Stress tuning of Ge nanocrystals embedded in dielectrics

Abstract

Germanium (Ge) nanocrystals have been synthesized by annealing cosputtered SiO2 + Ge or HfAlO + Ge samples in N2 ambient at temperatures ranging from 800 to 1000°C. We conclude that the annealing technique, the dielectric matrix, and the capping stressor have a significant influence on the formation and stress evolution of the nanocrystals. We show that a careful selective etching of the annealed samples in hydrofluoric acid solution enables the embedded Ge nanocrystals to be liberated from the matrix. From the Raman results of the as-prepared and the etched samples, we establish that the nanocrystals generally experience compressive stress in the Si oxide matrix and that the stress state of the nanocrystal can be tuned by the different matrix material as well as by the capping stressor. © 2008 American Chemical Society.