Epitaxial stabilisation of Ge1-xSnxalloys

Alfonso Sanchez-Soares, Conor O'Donnell, James C. Greer

Research output: Journal PublicationArticlepeer-review


The thermodynamic stability of germanium tin Ge1-xSnx alloys is investigated across the composition range 0 ≤ x ≤ 1 by applying density functional theory together with the cluster expansion formalism (CE). It is known that GeSn alloys are immiscible and that non-equilibrium growth techniques are required to produce metastable films and nanostructures. Insight into the driving forces behind component segregation is gained by investigating the equilibrium thermodynamics of GeSn systems. The alloy free energy of mixing is computed by combining enthalpies from the CE with entropy terms for configurational and vibrational degrees of freedom. Volume deformations due to the large mismatch in ionic radii are readily found to be the key driving force for immiscibility at all temperatures of relevance. This leads to a study of epitaxial stabilisation by employing latticed matched substrates to favour growth of alloys with fractional compositions of x = 0, approximately x = 0.5 and x = 1. The reduction in the free energy of mixing due to epitaxial strain in thin films is quantified for each substrate leading to indicators for growth of kinetically stable films.

Original languageEnglish
Article number325302
JournalJournal Physics D: Applied Physics
Issue number32
Publication statusPublished - Aug 2021


  • cluster theory expansion
  • epitaxial stabilization
  • germanium tin
  • nanoelectronics
  • phase diagram
  • photonics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Acoustics and Ultrasonics
  • Surfaces, Coatings and Films


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