Measurement of the Crystallization and Phase Transition of Niobium Dioxide Thin-Films for Neuromorphic Computing Applications Using a Tube Furnace Optical Transmission System

Significant research has focused on low-power stochastic devices built from memristive materials. These devices foster neuromorphic approaches to computational efficiency enhancement in merged biomimetic and CMOS architectures due to their ability to phase transition from a dielectric to a metal at an increased temperature. Niobium dioxide has a volatile memristive phase change that occurs ∼800^∘C that makes it an ideal candidate for future neuromorphic electronics. A straightforward optical system has been developed on a horizontal tube furnace for in situ spectral measurements as an as-grown film is annealed and ultimately crystallizes as . The system measures the changing spectral transmissivity of as it undergoes both reduction and crystallization processes. We were also able to measure the transition from metallic-to-non-metallic during the cooldown phase, which is shown to occur about 100^∘C  lower on a sapphire substrate than fused silica. After annealing, the material properties of the and were assessed via X-ray photoelectron spectroscopy, X-ray diffraction, and 4-point resistivity, confirming that we have made crystalline .