Material For Phase Change Memory Application Research Articles

High-speed and large-window C-doped Sb-rich GeSbTe alloy for phase-change memory applications

In order to improve the phase transition properties of CGe2Sb2Te5 (CGST) phase-change materials, we proposed and demonstrated a carbon-doped Sb-rich Ge0.6Sb3Te phase-change material [C0.05(Ge0.6Sb3Te)0.95, named Sb-rich GSTC]. The phase transition of Sb-rich GSTC can be triggered by a 10 ns electric pulse with a large resistance ratio, which is much better than that of CGST. Meanwhile, the Sb-rich GSTC film maintains good thermal stability with a crystallization temperature and data retention of 203.1 °C and 114.8 °C@10-year, respectively. The above results imply carbon-doped Sb-rich GeSbTe alloy is a promising material for phase-change memory applications with high operation speed, a large memory window, and good stability and process compatibility.

Ge rich Chalcogenide material for Non volatile memory applications

A phase-change memory (PCM) material, in device, has been prepared by melt-quenching technique, which has a better glass forming ability. The device is formed on glass substrate coated with ITO as bottom electrode and Al as top electrode. This device switches with a threshold voltage of 4.5V in voltage sweep mode, with resistance difference of 3 orders. This device has set and resettable state for several cycles, with input current of 0.5mA for SET and 15mA RESET state. And the device data retention with various temperature shows that is likely to be a thermally suitable material for phase-change memory applications.

Trilayer Graphene as a Candidate Material for Phase-Change Memory Applications

ABSTRACTThere is pressing need in computation of a universal phase change memory consolidating the speed of RAM with the permanency of hard disk storage. A potentiated scanning tunneling microscope tip traversing the soliton separating a metallic, ABA-stacked phase and a semiconducting ABC-stacked phase in trilayer graphene has been shown to permanently transform ABA-stacked regions to ABC-stacked regions. In this study, we used density functional theory (DFT) calculations to assess the energetics of this phase-change and explore the possibility of organic functionalization using s-triazine to facilitate a reverse phase-change from rhombohedral back to Bernal in graphene trilayers. A significant deviation in the energy per simulated atom arises when s-triazine is adsorbed, favoring the transformation of the ABC phase to the ABA phase once more. A phase change memory device utilizing rapid, energy-efficient, reversible, field-induced phase-change in graphene trilayers could potentially revolutionize digital memory industry.

Effects of germanium and nitrogen incorporation on crystallization of N-doped Ge2+xSb2Te5 (x = 0,1) thin films for phase-change memory

The phase-change behavior and microstructure changes of N-doped Ge3Sb2Te5 [N-GST(3/2/5)] and Ge2Sb2Te5 [GST(2/2/5)] films during the phase transition from an amorphous to a crystalline phase were studied using in situ temperature-dependent sheet resistance measurements, X-ray diffraction, and transmission electron microscopy. The optical band gaps of N-GST(3/2/5) films are higher than that of GST(2/2/5) film in both the amorphous and face-centered-cubic (fcc) phases. Ge nitride formation by X-ray photoelectron spectroscopy analysis increased the optical band gap and suppressed crystalline grain growth, resulting in an increase in the crystallization temperature and resistance in the fcc phase. As a result, the Ge- and N-doped GST(2/2/5) composite films can be considered as a promising material for phase-change memory application because of improved thermal stability and reduced power consumption.

Investigation on nitrogen-doped Ge2Sb2Te5 material for phase-change memory application

Nitrogen-doped Ge2Sb2Te5 thin film is proposed to present the feasibility for electrical phase-change memory application. The effect of nitrogen doping on the structure is studied by in situ sheet resistance measurement and X-ray diffraction method. The temperature upon crystallization from amorphous to cubic structure is increased by nitrogen addition, while the phase transformation to hexagonal phase occurs at a lower temperature compared with the nitrogen-free Ge2Sb2Te5 material. The X-ray diffraction test reveals that the grain size has been refined significantly by the incorporation of nitrogen atoms in the film. Phase-change memory device based on nitrogen incorporated Ge2Sb2Te5 material is fabricated using complementary metal oxide semiconductor technology. A complete crystallization of the phase-change cell is realized in the current–voltage sweeping process. Nitrogen-doped Ge2Sb2Te5 with higher sheet resistance in the crystalline state is favored for phase-change memory application due to the decreased reset voltage and promoted resistance ratio of the reset and set states.

Structural origin of set-reset process in a new bulk Si15Te83Ge2 phase-change memory material

A new phase-change memory material, in bulk, has been prepared by melt-quenching technique, which has a better glass forming ability. This sample is set and resettable relatively easily for several cycles at 2mA SET and RESET input currents, and is likely to be a suitable material for phase-change memory applications. Raman scattering studies have been undertaken during the SET and RESET operations to elucidate the local structural transformations that occur during these operations.

Atomic structure of amorphous and crystallized Ge15Sb85

Ge 15 Sb 85 is a promising material for phase-change memory applications owing to its very short crystallization times. As deposited amorphous samples of sputter deposited Ge15Sb85 have been investigated by extended x-ray absorption fine structure (EXAFS) measurements on both, Sb and Ge K absorption edges. After crystallizing the specimen, x-ray diffraction (XRD) and EXAFS measurements have been performed to analyze the atomic structure at different annealing conditions. Thus, experimental techniques focusing on the long range order as well as on the local order have been combined. Sb atoms have on average 3.2(2) nearest neighbors, while Ge atoms have 4.0(3). The Ge–Ge and Ge–Sb bond lengths are determined to 2.46(2) and 2.66(1) Å, respectively and agree well with those observed in the amorphous phase of the common phase-change material Ge2Sb2Te5. After crystallizing the sample at 250 °C, very different EXAFS spectra with modified Ge–Sb bond lengths are observed. The higher concentration of Ge neighbors at the Ge edge as compared to the as-deposited sample is indicative for phase separation. For the corresponding sample, XRD does not show reflections of Ge, which indicates that the agglomeration of Ge is amorphous or below the coherence length of the x-radiation. The EXAFS spectrum shows a superposition of two phases: one with bond lengths which agree with sp3-hybridized Ge [2.43(1) Å] and another one with longer Ge–Ge bond lengths [2.79(8) Å]. This result can be explained by phase separation in the material.