Pattern formation and evolution on Pt(111) by grazing incident ion bombardment

By analyzing by scanning tunnelling microscopy (STM) the amount of material which is removed during grazing incidence ion bombardment from a Pt(111) sample, it was possible to determine the different sputtering yields of ions impinging either on ascending step edges or hitting onto flat terraces. From the analysis of damage patterns of single ion impacts and low fluence experiments it was possible to elaborate a model to explain pattern formation during grazing incidence ion bombardment. For temperatures T < 450K the development of the patterns is solely due to the effects of the ion beam, which removes preferentially material at ascending step edges. At higher temperatures T > 450 K diffusion processes overshadow the effects of the ion beam. In this temperature regime ions channelling underneath the topmost layer create chains of vacancy islands. These islands coalesce preferentially along the ion beam direction and are therefore essential fort he formation of the ripple patterns. Temperature dependent measurements reveal that the ripple formation is only possible within a temperature window. This temperature range can be divided into two distinct ranges: for T < 450 a pattern with a constant wavelength forms while for T > 450 K the wavelength increases rapidly with rising temperatures. The RMS roughness increases up to T = 550 K and decreases for higher temperatures. The temperature dependence of the rescaled defect densities behaves similar to the wavelength. The increase for T > 450 K is related to the onset of step edge diffusion at this temperature. The fluence dependency is analyzed for different sample temperatures. The RMS roughness follows in each case a power law. The wavelength too follows a power law up to an ion fluence of 70 monolayers. For even higher ion fluences the coarsening speed increases. Founded on the higher sputtering yield at ascending step edges a coarsening model based on the erasure of ripples is developed. Changing the angle of incidence reveals that the wavelength depends only slightly onto the angle of incidence while the RMS roughness changes much strongly with increasing angles of incidence. Both behaviours are explained by the decrease of the removed material with increasing angle of incidence. The wavelength as well as the RMS roughness increases linearly with increasing ion energy. The increase of the RMS roughness can be explained by solely considering the increase of the removed material by increasing the ion energy. To explain the behaviour of the wavelength additionally to the increase of the removed material, the initial wavelength, which is energy dependent, has to be considered.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2005

Author dc:creator

• Hansen, Henri

Contributors dc:contributor

• Michely, Thomas

• info:eu-repo/classification/ddc/530
• Platin
• Kristallfläche
• Musterbildung
• Ionenbestrahlung
• Streifender Einfall
• Physik
• streifender Ionenbeschuss
• Rastertunnelmikroskopie
• Defekt
• Zerstäubungsausbeute

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123727%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:62134