Internal (SiH)_{X} groups, X = 14, in microcrystalline hydrogenated silicon and their IR spectra on the basis of periodic DFT modelling
Abstract
Vibrational SiH frequencies were calculated on the basis of density functional theory (DFT) using periodic boundary conditions for NSi voids, N < 8, in microcrystalline hydrogenated silicon (MHS) and (100), (110), and (111) slabs of 8, 5, and 8 layers, respectively, with the dangling bonds being saturated with hydrogen atoms. The slabs are considered as the models of intergrain boundaries (IGB) in MHS. The NSi voids of different shapes have been obtained via random deleting N silicon atoms. It was shown that the high stretching modes (HSM) of SiH vibrations, which are usually assigned to SiH_{X}, appear also due to (SiH)_{X} groups, X = 24, in the NSi voids. No such (SiH)_{X} groups were formed with X > 1 at the IGB. The low stretching modes (LSM) are thus assigned to SiH groups presented at both NSi voids and IGB. Similar relative stability of the voids is obtained with two different DFT approaches, i.e., B3LYP with atomic basis set and PerdewBurkeErnzerhof (PBE) with plane wave basis set. This result allows a simple interpretation of usually small I_{HSM}/(I_{LSM} + I_{HSM}) intensity ratio as a consequence of minor concentration of any voids in device quality MHS.
 Publication:

Molecular Physics
 Pub Date:
 April 2014
 DOI:
 10.1080/00268976.2013.817621
 Bibcode:
 2014MolPh.112..956L
 Keywords:

 microcrystalline hydrogenated silicon;
 DFT;
 void stability;
 IR spectra;
 (SiH)<SUB>X</SUB> groups