Large-area homogeneous periodic surface structures generated on the surface sputtered boron carbide thin films by femtosecond laser processing
2015 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 331, 161-169 p.Article in journal (Refereed) Published
Amorphous and crystalline sputtered boron carbide thin films have a very high hardness even surpassing that of bulk crystalline boron carbide (approximate to 41 GPa). However, magnetron sputtered B-C films have high friction coefficients (C.o.F) which limit their industrial application. Nanopatterning of materials surfaces has been proposed as a solution to decrease the C.o.F. The contact area of the nanopatterned surfaces is decreased due to the nanometre size of the asperities which results in a significant reduction of adhesion and friction. In the present work, the surface of amorphous and polycrystalline B-C thin films deposited by magnetron sputtering was nanopatterned using infrared femtosecond laser radiation. Successive parallel laser tracks 10 mu m apart were overlapped in order to obtain a processed area of about 3 mm(2). Sinusoidal-like undulations with the same spatial period as the laser tracks were formed on the surface of the amorphous boron carbide films after laser processing. The undulations amplitude increases with increasing laser fluence. The formation of undulations with a 10 mu m period was also observed on the surface of the crystalline boron carbide film processed with a pulse energy of 72 mu J. The amplitude of the undulations is about 10 times higher than in the amorphous films processed at the same pulse energy due to the higher roughness of the films and consequent increase in laser radiation absorption. LIPSS formation on the surface of the films was achieved for the three B-C films under study. However, LIPSS are formed under different circumstances. Processing of the amorphous films at low fluence (72 mu J) results in LIPSS formation only on localized spots on the film surface. LIPSS formation was also observed on the top of the undulations formed after laser processing with 78 mu J of the amorphous film deposited at 800 degrees C. Finally, large-area homogeneous LIPSS coverage of the boron carbide crystalline films surface was achieved within a large range of laser fluences although holes are also formed at higher laser fluences.
Place, publisher, year, edition, pages
2015. Vol. 331, 161-169 p.
Surface nanostructuring, Boron carbide, Sputtering, Femtosecond laser, LIPSS
Physical Sciences Engineering and Technology
Research subject Engineering Science with specialization in Electronics
IdentifiersURN: urn:nbn:se:uu:diva-248804DOI: 10.1016/j.apsusc.2015.01.060ISI: 000350145700022OAI: oai:DiVA.org:uu-248804DiVA: diva2:801727