Nanolayered Natural Mineral Muscovite - Single fs Laser Pulse Interaction: A Tool to Uncover Material Variability

High quality sheet muscovite mica is a natural mineral with numerous applications in electronics and science. Flexible electronics and energy storage are significant research topics involving it at this time. Its many uses rely on its physical characteristics: being transparent (fig. 1(a)), electrically insulating, chemically inert, flexible, elastic, infusible, birefringent, having a high dielectric constant, low dielectric loss, low thermal conductivity, and a perfect cleavage plane within its crystal structure. The latter leads to its ubiquitous use as an atomically flat, clean substrate. Muscovite's potential as a 2D material is also starting to gain attention (eg. [1]). High quality sheet muscovite is assumed to be a staple commodity. Most research publications using it as a substrate omit its source and report no characterization of the muscovite. An assumption is made by researchers that the muscovite is equivalent to that used by all others. Our studies, of a single fs laser pulse interacting with high quality sheet muscovite, conclude this is not always appropriate. Our studies have been conducted with two different laser systems. One at 800 nm with ~150 fs pulse duration [2], [3]. The second at 515 nm and ~190 fs pulse duration [4]. The laser beam is Gaussian, in both cases, with a focused spot size of 6–7 μm. The laser-modified site is characterized in multiple ways. Measurement of the laser modified site diameter differentiates four non-standard regions-of-outcome at 800 nm, and finds a polymer-like material modification at 515 nm (fig. 1 (b)). In the case of 800nm, a rich, systematic evolution of the modified site topography is found. Key reasons for the differences in fs laser pulse interaction for muscovite compared to other crystalline optical materials are: (i) its nanolayered structure; (ii) the impact of mineral water; and (iii) band-gap differences due to natural variations in the standard chemical composition
$(\text{KA}1_{2}(\text{Si}3\mathrm{A}1)\mathrm{O}_{10}(\text{OH})_{2})$
. Laser/material interaction studies, combined with microscopies, time of flight secondary ion mass spectroscopy [5] and light-based spectroscopies, emerge as tools for studying the mineral, in addition to achieving laser shaping, patterning, and chemical modification outcomes. A full description of muscovite fs laser processing to date will be presented.