Periodic patterning of silicon by direct nanosecond laser interference ablation

2012 International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3m-Nano)

Zhang³

et al. 2012

Periodic and quasi-periodic structures on silicon surface have numerous significant applications in photoelectronics and surface engineering. A number of technologies have been developed to fabricate these structures in various research areas. In this work, we take the strategy of direct nanosecond laser interference patterning technology. Well-defined grating and dot structures have been achieved and interactive thermal effect was observed obviously. Additionally, the height and width of different structures were analyzed by AFM. It can be demonstrated that direct laser interference lithography is a promising technology which has the capability for the manufacturing of micro and nano structures.Index Terms-Direct laser interference patterning, micro and nano structures, thermal effect.

Section: Discussionmentioning

confidence: 90%

Modification of silicon surface by direct laser interference

2012 International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3m-Nano)

Zhang³

et al. 2012

“…Fig.2 Simulation results of (a) two-dimensional and (b) three-dimensional intensity distribution of three-beam laser interference with the incident angle of 3° and the period of 12 µm A three-beam interference system was built to produce the interference pattern for inducing concave structures on the stent surface. The structure is a direct consequence of the intensity modification [20] . Due to the high laser fluence, melt and evaporation behaviors of the laser ablation are the main mechanisms to modify the surface [19] .…”

Section: Fig1 Photo Of the Compressed And Expanded Coronary Artery Smentioning

confidence: 99%

Fabrication of hydrophobic structures on coronary stent surface based on direct three-beam laser interference lithography

Gao

Zhou

et al. 2016

Optoelectron. Lett.

To solve the problems with coronary stent implantation, coronary artery stent surface was directly modified by three-beam laser interference lithography through imitating the water-repellent surface of lotus leaf, and uniform micro-nano structures with the controllable period were fabricated. The morphological properties and contact angle (CA) of the microstructure were measured by scanning electron microscope (SEM) and CA system. The water repellency of stent was also evaluated by the contact and then separation between the water drop and the stent. The results show that the close-packed concave structure with the period of about 12 µm can be fabricated on the stent surface with special parameters (incident angle of 3°, laser energy density of 2.2 J·cm -2 and exposure time of 80 s) by using the three-beam laser at 1 064 nm, and the structure has good water repellency with CA of 120°.The coronary artery stent implantation has become the first choice for the treatment of coronary heart disease (CHD) in the world currently. Although the equipment and medication are increasingly improved, in-stent restenosis (ISR) is still a major defect of stent implantation [1] . Due to the occurrence of restenosis, still more than 15% patients with coronary stent implantation will accept interventional therapy in a year [2] . Therefore, it is of great significance to develop a new type of coronary stent, which has low restenosis rate and can prevent late stent thrombosis. In recent years, the studies show that the biocompatibility of the materials could be increased by the biomimetic process of surface and coating [3][4][5][6][7][8] . Consequently, the preparing bionic surface with regular geometric structure is beneficial to the rapid, directional and orderly adhesion and the growth of endothelial cells, which can reduce the formation of restenosis and late thrombosis.Laser interference lithography (LIL) has been applied in many fields, such as solar cells [9,10] , nano-scale patterned sapphire substrate [11] and bionics [12,13] . And studies have shown that the minimum feature size of direct LIL can reach 27 nm (laser wavelength of 308 nm, pulse width no more than 10 ns) [14] , which can fully meet the requirements of the process in this paper. Compared with other approaches, such as electron beam lithography, ion beam lithography and scanning probe lithography, which adopt the point by point writing strategy [15,16] , LIL reduces the required processing time by using multi-beam simultaneously. In addition, the long focal depth and the maskless process of LIL lower the flatness requirements of substrate and can realize imaging on a non-planar surface without affecting the resolution and image contrast.In this paper, LIL is used to modify the surface of coronary stent by imitating the water-repellent surface of lotus leaf. Test results show that the processed stent has good water repellency, which can achieve the desired effects.LIL is very suitable to process the coronary stent with the structure of mesh tubes, as shown in Fig....

“…The intensities of interference is expressed as To study the interaction between the effective intensity distribution and the threshold of the material, the simulation of direct four-beam laser interference exposure is performed to obtain the interference patterns. [21][22][23][24] In the simulation, the interference patterns with different effective intensity distribution shapes are obtained, as shown in Fig. 2.…”

Section: Direct Four-beam Interferencementioning

confidence: 99%

Effective intensity distributions used for direct laser interference exposure

Zhang

et al. 2015

RSC Adv.

This paper presents a method to obtain the periodic structures with different feature shapes in direct laser interference lithography. In the method, the desired structures are produced by controlling the effective intensity distributions of interference patterns during the exposure process. The effective intensity distributions are adjusted by changing the exposure beam intensity based on the material modification thresholds. In the simulations and experiments, the different exposure intensities were used to study the interactions between effective intensity distributions and materials, and the direct four-and six-beam laser interference lithography systems were set up to pattern silicon wafers. The shapes and sizes of the fabricated surface structures were changed with the effective intensities. The experimental results are in accordance with the theoretical models and simulations.