A close-space sublimation approach to tungsten oxide and sulfide nanostructure formation

We present a highly resource-efficient Close-Space Sublimation (CSS) approach, along with versatile one-step and two-step process designs, for the controlled synthesis of a wide range of tungsten (sub)oxide (WO_3-x) and tungsten disulfide (WS₂) nanostructures. By applying a simple sublimation model and leveraging graded CSS flux profiles in conjunction with operando experimentation, we accelerate process discovery and establish CSS flux and substrate temperature as key parameters governing nanostructural formation. Our CSS methodology enables the synthesis of W (sub)oxide structures within process times of less than 10 minutes, a significant improvement over the hour-long durations typically required in conventional hot-wall furnace systems. We elucidate how nanostructural control in the CSS approach arises from the kinetic interplay between the tungsten oxide sublimation flux and the rate of oxygen depletion in the deposited layers, thereby facilitating the formation of distinct W suboxide templates with varied structural motifs. These findings highlight CSS as a highly promising alternative to conventional powder-furnace chemical vapour deposition, offering superior efficiency, precise structural control, scalability, and adaptable process designs tailored to applications spanning photo-/electro-catalysis, photovoltaics, sensors, and highly integrated optoelectronic devices.