In Situ Research On Phase-Changed Of Metal Elements-Doped GST Nanofilm By Electric Field

PCRAM has been widely used for data storage applications, because of its special different resistance between amorphous and crystallization. In order to satisfy the requirements of PCRAM, the nano-structural characteristics of the material were investigated. The analyze method is the key to recognize the mechanism of phase change. So in-situ technique becomes most essential to research the correlation between property with phase changed.Different elements of Zn and Ag doped Ge-Sb-Te flims were prepared via magnetron co-sputtering. These films were systemically investigated by scanning tunneling microscope-transmission electron microscope(STM-TEM, Nanofactory Instruments) and advanced Transmission electron microscopy(TEM) techniques. We mainly focused on the relationship between the structure and the properties. The achievements are following:1. By using the principle of TEM and STM-TEM holder, the film directly sputtering in the carbon film of copper. The nanofilm can be used in TEM by regulating the thickness of the thin film. Thus, we can analyze the principle of the phase transition induced by electric field and acquire the electrical properties of phase change materials. It provides a key to observe the relationship between the changed structure and electrical properties at the same time, using in-situ transmission electron microscopy technique.2. By using the principle of TEM and STM-TEM holder, we can record the trend of Zn-GST nanofilm changed, the switching behaviors, a cell showing failure after applied switching volume. It observes that Zn-doped GST can reduce the threshold switching, by the value of the applied volume and holding time. The nanofilm damaged because of the temperature gradient of the thin film caused by joule heat. Combined with Radial distribution function(RDF), we obtain that the Zn-GST nanofilm produced selective during crystallization, which provides the basis to find the failure parts of PCRAM.3. By using the principle of TEM and STM-TEM holder, we can record the color, structure and electrical properties changed of Ag-GST nanofilm by applied voltage. It can reduce the threshold switching, with Ag doped. So that it reduces the wastage of work power and improves work speed. The most important is that nanofilm appears an intermediate resistance when applied the negative voltage. It is simple and repetitive to apply the positive and negative voltage to the nanofilm, which provides the foundation to research multi-configuration memory.4. By using the method of combining the STM-TEM holder with optical microscope, it expands application scope of the STM-TEM holder. Then, it can analysis further, without electron beam irradiation introduced. Combined the EDS, we prove that Ag filaments formed under the electric field, which improves the conductivity and reduces the resistance. While the broken Ag filaments reduced the conductivity. The migration movement of Ag changed the structure of the Ag-GST nanofilm, increasing the intermediate resistance. It makes the resistance of the nanofilmin transform between highest-resistance, lowest-resistance and intermediate resistance, forming multiconfiguration memory.