One-dimensional tungsten oxide growth through a grain-by-grain buildup process

One-dimensional (1D) tungsten oxide crystals (wires, wire bundles, and tubes) were synthesized by a catalyst-free, physical evaporation–condensation process using a mini-arc plasma source. The growth process of the 1D tungsten oxide structure was deciphered through sequential scanning electron microscopy observations. Crystalline tungsten oxide grains form first and then rotate and align their positions to build up 1D crystals as wires, wire bundles, and tubes to minimize the surface energy because of the anisotropic nature of the tungsten oxide crystal. The influence of temperature and growth time on the crystal synthesis is analyzed.