Effects of oxygen incorporation in GeSbTe films on electrical properties and thermal stability

Abstract

Oxygen incorporated Ge2Sb2Te5 (GST) films were prepared by an ion beam sputtering deposition method. I-V curves of the oxygen incorporated GST active layer showed that the threshold voltage (Vth) varied, depending on the level of incorporated oxygen. In the case of a GST film with an elevated oxygen content of 30.8%, the GST layer melted at 9.02 V due to the instability conferred by the high oxygen content. The formation of Ge-deficient hexagonal phases such as GeSb2Te4 and Sb2Te3 appear to be responsible for the Vth variation. Impedance analyses indicated that the resistance in GST films with oxygen contents of 16.7% and 21.7% had different origins. Thermal desorption spectroscopy data indicate that moisture and hydrocarbons were more readily desorbed at higher oxygen content because the oxygen incorporated GST films are more hydrophilic than undoped GST films.

Intrinsic memristance mechanism of crystalline stoichiometric Ge2Sb2Te5

“…IS is a powerful tool to study the electrical characteristics of various materials and is already utilized to investigate the conduction behaviors of polycrystalline chalcogenides. [38][39][40][41][42] The Cole-Cole plots and the equivalent circuit used to fit the data are shown in Fig. 3(a).…”

“…The high-and low-frequency regions are attributable to the grains and grain boundaries, respectively. [38][39][40][41][42][43] The grain boundary traps typically have longer relaxation lifetimes (s ¼ RC), because grains are more ordered. The impedance spectra as a function of bias are shown in Fig.…”

A study of phase transition behaviors of chalcogenide layers using in situ alternative-current impedance spectroscopy

“…32 In oxygen-doped GST samples, impedance analysis revealed the dopant indeed affects the phase-transition behaviors of GST 33 and alters the contribution of grain and grainboundary to the electrical properties of doped GST. 34 This work establishes an in situ alternative-current (AC) impedance measurement for analyzing the phase-transition behaviors of pristine Ge 2 Sb 2 Te 5 (GST) and cerium-doped GST (Ce-GST) in conjunction with the equivalent circuit models, e.g., the brick-layer model (BLM) [35][36][37] and the nanograin composite model (n-GCM). 38 In addition to distinguishing the roles of grain and grain-boundary to electrical properties, the feasibility of impedance spectroscopy to characterize the phase-change kinetics of chalcogenides is also discussed.…”

Thermo-desorption measurements during N-doped Ge-rich Ge2Sb2Te5 crystallization

“…These results are in agreement with a previous work reporting O 2 , C, CH 4 , and H 2 O thermal desorption from an uncovered oxygen-doped Ge 2 Sb 2 Te 5 layer. All the molecules were found to desorb at the same temperature, but the desorption temperature was observed to vary with the O content of the layer, which was shown to modify the crystallization process [31]. The surface desorption process is not the mechanism driving the observed desorption temperatures, which is more likely linked to the structural evolution of the GGST layer upon annealing [32].…”