Font Size: a A A

Laser Fabrication Of Large-area Periodic Micro/nano-Structures

Posted on:2016-02-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:L WangFull Text:PDF
GTID:1108330473961744Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
Periodic micro/nano structure processing technology has been playing an important role in microelectronics, microfluidics, micro-optics for surface modification, super-hydrophobic structure surface, optics polarizer. There are lots of technologies for fabricating periodic microstructure on hard materials, such as nanoimprint technology, photolithography, self-assembly technology. By using these technologies, the process can be divided into two steps. The first step was to make a mask or sacrificial layer, for example, periodic gratings or dots in photoresist by two-beam-interference exposure, mold for nanoimprint, spheres for self-assembling. Then dry and wet etching, such as solution etching, ICP, RIE, EBL, and nanoimprint was executing to transfer the structures from mask to substrate. Although these technologies have their advantages, it’s troubled by template production, corrosion solution and material choices.Laser processing has the advantages of direct writing by light-absorbing under high energy density of pulsed laser of low costs, high quality, fine precision, non-flat three dimensional fabrication ability in transparent medium. In this paper, we achieved the following outcomes using two-beam interference nanosecdrid laser ablation technology, femtosecond laser tailoring technology, femtosecond laser induced micro/nano-structure technology:(1) Fabrication of large-area infrared subwavelength antireflection structure surface by multiple exposure of two-beam interference ablation:In order to solve the falling of antireflection coatings due to mismatch of coating and substrate, difference of thermal expansion coefficient, inspired by subwavelength structures called "moth eye", we studied the mechanism of antireflection structures and fabricated large-area antireflection structure surface by multiple exposure of two-beam interference on infrared znic sulfide (ZnS) windows. The transmittance achieved at 7μm~10μm is more than 90% and keeps more than 80% when the tilting angle is more than 40o at 7.5μm~10μm. We also studied the multiple beam interference and fabricated periodic or quasi-periodic structures by multiple exposure of two-beam interference. The structures possess high transmittance and hydrophobic ability. By adding difference period, we achieved hybrid structures with multi-functional abilities.(2) Large-area hybrid micro/nano-structures by femtosecond laser tailoring ablation:Nanosecond laser interference ablation is a technology for fabrication of large-area periodic structure surface. For femtosecond laser, it seems a wider application due to higher intensity, less selective ability to materials, finer precision. However, the short coherence length of only a few microns to tens of microns obstructs it and limits the wide application of femtosecond laser interference. We propose here a method, using a phase mask and a cylindrical lens processing, to achieve long distance femtosecond laser interference in one direction. While in the vertical direction, a motor was used to drag the sample to achieve large-scale periodic micro-nano hybrid structures. Additionally, subwavelength structures can be induced by femtosecond laser. By using femtosecond laser interference, large-area hybrid structures are supposed to surface modification, such as hydrophobic of water and oil. Here, large-area periodic micro/nano structure surface were fabricated by optimized laser power, exposure time and polarization.(3) Large-area micro/nano structures induced by femtosecond laser:Femtosecond laser induced micro/nano-structures has been demonstrated on metals, semiconductors and inside transparent mediums. By using this phenomenon, we can fabricate periodic structures quickly. However, it is difficult to fabricate large-area uniform periodic structure for the ablation pits is usually severval microns to hundrunds of microns. Scaning was used to solve this prolem to obtain large-area but chaos structure surface. Here we used a cylindrical lens scanning technology to obtain a good periodic extensive deep subwavelength structure surface; By doping AgNO3 into PVA, we achieve the preparation of periodic structures, and validated the localized surface plasma model in structure origination; By covered method, we achieved fabrication of large-area structure surface on narrow band semiconductors.
Keywords/Search Tags:Laser fabrication, two-beam interference, antireflection, sub-wavelength structures, femtosecond laser interference, light tailoring, hybrid structures, laser induced periodic structure, large-area, deep-subwavelength structures
PDF Full Text Request
Related items