Free-volume correlations in positron-sensitive annihilation modes
in chalcogenide vitreous semiconductors: on the path from illusions towards realistic physical description
O.I. Shpotyuk1,* , M.M. Vakiv1, M.V. Shpotyuk1,2, A. Ingram3, J. Filipecki4, A.P. Vaskiv5
1Institute of Materials of SRC "Carat", 202, Stryjska str., 79031 Lviv, Ukraine 2Lviv Polytechnic National University, 12, Bandera str., 79013 Lviv, Ukraine 3Opole University of Technology, 75, Ozimska str., Opole, 45370, Poland 4Institute of Physics of Jan Dlugosz University,
13/15, al. Armii Krajowej, Czestochowa, 42200, Poland 5
Ivan Franko Lviv National University, 6, Kyryla & Mefodia str., 79005 Lviv, Ukraine *The corresponding author e-mail: shpotyuk@novas.lviv.ua
Abstract. A newly modified correlation equation between defect-related positron
lifetime τ2 (ns) defined within two-state model and corresponding radius R (A) of free-
volume positron traps in the full non-linear form
τ2=0.285[1-R/(R+5.50)+1/2πsin(2πR/(R+5.50))]-1
or simplified linear-approximated form
τ2=0.212(1+0.244R)
is proved to account for compositional trends in void volume evolution of chalcogenide
semiconductor compounds like binary As-S(Se) glasses. Specific chemical environment
of free-volume voids associated with neighbouring network-forming polyhedrons is
shown to play a decisive role in this correlation, leading to systematically enhanced
estimated void sizes in comparison with typical molecular substrates, such as polymers.