Electronic transport through Si nanocrystal films: Spin-dependent conductivity studies

We have investigated paramagnetic defects and their influence on the charge transport in thin films composed of Si nanocrystals (Si-ncs) by means of electrically detected magnetic resonance (EDMR) and conventional electron paramagnetic resonance (EPR). EPR measurements show that the processing applied in the production of films of Si-ncs leads to a considerable generation of Si dangling bonds (Si-dbs). From EDMR spectra, we conclude that the Si-dbs influence the charge transport through Si-ncs networks at room temperature. The low temperature EDMR spectra of P-doped films exhibit, along with Si-dbs resonances, two additional signals: (i) the characteristic hyperfine signature of isolated substitutional P in crystalline Si and (ii) the g=1.998 line, due to exchange-coupled donor electrons. All these resonances give rise to a quenching of the photocurrent through the films, demonstrating that Si-dbs and P-related states are recombination centers of excess charge carriers. The pronounced differences observed between the EDMR and EPR spectra are also discussed.