Effect of P Incorporation on Aggregation of Nanocrystallites in Amorphous and Nanocrystalline Mixed-Phase Silicon Thin Films

C. S. Jiang, B. Yan, Y. Yan, C. W. Teplin, R. Reedy, H. R. Moutinho, M. M. Al-Jassim, J. Yang, S. Guha

Research output: Contribution to journalArticlepeer-review

5 Scopus Citations

Abstract

We report the effects of P incorporation on the nanometer-scale structural and electrical properties of amorphous and nanocrystalline mixed-phase Si:H films. In the intrinsic and weakly P-doped (3 × 1018 at/cm3) films, the nanocrystallites aggregate to cone-shaped structures. Conductive atomic force microscopy images showed high current flows through the nanocrystalline cones and a distinct two-phase structure in the micrometer range. Adding PH3 into the processing gas moved the amorphous/nanocrystalline transition to a higher hydrogen dilution ratio required for achieving a similar Raman crystallinity. In a heavily P-doped (2 × 1021 at/cm3) film, the nanocrystalline aggregation disappeared, where isolated grains of nanometer sizes were distributed throughout the amorphous matrix. The heavily doped mixed-phase film with 5-10% crystal volume fraction showed a dramatic increase in conductivity. We offer an explanation for the nanocrystalline cone formation based on atomic hydrogen enhanced surface diffusion model, and propose that the coverage of P-related radicals on the existing nanocrystalline surface during film growth and the P segregation in grain boundaries are responsible for preventing new nucleation on the surface of the existing nanocrystallites, resulting in nanocrystallites dispersed throughout the amorphous matrix. Crown

Original languageAmerican English
Pages (from-to)2276-2281
Number of pages6
JournalJournal of Non-Crystalline Solids
Volume354
Issue number19-25
DOIs
StatePublished - 2008

NREL Publication Number

  • NREL/JA-520-41991

Keywords

  • Amorphous silicon
  • Atomic force microscopy
  • Nanocrystalline materials
  • Thin films

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