Silicon fine structure studies

Hessel CM, Henderson EJ, Kelly JA, Cavell RG, Sham TK, Veinot JCG (2008) Origin of luminescence from silicon nanocrystals a near edge X-ray absorption fine structure (NEXAFS) and X-ray excited optical luminescence(XEOL) study of oxide-embedded and free-standing systems. J Phys ChemC 112 14247-14254... 

Tang YH, Sham TK, Jurgensen A, Hu YF, Lee CS, Lee ST (2002) Phosphorus-doped silicon nanowires studied by near edge x-ray absorption fine structure spectroscopy. Appl Phys Lett 80 3709-3711 Teo BK, Sun XH (2007) Silicon-based low-dimensional nanomateiials and nanodevices. Chem Rev 107 1454-1532 Thanh NTK, Green LAW (2010) Fnnctionalisation of nanoparticles for biomedical applications. Nano Today 5 213-230... 

The concept that by carrying out a surface analysis on a model specimen one can obtain direct access to the interphase chemistry is a potentially very exciting and rewarding idea. The interaction of PMMA with various metals (as exemplified hyO Fig. 10.14 above) has been studied in some detail using high resolution XPS (Leadley and Watts 1997). In this work the manner in which PMMA formed specific interactions with oxidized metal surfaces was studied by the nature of the fine structure in the XPS spectrum. In this manner, it was possible to show that the polymer formed hydrogen bonds with oxidised silicon (an acidic substrate), a bidentate structure with oxidised aluminum (an amphoteric substrate) and would undergo acyl nucleophilic attack with oxidised nickel (a basic substrate). 

Cartledge and Profeta have used molecular mechanics in combination with ab initio calculations to study conformations and rotational potential energy functions.They fine-tuned silicon parameters for the MM2 force field. The goodness of fit was determined by the fit to experimental structures and ab initio torsional barriers. 

The study of small and intermediate-sized clusters has become an important research field because of the role clusters play in the explanation of the chemical and physical properties of matter on the way from molecules to solids/ Depending on their size, clusters can show reactivity and optical properties very different from those of molecules or solids. The great interest in silicon clusters stems mainly from the importance of silicon in microelectronics, but is also due in part to the photoluminescence properties of silicon clusters, which show some resemblance to the bright photoluminescence of porous silicon. Silicon clusters are mainly produced in silicon-containing plasma as used in chemical vapor deposition processes. In these processes, gas-phase nucleation can lead to amorphous silicon films of poor quality and should be avoided.On the other hand, controlled production of silicon clusters seems very suitable for the fabrication of nanostructured materials with a fine control on their structure, morphological, and functional properties. ... 

Broadhead and Tresco studied the effects of fabrication conditions on the structures and performances of membranes formed from poly(acrylonitrile-vinylchloride) (PAN-PVC) by using the phase inversion process [85]. They reported the relationship of the fine-surface structure of PAN-PVC membranes to the membrane performance and membrane fabrication method. The fine-surface structure of nodular elements and the size of these elements could be altered by changing the precipitation conditions. Membranes were prepared at 22 on 55 mm diameter polished silicon wafers by spinning at 1500 rpm for 20 s with a spin coater [86]. The film was immediately precipitated in one of the four different precipitation media. The first three media consisted of deionized water at 4,22, and 54 °C. These membranes were referred to as Type 1 , Type 2 , and Type 3 , respectively. The fourth medium was a 50/50 mixture of deionized water and N,iV-dimethylformamide (DMF) at 54 °C and coded as Type 4 . Figure 4.53 shows the histograms of the nodule size distributions observed at the skinned surface of the membranes made under four different precipitation conditions. The sizes of these nodular elements became smaller and more uniform with milder precipitation conditions, which supports the theory that nodules are formed through spinodal decomposition under these conditions. In addition, the size of these nodules could be related to water permeability. Hence, water transport occurred through the interstitial spaces where the pores could be situated. 

Nuclear magnetic resonance (NMR) cryoporometry is an experimental technique of structural characterization of mesoporous materials. In this contribution, different aspects of its application to study details of the pore structure in mesoporous silicon are presented. In particular, the information obtained with help of NMR cryoporometry is eompared to that assessed using more conventional gas sorption techniques. The potentials of NMR cryoporometry to reveal fine details of the pore structure in intentionally multilayered mesoporous silicon are demonstrated. 

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