Flash Roasting of ZnS: A Method to Produce Defect‐Engineered ZnO

Flash roasting, an adaptation of reactive flash sintering, enables rapid synthesis of dense ZnO from ZnS through simultaneous roasting and densification in a single step. Phase‐pure ZnO was obtained at a minimum current density of 40 mA/mm ² within 60 s at a furnace temperature of 650 °C, albeit with less densification. A relative density of ~95% was achieved at 100 mA/mm ² with an average grain size of ~0.4 µm. Detailed microstructural analyses revealed the formation of shell‐like structures during flash roasting, attributed to power bursts during traditional flash roasting that resulted in inhomogeneities in densification and microstructure. These issues were minimized using current‐controlled flash roasting, resulting in controlled grain growth and a narrow grain size distribution. Spectrochemical analysis confirmed the presence of oxygen vacancies, indicating their potential use in resistive switching applications. The introduction of these vacancies reduced the optical band gap of ZnO from 3.370 to 3.225 eV. A ZnO device using Pt electrodes was fabricated, and its memristive response was investigated under dark and illuminated conditions. The flash‐roasted ZnO‐based lateral memristive device exhibits pronounced hysteresis in its current–voltage response, demonstrating remarkable resistive switching behavior triggered by light (photon) interaction.