|Author||Kuschel, Thomas ♦ Keudell, Achim von|
|Source||United States Department of Energy Office of Scientific and Technical Information|
|Subject Keyword||MATERIALS SCIENCE ♦ CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY ♦ ALUMINIUM ♦ ALUMINIUM OXIDES ♦ ARGON ♦ ARGON IONS ♦ CHEMISORPTION ♦ DEPOSITION ♦ DIFFUSION ♦ ELECTRIC FIELDS ♦ HYSTERESIS ♦ ION BEAMS ♦ LAYERS ♦ MOLECULES ♦ OXIDATION ♦ OXYGEN ♦ PLASMA ♦ QUARTZ ♦ SPUTTERING ♦ SURFACES ♦ X-RAY PHOTOELECTRON SPECTROSCOPY ♦ ALUMINIUM COMPOUNDS ♦ BEAMS ♦ CHALCOGENIDES ♦ CHARGED PARTICLES ♦ CHEMICAL REACTIONS ♦ ELECTRON SPECTROSCOPY ♦ ELEMENTS ♦ FLUIDS ♦ GASES ♦ IONS ♦ METALS ♦ MINERALS ♦ NONMETALS ♦ OXIDE MINERALS ♦ OXIDES ♦ OXYGEN COMPOUNDS ♦ PHOTOELECTRON SPECTROSCOPY ♦ RARE GASES ♦ SEPARATION PROCESSES ♦ SORPTION ♦ SPECTROSCOPY|
|Abstract||Plasma deposition of aluminum oxide by reactive magnetron sputtering (RMS) using an aluminum target and argon and oxygen as working gases is an important technological process. The undesired oxidation of the target itself, however, causes the so-called target poisoning, which leads to strong hysteresis effects during RMS operation. The oxidation occurs by chemisorption of oxygen atoms and molecules with a simultaneous ion bombardment being present. This heterogenous surface reaction is studied in a quantified particle beam experiment employing beams of oxygen molecules and argon ions impinging onto an aluminum-coated quartz microbalance. The oxidation and/or sputtering rates are measured with this microbalance and the resulting oxide layers are analyzed by x-ray photoelectron spectroscopy. The sticking coefficient of oxygen molecules is determined to 0.015 in the zero coverage limit. The sputtering yields of pure aluminum by argon ions are determined to 0.4, 0.62, and 0.8 at 200, 300, and 400 eV. The variation in the effective sticking coefficient and sputtering yield during the combined impact of argon ions and oxygen molecules is modeled with a set of rate equations. A good agreement is achieved if one postulates an ion-induced surface activation process, which facilitates oxygen chemisorption. This process may be identified with knock-on implantation of surface-bonded oxygen, with an electric-field-driven in-diffusion of oxygen or with an ion-enhanced surface activation process. Based on these fundamental processes, a robust set of balance equations is proposed to describe target poisoning effects in RMS.|
|Learning Resource Type||Article|
|Publisher Place||United States|
|Journal||Journal of Applied Physics|
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