Air-stable
luminescent silicon nanoparticles with effective surface protection
are reported as a quantum dot material with high emission quantum
yield. The silicon nanoparticles are prepared by a novel reaction
of SiO2 with phenol resins and characterized using X-ray
diffraction (XRD) and transmission electron microscopy (TEM). The
average particle size of the silicon nanoparticles is controlled by
an acid-etching process with hydrofluoric and nitric acids in methanol.
The particle size estimated from emission spectra was less than 5
nm. The surfaces of the silicon nanoparticles are protected using
a photoassisted reaction with styrene molecules after the acid-etching
process. The surface-protected silicon nanoparticles exhibit luminescence
at around 650 nm, and their emission quantum yield is estimated to
be 55%.
We have fabricated an H-phase TaS 2 crystal in the surface layer of a T-phase TaS 2 single crystal using a scanning tunneling microscope ͑STM͒ tip. After applying a relatively high bias voltage to the STM tip, we observed a significant change of the surface indicating the formation of the H phase near the exposed region. The STM image shows the characteristic triangular phase boundary between the original T phase (ͱ13 ϫͱ13 charge-density-wave superstructure͒ and the newly fabricated H phase ͑a triangular atomic lattice͒.Around the phase boundary, the local distortions of the ͱ13ϫͱ13 charge-density-wave superstructure have also been observed. The high-resolution STM image near the phase boundary suggests a sliding of the surface S atomic sheet by the STM modification procedure. ͓S0163-1829͑97͒50248-7͔
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