In Situ Measurement of Crystallization and Volatile Phase Transition in Niobium Dioxide Memristive Materials

Crystalline niobium dioxide has a volatile memristive phase change that occurs ∼800 °C that makes it an ideal candidate for future neuromorphic electronics. In this talk, I will discuss some of our recent work understanding synthesis and post-deposition annealing strategies for crystallizing this material. Specifically, we developed a straightforward optical system that operates on a horizontal tube furnace for in situ spectral measurements as an as-grown Nb₂O₅ film is annealed and ultimately crystallizesas NbO₂. The system is based on an automated filter wheel apparatus that has 1in narrow band optical filters spanning 900nm - 1650nm. The system measures the changing spectral transmissivity of Nb₂O₅ as it undergoes both reduction and crystallization processes. The system was designed and built by undergraduate students, and uses a python-based control system that runs on a Raspberry Pi microcontroller. After annealing, the material properties of the Nb₂O₅ and NbO₂ were assessed via X-ray photoelectron spectroscopy, X-ray diffraction, and 4-point resistivity, confirming that we have made crystalline NbO₂.