Vacuum Deposition by High-Energy Laser with Emphasis on Barium Titanate Films

Abstract
A laser beam capable of energy outputs up to 500 Joule was directed through a glass window into a vacuum system onto fine grain powder of Cr, W, Ti, C, Sb2S3, ZnS, SrTiO3, and BaTiO3. A neodymium-doped glass laser of 1.06-μ wavelength was mostly used without Q spoiling. Sometimes the beam was focused. Films up to 2000 Å were achieved on glass with one laser burst only, which corresponds to deposition rates of up to 106 Å/sec. The substrate was positioned between the vapor source and laser so that the laser beam passed through it, and therefore, also served as a shield. Electron micrographs were taken. From electron transmission diffraction patterns it appeared as if BaTiO3 had not been decomposed. In order to evaluate electrical properties of the films, platinum-rhodium films were sputtered or “laser-deposited” onto glass slides to serve as base electrode. Then a barium titanate film was evaporated with a laser. On top of this, an array of thin aluminum dots were evaporated through a mask, so that it was possible to investigate different areas of the films. Values of up to 2.5 μF/cm2 at 1 kHz and relative dielectric constants of up to 1000 were measured. Dissipation factors were in a range from 1%–10%. The capacitance at 1 kHz was constant within 0.1% between 50 ° and 105 °C as well as above 160 °C. A sharp peak of the temperature dependence curve could be observed at about 125 °C where the capacitance increased by 30%. For most films the onset of breakdown was observed at a field strength of around 5×105 Vcm−1. Both the capacitance and dissipation factor decrease almost linearly when increasing the frequency from 60 Hz to 500 kHz with the capacitance reaching 90% of its 60-Hz value.