Selective Growth of Al Nanowhiskers on the Patterned Substrate by Glancing Angle Deposition at High Temperature
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1054-FF09-04
Selective Growth of Al Nanowhiskers on the Patterned Substrate by Glancing Angle Deposition at High Temperature Motofumi Suzuki, Ryo Kita, Kenji Hamachi, Koji Nagai, Kaoru Nakajima, and Kenji Kimura Department of Micro Engineering, Kyoto University, Yoshida, Sakyo, Kyoyo, 606-8501, Japan ABSTRACT We have demonstrated high-temperature glancing angle deposition (HT-GLAD) of Al on a heated substrate with trench patterns. When Al is deposited under the condition where the Al vapor is incident at the glancing angle on the sidewall but not on the surface, Al nanowhiskers grew only on the sidewall of the trenches since the HT-GLAD condition was achieved only for the sidewall. However, when Al is deposited at the glancing angles both on the surface and on the sidewalls, nanowhiskers grew both on the surface and on the sidewalls of the trenches. The selective growth of the nanowhiskers has been successfully achieved by controlling the geometrical deposition conditions. Remarkably, the nanowhiskers grow not only on the illuminated sidewall but also on the shadowed sidewall. In addition, few nanowhiskers grow on the shadowed region at the bottom of the trenches. In order to understand the peculiar growth of Al nanowhiskers, novel transport processes of Al atoms other than surface diffusion need to be elucidated. The reevaporation or reflective scattering on the sidewalls of the trenches is likely to play an important role in the growth of nanowhiskers. INTRODUCTION Very recently, we have found that peculiar Al nanowhiskers are grown when Al is deposited at a glancing angle on a high-temperature substrate (HT-GLAD) [1, 2]. Not only Al nanowhiskers but also various metal nanowhiskers are expected to be grown by HT-GLAD [2, 3]. The key factors for producing nanowhiskers are a glancing deposition angle larger than 80° and a temperature higher than almost half of the melting point of the metal. Since the growth of the nanowhiskers may be concerned with the general crystal growth mechanisms, an understanding of the growth mechanisms will provide a novel technique to fabricate nanostructures. Further, if the growth of nanowhiskers is controlled, metal nanowhiskers will become important components for nanoelectromechanical devices because of their mechanical compliance, high electric and thermal conductance, catalysis, plasmonic properties, magnetism, etc. Since the growth of the nanowhiskers by using the HT-GLAD method is very sensitive to the geometric deposition conditions, the growth position of the nanowhiskers is expected to be controlled by using a patterned substrate. From a fundamental viewpoint, by utilizing the shadow cast by micropatterns, we can obtain important information on the influence of the surface diffusion and other transport processes on the growth of the nanowhiskers. In this paper, we report the first experimental results of the growth of Al nanowhiskers by using HT-GLAD on a substrate with trench patterns.
Figure 1. Schematic drawings of the deposition geometry. (a) Relation between the source
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