  In the present work, we study morphologies arising due to competing substrate
interaction, electric field and confinement effects on a symmetric diblock
copolymer. We employ a coarse grained non-local Cahn-Hilliard phenomenological
model taking into account the appropriate contributions of substrate
interaction and electrostatic field. The proposed model couples the
Ohta-Kawasaki functional with Maxwell equation of electrostatics, thus
alleviating the need for any approximate solution used in previous studies. We
calculate the phase diagram in electric field-substrate strength space for
different film thicknesses. In addition to identifying the presence of
parallel, perpendicular and mixed lamellae phases similar to analytical
calculations, we also find a region in the phase diagram where hybrid
morphologies (combination of two phases) coexist. These hybrid morphologies
arise either solely due to substrate affinity and confinement or are induced
due to the applied electric field. The dependence of the critical fields for
transition between the various phases on substrate strength, film thickness and
dielectric contrast is discussed. Some preliminary 3D results are also
presented to corroborate the presence of hybrid morphologies.
