  In metal/degenerately doped silicon bilayer structure, the interfacial
flexoelectric effect due to strain gradient leads to charge carrier transfer
from metal layer to the silicon layer. This excess charge carrier concentration
is called flexoelectronic doping or flexoelectronic charge transfer, which
gives rise to an electronically polarized (order of magnitude larger than
ferroelectric materials) silicon layer. In the transport measurements, the
charge carrier concentration in silicon is found to increase by two orders of
magnitude due to flexoelectronic doping, which changes the Fermi level and the
Hall response. The flexoelectronic charge accumulation modifies the
electron-electron and the electron phonon coupling, which gives rise to Mott
metal-insulator transition and magnetism of phonons, respectively. The
coexistence of flexoelectronic polarization and magnetism gives rise to a new
class of materials called electronic multiferroics. By controlling the
flexoelectronic doping, material behavior can potentially be engineered for
quantum, spintronics and electronics applications in semiconductor materials.
