title: Short range order and stability of amorphous Ge(x)Te(100-x) alloys (12 ≤ x ≤ 44.6).
abstract: Amorphous Ge(x)Te(100-x) alloys were obtained over a broad composition range (12 ≤ x ≤ 44.6) by thermal co-evaporation. Their structure was investigated by x-ray diffraction and extended x-ray absorption fine structure measurements. Experimental datasets were fitted simultaneously by the reverse Monte Carlo simulation technique. It is concluded that Te is mostly twofold coordinated and the majority of Ge atoms have four neighbours. The number of Ge-Ge and Te-Te bonds evolves monotonically with composition. Ge-Ge bonding can be observed already at x = 24 while Te-Te bonds can be found even in Ge44.6Te55.4. The models obtained by simulation show that the structure of compositions with x > 24 should be considered as a random covalent network but there is chemical ordering for x ≤ 24, exactly in the composition range where glasses can be obtained from the melt by fast quenching. The composition dependences of some physical properties also point to the connection between chemical short range order and the stability of the amorphous phase: while the glass transition temperature and microhardness increase monotonically with the composition, the thermal stability of the amorphous films goes through a maximum around x = 20-24.
authors.affiliation: Wigner Research Centre for Physics, Institute for Solid State Physics, Budapest, Hungary. jovari.pal@wigner.mta.hu
authors.forename: P
authors.initials: P
authors.lastname: Jóvári
authors.forename: A
authors.initials: A
authors.lastname: Piarristeguy
authors.forename: R
authors.initials: R
authors.lastname: Escalier
authors.forename: I
authors.initials: I
authors.lastname: Kaban
authors.forename: J
authors.initials: J
authors.lastname: Bednarčik
authors.forename: A
authors.initials: A
authors.lastname: Pradel
mesh_terms: D000497:Alloys / Q000737:chemistry*; D005857:Germanium / Q000737:chemistry*; D006244:Hardness; D006358:Hot Temperature; D008422:Materials Testing; D010316:Particle Size; D044367:Phase Transition; D013499:Surface Properties; D013691:Tellurium / Q000737:chemistry*; D044366:Transition Temperature
chemical_list: D000497:Alloys; D005857:Germanium; D013691:Tellurium