The role of surface properties in the cathodoluminescence of Zn2GeO4/SnO2 nanowire heterostructures

Abstract

Herein, we report the influence of the surface conditions on the cathodoluminescence (CL) emissions from Zn_2GeO_4 nanowires and Zn_2GeO_4/SnO_2 heterostructures obtained by thermal evaporation technique. A Zn_2GeO_4 nanowire surrounded by a discontinuous shell of SnO_2 crystals composed the Zn_2GeO_4/SnO_2 heterostructures. Local CL measurements at different acceleration voltages allow monitoring the emission bands originated at the interface region, showing an additional deep-ultraviolet (UV) emission at 4.40 eV, which has not been previously reported. CL spectra from SnO_2 coated Zn_2GeO_4 nanowires also show this deep-UV emission. The results would confirm the presence of a shallow energy level close to the conduction band, which becomes active by passivation of Zn_2GeO_4 nanowires surface by the SnO_2 coating.