Structure and sheet resistance of boron-implanted Ge2Sb2Te5 phase change film

Ge2Sb2Te5 films were deposited by RF sputtering on Si(1 0 0)/SiO2 substrates and the effect of boron implantation on the structure, sheet resistance and surface topography of Ge2Sb2Te5 film is studied intensively. Due to boron implantation, phase separation takes place and the structure changes from face-centered-cubic into multi-phases composing of hexagonal GeTe and Sb2Te3 crystalline phases when the annealing temperature is low. However, phase separation is suppressed by boron implantation under the conditions of high boron implant dose and high annealing temperature. Also the boron implantation has great effect on the sheet resistance of Ge2Sb2Te5 film. The major reason may be microstructure changes induced by boron implantation, which include defects formation, phase separation, and grain refinement. There may be many advantages, such as improving the resistance stability, reducing the required heating power, increasing the crystallization speed, and improving the temperature stability, for the application potential of the B-doped Ge2Sb2Te5 film if the implant dose is properly selected.