The Phase Change Effect of Oxygen-Incorporation in GeSbTe Films

Abstract

Reflectivity changes in oxygen-incorporated Ge2Sb2Te5 (GST) films were investigated via a laser-induced crystallization process. The crystallization process showed that the phase change speed and the laser power required for crystallization become faster and larger in GST films with a characteristic quantity of oxygen. We confirmed that a dominant grain growth mode during the laser crystallization is a major determinant for the speed of phase change in GST films with a characteristic quantity of oxygen. JMA results and changes in surface morphology indicate that the origin of the growth mode change is due to an increase in the number of initial nucleation sites produced in the oxygen-incorporated GST films. After the re-amorphization process, oxygen-incorpo-rated GST films show more rapid and more stable phase change properties than that of GST films. VC 2011 The Electrochemical Society. [DOI: 10.1149/1.3556609] All rights reserved. Manuscript submitted December 10, 2010; revised manuscript received January 19, 2011. Published March 8, 2011. GeSbTe-based materials, especially Ge2Sb2Te5 (GST), which is located on the tie-line in the ternary diagram of the GeTe-Sb2Te3 system, have been the subject of extensive studies. GST has many potential applications such as in optical storage media and phase change random access memory devices (PRAM).1–3 Even though GST has many potential uses it also has some disadvantages, whic

Effect of Electrode Material on the Crystallization of GeTe Grown by Atomic Layer Deposition for Phase Change Random Access Memory

“…are the values of resistance in the fully amorphous and crystalline phases. The JMA kinetics is an equation for kinetics in the phase transition mechanism, generally expressed as shown in Equation (2) [21,22]. xfalse(tfalse)=1−expfalse[−false(ktfalse)nfalse] where n is the Avrami coefficient and k is the effective rate constant.…”

“…xfalse(tfalse)=1−expfalse[−false(ktfalse)nfalse] where n is the Avrami coefficient and k is the effective rate constant. Equation (2) can be modified to deal with the R–t curve, as follows: [21,22,23] lnfalse[lnfalse[11−xfalse(tfalse)false]false]=nlnt+nlnk…”

“…According to Equation (3), n can be acquired from the slope of ln(t) versus ln[−ln(1− x (t))] plot. The Avrami coefficient, n , can be expressed as the sum of two elements, n = a + b , where a indicates the nucleation index, b indicates the dimensionality of the growth (such as b = 1, 2, or 3 for one-, two-, or three-dimensional growth, respectively, where nuclei grow like needles, disks, or spheres) [21,22,23,24,25].…”

Ultrafast phase change and long durability of BN-incorporated GeSbTe

“…Although the JMA plot characterizes the isothermal crystallization on the minute time scale, it is also possible to subtract the Avrami coefficient, n, from the nanosecond time scale, as we previously reported. 26 Fig. 3(e)-(h) show JMA plots on the nanosecond time scale at a laser power of 40 mW.…”

“…By comparing our previous results on oxygen-incorporated GST lms with the results of this study, BN-incorporated GST lms were found to have better phase change speed and stability. 26,28 The JMA plot for oxygen-doped GST indicates that, for the generation of nucleation sites, it is required to wait for about 30 ns. However, in BN-incorporated GST, there is no incubation period for nucleation sites because BN molecules already act as nucleation sites.…”