Two-dimensional metal layers

The structure of growing crystal faces is inhomogeneous (Fig. 14.11a). In addition to the lattice planes (1), it featnres steps (2) of a growing new two-dimensional metal layer (of atomic thickness), as well as kinks (3) formed by the one-dimensional row of metal atoms growing along the step. Lattice plane holes (4) and edge vacancies (5) can develop when nniform nucleus growth is disrupted. 

Conductivity through disordered iron layers during its formation on Si(l 1 l)-7x7 and Si(l 11)-[(V3x i3)/30°]-Cr surface phase was investigated. Silicide formation on Si(l 11)7x7 surface is observed, but Si(U l)-( J3x 3)/30°-Cr surface phase behaves like a diffusion barrier for iron atoms. Nucleation and growth of iron islands proceeds with increasing of metal thickness without formation of iron silicide. Iron forms continuous two dimensional metal layer with near bulk parameters starting from the thickness of 1 nm. 

Two-dimensional phase formation occurs preferentially when a strong suhstrate-metal interaction exists, a process that typically involves the formation of growth centers a few atoms thick, that expand and coalesce to form a monolayer that serves as a precursor deposit to subsequent two-dimensional metal layers. 

In the last decade two-dimensional (2D) layers at surfaces have become an interesting field of research [13-27]. Many experimental studies of molecular adsorption have been done on metals [28-40], graphite [41-46], and other substrates [47-58]. The adsorbate particles experience intermolecular forces as well as forces due to the surface. The structure of the adsorbate is determined by the interplay of these forces as well as by the coverage (density of the adsorbate) and the temperature and pressure of the system. In consequence a variety of superstructures on the surfaces have been found experimentally [47-58], a typical example being the a/3 x a/3- structure of adsorbates on a graphite structure (see Fig. 1). 

Two-dimensional protein layer orientation could be also effected by metal-ion coordination Monolayer of iminodiacetate-Cu(II) lipid was successfully employed as substrate for oriented immobilization of proteins naturally displaying histidine residues on their surface [37]. Affmity-resin-displaying Ni(II) complexes could also be successfully employed for oriented protein immobilization [38]. 

A large fraction of the material science research, and an important chapter of solid state physics are concerned with interfaces between solids, or between a solid and a two dimensional layer. Solid state electronics is based on metal-semiconductor and insulator-semiconductor junctions, but the recent developments bring the interface problem to an even bigger importance since band gap engineering is based on the stacking of quasi two dimensional semiconductor layers (quantum wells, one dimensional channels for charge transport). 

Mo03 is known to crystallize in a layer lattice in which two-dimensional metal oxide sheets are separated by a van der Waals gap. Son et al.20) prepared linear Ni(II)-rubeanic acid coordination polymer (23) in the interlayer space of Mo03. 

Among the inorganic open-framework compounds, the family of phosphates is a large one [3]. A large variety of open-framework metal phosphates of different architectures have been synthesized in the last few years. They include one-dimensional (ID) linear chain and ladder structures, two-dimensional (2D) layer structures and three-dimensional (3D) channel structures [4]. In the linear chain and ladder structures, four-membered metal phosphate units of the type M2P2O4 share comers and edges respectively. Zero-dimensional four-membered zinc phosphates have been synthesised and characterized recently [5]. Several open-framework metal carboxylates have also been reported [6] and the presence of a hierarchy of zinc oxalates covering the monomer, dimer, chain, honeycomb-layer and 3D structures has indeed been established [7]. 

The two-dimensional ordered layered linear chain carbon films were produced using a pulsed plasma ion-assisted technology [10]. The films were obtained at a rate of lOOnm/min on various substrates (metals, ceramics, polymers, etc.) with good adhesion and homogeneity of the films on the areas of 150 x ISOmm. ... 

ZrNCl Co(Cp)2 o,io has been shown to be a Type II superconductor with a superconducting transition at 14 K. This is the highest for any metallocene intercalation compound. The superconducting transition temperatures for all three metallocene intercalation compounds are the same as those in the alkali metals intercalates with the same doping level reported by Yamanaka et The transition temperature appears not to be dependent on the interlayer separation and on the doping level which suggests that the superconductivity is largely confined to the thin two-dimensional ZrN layers of the host lattice. 

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