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Fabrication of periodic arrays of microholes in thin Ag-films by femtosecond laser pulses

The threshold parameters of laser radiation for their formation are also determined by the thickness of a modified film (“size effect”) and by the duration of a laser pulse owing to the lateral heat conduction in the films (nonlocal energy deposition effect). The mechanisms for microholes formation in the silver thin films by using the femtosecond laser pulses have been discussed. | Journal of Science and Technology 55 (1) (2017) 35-43 DOI: 10.15625/0866-708X/55/1/7904 FABRICATION OF PERIODIC ARRAYS OF MICROHOLES IN THIN Ag-FILMS BY FEMTOSECOND LASER PULSES Nguyen Thi Huyen Trang1, 2, 3 1 2 Ha Tinh University, Ha Tinh, 447, 26/3 street, Dai Nai ward, Ha Tinh city, Vietnam Lebedev Physical Institute, Russian Academy of Sciences, Leninskii pr. 53, Moscow, 119991 Russia 3 Moscow Institute of Physics and Technology (State University), Institutskii per. 9, Dolgoprudnyi, Moscow region, 141700 Russia * Email: trang.nguyenthihuyen@htu.edu.vn Received: 16 March 2016; Accepted for publication: 25 November 2016 ABSTRACT Arrays of microholes with different diameters of 2, 3, 4 µm and period 6 µm were produced in thin silver films with thicknesses of 100, 150 nm by using single femtosecond laser pulses with variable pulse energies, focused by different strong focusing optics. The fabricated microholes are regular in size and shape throughout large sample area. The irradiation using an ultrashort laser pulse results concern not only the melting of the film but also the exfoliation in the form of nanojets. Atomic force and electron microscopy studies have demonstrated the shape and dimension of the nanostructures. The threshold parameters of laser radiation for their formation are also determined by the thickness of a modified film (“size effect”) and by the duration of a laser pulse owing to the lateral heat conduction in the films (nonlocal energy deposition effect). The mechanisms for microholes formation in the silver thin films by using the femtosecond laser pulses have been discussed. Keywords: femtosecond laser, microholes, thin film, SEIRA. 1. INTRODUCTION Nanoholes in thin metallic films are the most simple and popular nano-optical elements, providing in their apertures nanoscale transmission, frequency conversion and local enhancement of electromagnetic waves [1 - 3]. Currently, the basic nanohole characteristics (diameter, depth) are .