Silicon nanocrystals (Si NCs) are
intensively studied for optoelectronic
and biological applications due to having highly attractive features
such as band engineering. Although doping is often used to control
the optical and electrical properties, the related structural properties
of solely doped and codoped Si NCs are not well-understood. In this
study, we report the boron (B) and/or phosphorus (P) distribution
in Si NCs embedded in borosilicate glass (BSG), phosphosilicate glass
(PSG), and borophosphosilicate glass (BPSG) using atom probe tomography
(APT). We compared solely and codoped Si NCs grown at different temperatures
so that we may compare the effects of codoping and temperature on
the B and/or P distribution. Proximity histograms and cluster analyses
reveal that there exist boron-rich layers surrounding Si NCs and also
B–P clusters within the Si NCs. Raman spectra also show a structural
change between codoped Si NCs in solids and free-standing codoped
Si NCs. These results lead us to understand that codoped Si NCs disperse
in polar solvents.
Nanometer wide silicon filaments embedded in an amorphous silicon oxide matrix are grown at low temperatures over a large area. The optical and electrical properties of these mixed-phase nanomaterials can be tuned independently, allowing for advanced light management in high efficiency thin-film silicon solar cells and for band-gap tuning via quantum confinement in third-generation photovoltaics.
We fabricated p-i-n diodes by sputtering alternating layers of silicon dioxide and silicon rich oxide with a nominal atomic ratio O/Si=0.7 onto quartz substrates with in situ boron for p-type and phosphorus for n-type doping. After crystallization, dark and illuminated I-V characteristics show a diode behavior with an open circuit voltage of 373 mV. Due to the thinness of the layers and their corresponding high resistivity, lateral current flow results in severe current crowding. This effect is taken into account when extracting the electronic bandgap based on temperature dependent diode I-V measurements.
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