Crystallization of sputtered-deposited and ion implanted amorphous Ge2Sb2Te5 thin films

X-ray diffraction and transmission electron microscopy have been utilized to measure the ion irradiation-induced modification in amorphous Ge2Sb2Te5 thin films. The isothermal crystallization of sputtered-deposited and Sb+ ion irradiated amorphous samples has been studied, focusing on the evolution of the microstructure during the initial stage of the transformation. In both samples, the amorphous to crystal transition occurs through the nucleation of face centered cubic (fcc) crystal domains at the film surface. A fast bidimensional growth of the crystalline nuclei in the sputtered-deposited films occurs by the generation of transrotational grains. The lattice parameter decreases as the crystalline fraction increases above 80%, and it approaches the fcc bulk value at the end of the transformation. Ion irradiation produces a densification of the deposited amorphous film (∼4% vertical shrinkage measured by atomic force microscopy) and an enhancement of the crystallization rate. Even in the irradiated amorp...

[1]  Myong R. Kim,et al.  Crystallization behavior of sputter-deposited amorphous Ge2Sb2Te5 thin films , 1999 .

[2]  Keiji Tanaka,et al.  Electronic Properties of Amorphous and Crystalline Ge2Sb2Te5 Films , 2005 .

[3]  A. Piro,et al.  Ion irradiation-induced local structural changes in amorphous Ge2Sb2Te5 thin film , 2008 .

[4]  J. Ziegler,et al.  stopping and range of ions in solids , 1985 .

[5]  J. Hosson,et al.  Electron diffraction and high-resolution transmission electron microscopy of the high temperature crystal structures of Gexsb2Te3+x (x=1,2,3) phase change material , 2002 .

[6]  A. Thölén,et al.  Transmission electron microscopy studies of the specific structure of crystals formed by phase transition in iron oxide amorphous films , 2000 .

[7]  Noboru Yamada,et al.  Structure of laser-crystallized Ge2Sb2+xTe5 sputtered thin films for use in optical memory , 2000 .

[8]  Dae-Hwan Kang,et al.  Investigation of the optical and electronic properties of Ge2Sb2Te5 phase change material in its amorphous, cubic, and hexagonal phases , 2005 .

[9]  H. Hamann,et al.  Ultra-high-density phase-change storage and memory , 2006, Nature materials.

[10]  J. Hosson,et al.  On the crystallization of thin films composed of Sb3.6Te with Ge for rewritable data storage , 2004 .

[11]  C. Wen,et al.  Crystal morphology and nucleation in thin films of amorphous Te alloys used for phase change recording , 2005 .

[12]  Pseudoepitaxial transrotational structures in 14 nm-thick NiSi layers on [001] silicon. , 2005, Acta crystallographica. Section B, Structural science.

[13]  Matthias Wuttig,et al.  Laser induced crystallization of amorphous Ge2Sb2Te5 films , 2001 .

[14]  N. Yamada,et al.  Rapid‐phase transitions of GeTe‐Sb2Te3 pseudobinary amorphous thin films for an optical disk memory , 1991 .

[15]  S. Han,et al.  Thermomechanical properties and mechanical stresses of Ge2Sb2Te5 films in phase-change random access memory , 2008 .

[16]  Tae-Yon Lee,et al.  Separate domain formation in Ge2Sb2Te5–SiOx mixed layer , 2006 .

[17]  Masud Mansuripur,et al.  Crystallization behavior of as-deposited, melt quenched, and primed amorphous states of Ge2Sb2.3Te5 films , 2000 .

[18]  V. Weidenhof,et al.  Structural transformations of Ge2Sb2Te5 films studied by electrical resistance measurements , 2000 .

[19]  A. Pirovano,et al.  Phase change mechanisms in Ge2Sb2Te5 , 2007 .

[20]  Martin Laurenzis,et al.  Electrical percolation characteristics of Ge2Sb2Te5 and Sn doped Ge2Sb2Te5 thin films during the amorphous to crystalline phase transition , 2005 .

[21]  M. Wuttig,et al.  Phase-change materials for rewriteable data storage. , 2007, Nature materials.

[22]  Effect of ion irradiation on the stability of amorphous Ge2Sb2Te5 thin films , 2008 .

[23]  M. Lankhorst,et al.  Low-cost and nanoscale non-volatile memory concept for future silicon chips , 2005, Nature materials.

[24]  Yuji Mori,et al.  Crystal structure of GeTe and Ge2Sb2Te5 meta-stable phase , 2000 .

[25]  J. F. Webb,et al.  One-dimensional heat conduction model for an electrical phase change random access memory device with an 8F2 memory cell (F=0.15 μm) , 2003 .

[26]  J. H. Coombs,et al.  Laser‐induced crystallization phenomena in GeTe‐based alloys. II. Composition dependence of nucleation and growth , 1995 .

[27]  J. Tominaga,et al.  Understanding the phase-change mechanism of rewritable optical media , 2004, Nature materials.

[28]  Matthias Wuttig,et al.  The quest for fast phase change materials , 2002 .