Flexible Memory Application of Nanoscale Ti–Ge–Te Thin Film as Information Storage Medium With Excellent Thermal Stability, Low Resistance Drift and Superior Bending Characteristic

The flexible Ti-Ge-Te phase change material was proposed and fabricated by magnetron cosputtering method. The impact of titanium dopant and mechanical bending on the thermal stability, electrical resistance, surface morphology, microstructure, and crystallization mechanism of GeTe thin film are investigated systematically. With the incorporation of appropriate titanium dopant, the crystallization process and grain size of GeTe material can be hindered. Meanwhile, the thermal stability, surface morphology, and crystal structure have not been changed obviously when the bending times reaching 10⁶, demonstrating the distinguished mechanical bending performance. The phase change memory devices with Ti-doped GeTe were prepared based on flexible polyimide substrates, and the electronical properties are evaluated. The consequences show that the phase change memory can still exhibit the negative resistance phenomenon and complete the erase/write operation after bending 10⁶ cycles. The density functional theory calculations of band structure illustrate that titanium dopant can convert the indirect band gap of GeTe material to the direct type. The formation energy and charge density difference indicate the massive electron cloud agglomerate between the Ti and Te atoms, deducing that the foreign Ti may occupy the position of Ge and form the covalent bonds with Te.