Surface analysis of nanomachined films using atomic force microscopy

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Materials Chemistry and Physics 92 (2005) 379–383

Surface analysis of nanomachined films

using atomic force microscopy

Te-Hua Fang

a

, Win-Jin Chang

b,∗

, Cheng-I Weng

c

a_{Department of Mechanical Engineering, Southern Taiwan University of Technology, Tainan 710, Taiwan} b_{Department of Mechanical Engineering, Kun Shan University of Technology, Tainan 710, Taiwan}

c_{Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan}

Received 13 July 2004; received in revised form 28 December 2004; accepted 9 January 2005

Abstract

Surface analyses of nanomachined films are performed using atomic force microscopy. Both surface roughness and fractal dimension are the important factors in all areas of nanotribology and in evaluating the quality of a nanomachining operation. Nanomachining experiments are conducted to investigate the influence of the hardness of a material on the surface properties. Results indicate that the same load causes different depths of groove in the different materials studied (Ta, Pt). Rougher surfaces are produced by larger depths of groove. In addition, the fractal dimension increases as the load increases.

Keywords: Nanomachining; Atomic force microscopy; Roughness; Fractal dimension; Nanolithography

1. Introduction

Atomic force microscopy (AFM) has recently been ap-plied to nanoscale lithography. The advantage of using the AFM-based technique over the conventional optical and electron-beam lithography techniques is that the resolution may be much better. This is because the resolution is solely determined by the geometry of the AFM probe [1], and thus the radius of the probe’s tip determines the resolution. Conventional and AFM-based lithographic techniques can be combined to improve the resolution of fabrication tech-nologies [2]. This can contribute to the research in low-dimensional physics and to the fabrication of nanoelectronic devices[2,3]. Thus, further study of AFM-based lithography is needed to increase the understanding of its nanomechanical and processing characteristics.

AFM-based lithography research can be roughly divided into three categories: (1) local electro-chemical reactions

∗_{Corresponding author. Tel.: +886 6 2050883.}

E-mail address: [email protected] (W.-J. Chang).

of silicon and metals [4,5]; (2) direct atomic and molec-ular manipulation [6]; (3) direct cutting of the material

[1–3,7]. The direct cutting of materials has so far been use-ful for fabricating nanodevices. An AFM probe is com-monly used to scratch a fine groove or hole in a soft metal or polymer surface [7]. This technique has been success-fully used in conjunction with appropriate etching processes to fabricate multilayer nanodevices [1,2]. Previous AFM-based lithographic studies [8–10]are focused on the nan-otribological properties. However, studies on AFM-based lithography machining processes are scarce, but a better understanding of these processes is indispensable to in-crease the reliability, stability and controllability of this tech-nique.

Two different analyses, namely surface roughness and fractal analysis, are of fundamental importance in observ-ing physical phenomena on a film surface such as roughness

[11–14]. In this study, the characteristics of surface roughness and fractal dimension are investigated by conducting AFM-based nanomachining experiments on both hard and soft film surfaces.

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T.-H. Fang et al. / Materials Chemistry and Physics 92 (2005) 379–383 383 Acknowledgement

This work was supported by the National Science Council of Taiwan, under Grant Nos. NSC 93-2212-E-218-005 and NSC 93-2212-E-168-020.

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