Single crystal-like thin films of blue bronze

Highlights: • Charge density wave (CDW) in thin film of blue bronze $K_{0.3}{\mathrm{MoO}}_3$ close to single crystal quality. • Film quality assessed by transport and ultrafast pump-probe spectroscopy studies. • Surface imaging and X-ray diffraction point to well oriented and long grains. • Grain length up to 4 µm approaches CDW coherence length. Pulsed laser deposition technique was employed to grow thin films of $K_{0.3}Mo{O}_3$ on $A{l}_2{O}_3$ (1-102) and $SrTi{O}_3$ (510) substrates. Structural and imaging characterization revealed good quality films with well oriented grains of few microns in length. Both non-selective (transport) and order-selective (femtosecond pump-probe spectroscopy) probes revealed charge density wave properties that are very close to those of the single crystals. The films exhibit metal-semiconductor phase transition in resistivity, pump-probe data show phase transition at the same temperature as the single crystal and the threshold for the photo-induced phase transition is approximately the same as in single crystal. We compare the properties of films with grains differing by an order of magnitude in length.