- 作者：H. Gleitera ; b ; herbert.gleiter@kit.edu" class="auth_mailAuthor Vitae ; Th. Schimmela ; b ; thomas.schimmel@kit.edu" class="auth_mailAuthor Vitae ; H. Hahna ; b ; horst.hahn@kit.edu" class="auth_mailAuthor Vitae
- 关键词：Amorphous nanomaterials ; Nanostructured solids ; Nanoglasses ; Noncrystalline materials ; Single-Atom transistor ; Self-assembly
- 刊名：Nano Today
- 出版年：February, 2014
- 年：2014
- 卷：9
- 期：1
- 页码：17-68
- 全文大小：16276 K
Summary
It is the aim of this review to discuss the preparation, the atomic structure and the properties of nanometer structured solids that consist either totally or partially of amorphous components. We shall try to present evidence suggesting that it is the variation of the boundary conditions applied for preparing these nano-structures that open the way to a variety of materials with new atomic arrangements/new properties ranging from nano-glasses to switchable atomic quantum transistors.In order to discuss the basic ideas, we shall consider (in the first part of this review) solid materials that are assembled of nanometer-sized crystalline or amorphous building blocks connected by interfaces. The resulting materials are called nano-crystalline materials (nc) and nano-glasses (NG). Nano-crystalline materials and nano-glasses are solid materials composed of nanometer-sized crystalline or nanometer-sized glassy regions connected by crystal/crystal or glass/glass interfaces. As the atomic structures of these interfaces differ from the ones in the building blocks, the atomic and electronic structures of these interfaces differ from the ones in the building blocks. The atomic and the electronic structures (and hence the properties) of nano-crystalline materials and/or nano-glasses differ from the ones of single crystals or of glasses, respectively, that are available today with the same chemical compositions.
In the second part of this review solid materials will be discussed the properties of which are controlled by nanometer spaced solid/liquid or solid/gas interfaces. The first group of materials of this kind to be discussed are nano-porous metals with electrolyte or gas filled interconnected nanometer-sized ligaments. The properties of the resulting numerous solid/liquid or solid/gas interfaces may be controlled reversibly by external variables e.g. by applying an external voltage between an aqueous electrolyte in the pores and the nano-porous metal or by varying the chemical composition of the gas in the pores. Due to the high density (鈭?015 mm鈭?) of nano-scale ligaments, the entire nano-porous material reacts and becomes a solid of macroscopic dimensions with tunable mechanical, electric, magnetic, etc. properties. The other group of materials to be discussed in the second section of this review are nanometer-sized single crystals embedded in an aqueous electrolyte. By varying the boundary conditions for the formation of these nanometer-sized crystals, the size, the shape and the electronic structure of these nanometer-sized crystals can be switched reversibly so that switchable quantum transistors are obtained.
All of these findings may also be interpreted in a more general context suggesting that in all the above mentioned cases, complex structures evolve if the following four conditions are met: (i) a substrate or nucleation site, on which the structures can organize, (ii) a free volume providing the sterical degrees of freedom for building the new structures, (iii) a reservoir of building blocks (molecules, atoms, ions, crystallites, glassy clusters) from which the structures can be (reversibly or irreversibly) formed and finally (iv) confined geometries preventing the return to thermal equilibrium by preventing the growth of macroscopic single crystals. This general approach seems to open the way for understanding and developing the guidelines for the growth of new self-organized complex material systems far from thermal equilibrium.