Berlin 2012 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 38: Poster III: Resistive switching (jointly with DF, KR, HL); Thermoelectric materials (Focused session); Micro- and nanopatterning (jointly with O); Ion irradiation effects

DS 38.29: Poster

Donnerstag, 29. März 2012, 17:30–19:00, Poster E

Ripple pattern formation on single crystalline magnesium oxide. — •Omar Bobes, Hans Hofsäss, and Kun Zhang — II. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Magnesium oxide MgO is a highly ionic bound crystal with cubic rock salt structure. Because of its high ionicity MgO is almost impossible to amorphize by ion irradiation. MgO could therefore act as a model system to investigate pattern formation by ion beam erosion on a crystalline substrate. Furthermore, the sputter yield is quite low and therefore MgO could be also a model system to investigate the role of sputtering itself for pattern formation. We have irradiated single crystalline MgO samples at 60^∘ incidence angle with 1 keV Ar⁺- and O₂⁺-ions at room temperature. The sputter yield under these conditions is 3.5 for oxygen and 4.2 for magnesium. The maximum projected ion range is only about 3 nm. The as grown samples were flat with rms roughness < 0.7 nm. Only µm wide weak wavy structures could be seen in AFM. After irradiation with fluence of 1*10¹⁸ Ar/cm² a complex ripple structure with rms roughness of 5.3 nm and maximum ripple amplitudes of 10-20 nm are observed. The pattern consists of ripples with up to 400 nm in length oriented perpendicular to the projected ion beam direction. The width of the ripples varies between about 30 nm and 100 nm. For O₂⁺-irradiation, dot-pattern appears at the ion fluence of 1*10¹⁸ Ar/cm². With increasing the ion fluence, these dots tend to orient along the direction perpendicular to ion-beam. The pattern formation is discussed based on existing models.