Abstract: Alkylated silicon nanocrystals (C11-SiNCs) were
prepared successfully by galvanostatic etching of p-Si(100) wafers
followed by a thermal hydrosilation reaction of 1-undecene in
refluxing toluene in order to extract C11-SiNCs from porous silicon.
Erbium trichloride was added to alkylated SiNCs using a simple
mixing chemical route. To the best of our knowledge, this is the first
investigation on mixing SiNCs with erbium ions (III) by this
chemical method. The chemical characterization of C11-SiNCs and
their mixtures with Er3+(Er/C11-SiNCs) were carried out using X-ray
photoemission spectroscopy (XPS). The optical properties of C11-
SiNCs and their mixtures with Er3+ were investigated using Raman
spectroscopy and photoluminescence (PL). The erbium mixed
alkylated SiNCs shows an orange PL emission peak at around 595
nm that originates from radiative recombination of Si. Er/C11-SiNCs
mixture also exhibits a weak PL emission peak at 1536 nm that
originates from the intra-4f transition in erbium ions (Er3+). The PL
peak of Si in Er/C11-SiNCs mixture is increased in the intensity up to
three times as compared to pure C11-SiNCs. The collected data
suggest that this chemical mixing route leads instead to a transfer of
energy from erbium ions to alkylated SiNCs.
Abstract: Metal-enhanced Luminescence of silicon nanocrystals
(SiNCs) was determined using two different particle sizes of silver
nanoparticles (AgNPs). SiNCs have been characterized by scanning
electron microscopy (SEM), high resolution transmission electron
microscopy (HRTEM), Fourier transform infrared spectroscopy
(FTIR) and X-ray photoelectron spectroscopy (XPS). It is found that
the SiNCs are crystalline with an average diameter of 65 nm and FCC
lattice. AgNPs were synthesized using photochemical reduction of
AgNO3 with sodium dodecyl sulphate (SDS). The enhanced
luminescence of SiNCs by AgNPs was evaluated by confocal Raman
microspectroscopy. Enhancement up to x9 and x3 times were
observed for SiNCs that mixed with AgNPs which have an average
particle size of 100 nm and 30 nm, respectively. Silver NPs-enhanced
luminescence of SiNCs occurs as a result of the coupling between the
excitation laser light and the plasmon bands of AgNPs; thus this
intense field at AgNPs surface couples strongly to SiNCs.
Abstract: A thin gold metal layer was deposited on the top of
silicon oxide films containing embedded Si nanocrystals (Si-nc). The
sample was annealed in a gas containing nitrogen, and subsequently
characterized by photoluminescence. We obtained 3-fold
enhancement of photon emission from the Si-nc embedded in silicon
dioxide covered with a Gold layer as compared with an uncovered
sample. We attribute this enhancement to the increase of the
spontaneous emission rate caused by the coupling of the Si-nc
emitters with the surface plasmons (SP). The evolution of PL
emission with laser irradiated time was also collected from covered
samples, and compared to that from uncovered samples. In an
uncovered sample, the PL intensity decreases with time,
approximately with two decay constants. Although the decrease of
the initial PL intensity associated with the increase of sample
temperature under CW pumping is still observed in samples covered
with a gold layer, this film significantly contributes to reduce the
permanent deterioration of the PL intensity. The resistance to
degradation of light-emitting silicon nanocrystals can be increased by
SP coupling to suppress the permanent deterioration. Controlling the
permanent photodeterioration can allow to perform a reliable optical
gain measurement.