Understanding the Parameters Affecting the Photoluminescence of Silicon Quantum Dots

LLANSOLA PORTOLÉS,M.J.; PIS DIEZ,R.; DELL´ARCIPRETE,M.L.; CAREGNATO,P.; ROMERO,J.J.; MÁRTIRE,D.O.; AZZARONI, O.; CEOLÍN, M.; GONZALEZ,M.C.

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Lugar: Washington; Año: 2012 vol. 116 p. 11315 - 11325

1932-7447

Silicon nanoparticles of 1−5 nm size (SiNPs) were synthesizedby a bottom-up (BU) approach involving a chemical wet method. Thecontribution of different emitters to the overall excitation−emission matrix wasanalyzed on the assumption that pure substances existing in a unique formshow an excitation wavelength-invariant emission spectrum. The occurrence ofemitters differing in size and aggregation was supported by transmissionelectron microscopy (TEM), small-angle X-ray scattering (SAXS), time resolvedsingle photon counting, and time-resolved anisotropy experiments. The effect on photoluminescence (PL) of the particle surface oxidation as a result of aging is studied and compared to that of surface oxidized particles obtained by a top-down (TD) approach following an electrochemical method with HF etching. Surface oxidation to SiOx seems to introduce two different effects on the SiNP PL. An emission originated in surface states associated to SiOx was identified and observed for SiNPs synthesized by both BU and TD approaches. Blue-shifted excitation−emission spectra associated to a silicon core in embedded SiOx nanostructures were also identified. Theoretical studies were carried out to help understand the observed results.