| Popis: |
Semiconducting gallium nitride (GaN) quantum dots (QDs) were synthesized at low temperatures (650 degrees C), using ammonia flow without any organogallium precursor compound, assisted and controlled by an ordered mesoporous silica MCM-41 as host matrix. The final materials exhibit an intense blue shift of the band gap energy compared to the three-dimensional (3D) GaN. MCM-41 hosted GaN QD synthesis is also reported from pyrolysis of an organic precursor, tris(dimethylamido)gallium(M), at 365 degrees C under ammonia flow, with the largest band gap blue shift reported for such synthesized GaN of 0.6 eV. The QDs, involving inorganic precursor, exhibit an average X-ray diffraction estimated diameter of 12.6 angstrom and crystallize in the zinc blende lattice with cubic symmetry (beta-GaN), whereas the hexagonal system is thermodynamically preferred. QDs, based on organic precursor, have hexagonal symmetry (alpha-GaN, wurtzite structure) with an average diameter of 20.6 angstrom. Spectroscopic and structural characterization of the QD-MCM composites showed the successful synthesis of well-defined distributions of QDs, exhibiting luminescence at high energies in the UV region and in some cases defect luminescence, depending on the specific synthetic route. Journal of Physical Chemistry C |
