On‐Demand Preparation of α‐Phase‐Dominated Tungsten Films for Highly Qualified Thermal Reflectors

Abstract Phase‐structure diversity affords tungsten thin films with fascinating physical/chemical properties for varied applications. However, the on‐demand preparation of W films with specific phase is still an important but unmet scientific issue. In this report, an easy‐to‐achieve preparation recipe is implemented for addressing the phase tailoring of tungsten films. The phase transformation evolution during deposition is governed by enhanced diffusion of W adatoms and selective atomic etching on the crystal planes. It is experimentally demonstrated that the orientation relation between {210} β and {110} α planes plays a vital role in coupling with the competitive growth behaviors between β‐ and α‐W. The phase‐dependent electrical/optical properties of W films are experimentally observed and unambiguously figured out by theoretical simulations. Alpha‐phase‐dominated W films are prepared successfully under relatively tolerant conditions, demonstrating a low resistivity of ≈13.6 µΩ cm and a high infrared reflectance larger than 93%. Alpha‐W also serves as thermal reflector to construct a solar absorber, exhibiting a low thermal emissivity of ≈9.8%@500 °C. Understanding the (α, β) phase transformation mechanism means a big step forward in the development of the on‐demand preparation, which allows to build a scalable platform for making W films with specific phase in a more controllable way.