4 research outputs found
Application of method of projective representations to the analysis of exciton-phonon transitions in enantiomorphous tetragonal crystals ZnP₂ and CdP₂
The projective representations of the wavevector group were applied to the analysis of exciton-phonon transitions in enantiomorphous tetragonal crystals ZnP₂ and CdP₂. Selection rules for indirect transitions were derived. Using pkrr-method, the different points in the Brillouin zone were examined to identify zero slopes and extremums of the dispersion curves E(k). Photoluminescence and edge absorption polarized spectra were interpreted taking into account the results of above theoretical analysis
Optical Properties of ZnP2 Nanoparticles in Zeolite
We report that for the first time the nanoparticles of II-V semiconductor
(ZnP2) were prepared and studied. ZnP2 nanoparticles were prepared by
incorporation into zeolite Na-X matrix. Absorption, diffuse reflection (DR) and
photoluminescence (PL) spectra of the ZnP2 nanoclusters incorporated into the
supercages of zeolite Na-X were measured at the temperature 77 K. Five bands
B1-B5 are observed in both the DR and PL spectra demonstrating the blue shift
from the line of free exciton in bulk crystal. We attribute the B1-B5 bands to
some stable nanoclusters with size less than the size of zeolite Na-X
supercage. We observed Stokes shift of the PL bands from the respective
absorption bands. The nonmonotonic character of its dependence on the cluster
size can be explained as the result of competition of the Frank-Condon shift
and the shift due to electronic relaxation.Comment: Submitted to Microporous and Mesoporous Material
Fabrication, Study of Optical Properties and Structure of Most Stable (CdP2)n Nanoclusters
CdP2 nanoclusters were fabricated by incorporation into pores of zeolite Na-X
and by laser ablation. Absorption and photoluminescence (PL) spectra of CdP2
nanoclusters in zeolite were measured at the temperatures of 4.2, 77 and 293 K.
Both absorption and PL spectra consist of two bands blue shifted with respect
to bulk crystal. We performed the calculations aimed to find the most stable
clusters in the size region up to size of the zeolite Na-X supercage. The most
stable clusters are (CdP2)6 and (CdP2)8 with binding energies of 9.30 eV and
10.10 eV per (CdP2)1 formula unit respectively. Therefore, we attributed two
bands observed in absorption and PL spectra to these stable clusters. The Raman
spectrum of CdP2 clusters in zeolite was explained to be originated from
(CdP2)6 and (CdP2)8 clusters as well. The PL spectrum of CdP2 clusters produced
by laser ablation consists of the asymmetric band with low-energy tail that has
been attributed to emission of both (CdP2)8 cluster and CdP2 microcrystals.Comment: Accepted for publication in Physica E: Low-dimensional Systems and
Nanostructure
Optical Properties and Structure of Most Stable Subnanometer (ZnAs2)n Clusters
ZnAs2 nanoclusters were fabricated by incorporation into pores of zeolite
Na-X and by laser ablation. Absorption and photoluminescence spectra of ZnAs2
nanoclusters in zeolite were measured at the temperatures of 4.2, 77 and 293 K.
Both absorption and PL spectra consist of two bands which demonstrate the blue
shift from the line of free exciton in bulk crystal. We performed the
calculations aimed to find the most stable clusters in the size region up to
size of the zeolite Na-X supercage. The most stable clusters are (ZnAs2)6 and
(ZnAs2)8 with binding energies of 7.181 eV and 8.012 eV per (ZnAs2)1 formula
unit respectively. Therefore, we attributed two bands observed in absorption
and PL spectra to these stable clusters. The measured Raman spectrum of ZnAs2
clusters in zeolite was explained to be originated from (ZnAs2)6 and (ZnAs2)8
clusters as well. The PL spectrum of ZnAs2 clusters produced by laser ablation
consists of a single band which has been attributed to emission of (ZnAs2)8
cluster.Comment: Article accepted for publication in Physica B: Physics of Condensed
Matte