Solid-state nanocluster formation of praseodymium compounds in silicon and silicon dioxide

Nanoclusters of Pr compounds were formed in a silicon-on-insulator structure by ion beam synthesis in order to identify the most stable Pr compounds in contact with Si and SiO2. The processes of ion-induced atomic mixing, phase segregation, texturing, and nanocluster formation were investigated by transmission electron microscopy, Auger electron spectroscopy, and x-ray diffraction. After annealing at 900 degrees C an array of Si precipitates is formed in SiO2. The size distribution of Si precipitates corresponds to the concentration profile of excess Si atoms in SiO2. Implanted Pr atoms are accumulated at the periphery around the Si precipitates decorating them. During annealing at 1100 degrees C two types of crystalline silicate nanoclusters are formed, Pr2Si2O7 and Pr9.33Si6O26. In the top Si layer a narrow layer of Pr silicate nanoclusters is formed by self-organization rather equidistant to the Si/SiO2 interface. Pr oxide (Pr2O3), the most desired high-k material, was not definitely verified. The predominant process in the solid-state synthesis of Pr compounds is the Pr silicate formation that provides both high atomic package density and low reordering energy. (c) 2006 American Institute of Physics.