Preparation and characterization of zirconium films for first mirror application in fusion devices

• The nanostructured Zr films deposited on Al2O3 substrate are obtained by pulsed laser deposition (PLD) for the application of first mirror.
• The Zr films showed a very smooth surface and low values of root mean square roughness (RMS).
• The high reflectivities make it one of great candidate of first mirror materials for the applications of nuclear fusion.

The nanostructured zirconium (Zr) films deposited on Al2O3 substrate are obtained by pulsed laser deposition (PLD) for the application of first mirror. Structural features, optical properties and surface morphologies of as-grown Zr films are systematically investigated as a function of pulse repetition rate. It is found that the Zr films show a typical hexagonal close packed structure and all deposited films exhibit a very smooth surface. There are no voids and folds on the surface of Zr films. The root mean square roughness (RMS) values increase with increasing pulse repetition rate. The variation of pulse repetition rate has no obvious effects on the reflectivity because of the smooth film surface. Up to the wavelength of 800 nm, the reflectivity is higher than 70%, which is excellent for the application of first mirror.