Amorphous structure melt-quenched from defective GeSbTe

Sun, Zhimei
November 2012
Journal of Materials Science;Nov2012, Vol. 47 Issue 21, p7635
Academic Journal
GeSbTe (GST) is a technologically important phase-change material for data storage, where the fast reversible phase transition between crystalline and amorphous states is used for recording information. The encoding is achieved by the large contrast in physical properties between the two states. Ge vacancies (V) and Sb antisite atoms (Sb) are primary point defects in crystalline GST. The effect of V and Sb on the atomic arrangements in amorphous GST is unknown, which, however, has significant effects on the performance of GST. In this work, by means of ab initio molecular dynamics calculations, the atomic arrangements in amorphous ideal and defective GST have been investigated. The results show that the amorphous structure of GST with Sb ( St-GST) or with V ( V-GST) has the same cubic framework and close chemical ordering to ideal GST, and hence similar fast reversible phase transition behavior is expected in the defective phases. Furthermore, the presence of Sb or V in the crystalline phase will result in much more Ge atoms in a tetrahedral geometry as well as in a fourfold octahedral environment in the amorphous state. Especially in V-GST, around 36 % Ge atoms occupy a fourfold octahedral geometry. As fourfold octahedral Ge atoms can enhance the large contrast in physical properties between the crystalline and amorphous phases, introducing Ge vacancies would be an efficient way to improve the performance of GST phase-change materials.


Related Articles

  • Band gap widening with time induced by structural relaxation in amorphous Ge2Sb2Te5 films. Fantini, P.; Brazzelli, S.; Cazzini, E.; Mani, A. // Applied Physics Letters;1/2/2012, Vol. 100 Issue 1, p013505 

    In a phase change memory the device resistance corresponding to the amorphous phase monotonically increases with time after the reset programming operation. This phenomenon, called drift, affects the stability of the high resistive state, namely the reset state. In this work we investigate the...

  • Intrinsic evolutions of dielectric function and electronic transition in tungsten doping Ge2Sb2Te5 phase change films discovered by ellipsometry at elevated temperatures. Guo, S.; Ding, X. J.; Zhang, J. Z.; Hu, Z. G.; Ji, X. L.; Wu, L. C.; Song, Z. T.; Chu, J. H. // Applied Physics Letters;2/2/2015, Vol. 106 Issue 5, p1 

    Tungsten (W) doping effects on Ge2Sb2Te5 (GSTW) phase change films with different concentrations (3.2, 7.1, and 10.8%) have been investigated by variable-temperature spectroscopic ellipsometry. The dielectric functions from 210 K to 660 K have been evaluated with the aid of Tauc-Lorentz and...

  • Effect of InP Doping on the Phase Transition of Thin GeSbTe Films. Bang, Ki; Oh, Yong; Lee, Seung-Yun // Journal of Electronic Materials;Aug2015, Vol. 44 Issue 8, p2712 

    We report the crystallization and phase-transition behavior of GeSbTe thin films doped with indium phosphorus (InP). Pure GeSbTe thin films and InP-doped GeSbTe thin films were prepared by use of an rf magnetron sputtering method. After thermal annealing, electrical and optical changes in the...

  • Interface-controlled thermal transport properties in nano-clustered phase change materials. Lee, Dongbok; Kang, Stephen Dongmin; Kim, Hyun-Mi; Kang, Dae-Hwan; Lyeo, Ho-Ki; Kim, Ki-Bum // Journal of Applied Physics;Apr2012, Vol. 111 Issue 7, p073528 

    We measured the thermal conductivity of nano-clustered Ge2Sb2Te5(GST)-TiOx films in situ upon annealing from room temperature to 200 °C by the time-domain thermoreflectance method. The nano-clustered structure was found to significantly reduce the thermal conductivity of the crystallized...

  • Terahertz and direct current losses and the origin of non-Drude terahertz conductivity in the crystalline states of phase change materials. Shimakawa, Koichi; Wagner, Tomas; Frumar, Miloslav; Kadlec, Filip; Kadlec, Christelle; Kasap, Safa // Journal of Applied Physics;Dec2013, Vol. 114 Issue 23, p233105 

    THz and DC losses in crystalline states of GeSbTe and AgInSbTe phase-change material systems are re-examined and discussed. Although a simple free carrier transport has been assumed so far in the GeSbTe (GST) system, it is shown through recent experimental results that a series sequence of...

  • Relationship between melting and amorphization of ice. Mishima, Osamu // Nature;12/12/1996, Vol. 384 Issue 6609, p546 

    Describes experiments probing the relationship between pressure-induced amorphization and melting for a form of crystalline ice. The avoidance of the complication of crystal-crystal transformations interrupting the melting process; The sequence of transitions being a crossover from a two-phased...

  • Effects of Sn Substitution on Thermoelectric Properties of GeSbTe. Williams, Jared; Mather, Spencer; Morelli, Donald // Journal of Electronic Materials;Feb2016, Vol. 45 Issue 2, p1077 

    Phase-change materials are identified by their ability to rapidly alternate between amorphous and crystalline phases upon heating, exhibiting large contrast in the optical/electrical properties of the respective phases. Such materials are primarily used in memory storage applications, but...

  • Luminescence properties of Sm3+ impurities in strontium lithium bismuth borate glasses. Rajesh, D.; Ratnakaram, Y. C.; Seshadri, M.; Balakrishna, A. // AIP Conference Proceedings;6/5/2012, Vol. 1447 Issue 1, p581 

    In the present work, different concentrations of Sm3+-doped strontium lithium bismuth borate glasses (SLBiB) were prepared by melt quench technique. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction and SEM analysis. Using the J-O intensity parameters,...

  • Phase transformation mechanisms involved in excimer laser crystallization of amorphous silicon.... Im, James S.; Kim, H.J. // Applied Physics Letters;10/4/1993, Vol. 63 Issue 14, p1969 

    Investigates the phase transformation mechanisms and resulting microstructures of excimer laser-induced crystallization of amorphous silicon (Si) films on silicon oxide (SiO[sub 2]). Significance of large-grained polycrystal Si films; Characteristics of the transformation mechanisms involved in...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics