Photoluminescence of amorphous niobium oxide films synthesized by solid-state reaction

Niobium oxide amorphous films were deposited on silicon substrates at a temperature range of 300–400 °C by heating a pure niobium foil in a rough vacuum. The films were amorphous in structure and with morphology of vertically aligned nano-columns. This feature resulted in interesting photoluminescence (PL) property in the visible light range. The intensity of the photoluminescence spectrum of the as-deposited amorphous film is small. However, the PL intensity of the same sample after annealing below 500 °C increases greatly and consists of two peaks centered at ~ 630 nm (1.97 eV) and ~ 715 nm (1.74 eV). The mechanism for the PL behavior of the amorphous niobium oxide films was also investigated and discussed.