J. S. Palmer

Anomalous photoluminescence behavior from amorphous Ge quantum dots produced by buffer-layer-assisted growth

The authors present photoluminescence results from amorphous Ge quantum dots formed using buffer-layer-assisted growth. Their sizes, shapes, and densities were controlled by varying the thickness of the Xe buffer layer, with sizes varying from 2to8nm. A relatively weak signal was observed at ∼3K at ∼0.91eV that was independent of size and was insensitive to laser intensity. Its temperature-dependent magnitude showed a Berthelot-type behavior that they associate with hopping of carriers between radiative tail states and shallow nonradiative states. These findings are similar to those from porous semiconductors.

Photoluminescence of CdSe quantum dots and rods from buffer-layer-assisted growth

The traditional colloidal routes of fabrication of II-VI semiconductor quantum dots have been difficult to integrate with silicon technology. Here, we demonstrate that CdSe quantum dots and rods can be self-assembled and delivered in ultrahigh vacuum conditions on almost any substrate by means of buffer-layer-assisted growth (BLAG), where the buffer is thin solid Xe film. We determine the diffusivity of the particles on the buffer, and demonstrate the significance of the ionicity of the CdSe. Photoluminescence spectra are compared to the previous studies of colloidal CdSe structures. This study opens the door for the synthesis of tunable II-VI heterostructures.

Induced magnetism in Cu nanoparticles embedded in Co

One-dimensionally confined nonferromagnetic layers of Cu grown between ferromagnetic layers of Co have an average induced magnetic moment that decreases with Cu film thickness. We studied the effects of changing the nature of confinement to three dimensions by embedding Cu nanoparticles in a Co matrix and measuring the induced moments using x-ray magnetic circular dichroism. The nanoparticle spin moments were more than twice that of films of comparable thickness due to the three dimensional confinement and greater interfacial area.