e., converted to oxide. The above TEM observations clearly reveal that the growth and migration behaviors of Ge nanocrystallites are very sensitive to the presence and the content of Si interstitials that are Selleckchem JSH-23 provided either externally by adjacent Si3N4 layers or by small concentrations of residual Si interstitials remaining within the oxidized poly-SiGe pillars. The role of Si interstitials in the growth of Ge nanocrystallites under thermal annealing in an oxidizing ambient is sketched in Figures 2d, 3d, and 4c. Although a large body of work exists in the literature on the generation and role of Si interstitials, to our knowledge, the above phenomenon has never been reported before. Previous work has attributed the thermal oxidation

of Si inducing a drastic lateral expansion of the silicon lattice [12] and the generation of silicon self-interstitials buy NCT-501 as a means of partially relieving the compressive stress in the growing oxide layer that develops as a result of a 2.25× volume expansion when Si is converted to SiO2. The majority of these Si interstitials generated during Si oxidation diffuse into the growing oxide layer and are also oxidized [13, 14], while a relatively small, but significant, amount of interstitials diffuse into the Si substrate,

causing supersaturation of these interstitials and the consequent precipitation as oxidation stacking faults (OSFs) [5, 6] or oxidation-enhanced diffusion (OED) [1, this website 2] of some dopants. Interestingly, the OED of boron during the thermal oxidation of Si is effectively suppressed through the introduction of a thin layer of Si1 – x Ge x or Si1 – x Ge x C y over the Si substrate or even completely eliminated when the Ge or C concentration is high [15–17]. Moreover, the reduction of the Si interstitials has been shown to be Ge concentration dependent. Again, to our knowledge, we have not found previous work describing a cooperative mechanism, wherein the Si interstitials aid in both the migration of Ge nanocrystallites and in the coarsening of these nanocrystallites through Ostwald ripening as clearly shown above. The additional, interesting aspect of this novel mechanism is that as described by us previously

[9, 10], the Ge nanocrystallites also appear to enhance the decomposition Rucaparib chemical structure of the Si-bearing Si3N4 layers resulting in further generation of Si interstitials. The quality of the oxide generated by the thermal oxidation of the poly-Si0.85Ge0.15 could also play a significant role in facilitating the new mechanism that we have discovered. Diffusion lengths of Si interstitials in SiO2 calculated at 900°C for diffusion times of 10, 40, 70, 100, and 145 min are 0.72, 1.43, 1,89, 2.26, and 2.72 nm, respectively, based on the equation of D = 1.2 × 10-9⋅exp(-1.9/k B T) [18]. Obviously, these diffusion lengths are too small to explain the Si interstitial-mediated mechanism that we have observed. Hence, we believe that the oxide generated from poly-Si0.85Ge0.