Electrochemical Nanopatterning on Copper Surface Using an AFM Cantilever Tip
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Electrochemical Nanopatterning on Copper Surface Using an AFM Cantilever Tip Gyudo Lee1, Kihwan Nam1, Suho Jeong1, Huihun Jung1, Bumjoon Choi1, Sang Woo Lee1, Dae Sung Yoon1, Kilho Eom2 and Taeyun Kwon1 1 Biomedical Engineering, Yonsei University, Wonju, Kangwon, Korea, Republic of. 2 Mechanical Engineering, Korea University, Seoul, Korea, Republic of.
ABSTRACT In this paper, we present technique to fabricate nanopatterns on Cu thin films via an electrochemical nanomachining (ECN) using an atomic force microscope (AFM). A conductive AFM cantilever tip (Pt/Ir5 coated) was used to form an electric field between tip and Cu substrate with applying a voltage pulse, resulting in the generation of an etched nanopattern. In order to precisely construct the nanopatterns, an ultra-short pulse was applied onto the Cu film through the AFM cantilever tip. The line width of the nanopatterns (the lateral dimension) increased with increased pulse amplitude, on-time, and frequency. The tip velocity effect on the nanopattern line width was also investigated that the line width is decreased with increasing tip velocity. Experimental results were compared with an equivalent electrochemical circuit model representing an ECN technique. The study described here provides important insight for fabricating nanopatterns precisely using electrochemical methods with an AFM cantilever tip. INTRODUCTION For the investigation of micro- and nano-size materials including biomaterials such as DNA, RNA, and virus, the micro- and/or nano- structures were manufactured by MEMS and NEMS techniques [1,2]. In recent years, nano-scale features have been fabricated more precisely and easily using AFM, as a result of the development of a nano scaled AFM tip [3-5]. The first effort to create nanopatterns on a metal substrate by using ECN technique was reported by Abril et al. [6]. Applying an ultra-short pulse to the metal surface through the AFM cantilever tip in a solution, nano sized holes and lines were successfully built on the metal surface. Here we report the effect of the electrical pulse parameters on the fabrication of nanopatterns on a Cu film through a single-step ECN using AFM conductive probes. Various electrical pulse parameters can be manipulated to control the localization of the current distribution around a nanoscaled target region between the AFM tip apex and the metal surface [7], resulting in the successful fabrication of the nanopatterns with various line widths. In addition, a numerical study was performed employing the same parameters used in the experiment to model the ECN process. The experimental and numerical results were compared in order to gain insight into the effect of the electrical pulse parameters on the fabrication of nanomachined patterns.
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EXPERIMENT The schematic diagram for the experimental setup is shown in figure 1(a). A copper film was deposited on Si (100) wafer by a thermal evaporator, and its thickness (200 nm) was confirmed by a thickness monitor. A mixture of 0.1 mM HClO4 and 0.01 mM CuSO4 solutions was u
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