prof. Dr. Rainer Hippler

The main scientific activity is devoted to the diagnostics of deposition plasmas and to plasma-activated deposition of functional thin films. Time-resolved Langmuir probe diagnostics, optical emission spectroscopy, and energy-resolved ion mass spectrometry are employed for plasma diagnostics. The methods have been applied to magnetron sputtering (MS) discharges operated in different discharge modes and to hollow cathode (HC) discharges. MS discharges have been operated in direct current (DC) and in pulsed modes. The influence of anode biasing on the ion energy distribution has been investigated. 

Thin functional films have been deposited on various substrates. Upon annealing, tungsten oxide (WO_x) films deposited on glass substrates are influenced by sodium (Na) diffusion into the film and the formation of sodium tungstates (e.g., Na₂W₂O₇). Ternary oxide thin films deposited by either MS or HC discharges show unique properties. For example, annealed films deposited on FTO glass are composed of WO₃ and CuWO₄ or Cu₂WO₄ crystal phases. 

Cobalt nickel oxide films are deposited on Si(111) or fluorine-doped tin-oxide-coated (FTO) glass substrates employing a pulsed hollow-cathode discharge. Three different cathode compositions (Co20Ni80, Co50Ni50, and Co80Ni20) have and the formation of mixed metal oxide (MMO) phases been investigated. Upon annealing at 600 degrees, the mixed cobalt nickel oxide phase separates into two crystalline sub-phases which consist of cubic NiO and cubic Co₃O₄. Optical properties are investigated by spectroscopic ellipsometry and the optical bandgaps have been determined.

Plasma chemical reactions are investigated with a hollow cathode discharge with a copper nickel cathode (Cu50Ni50),. The discharge is operated with Ar/N₂/O₂ or Ar/H₂/N₂ gas mixtures. Gas samples are taken at the exhaust of the vacuum system. Samples are analysed using FTIR spectroscopy and the formation of either nitric oxide (NO) or ammonia (NH₃) has been revealed.