Abstract
Thermochemical laser-induced periodic surface structures (TLIPSS) are a relatively new type of periodic structures formed in the focal area of linear polarized laser radiation by the thermally stimulated reaction of oxidation. The high regularity of the structures and the possibility of forming high-ordered structures over a large area open up possibilities for the practical application for changing the optical and physical properties of materials surface. Since the mechanism of formation of these structures is based on a chemical oxidation reaction, an intriguing question involves the influence of air pressure on the quality of structure formation. This paper presents the results on the TLIPSS formation on a thin hafnium film with fs IR laser radiation at various ambient air pressures from 4 Torr to 760 Torr. Despite the decrease in the oxygen content in the ambient environment by two orders of magnitude, the formation of high-ordered TLIPSS (dispersion in the LIPSS orientation angle δθ < 5°) with a period of ≈700 nm occurs within a wide range of parameters variation (laser power, scanning speed). This behavior of TLIPSS formation is in agreement with experimental data obtained earlier on the study of the kinetics of high-temperature oxidation of hafnium at various oxygen pressures.
Highlights
Accepted: 4 November 2021Laser-induced periodic surface structures (LIPSS) were discovered for the first time by Birnbaum [1] five decades ago and since have attracted great interest for a theoretical explanation of the mechanism of structure formation and because of their potential for practical application
This paper presents the results of the study on the formation of Thermochemical laser-induced periodic surface structures (TLIPSS) with a quantitative assessment of the parameters of ordering, defectiveness and productivity of the creation of periodic structures formed on thin hafnium films when exposed to fs laser radiation at different concentrations of oxygen molecules in ambient atmosphere
TLIPSSofispowers based on thescanning analysis speeds, the productivity increases with an increasing in scanning speed
Summary
Laser-induced periodic surface structures (LIPSS) were discovered for the first time by Birnbaum [1] five decades ago and since have attracted great interest for a theoretical explanation of the mechanism of structure formation and because of their potential for practical application. LIPSS formation is based on thermo-stimulated reaction of oxidation that leads to periodic structures formation consisting of alternating areas of the oxidized ridges and unmodified metal with the orientation parallel to the laser polarization direction This type of thermochemical LIPSS (TLIPSS) is characterized by a high degree of ordering and has great potential for practical applications, especially for cost-effective micro-nanostructuring of surfaces in comparison with expensive lithographybased techniques. Thermochemical LIPSS are predominantly formed at atmospheric pressure, but with a 50-fold decrease in pressure, the appearance of ablative structures was observed alongside thermochemical LIPSS, which completely dominate with a further decrease in oxygen pressure to a high vacuum These structures formation transition is explained in [22] by a weakening of the oxidation process at low air pressure and the consequences of competitive excitation of the transverse-electric scattered surface wave and transverse-magnetic hybrid plasmon wave depending on the oxidation degree. This paper presents the results of the study on the formation of TLIPSS with a quantitative assessment of the parameters of ordering, defectiveness and productivity of the creation of periodic structures formed on thin hafnium films when exposed to fs laser radiation at different concentrations of oxygen molecules in ambient atmosphere
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