eV bandgap of CdSe. The EL intensity increases with the injection current and hot-deposited LEnJs produced a maximum EL intensity that is an order of magnitude higher than the cold-deposited LEnJs. Emitted photons are bimodal in energy with emission near the band gap of CdSe, and also at energies 200 meV below it; consistent with a mechanism of light emission involving the radiative recombination of injected holes with electrons at both band-edge and defect states. The quantum yield for "hot" electrodeposited nc-CdSe LEnJs is comparable to devices constructed from single crystalline nanowires of CdSe, and the threshold voltage of 1.9 (+/- 0.1) V (cold) and 1.5 (+/- 0.2) V (hot) is at the low end of the range reported for CdSe nanowire based devices.