Laser-induced molybdenum oxide formation by low energy (nJ)–high repetition rate (MHz) femtosecond pulses

► The very first report of femtosecond laser-induced molybdenum oxide thin films. ► Laser-induced, advantages over conventional thermal treatment for metallic oxides. ► Optical and morphological features, distinct stoichiometry and crystalline phases. Experimental results on femtosecond (fs) laser-i...

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Bibliographic Details
Published in:Optical materials 2011-09, Vol.33 (11), p.1648-1653
Main Authors: Cano-Lara, M., Camacho-López, S., Esparza-García, A., Camacho-López, M.A.
Format: Article
Language:English
Subjects:
Femtosecond
Femtosecond laser-induced processing
Irradiation
Lasers
Metal oxides
Micro-Raman
Molybdenum
Oxidation
Scanning electron microscopy
Spectroscopy
Thin films
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Summary:► The very first report of femtosecond laser-induced molybdenum oxide thin films. ► Laser-induced, advantages over conventional thermal treatment for metallic oxides. ► Optical and morphological features, distinct stoichiometry and crystalline phases. Experimental results on femtosecond (fs) laser-induced oxidation of molybdenum (Mo) thin films are presented. The Mo thin films were deposited on fused silica substrates by the magnetron DC-sputtering technique. The as-deposited thin films were characterized by X-ray diffraction, which indicates that bbc-molybdenum was grown. The films were irradiated in ambient air, using a femtosecond Ti:Sapphire laser (800 nm, 60 fs pulse duration, 70 MHz and 6.5 nJ per pulse). The molybdenum thin films were laser scanned in the form of several millimeters long straight line traces, by using a per pulse laser fluence well below the (previously reported) ablation threshold. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) were used to study the laser-induced optical and morphology changes on the exposed zone. Energy Dispersive Spectrometry (EDS) and Micro-Raman Spectroscopy (MRS) were used to determine the degree of oxidation and the phase change across the laser irradiated paths on the Mo thin film. Under the above described experimental conditions our results show that it is possible to laser-induce a specific oxide phase from the molybdenum starting material. Our micro-Raman results clearly demonstrate that the fs-laser irradiation induces the m-MoO 2 and o-Mo 4O 11 crystalline phases at the directly laser irradiated trace and its close proximity.
ISSN:0925-3467
1873-1252
DOI:10.1016/j.optmat.2011.04.029