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A study on the crystallization speed and thermal stability of N-doped Ge2Sb2Te5 thin film during amorphous-tocrystalline phase transition.

KI-HO SONG1, JUN-HYONG KIM1, JAE-HEE SEO1, HYUN-YONG LEE1,*

Affiliation

  1. Center for Functional Nano Fine Chemicals, Faculty of Applied Chemical Engineering, Chonnam National University, 300 Yongbong-dong, Gwangju 500-757, Korea

Abstract

In this work, we evaluated crystallization speed, thermal stability and optical property of the N-doped Ge2Sb2Te5 (GST) thin film, a candidate material for application to a phase-change random access memory (PRAM). The 200-nm-thick GST and N-GST films were deposited on p-type (100) Si and glass substrates using rf reactive sputtering at room temperature. Amorphous-to-crystalline phase transformation of GST and N-GST films was investigated by X-ray diffraction (XRD). The addition of N caused an increase of the crystallization temperature (TC), which means the enhancement of thermal stability for amorphous phase. Changes in the optical transmittance and sheet resistance (RS) of N-GST were observed using an UV-vis-IR spectrophotometer and 4-point probe, respectively. It was found that the added N causes the increase of Rs for both crystalline and amorphous phases and the optical energy gap (EOP). In particular, a high Rs is useful to reduce programming current. In addition, a speed of amorphous-to-crystalline transition and the surface morphology were evaluated by using a nano-pulse scanner (beam diameter < 2 m) and atomic force microscope, respectively. Conclusively, while the N-doping into GST causes the increase of Tc, Rs and EOP, it accompanies a decrease of crystallization speed..

Keywords

Crystallization temperature, Amorphous-to-crystalline transition, Phase-change.

Submitted at: July 5, 2009
Accepted at: Dec. 10, 2009

Citation

KI-HO SONG, JUN-HYONG KIM, JAE-HEE SEO, HYUN-YONG LEE, A study on the crystallization speed and thermal stability of N-doped Ge2Sb2Te5 thin film during amorphous-tocrystalline phase transition., Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 12, pp. 1988-1994 (2009)