Silicon surface reconstruction

In 1985 Car and Parrinello invented a method [111-113] in which molecular dynamics (MD) methods are combined with first-principles computations such that the interatomic forces due to the electronic degrees of freedom are computed by density functional theory [114-116] and the statistical properties by the MD method. This method and related ab initio simulations have been successfully applied to carbon [117], silicon [118-120], copper [121], surface reconstruction [122-128], atomic clusters [129-133], molecular crystals [134], the epitaxial growth of metals [135-140], and many other systems for a review see Ref. 113. 

For the deposition of silicon on Si(001) and Si(l 11) surfaces, Gossmann and Feldman determined that epitaxial growth occurs for substrate temperatures maintained over 570 K and 640 K, respectively . Above the epitaxial temperature the growth is single crystal, while below this temperature the growth is amorphous. This difference in epitaxial growth temperature between the two faces was ascribed by Gossmann and Feldman to be due to the different surface reconstructions, where the (111) surface presumably... 

In a different approach to this problem, Brenner and Garrison used molecular dynamics to examine the chemical mechanisms which lead to reordering of the atom-pairing reconstruction during atom deposition . This simulation incorporated a dissociative valence-force field potentiaF and consisted essentially of a high-temperature anneal of monolayers of silicon atoms which had been deposited on a silicon (001) reconstructed surface. 

To understand the meaning of the STM images of silicon surfaces, we review some basic facts of the crystallography of silicon. We will discuss the simpler Si(lll) surfaces first, then the complicated 7X7 reconstruction. In fact, the STM imaging of the simple Si(lll) surface is the most elementary case of imaging semiconductors, and perhaps the most instructive one. 

Fig. 4.15 (a) A 15 K He field ion image of a low temperature field evaporated silicon surface. (b) A computer simulation image of Si with (lxl) surfaces, (c) a 60 K Ne field ion image of a 720°C annealed silicon surface where well ordered atomic structures are developed at a few facets of the Si emitter surface, (d) When the Si tip is annealed at 800°C, almost all the facets are well developed. The atomic structures of all these facets are completely reconstructed. 

Takayanagi, K. et al. Structure Analysis of the Silicon(lll) 7x7 Reconstructed Surface by Transmission Electron Diffraction/5 Surface Science, 164, 367 (1985). Tromp, R.M. and E.J. van Loenen Ion-Beam Crystallography on Silicon Surfaces III. Si(lll),5 Surface Science, 155, 441 (1985)... 

Some of the most dramatic STM images have been recorded for the Si(l 11) 7X7 reconstruction, as depicted in Figure 3.14.138 These images have been recorded at several different biases (see Spectroscopy and Chemical Selectivity, below) and provide one of the best examples of how STM can be used to better understand the chemistry of such surfaces ( specifically, the electrophilicity and nucleophilicity of the individual surface atoms). Clearly depicted in these results are the orbitals associated with surface atoms, rest atoms, and backbonds. Such studies have continued and been greatly extended into the exploration of a variety of chemical reactions that occur on silicon surfaces. These studies are described in detail in a recent review.135... 

Figure 24.1 A surface reconstruction of a male antennal lobe of the moth Spodoptera littoralis. The brain was immunostained with synapsin antibody and optically sectioned using a confocal microscope. Stacks of images were integrated with the software Imaris 2,7 (Bitplane AG, Switzerland) on a Silicon Graphics workstation to obtain surface projections of the lobe. The macroglomerular complex (MGC) is located close to the entrance of the antennal nerve. M, medial D, dorsal (modified from Carlsson et at, 2002). B Synaptic organization of the major types of antennal lobe neurons. Sensory neurons (ORNs) make uniglomerular synapses both directly with projection neurons (PNs) and indirectly via local interneurons (LNs). In addition, local interneurons innervate several glomeruli and generally make inhibitory synapses. Cell bodies of PNs and LNs are located within the antennal lobe.

Silicon is a material of major technological importance since it forms the basis of a vast range of electronic devices such as transistors, microprocessors and solar cells. It is also likely to be used in numerous future technologies including atomic scale devices [17,18], ultra dense storage devices [19], quantum computers [20,21] and hybrid molecular devices [22]. The surfaces of silicon are the most thoroughly studied of all semiconductor surfaces and there are numerous known surface reconstructions [23]. In this section we... 

Topographic image of a reconstructed silicon surface showing outermost atomic positions, photograph of Dr. James Batteas. National Institute of Standards and Technology. Reproduced by permission p. 

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