Study of Surface Morphological Evolution by Cluster Ion Irradiation on Solid Targets
- PDF / 464,161 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 69 Downloads / 195 Views
W17.9.1
Study of Surface Morphological Evolution by Cluster Ion Irradiation on Solid Targets Takaaki Aoki1, Atsuko Nakai, Jiro Matsuo and Gikan Takaoka Ion Beam Engineering Experimental Laboratory, Kyoto University, Sakyo, Kyoto, 606-8501, JAPAN 1 Collaborative Research Center for Cluster Ion Beam Process Technology ABSTRACT Smoothing effect by large gas cluster ion irradiation was studied. Ar cluster ion beams were irradiated on rough Si surface with various ion dosage. 100×100µm2 AFM image was measured for each surface. These AFM images were treated with fast Fourier transform in order to examine the change of surface morphologies with cluster ion irradiation. Power spectra analysis showed that the intensity at each wave number (the inverse number of wavelength) exponentially decreases with ion dose. The relationship between smoothing rate and wave number was derived. The surface smoothing process was modeled with the use of this wave number dependence on decreasing rate. The calculated and the experimental surface profiles are in good agreements. With this model, roughness of cluster-irradiated surface can be calculated from initial surface images. INTRODUCTION For the last decade, gas cluster ion beam process has been proposed as the promised technique to achieve nano-scale surface modifications and thin film formations. Gas cluster can be generated by letting source gases such like Ar and O2 through Laval nozzle with high pressure [1]. By this method, high intensity (several hundred micro Amperes) and large size (ranges from several tens to several tens thousand) cluster ion irradiation can be achieved [2]. As shown in previous experiments and computer simulations, the impact process of such large cluster and solid surface is completely different from that by monomer ion [3,4,5]. This is due to the fact that cluster ion impact realizes low-energy and high-density atomic irradiation simultaneously. Therefore, when a cluster impacts onto a solid target, the target atoms at the shallow surface region are exposed by abundant collisions with incident atoms, which results in local heating, large motion and high chemical excitation of surface atoms. Many experiments have proved that cluster irradiation has advantages in thin film formation [6], surface smoothing [7] and high-rate and high-aspect etching [8]. Surface smoothing is one of the important applications of cluster ion irradiation and is started to be used for industrial applications [9]. The fundamental theories about smoothing effect with cluster ions were studied. The previous works [10] showed that, at the impact of cluster impact, the surface atoms are moved along the lateral direction to the surface, which contributes the reduction of hill-and-valley structure of the surface. Another group proposed the analytical formula to describe the smoothing effect during metal cluster ion deposition [11,12]. However, the quantitative study, such like smoothing effects dependence on surface structure, material, cluster size, etc., is still unknown. In this study, t
Data Loading...
