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}〈010〉Ag ∥ {100}〈010〉Si and {111}〈110〉Ag ∥ {111}〈110〉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 SiO2 layer was formed between Ag and Si. Photoluminescence spectra of the Ag NPs show ultraviolet emissions centered in the 340–343 nm range. The 〈111〉-oriented Ag particles show stronger emissions with an extra peak at 343 nm compared with 〈100〉-oriented Ag NPs. Raman spectra show that the 〈100〉- and 〈111〉-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.