Stress evolution of Ge nanocrystals in dielectric matrices

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Bahariqushchi R., Raciti R., KASAPOGLU A. E., GÜR E., Sezen M., Kalay E., ...Daha Fazla

NANOTECHNOLOGY, cilt.29, sa.18, 2018 (SCI-Expanded) identifier identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 29 Sayı: 18
  • Basım Tarihi: 2018
  • Doi Numarası: 10.1088/1361-6528/aaaffa
  • Dergi Adı: NANOTECHNOLOGY
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Anahtar Kelimeler: germanium nanostructures, superlattices, Raman spectroscopy, stress tuning, transmission electron microscopy, dielectric matrices, SOLID-PHASE CRYSTALLIZATION, GERMANIUM NANOCRYSTALS, AMORPHOUS-SILICON, VISIBLE PHOTOLUMINESCENCE, COMPRESSIVE STRESS, LATERAL GROWTH, ELASTIC STRESS, OPTICAL GAIN, FILMS, SIO2
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

Germanium nanocrystals (Ge NCs) embedded in single and multilayer silicon oxide and silicon nitride matrices have been synthesized using plasma enhanced chemical vapor deposition followed by conventional furnace annealing or rapid thermal processing in N-2 ambient. Compositions of the films were determined by Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy. The formation of NCs under suitable process conditions was observed with high resolution transmission electron microscope micrographs and Raman spectroscopy. Stress measurements were done using Raman shifts of the Ge optical phonon line at 300.7 cm(-1). The effect of the embedding matrix and annealing methods on Ge NC formation were investigated. In addition to Ge NCs in single layer samples, the stress on Ge NCs in multilayer samples was also analyzed. Multilayers of Ge NCs in a silicon nitride matrix separated by dielectric buffer layers to control the size and density of NCs were fabricated. Multilayers consisted of SiNy:Ge ultrathin films sandwiched between either SiO2 or Si3N4 by the proper choice of buffer material. We demonstrated that it is possible to tune the stress state of Ge NCs from compressive to tensile, a desirable property for optoelectronic applications. We also observed that there is a correlation between the stress and the crystallization threshold in which the compressive stress enhances the crystallization, while the tensile stress suppresses the process.