Quantification of Crystallinity in Ge–Sb–Te Chalcogenide Materials Using Energy-Filtered Electron Diffraction

Ge-Sb-Te based chalcogenide materials are widely used in non-volatile phase-change random-access memory and optical data storage devices due to their rapid phase change from amorphous to crystalline. The percentage of phase transition (or degree of crystallinity) strongly influences the electrical characteristics of the devices. Thus, quantitative analysis of crystallinity upon phase transition, induced by Joule heating or laser pulse, is necessary. We propose a technique for quantifying the crystallinity in Ge-Sb-Te chalcogenide materials using energy-filtered electron diffraction in transmission electron microscopy. The degree of crystallinity of carbon-doped Ge1Sb6Te4, which is stable under the high-energy electron beam irradiation, was investigated for various laser pulse durations. Crystallinity in carbon-doped Ge1Sb6Te4 was calculated by separation of the crystalline and amorphous intensities from the total intensity histogram, using the azimuthal average of the zero-loss filtered electron diffraction pattern. Crystallinity of the samples exposed to a laser pulse for 25, 50, 75, and 100 ns was successfully determined to be 41.2, 51.5, 57.2, and 60.8%, respectively.