자성 물질이 도핑된 InSbTe 의 구조적 전기적 특성 분석

Abstract

The operational mechanism of the phase-change memory is based on the fast and reversible phase-transition of the chalcogenide alloys. Among the phase-change chalcogenide alloys, Ge2Sb2Te5(GST) is known to have advantages in terms of speed, stability, and nonvolatility for next generation memory. However, the large amount of thermal threshold energy that is needed to generate a structural phase transition in thin films. So, in recent years, the phase change material InSbTe (IST) has received much attention as a promising candidate for phase change random access memory use in next-generation non-volatile memory devices. Core issues are to search improvement of stable non-GST materials and metal elements doped GST or IST materials as application to phase change random access memory. In this work, we investigated the variation of sheet resistance and phase change behavior on the doping of paramagnetic element Mn and ferromagnetic element Fe into the InSbTe (IST) material. We co-sputtered In3Sb1Te2 and Mn, Fe on a single crystal Si wafer. The particle size and distribution of doped elements Mn and Fe in InSbTe thin film was determined by High Resolution Transmission Electron Microscopy (HRTEM). We have studied the variation of sheet resistance by in-situ electrical sheet resistance measurements. The physical structure, chemical state and magnetic properties were analyzed by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and X-ray magnetic circular dichroism (XMCD) respectively. The MnInSbTe thin film was annealed at rate of 5℃/min. The sheet resistance was observed to suddenly drop at 97℃ and 310℃ during in-situ annealing. After undergone 97℃ area MIST2 specimen there was any crystalline peak on XRD. In the other hand, after undergone 310℃ area MIST3 specimen there is FCC structure peaks. For studdy on the reason of sheet resistance drop without any crystallization behavior, I have investigated chemical state by XPS measurement. In the result, initial binding energy 48.58eV of Mn 3p was shifted to 48.48 eV after annealing process. That result can be one evidence of sheet resistance drop without crystallization. The FeInSbTe thin film was annealed at a rate of 5℃/min. The sheet resistance was observed to suddenly drop from 1.0X10^3Ω/sq to 1.9X10^2Ω/sq at 45℃. XRD results confirmed that there was no crystallization in the amorphous FeInSbTe thin film even after the drop of sheet resistance. On the other hand, magnetic measurements by X-ray Magnetic Circular Dichroism (XMCD) technique showed that ferromagnetism of the FeInSbTe thin film disappears after the sheet resistance dropped at 45℃. This result implies that the cause of the change in sheet resistance in the FeInSbTe thin film at 45℃ is associated with the disappearance of ferromagnetism.