Thin polycrystalline electroluminescent thin films (TFEL) of ZnS:Mn (phosph
or) and Y2O3 (insulator) were deposited individually or as multilayers onto
Si (100) substrates. Their crystallinity and the luminescent efficiency of
the phosphor films were investigated at varying thermal annealing temperat
ures. It is shown that the luminescent quality of the phosphor layer increa
ses up to 700 degreesC, whereas the electroluminescence operating intensity
of TFEL devices saturates at 500 degreesC. The structural analysis of the
insulating and phosphor layers shows that they recrystallize at annealing t
emperatures of, respectively, 500 and 600 degreesC, and that their lattice
misfit doubles at processing temperatures>=500 degreesC. Since TFEL devices
should benefit from enhanced luminescence efficiency and crystallinity at
high annealing temperatures, we suggest that the lack of improvement in dev
ice performance beyond 500 degreesC is due to interface alterations. Accord
ing to previous works, we propose that the lattice misfit increase between
the phosphor and dielectric thin films modifies the morphology of the phosp
hor-insulator boundary inducing a modification of the interface states dens
ity, and hence, modifying high field electron transport properties of TFEL
devices. (C) 2001 American Institute of Physics.