Size dependence of P_b-type photoluminescence quenching defects at the Si nanocrystal interface

¹ Department of Physics, and INPAC-Institute for Nanoscale Physics and Chemistry, University of Leuven Celestijnenlaan 200D, B-3001 Leuven, Belgium, EU
² IMTEK, Faculty of Engineering, Albert-Ludwigs-University Freiburg - Georges-Köhler-Allee 103, D-79110 Freiburg, Germany, EU

^a mihaela.jivanescu@fys.kuleuven.be

Received: 4 July 2011
Accepted: 29 August 2011

Abstract

Size-controlled Si nanocrystals (nc's) of ∼ 2 to 5 nm diameter embedded in amorphous (a-)SiO₂ are extensively studied by electron spin resonance (ESR) and photoluminescence (PL). The PL quenching P_b-type (Si dangling bond) interface defects ––P_b(0) and P_b1 centers–– are investigated as a function of Si nc's size and effective interface area with the embedding SiO₂. It is shown that the effective areal P_b-type defect density at the nc-Si/SiO₂ interface remains approximately constant, indifferent of the nc size. While Si nc's larger than ≈3.5 nm are found to house, on average, at least one PL quenching P_b-type defect, about 75% of the as-annealed 2 nm Si nc's appear P_b-free. Additional study on the effect of heat treatment in H₂ indicates this step to be more efficient in inactivating P_b(0) than P_b1 for all Si nc sizes.