Low-Temperature Synthesis and Characterization of Gallium Nitride Quantum Dots in Ordered Mesoporous Silica

Abstract

Semiconducting gallium nitride (GaN) quantum dots (QDs) were synthesized at low temperatures (650 °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(III), at 365 °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 A and crystallize in the zinc blende lattice with cubic symmetry (β-GaN), whereas the hexagonal system is thermodynamically preferred. QDs, based on organic precursor, have hexagonal symmetry (α-GaN, wurtzite structure) with an average diameter of 20.6 A. Spectroscopic and structural characterization of the QD-MCM com...