The role of Si interstitials in the migration and growth of Ge nanocrystallites under thermal annealing in an oxidizing
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NANO EXPRESS
Open Access
The role of Si interstitials in the migration and growth of Ge nanocrystallites under thermal annealing in an oxidizing ambient Kuan-Hung Chen1, Ching-Chi Wang1, Tom George2 and Pei-Wen Li1*
Abstract We report a unique growth and migration behavior of Ge nanocrystallites mediated by the presence of Si interstitials under thermal annealing at 900°C within an H2O ambient. The Ge nanocrystallites were previously generated by the selective oxidation of SiGe nanopillars and appeared to be very sensitive to the presence of Si interstitials that come either from adjacent Si3N4 layers or from within the oxidized nanopillars. A cooperative mechanism is proposed, wherein the Si interstitials aid in both the migration and coarsening of these Ge nanocrystallites through Ostwald ripening, while the Ge nanocrystallites, in turn, appear to enhance the generation of Si interstitials through catalytic decomposition of the Si-bearing layers. Keywords: Germanium nanocrystallites; Migration; Annealing
Background Silicon-based technology is the prime enabler for highdensity integrated microelectronic circuits, optoelectronics, and photovoltaic devices with ubiquitous applications ranging from mobile devices to high-end computing and communications. As Si complementary metal-oxidesemiconductor (CMOS) circuits are relentlessly scaled down to 16 nm or smaller dimensions, knowledge about fundamental nanoscopic processes in Si is becoming crucial for developing a good understanding on the limitations of nanofabrication and the development of future evolutionary directions for the technology as a whole. Many processing reactions including epitaxial growth, doping, oxidation, and silicidation are affected by the native defects in Si such as vacancies, self-interstitials, and their complexes. It is believed that Si interstitials play an important role in these processes, mostly detrimental, for instance causing such effects as undesirable transient-enhanced diffusion of dopants in p/n junctions [1,2], metal spiking at silicide/Si interfaces [3], interfacial traps along the gate oxide/Si interface [4], and stacking faults/dislocations in the epitaxial layer [1,5,6]. * Correspondence: [email protected] 1 Department of Electrical Engineering and the Center for Nano Science and Technology, National Central University, 300 JongDa Road, ChungLi 32001, Taiwan Full list of author information is available at the end of the article
In this paper, we report a unique effect, hitherto unreported, that is attributable to Si interstitials present within oxide layers previously generated by the selective oxidation of polycrystalline-SiGe (poly-SiGe) nanopillars leaving behind Ge quantum dots (QDs) or nanocrystallites when the preferential oxidation of Si is complete. In this novel phenomenon, these Ge QDs or nanocrystallites appear to be very sensitive to the presence of Si interstitials, almost acting as detectors for these interstitial species. The mechanism appears to be complex and long range in comparison to the typical dif
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