Thermal stability and crystallization speed of Cu-doped Ge8Sb2Te11 thin films

Abstract

The objective of this study was to evaluate structural and electrical properties of Cu-doped Ge8Sb2Te11 thin films. Thermal stability and crystallization speed in nanosecond time scale of these of Cu-doped Ge8Sb2Te11 thin films prepared by a radio frequency (RF) magnetron reactive sputtering were also determined. A one-step phase transformation from an amorphous phase to a face-centered-cubic (fcc) phase and an increase of crystallization temperature (Tc) were observed for the Cu-doped film, indicating an enhanced thermal stability in the amorphous state. The sheet resistance (Rs) of the amorphous phase in the Cu-doped film was about 1.5 orders of magnitude larger than that in undoped film. The larger Rs, in the amorphous phase will reduce the programming current in the memory device. An increase of threshold voltage (Vth) was seen in the Cu-doped thin film, implying a high thermal efficiency. The SET voltage of the Cu-doped film was improved with an increase of the pulse voltage. The SET speed of the Cu-doped thin film was about 30 ns, suggesting that such thin film could be a good candidate for the fast crystallization PRAM.