Time resolved plasma probe measurements of a novel high power density pulsed plasma discharge are presented. Extreme peak power densities in the pulse (on the order of several kW cm−2) result in a very dense plasma with substrate ionic flux densities of up to 1 A cm−2 at source-to-substrate distances of several cm and at a pressure of 0.13 Pa (1 mTorr). The pulse duration was ∼100 μs with a pulse repetition frequency of 50 Hz. The plasma consists of metallic and inert gas ions, as determined from time resolved Langmuir probe measurements and in situ optical emission spectroscopy data. It was found that the plasma composition at the beginning of the pulse was dominated by Ar ions. As time elapsed metal ions were detected and finally dominated the ion composition. The effect of the process parameters on the temporal development of the ionic fluxes is discussed. The ionized portion of the sputtered metal flux was found to have an average velocity of 2500 m s−1 at 6 cm distance from the source, which conforms to the collisional cascade sputtering theory. The degree of ionization of the sputtered metal flux at a pressure of 0.13 Pa was found to be 40%±20% by comparing the total flux of deposited atoms with the charge measured for the metal ions in the pulse.
We describe the hydrogen uptake during the synthesis of alumina films from H2O present in the high vacuum gas background. The hydrogen concentration in the films was determined by the H1(N15,αγ)C12 nuclear resonance reaction. Furthermore, we show the presence of hydrogen ions in the plasma stream by time-of-flight mass spectrometry. The hydrogen content increased in both the film and the plasma stream, as the oxygen partial pressure was increased. On the basis of these measurements and thermodynamic considerations, we suggest that an aluminum oxide hydroxide compound is formed, both on the cathode surface as well as in the film. The large scatter in the data reported in the literature for refractive index and chemical stability of alumina thin films can be explained on the basis of the suggested aluminum oxide hydroxide formation.
Carbon nitride CNx thin films were grown by unbalanced dc magnetron sputtering from a graphite target in a pure N2 discharge, and with the substrate temperature Ts kept between 100 and 550 °C. A solenoid coil positioned in the vicinity of the substrate was used to support the magnetic field of the magnetron, so that the plasma could be increased near the substrate. By varying the coil current and gas pressure, the energy distribution and fluxes of N2+ ions and C neutrals could be varied independently of each other over a wide range. An array of Langmuir probes in the substrate position was used to monitor the radial ion flux distribution over the 75-mm-diam substrate, while the flux and energy distribution of neutrals was estimated through Monte Carlo simulations. The structure, surface roughness, and mechanical response of the films are found to be strongly dependent on the substrate temperature, and the fluxes and energies of the deposited particles. By controlling the process parameters, the film structure can thus be selected to be amorphous, graphite-like or fullerene-like. When depositing at 3 mTorr N2 pressure, with Ts>200 °C, a transition from a disordered graphite-like to a hard and elastic fullerene-like structure occurred when the ion flux was increased above ∼0.5–1.0 mA/cm2. The nitrogen-to-carbon concentration ratio in the films ranged from ∼0.1 to 0.65, depending on substrate temperature and gas pressure. The nitrogen film concentration did, however, not change when varying the nitrogen ion-to-carbon atom flux ratios from ∼1 to 20.
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