RESET-first unipolar resistance switching behavior in annealed Nb_2O_5 films

摘要

In this work, the effect of thermal annealing on the resistance switching behavior of Nb_2O_5 films was investigated in conjunction with an analysis of the chemical bonding states and crystal structure. The Nb_2O_5 films were deposited via reactive sputtering, and annealed via rapid thermal annealing at various temperatures up to 650 ℃. The crystal structure of the as-deposited Nb_2O_5 films transformed from amorphous to a hexagonal Nb_2O_5 crystalline phase with tetragonal NbO_2 following thermal annealing at 500 ℃. The conductivity of the Nb_2O_5 films increased drastically as the annealing temperature increased. An increase in the non-lattice oxygen in the Nb_2O_5 films was also observed with thermal annealing. Pt/Nb_2O_5/Pt stacks with the as-deposited Nb_2O_5 showed typical unipolar resistance switching behaviors after electro-forming; however, the Nb_2O_5 film devices annealed at 500 ℃ showed RESET-first resistance switching behavior without prior electro-forming. The RESET-first resistance switching in annealed Nb_2O_5 is believed to be due to the nano-scale conductive path formed in the annealed Nb_2O_5 films.