Structures and Properties of Quasi-Multilayered Nanocomposites
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STRUCTURES
AND PROPERTIES OF
QUASI-NULTILAYERED
NANOCOMPOSITES
T.Motohiro, Y.Watanabe, Y.Takeda & S.Noda, Toyota Central R & D Labs., Inc. Nagakute-cho, Aichi-gun, Aichi-ken,480-11,Japan. Nagoya Univ. Furou-cho, Chikusa-ku, T.Tokizaki and A. Nakamura. Nagoya-shi, Japan. ABSTRACT Vertical sections of multilayers (VSM) should provide excellent testing grounds for physics and chemistry on surfaces with densely populated heterogeneous interfaces. Although VSM can be obtained from usual horizontal multilayers stacks by crushing them into pieces or by partial ion etching through masks from the top surfaces, a better way to get VSM is to form vertical multilayers. Employing simultaneous oblique deposition of ZnTe and Si0 2 from opposite azimuthal directions, we have obtained nanometer-scale heterogeneous structures with anisotropic optical properties for the light coming perpendicularly to the surface. TEM revealed that successive annealing caused relaxation and recrystallization of ZnTe in the framework of SiO porous nanostructure. The resultant mosaic image of dark ZnTe regions and bright S10 2 regions of 5-10 nm wide and 30nm (or more) long told the development of VSM over the substrate although the perfect periodicity and two-dimensionality were missing. The structural modification of these quasi-multilayers was studied making reference to the similar but horizontal system of ZnTe particles periodically buried between Si0 2 isolation layers. INTRODUCTION In our previous work[l], we developed an idea to form anisotropic nanometer-scale composte structures(ANSC) by simultaneous oblique sputter-deposition of two materials from different direction by the aid of a computer-simulation which had been originally developed to explain the mechanism of the development of anisotropic connectivity in nanometer-scale range in obliquely deposited thin films[2]. By constructing a specially designed sputter-deposition apparatus, we also reported some preliminary experimental results of ANSC formation including a ZnTe-Si0 2 system[l]. Focusing on this ZnTe-SiO2 system, we proceeded a further study on relaxation or recrys~allization of this ANSC system to find a clear mosaic image of ANSC which can be regarded as a vertical quasi-multilayered nanocomposite(VQMNC) whose stacking direction is parallel with the substrate plane. Here, we report this, starting with the feature of sputter-deposition of ZnTe, through the study of horizontal multilayer stacks of thin discontinuous ZnTe layers separated by Si02 layers which may have much similarity with VQMNC but can be defined better, to the feature of VQMNC. SPUTTER-DEPOSITION OF ZINC TELLURIDE Prior to the formation of ZnTe-Si0 2 nanocomposites, features of sputter-deposition of pure ZnTe were studied. A ZnTe target of 2 inches in diameter and 99.99% purity was spu tered by rfsputtering at 15W in the argon gas pressure of 2x10-s Torr in the previously reported apparatus used for formation of ANSC. However, the substrate holder used this time does not hold a substrate horizontally to attai
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