Growth of Nb2O5 quantum dots by physical vapor deposition

The crystalline quantum dots of Nb2O5 in the range 1-20 nm have been grown by vacuum thermal evaporation using the bottom-up approach of early nucleation and growth stage. The dot sizes were controlled by growth time for an optimized constant molecular flux rate of growth. The dots were characterized by TEM and UV/Vis absorption spectroscopy. The variation of optical band gap of dots scaling with inverse square of their size demonstrates the quantum confinement effect in the dots. The reduced mass of electron-hole pair (exciton) was determined to be 0.532 m(e) from this behavior. (C) 2014 Elsevier B.V. All rights reserved.