content_image/323322.jpg content_image/323323.jpg
Hofmeister and co-workers also investigated the spacing of a (111) lattice as a function of cluster size. They found that large silicon clusters exhibited compressed (111) lattices compared to bulk crystalline silicon. However, clusters smaller than 3 nm in diameter were found to be dilated. The dependence of the (111) lattice spacing on the cluster diameter followed: 

where D is the cluster diameter. 

Because the photoluminescence of silicon was found to depend on pressure, the authors concluded that the size-dependent lattice separation must be taken into account in a modified equation for the photoluminescence energy caused by quantum confinement (Ledoux et al., 2000). 

Here, E corr PL is the energy of the photoluminescent band, as corrected for size-dependent lattice separation, in eV. E$_{0}$ is the band gap energy of bulk crystalline silicon at room temperature (1.17 eV) (Ledoux et al., 2000). 

It is important to note that all samples had been transferred to air testing for photoluminescence. The samples were kept in an argon atmosphere during transfer (Ehbrecht et al., 1997). After production and exposure to air, the crys- talline core section of the particles was found to reduce in diameter (Ledoux et al., 2000, 2001). Also, the photoluminescence energy was found to blue-shift, which was attributed to the smaller sizes of the silicon clusters, supporting the assertion that quantum confinement was controlling fluorescence properties (Ledoux et al., 2001). The effect of quantum confinement was also investigated 

<img src='content_image/323322.jpg'>

<img src='content_image/323323.jpg'>

