Structural characteristics of optical quality poly(2-methoxy-5-(2‘-ethylhexyloxy)-1,4-phenylenevinylene) (MEH−PPV) films drop-cast from toluene solutions have been examined by use of wide-angle (WAXS) and small-angle X-ray scattering (SAXS) as well as field-emission scanning electron microscopy. For the as-cast film SAXS and WAXS patterns clearly suggest existence of nanodomains of mesomorphic order. Under grazing incidence, both SAXS and WAXS patterns of the as-cast film exhibit impressive uniaxial symmetry with strong scattering along the film normal; however, the corresponding normal-incidence patterns are circularly isotropic, implying in-plane random orientation. A structural model consisting of preferentially uniaxial-oriented nanodomains and disordered matrix is therefore proposed for the as-cast film. Annealing at 210 °C results in disorientation of nanodomains:  this decrease in structural asymmetry upon heat treatment correlates well with concomitant changes in charge transport behavior determined from time-of-flight measurements, manifesting dramatically decreased charge mobility as well as transition from nondispersive to dispersive modes.

Ga 2 O 3 ( Gd 2 O 3 ) ∕ Ga As heterostructures have been annealed up to ∼780°C. Studies using x-ray reflectivity and high-resolution transmission electron microscopy have shown that the samples annealed under ultrahigh vacuum have maintained smooth and abrupt interfaces with the interfacial roughness being less than 0.2nm. The oxide remains amorphous, an important parameter for device consideration. Current–voltage and capacitance–voltage measurements have shown low leakage currents (10−8–10−9A∕cm2), a high dielectric constant of 15, and a low interfacial density of states (Dit) between gate dielectrics and GaAs. The attainment of a smooth interface between the gate dielectric and GaAs, even after high temperature annealing for activating implanted dopant, is a must to ensure the low (Dit) and to maintain a high carrier mobility in the channel of the metal–oxide–semiconductor field-effect transistor.