Tailoring the spatial-dependent Rashba parameter and spin fluctuations in nanomaterials for improved spin-FET functionality

•.The non-uniform Rashba parameters is observed.•.The size effect of the spatial pattern of the Rashba parameters is studied.•The stability of the Rashba effect as a function of temperature is analyzed. The spatial fluctuation of the Rashba parameter has been a major issue in the development of state-of-the-art spintronic nanodevices. Since stable spin-precession is of vital importance in the spin field-effect transistor (spin-FET), we have developed a Monte Carlo model to justify that the local E-field of heavy dopants is the origin of the fluctuating Rashba parameter. To maintain a stable drain current in spin-FETs, we study how the size of lattice, doping condition, E-field screening, exchange interaction and temperature influence the Rashba interaction in nanomaterials. Our Monte Carlo model can predict the Rashba effect of Graphene/Nickel(111) substrate at room temperature and presents a path to enhance the Rashba interactions via proximity coupling. More importantly, we have discovered a dip-like structure in the Rashba parameter that strongly scatters the spin states, and we have figured out how to suppress spin fluctuations in the semiconductor channel. Our results are important for the development of the next generation of spin transistors.