Raman spectra and XPS studies of phase changes in Ge2Sb2Te5 films
Liu Bo (刘波)a, Song Zhi-Tang (宋志棠)a, Zhang Ting (张挺)a, Feng Song-Lin (封松林)a, Chen Bomyb
a Research Centre of Functional Semiconductor Film Engineering Technology, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China; b Silicon Storage Technology, Inc., 1171 Sonora Court, Sunnyvale, CA 94086, USA
Abstract Ge$_2$Sb$_2$Te$_5$ film was deposited by RF magnetron sputtering on Si (100) substrate. The structure of amorphous and crystalline Ge$_2$Sb$_2$Te$_5$ thin films was investigated using XRD, Raman spectra and XPS. XRD measurements revealed the existence of two different crystalline phases, which has a FCC structure and a hexagonal structure, respectively. The broad peak in the Raman spectra of amorphous Ge$_2$Sb$_2$Te$_5$ film is due to the amorphous －Te－-Te－ stretching. As the annealing temperature increases, the broad peak separates into two peaks, which indicates that the heteropolar bond in GeTe$_4$ and the Sb－Sb bond are connected with four Te atoms, and other units such as (TeSb) Sb－Sb (Te$_2$) and (Sb$_2$) Sb－Sb (Te$_2$), where some of the four Te atoms in the above formula are replaced by Sb atoms, remain in crystalline Ge$_2$Sb$_2$Te$_5$ thin film. And from the results of Raman spectra and XPS, higher the annealing temperature, more Te atoms bond to Ge atoms and more Sb atoms substitute Te in (Te$_2$) Sb－Sb (Te$_2$).
Received: 14 April 2004
Revised: 27 May 2004
Accepted manuscript online:
Fund: Project supported by the National High Technology Development Programme of China (Grant No 2003AA302720), Shanghai Nanotechnology Promotion Centre (0352nm016, 0359nm204, 0252nm084), China Postdoctoral Foundation (2003034308), K. C. Wong Education Foundati
Cite this article:
Liu Bo (刘波), Song Zhi-Tang (宋志棠), Zhang Ting (张挺), Feng Song-Lin (封松林), Chen Bomy Raman spectra and XPS studies of phase changes in Ge2Sb2Te5 films 2004 Chinese Physics 13 1947
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