Laser-induced patterning of Co nanostructures under ambient conditions
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0890-Y04-06.1
Laserinduced patterning of Co nanostructures under ambient conditions C.Favazza*, J.Trice, H.Krishna, and R.Kalyanaraman Dept. of Physics, Washington University, St. Louis, MO Center for Materials Innovation, Washington University, St. Louis, MO ABSTRACT Increasing the efficiency and the relative ease of creating ordered nanostructures is essential to the advancement of nanotechnology. The practical benefits from ambient processing of nanostructures, like reduced complexity and increased efficiency, make it an important avenue for investigation as nanomanufacturing processes. We have recently shown that pulsed laser melting of ultrathin metal films in vacuum leads to nanostructure ordering presumably due to metal dewetting. Here we show that UV pulsed laser irradiation (9 ns pulse width) of ultrathin Co films on SiO2 substrates under ambient conditions with a twobeam laser interference pattern generates Co nanoparticles with both long and shortrange order (LRO and SRO) and are qualitatively comparable to those created in vacuum. Furthermore, preferential etching of the metal shows that there is minimal interaction of the Co with the substrate. These results show that the presence of oxygen in the ambient does not substantially influence the resulting nanostructure formation. Therefore, ns pulsed laser processing under ambient conditions may be a practical way to realize ordered metal nanostructures. INTRODUCTION Developing new methods to create ordered nanostructures in an easy and efficient manner is appealing for purposes of both experimental study and manufacturing. We have recently shown that melting a thin metal film with a laser interference pattern to change its morphology and in turn create ordered nanostructures appears to be an effective technique. These previous studies concentrated on understanding the processing of thin metal films in ultrahigh vacuum [1,2]. In this work, we report on our preliminary investigations of the processing of Co films on SiO2 using a 9 ns pulse width UV laser under ambient conditions. There are many motivations for processing in ambient conditions, including the ease of sample handling and the ability to rapidly generate a large amount of quantitative information on the pattern formation. Our preliminary experiments show that when ultrathin Co films are irradiated in air, pattern formation is qualitatively similar to irradiation in vacuum [3]. Using twobeam interference irradiation, we show long range ordering of Co nanoparticles. Furthermore, etching of the patterns using a preferential metal etch suggest that interfacial interactions of the Co with the SiO2 substrate are minimal.
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Contact author at [email protected]
0890-Y04-06.2
EXPERIMENT A Cobalt film with a thickness of 4 nm was deposited onto SiO2/Si(100) substrate using e beam evaporation. The substrate was commercially obtained from Silicon Quest International and had a 400 nm thick thermallygrown oxide layer on polished Si(100)
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