Title:
Orientation-controlled growth and optical properties of diverse Ag nanoparticles on Si(100) and Si(111) wafers.

Abstract:
Well-controlled growth of Ag nanoparticles (NPs) on Si substrates is important for next generation Si-based optoelectronic devices, but only randomly oriented Ag NPs have been previously reported. In this work, well-oriented Ag NPs with regular shapes are pseudomorphically grown on Si(100) and Si(111) substrates with crystallographic relationships of {100} mathematical left angle bracket 010 mathematical right angle bracket Ag ∥ {100} mathematical left angle bracket 010 mathematical right angle bracket Si and {111} mathematical left angle bracket 110 mathematical right angle bracket Ag ∥ {111} mathematical left angle bracket 110 mathematical right angle bracket Si, respectively. From a cross-sectional image, the Ag NPs on Si(100) substrates penetrate into Si and generate an inverted pyramid-like structure terminated by {111} planes embedded in Si substrates. In contrast, the Ag NPs on Si(111) substrates show flat morphology with the top plane terminated by Ag {111}. The Si underneath Ag NPs was not penetrated by Ag and a SiO(2) layer was formed between Ag and Si. Photoluminescence spectra of the Ag NPs show ultraviolet emissions centered in the 340-343 nm range. The mathematical left angle bracket 111 mathematical right angle bracket-oriented Ag particles show stronger emissions with an extra peak at 343 nm compared with mathematical left angle bracket 100 mathematical right angle bracket-oriented Ag NPs. Raman spectra show that the mathematical left angle bracket 100 mathematical right angle bracket - and mathematical left angle bracket 111 mathematical right angle bracket-oriented Ag NPs can enhance the peak intensity of Si(100) and Si(111) by 45.3% and 32.5%, respectively. The orientation-controlled Ag NPs with anisotropic optical properties are promising materials for Si-based optoelectronics.