TY  - JOUR
AU  - Shchur, Yaroslav
AU  - Pavlyuk, O.
AU  - Andrushchak, A. S.
AU  - Vitusevich, S.
AU  - Kityk, A. V.
TI  - Porous Si Partially Filled with Water Molecules—Crystal Structure, Energy Bands and Optical Properties from First Principles
JO  - Nanomaterials
VL  - 10
IS  - 2
SN  - 2079-4991
CY  - Basel
PB  - MDPI
M1  - FZJ-2020-01559
SP  - 396 -413
PY  - 2020
AB  - The paper reports the results on first-principles investigation of energy band spectrum andoptical properties of bulk and nanoporous silicon. We present the evolution of energy band-gap,refractive indices and extinction coefficients going from the bulk Si of cubic symmetry to porous Siwith periodically ordered square-shaped pores of 7.34, 11.26 and 15.40 Å width. We consider twonatural processes observed in practice, the hydroxylation of Si pores (introduction of OH groups intopores) and the penetration of water molecules into Si pores, as well as their impact on the electronicspectrum and optical properties of Si superstructures. The penetration of OH groups into the pores ofthe smallest 7.34 Å width causes a disintegration of hydroxyl groups and forms non-bonded protonswhich might be a reason for proton conductivity of porous Si. The porosity of silicon increasesthe extinction coefficient, k, in the visible range of the spectrum. The water structuring in pores ofvarious diameters is analysed in detail. By using the bond valence sum approach we demonstratethat the types and geometry of most of hydrogen bonds created within the pores manifest a structuralevolution from distorted hydrogen bonds inherent to small pores (7 Å) to typical hydrogen bondsobserved by us in larger pores (about15 Å) which are consistent with those observed in a wide databaseof inorganic crystals.
LB  - PUB:(DE-HGF)16
C6  - pmid:32102303
UR  - <Go to ISI:>//WOS:000522456300215
DO  - DOI:10.3390/nano10020396
UR  - https://juser.fz-juelich.de/record/874639
ER  -