Kinetic Study of Ge Nanocluster Formation in Composite GeO_x[SiO₂] Films

One of the promising materials for opto- and nanoelectronics is nonstoichiometric germanium silicate glass <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left(\text{GeO}_{x}\left[\text{SiO}_{2}\right]\right)$</tex>. Composite <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{GeO}_{x}\left[\text{SiO}_{2}\right]$</tex> films were obtained using co-evaporation of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{GeO}_{2}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiO}_{2}$</tex> powders by electron beams in vacuum and by vapor deposition on a Si substrate. The effect of temperature on the kinetics of Ge nanocluster formation in nonstoichiometric germanium silicate glasses during disproportionation is studied using Raman spectroscopy and Fourier transform infrared absorption spectroscopy. The saturation time of amorphous Ge nanoclusters formation in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{G e O}_{\mathbf{x}}\left[\mathbf{S i O}_{\mathbf{2}}\right]$</tex> films is significantly reduced with an increase in the annealing temperature from 400 to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$500{ }^{\circ} \mathrm{C}$</tex>. Infrared absorption spectra indicate a different disproportionation depth of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{GeO}_{x}\left[\text{SiO}_{2}\right]$</tex> films during annealing. The Kolmogorov-Johnson-Mehl-Avrami equation is used to approximate the disproportionation kinetics of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{G e O}_{\mathbf{x}}\left[\mathbf{S i O}_{\mathbf{2}}\right]$</tex> films. For the first time, the activation energy of disproportionation for a film of the composition <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left[\text{GeO}_{x}\right]_{0.75}\left[\text{SiO}_{2}\right]_{0.25}$</tex> on a Si substrate was determined, and it equals <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.71 \text{eV} \pm 0.16 \text{eV}$</tex>.