Surface irradiation and materials processing using polyatomic cluster ion beams

Abstract

We developed a polyatomic cluster ion beam system for materials processing, and polyatomic clusters of materials such as alcohol and water were produced by an adiabatic expansion phenomenon. In this article, cluster formation is discussed using thermodynamics and fluid dynamics. To investigate the interactions of polyatomic cluster ions with solid surfaces, various kinds of substrates such as Si (100), SiO 2 , mica, polymethyl methacrylate, and metals were irradiated by ethanol, methanol, and water cluster ion beams. To be specific, chemical reactions between radicals of polyatomic molecules and surface Si atoms were investigated, and low-irradiation damage as well as high-rate sputtering was carried out on the Si(100) surfaces. Furthermore, materials processing methods including high-rate sputtering, surface modification, and micropatterning were demonstrated with ethanol and water cluster ion beams.

Nanocluster Ions and Beam Techniques for Material Modification

“…The equation indicates that the rate of chemical reaction increases with increasing temperature. Figure 11 shows the sputtering yields for Al, Si, Ti, Ni, Cu, Ag, and Au surfaces at an acceleration voltage of 9 kV [27]. In the figure, the sputtering yields due to irradiation of Ar monomer ion beams at the same acceleration voltage are also shown, and these agree with the values estimated by computer simulations [51].…”

“…The cluster size was measured by the time-of-flight (TOF) method [27]. As shown in Figure 1, the cluster size was distributed between a few hundred molecules and a few tens of thousands of molecules.…”

“…This indicates that a more conductive IL is obtained when it contains Au clusters. Figure 8 shows a schematic of the impact of cluster ions on a solid surface [27,46]. The diameter of a cluster comprising several thousand molecules is a few nanometers, and these clusters penetrate the solid surface to a depth of only a few nanometers.…”

“…For physical sputtering, the energy range is larger than a few tens of electron volts per molecule. For chemical sputtering, it is a value between a few electron volts and a few tens of electron volts per molecule [27]. For energy less than a few electron volts per molecule, a damage-free region is achieved [49,52].…”

“…In particular, radicals contained in a liquid molecule have attracted much interest in terms of chemical reactions on the surface. Thus, the liquid cluster ion beam technique plays an important role in advanced material processing as a new way of using liquid materials [27].…”