A study of structural and electronic effects in erbium (III) doped and undoped Group 14 nanostructures

Abstract

The microelectronic industry has evolved in a relatively short amount of time to produce smaller, powerful, yet affordable circuits. As silicon based circuits become more complex scientific challenges are faced. A highly sought advancement is optoelectronics, where data is transferred with photons instead of electrons. Silicon is well suited for this application except for the need of efficient light emission. There exist other semiconductors better suited, however they must compete with the established infrastructure. One strategy for overcoming this limitation in silicon is the incorporation of luminescent rare earth ions. Er 3+ is of particular interest because its emission lies at the absorption minimum for silica. This work continues previous research by describing the synthesis of a new form of erbium doped silicon nanoparticles. This material consists of erbium directed at the surface compared with the previous samples in which erbium was incorporated during synthesis. The samples were characterized with electron microscopy and show erbium rich surfaces on silicon nanocrystals. Activation of the emission associated with Er 3+ ions is subsequently described. The erbium local environment was probed in both types of material as well as the activated surface enriched samples. Silica samples were then prepared impregnated with randomly dispersed Er 3+ doped silicon nanocrystals. The effects of thermal activation were probed by changing either the heating time or temperature and examining the resulting excitation profile. Subtle changes associated with diffusion of the erbium ions away from the silicon nanocrystals as well as oxidation of the nanocrystals are described. The dopant's influence on the structural stability of silicon nanocrystals was then probed. It is known that 10¿50 nm silicon nanocrystals exhibit an elevated solid-solid phase transition pressure, allowing for a comparison of our doped and undoped silicon nanocrystals phase transition pressure. It was shown to be sensitive to the dopant, its location and thermal treatments. Lastly the impact of structural confinement was probed on silicon and germanium nanowires. It was indicated with Raman measurements that nanowires are more sensitive to quasi-hydrostatic conditions than silicon nanocrystals. However under hydrostatic conditions only annealed germanium nanowires exhibited an elevated phase transition pressure.