Second-harmonic spectroscopy of two-dimensional Si nanocrystal layers embedded in SiO2 films

Abstract

We present observations of optical second-harmonic generation (SHG) from dense (1010 or 6×1011cm-2) layers of 5 or 8 nm average diameter silicon nanocrystals (NCs) embedded in thin (6-15 nm) SiO2 films on silicon substrates. Time-dependent SHG monitors optically-driven electrostatic charging of the Si NC layer as well as subsequent charge leakage, and thus provides noncontact electrical characterization of Si-NC-based device structures. SHG intensity and phase spectra of Si NCs are distinguished from contributions of the Si substrate by polarization-dependent and frequency-domain interferometric SH spectroscopy, which reveal a NC-size-dependent blueshift of the E1 resonance consistent with quantum confinement. © 2002 American Institute of Physics.