Iron films deposited on porous alumina substrates
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Iron films deposited on porous alumina substrates Yasuhiro Yamada1 · Kenichi Tanabe1 · Naoki Nishida1 · Yoshio Kobayashi2,3
© Springer International Publishing Switzerland 2016
Abstract Iron films were deposited on porous alumina substrates using an arc plasma gun. The pore sizes (120 – 250 nm) of the substrates were controlled by changing the temperature during the anodic oxidation of aluminum plates. Iron atoms penetrated into pores with diameters of less than 160 nm, and were stabilized by forming γ -Fe, whereas α-Fe was produced as a flat plane covering the pores. For porous alumina substrates with pore sizes larger than 200 nm, the deposited iron films contained many defects and the resulting αFe had smaller hyperfine magnetic fields. In addition, only a very small amount of γ -Fe was obtained. It was demonstrated that the composition and structure of an iron film can be affected by the surface morphology of the porous alumina substrate on which the film is grown. Keywords Iron film · Porous alumina · Gamma-iron · Alpha-iron
1 Introduction The properties of thin iron films are affected by the surface morphology of the films and their substrates. We previously demonstrated that when an aluminum foil with 100-nm grooves was employed as a substrate, the surface of the iron film also contained grooves.
This article is part of the Topical Collection on Proceedings of the 2nd Mediterranean Conference on the Applications of the M¨ossbauer Effect (MECAME 2016), Cavtat, Croatia, 31 May-3 June 2016 Yasuhiro Yamada
[email protected] 1
Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
2
The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan
3
RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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Furthermore, the nuclear spin orientation of the iron tended to be linear along the grooves [1]. The energy of the evaporated iron atoms is also important to control the orientation of the iron lattice structure [2]. An arc plasma gun is an adequate tool for depositing iron films that reflect the morphology of the substrate. In this study, iron films were prepared on porous alumina substrates, and the effects of pore size were investigated using M¨ossbauer spectroscopy. Porous anodic alumina films have attracted considerable attention in the field of nanotechnology, because they have a nanoscale porous structure. The pores are produced over a wide area of the aluminum surface, and the surface structure contains a huge number of nanoscale holes. The formation mechanism of porous alumina has been studied extensively [3]. The morphology of porous alumina on an aluminum film can be controlled by an appropriate selection of the electrolyte and film-forming conditions. Furthermore, porous alumina has been used as a template for producing nanomaterials. The preparation of Ni, Co, and Fe nanowires using an electrochemical method has been reported [4]. Lepidocrocite γ -FeOOH nanowire arrays in alumina pores w
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