Low temperature stress-induced crystallization of germanium on plastic

Davood Shahrjerdi, B. Hekmatshoar, L. Rezaee, S. S. Mohajerzadeh

Research output: Contribution to journalArticle

Abstract

Crystallization of a-Ge was performed on flexible plastic substrates at temperatures as low as 130 °C. Copper has been primarily used as the seed of crystallization, while an external stress was applied onto the flexible substrate to enhance the crystallization. The substrates used for this study were mainly 0.1 mm thick Polyethylene terephthalate (PET) films, which remain flexible during post treatment at low temperatures. Various samples were subject to tensile or compressive stress for the annealing step. It has been observed that only in the case of a compressive stress, crystallization becomes possible. A final electrical sheet resistance of less than 45 kΩ/□ is achieved after an annealing period of 3 h. XRD, SEM and Hall mobility measurement have been exploited to study the crystallization and explain the drastic drop of electrical resistance in samples subjected to external compressive stress. The 〈2 2 0〉 peak of Ge is discernible in the XRD spectra, confirming the crystallization. Also the study of surface morphology using SEM corroborates the crystalline nature of the annealed Ge film and the evolution of cracks. A carrier mobility of more than 110 cm2/V s is observed for holes using Hall measurement. The shrinkage of PET during annealing induces compressive stress both in the substrate and the over-layer, in addition to the externally applied stress. This causes the progressive evolution of cracks in the Ge layer and a weak interfacial buckling of the Ge film.

Original languageEnglish (US)
Pages (from-to)330-334
Number of pages5
JournalThin Solid Films
Volume427
Issue number1-2
DOIs
Publication statusPublished - Mar 3 2003

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Keywords

  • Compressive stress
  • External stress
  • Flexible substrates
  • Low temperature crystallization
  • Polycrystalline germanium

ASJC Scopus subject areas

  • Surfaces, Coatings and Films
  • Condensed Matter Physics
  • Surfaces and Interfaces

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