Chemical modification of semiconductor surfaces

Uniform n-Si/CHsOH-dmFc contact (bare n-Si surface) Heterogeneous n-Si/Ni/E prepared using 174 nm diameter spheres Uniform n-Si/Ni contact (completely metallised surface) n-Si/Ni/E theory interacrting contact model n-Si/Ni/E theory independent contact model n-Si/Ni/E photoresponse predicted from dark response 

Adsorbates that can bind specifically to electron-deficient or electron-rich dangling surface atoms can, in principle, eliminate Shockley-type recombination sites. If the chemical interaction, i.e. bonding, between the surface atom and the adsorbate is sufficiently sfrong, the bonding and antibonding orbitals of the surface 

A different phenomenon involving metallic cation/surface interactions is photointercalation (Ang and SammeUs, 1982 Rauh, 1982 Betz, 1985 Sharon et al, 1991). For lamellar semicondnctors nnder illumination, small cations can intercalate 

Nucleophilic adsorbates have also yielded interesting system improvements. Lamellar chalcogenides exhibit a strong sensitivity towards dissolved Lewis bases. For example, the photoelectrochemical behaviour of WSc2 and MoSe2 photoelectrodes dramatically improved after exposure to solutions that contained pyridines or ethylenediaminetetraacetic acid, respectively (Canfield and Parkinson, 1981 Fan 

Adsorption as a means to improve the behaviour of semiconductor interfaces is strongly system-dependent, and the benefits are generally short-lived. Additionally, the resultant surface properties after modification by adsorbates are difficult to predict a priori. To control semiconductor surfaces deterministically, and to impart long-lasting enhancements, several groups have pursued covalently grafting specific chemical functionalities to the semiconductor surface. 

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Semiconductor/Liquid Junction Photoelectrochemical Solar Cells 9.4 Chemical modification of semiconductor surfaces... 

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