Effect of O-implantation on the structure and resistance of Ge2Sb2Te5 film

Abstract Ge 2 Sb 2 Te 5 films were deposited by rf magnetron sputtering on Si(1 0 0)/SiO 2 substrates. In order to increase the Ge 2 Sb 2 Te 5 sheet resistance, O + ion was implanted into Ge 2 Sb 2 Te 5 films. The effect of oxygen implantation on the structure of Ge 2 Sb 2 Te 5 film was studied in details using XRD, Raman spectra, and XPS methods. It is indicated that the structure of crystalline Ge 2 Sb 2 Te 5 -O annealed at 250 °C is identified as a FCC structure even when oxygen implant fluence reaches 1.29 × 10 17 ions per cm 2 and the lattice parameter increases as oxygen implant fluence increasing. However, phase separation takes place when annealing temperature is 450 °C. In the case of the high fluence (higher than 6.44 × 10 16 ions per cm 2 ) samples, phase separation no longer takes place and phase transition from FCC to hexagonal structure is suppressed by oxygen implantation. Oxygen implantation has great effect on the resistance-annealing behaviour of Ge 2 Sb 2 Te 5 film, which may be origin from the structural changes including defect formation, phase separation, suppression of phase transition from FCC to hexagonal structure, and the refinement of grain size, etc. The R s of Ge 2 Sb 2 Te 5 -O film is higher than that of Ge 2 Sb 2 Te 5 film when annealing temperature is higher than 340 °C, which may be caused by phase separation and current carrier scattering by crystallite boundary.