Domain reorientation of nematic in p - n junction field in sensor of organic reagents vapor

The formation of a domain texture in a nematic in the electric field of a silicon $p-n$ junction and the influence of reagent vapors (dimethylformamide, isopropyl alcohol, toluene) on a uniformly reoriented nematic and domains were experimentally studied. At a threshold voltage, the initiator of the generation of linearly located domains is a local heterogeneity in the orientation of the molecules moving along the $p-n$ junction line in a uniformly reoriented nematic, the speed of which depends on the applied voltage. The step of periodicity in the arrangement of domains depends on the speed of motion of this heterogeneity. The effect of reagents on a uniformly reoriented nematic by the $p-n$ junction field at a fixed voltage is manifested as a change in the intensity of reflected light from the reoriented region of the nematic. The intensity increases with increasing concentration of the reagent. For a domain texture, also at a fixed voltage, the effect of vapor is manifested in a change in the step of the periodicity of their location along the $p-n$ junction line. Two possible contributions to the mechanism of influence of reagents vapor are noted, namely: a change in the order parameter and surface tension of the nematic, the latter factor being clearly gradient in nature, which allows the spatial directional displacement of domains from the $p-n$ junction line in the sensor prototype to define the direction to the source of the reagent vapor.