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The influence of different amounts of Bi, Ti and In on the thermal properties and crystallization kinetics of GeSbTe thin films for phase change memory devices was investigated. Temperatures and heat effects of crystallization were evaluated for all investigated compositions. Joint utilization of model-free Ozawa-Flynn-Wall and model-fitting Coates-Redfern methods allowed to estimate effective activation energies and pre-exponential factors for crystallization processes of amorphous films as functions of conversion, and determine reaction models. It was found that crystallization process most adequately can be described by the second- or third-order reaction. Storage and data processing times of the phase change memory cells on the basis of investigated materials were calculated with using of determined kinetic triplets of crystallization processes. Calculations showed that crystallization time decreases nearly on the order of magnitude for GeSbTe+1 mass% In in comparison with undoped GeSbTe. On the other hand, compositions with 0.5 and 3 mass% In allow to increase sufficiently storage time. Introduction of Ti does not significantly affect data processing time of phase change memory cell; however, it decreases storage time. GeSbTe+0.5 mass% Bi composition have the most suitable kinetic parameters for phase change memory among the studied thin films. [ABSTRACT FROM AUTHOR]

The non-isothermal method for estimating the kinetic parameters of crystallization for the phase change memory (PCM) materials was discussed. This method was applied to the perspective PCM material of GeSbTe with different Bi contents (0, 0.5, 1, 3 mass%) for defining the kinetic triplet. Rutherford backscattering spectroscopy and X-ray diffraction were used to carry out elemental and phase analysis of the deposited films. Differential scanning calorimetry at eight different heating rates was used to investigate kinetics of thermally induced transformations in materials. Dependences of activation energies of crystallization ( E) on the degree of conversion were estimated by model-free Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, Tang and Starink methods. The obtained values of E were quite close for all of these methods. The reaction models of the phase transitions were derived with using of the model-fitting Coats-Redfern method. In order to find pre-exponential factor A at progressive conversion values, we used values of E already estimated by the model-free isoconversional method. It was established that the crystallization processes in thin films investigated are most likely describes by the second and third-order reactions models. Obtained kinetic triplet allowed predicting transition and storage times of the PCM cells. It was found that thin films of GeSbTe + 0.5 mass% Bi composition can provide the switching time of the phase change memory cell less than 1 ns. At the same time, at room temperature this material has a maximum storage time among the studied compositions. [ABSTRACT FROM AUTHOR]