Electron. Mater. Lett., Vol. 10, No. 2 (2014), pp. 351-355 Fabrication of Nano-Structures on Glass Substrate by Modified Nano-Imprint Patterning with a Plasma-Induced Surface-Oxidized Cr Mask So Hee Lee, 1 Su Yeon Lee, 1 Seong Eui Lee, 1 Heon Lee, 2, * and Hee Chul Lee 1, * 1 Department of Advanced Materials Engineering, Korea Polytechnic University, Korea 2 Division of Materials Science and Engineering, Korea University, Korea (received date: 24 July 2013 / accepted date: 28 August 2013 / published date: 10 March 2014) In this study, we introduce a process for fabrication of nano-sized structural arrays on glass using modified nano- imprint patterning. A PVC (polyvinyl chloride) stamp was prepared by hot embossing, and a Cr-oxide-pattern etch-mask was used. The etch-mask was formed by oxidizing the surface of exposed Cr region by oxygen plasma treatment at room temperature. The fabrication of the etch-mask was conducted by immersing the locally oxidized Cr pattern in resin remover and Cr-etchant. The residual UV resin and un-oxidized Cr pattern were selectively removed, resulting in the obvious array of Cr-oxide etch-mask-pattern. The array of glass nano- structures was formed by reactive ion etching (RIE) using CF4 and Ar gas discharge. After removing the Cr- oxide mask, the final nano-structure had a height of 40 nm and a diameter of 170 nm, which was slightly less than the diameter of the original master-mold. The plasma treatment gave rise to a rough glass surface with root- mean-square (RMS) roughness of 29.25 nm, while that of bare glass was 0.66 nm. A high optical transmittance due to reduction in reflectance was observed at the plasma-treated rough surface, as well as for the array of nano- structures. The highest measured optical transmittance was 97.2% at a wavelength of 550 nm; an increase of about 7.2% compared to bare glass. Keywords: nano-imprint lithography, nano-structures, glass patterning, optical transmittance, plasma oxidation 1. INTRODUCTION Recently, glass substrates are in great demand for industrial applications such as solar cells, flat panel display, and touch sensor panels. For such optical devices, efficient use of light through functional patterning is greatly needed. However, fine patterning of glass is difficult, and up-to-date glass- patterning methods include random chemical etching and direct laser writing. In chemical etching, it is hard to form structures with arbitrary micro- to nano-dimensions, [1-3] while laser writing has the problems of not only slow production yield, but also thermal deformation of the glass substrate during the process. [4] Accordingly, in this study, fabrication of nano-structures has been carried out by nano-imprint lithography (NIL) owing to its high throughput and dimensional accuracy. [5-9] Also, NIL has the potential to generate sub- 10 nm fine patterns. [10] For the etch-masks used for nano- imprinting, metal films are preferred to oxide ones because they are easy to form on substrates. However, metal masks suffer from low etch selectivity. Oxide masks require long deposition times as well as high temperatures which could cause bending of the glass substrates. In the present work, we have adopted a modified nano- imprint patterning technique that includes successive plasma surface oxidation of pre-deposited metal masks at room temperature. Additionally, plasma treatment using CF 4 and Ar was introduced in order to obtain better optical trans- mittance of the glass substrate after creation of the array of nano-patterns. 2. EXPERIMENTAL PROCEDURE 2.1 Fabrication of a PVC stamp Figure 1 depicts our whole procedure for nano-sized patterns on glass. Hot embossing was used to fabricate a polyvinyl chloride (PVC) thermo-plastic polymer stamp for UV nano-imprint patterning. As shown in Fig. 1(a), hot embossing was implemented at 120°C, which is above the glass temperature of PVC. With a pressure of 20 bar, the pattern of the master mold could be replicated to the surface of the PVC substrate. For fine pattern transfer, the master mold was treated with releasing agent for easy detachment from the embossed polymer after imprinting. [11] Otherwise, the polymer sticks to the grooves of the master mold and causes severe distortion of the transferred patterns. The monolayer of releasing material [(heptadcafluoro-1,1,2,2- tetra-hydrodecyl) tricholoro-silane (CF 3 (CF 2 ) 5 (CH 2 ) 2 SiCl 3 )] was formed on the mold surface by self-assembly in the DOI: 10.1007/s13391-013-3230-z *Corresponding author: heon.lee@gmail.com *Corresponding author: eechul@kpu.ac.kr ©KIM and Springer