Ziang Zhang

Effects of polarization on four-beam laser interference lithography

This paper demonstrates that polarization plays an important role in the formation of interference patterns, pattern contrasts, and periods in four-beam interference lithography. Three different polarization modes are presented to study the effects of polarization on four-beam laser interference based on theoretical analysis, simulations, and experiments. A four-beam laser interference system was set up to modify the silicon surface. It was found that the secondary periodicity or modulation was the result of the misaligned or unequal incident angles only in the case of the TE-TE-TM-TM mode. The resulting patterns have shown a good correspondence with the theoretical analysis and simulations.

Fabrication of moth-eye structures on silicon by direct six-beam laser interference lithography

This paper presents a new method for the generation of cross-scale laser interference patterns and the fabrication of moth-eye structures on silicon. In the method, moth-eye structures were produced on a surface of silicon wafer using direct six-beam laser interference lithography to improve the antireflection performance of the material surface. The periodic dot arrays of the moth-eye structures were formed due to the ablation of the irradiance distribution of interference patterns on the wafer surface. The shape, size, and distribution of the moth-eye structures can be adjusted by controlling the wavelength, incidence angles, and exposure doses in a direct six-beam laser interference lithography setup. The theoretical and experimental results have shown that direct six-beam laser interference lithography can provide a way to fabricate cross-scale moth-eye structures for antireflection applications.

Superhydrophobic dual micro- and nanostructures fabricated by direct laser interference lithography

Abstract. A method for the fabrication of highly ordered superhydrophobic dual micro- and nanostructures on silicon by direct laser interference lithography (LIL) is presented. The method offers its innovation that the superhydrophobic dual micro- and nanostructures can be fabricated directly by controlling the process of four-beam laser interference and the use of hydrofluoric acid (HF) to wipe off the silica generated during the process. Different laser fluences, exposure durations, and cleanout times have been investigated to obtain the optimum value of the contact angle (CA). The superhydrophobic surface with the CA of 153.2 deg was achieved after exposure of 60 s and immersion in HF with a concentration of 5% for 3 min. Compared with other approaches, it is a facile and efficient method with its significant feature for the macroscale fabrication of highly ordered superhydrophobic dual micro- and nanostructures on silicon.

Periodic antireflection surface structure fabricated on silicon by four-beam laser interference lithography

Silicon surface structures with excellent antireflection property arouse wide interest. Chemical and physical methods such as femtosecond, nanosecond, and picosecond laser processing, wet-chemical etching, electrochemical etching, and reactive ion etching have been developed to fabricate them. However, the methods can only produce a quasi-ordered array of sharp conical microspikes on silicon surface. In this paper, we present a method to fabricate periodic silicon antireflection surface structures using direct four-beam laser interference lithography (LIL). With 1 atm ambient atmosphere of SF6 and the laser fluence of the four beams irradiated on the silicon surface at 0.64 J cm−2, the periodical conical spikes were generated. Changing the polarization directions of the opposite incident beam pairs in a four-beam LIL system could convert conical spikes structure into an array of holes. Antireflection in a wide spectral range was measured by a spectrophotometer from ultraviolet to near-infrared. The averag...

Both antireflection and superhydrophobicity structures achieved by direct laser interference nanomanufacturing

Inspired by nature, a number of techniques have been developed to fabricate the bionic structures of lotus leaves and moth eyes in order to realize the extraordinary functions of self-cleaning and antireflection. Compared with the existing technologies, we present a straightforward method to fabricate well-defined micro and nano artificial bio-structures in this work. The proposed method of direct laser interference nanomanufacturing (DLIN) takes a significant advantage of high efficiency as only a single technological procedure is needed without pretreatment, mask, and pattern transfer processes. Meanwhile, the corresponding structures show both antireflection and superhydrophobicity properties simultaneously. The developed four-beam nanosecond laser interference system configuring the TE-TE-TE-TE and TE-TE-TE-TM polarization modes was set up to generate periodic micro cone and hole structures with a huge number of nano features on the surface. The theoretical and experimental results have shown that the periodic microcone structure exhibits excellent properties with both a high contact angle (CA = 156.3°) and low omnidirectional reflectance (5.9–15.4%). Thus, DLIN is a novel and promising method suitable for mass production of self-cleaning and antireflection surface structures.

Fabrication of Pt nanowires with a diffraction-unlimited feature size by high-threshold lithography

Although the nanoscale world can already be observed at a diffraction-unlimited resolution using far-field optical microscopy, to make the step from microscopy to lithography still requires a suitable photoresist material system. In this letter, we consider the threshold to be a region with a width characterized by the extreme feature size obtained using a Gaussian beam spot. By narrowing such a region through improvement of the threshold sensitization to intensity in a high-threshold material system, the minimal feature size becomes smaller. By using platinum as the negative photoresist, we demonstrate that high-threshold lithography can be used to fabricate nanowire arrays with a scalable resolution along the axial direction of the linewidth from the micro- to the nanoscale using a nanosecond-pulsed laser source with a wavelength λ0 = 1064 nm. The minimal feature size is only several nanometers (sub λ0/100). Compared with conventional polymer resist lithography, the advantages of high-threshold lithogra...

Effective intensity distributions used for direct laser interference exposure

This paper presents a method to obtain periodic structures with different feature shapes using 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, different exposure intensities were used to study the interactions between the effective intensity distributions and the materials, and 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 changed with the effective intensities. The experimental results are in accordance with the theoretical models and simulations.

Tunable oscillatory phenomenon during anodic of n-InP (100) by the CPCR model

Tunable potential oscillations were observed during electrochemical etching of n-InP(100) in 3M NaCl solution at the model of the chronopotentiometry with current ramp. These results demonstrated that the scan rate, stirring and front illumination can regulate on the amplitude of potential oscillation, which indicated that the amplitude can be designed at certain electrochemical parameters, such as the range of current density and the scan rate.

Silicon wafer modification by laser interference

This paper presents the study of silicon wafer modification by two-beam laser interference. In the work, two-beam laser interference was used to pattern single crystal silicon wafers for the fabrication of gratings, and different laser fluences and pulses were applied to the process in the air. The results were obtained from single laser pulse exposures with the laser fluences of 637mJ/cm2, 780mJ/cm2 and 1280mJ/cm2. The role of multiple laser pulses was also investigated. In the experiment, the laser wavelength was 1064nm, the pulse duration 7-9ns and the repetition rate 10Hz. The results indicate that the laser fluence and number of pulses have to be properly selected for the fabrication of gratings using laser interference.

Modification of silicon surface by direct laser interference

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.