Migration of open volume deficiencies in hydrogenated amorphous silicon during annealing

J. Melskens, S.W.H. Eijt, M. Schouten, A.S. Vullers, A. Mannheim, H. Schut, B. Macco, M. Zeman, A.H.M. Smets

Research output: Contribution to journalArticleAcademicpeer-review

11 Citations (Scopus)
98 Downloads (Pure)

Abstract

The nanostructure of hydrogenated amorphous silicon (a-Si:H) is studied by means of doppler broadening positron annihilation spectroscopy (DB-PAS) and Fourier transform infrared (FTIR) spectroscopy. The evolution of open volume deficiencies is monitored during annealing, demonstrating that small vacancies and other small vacancy clusters that are initially present in the a-Si:H nanostructure agglomerate into larger vacancy clusters. The migration of open volume deficiencies is less pronounced for a-Si:H deposited at higher hydrogen-to-silane gas flow rate ratio, R. FTIR spectroscopy reveals the presence of a peculiar peak in the refractive index in the infrared - and hence the calculated mass density - which occurs just before H effusion from the films starts. The combined results of DB-PAS and FTIR spectroscopy indicate that a stress buildup caused by the accumulation of H 2 in agglomerating vacancies during annealing can explain the sudden mass density increase. At higher temperatures, stress is released with the onset of H effusion. The H effusion consists of a two-stage process involving small open volume deficiencies and nanosized voids, contrasting earlier interpretations. The reduced amount of hydrogen migration and enhanced hydrogen passivation degree are suggested as key factors to the reduced light-induced degradation associated with increased R values.

Original languageEnglish
Article number7828138
Pages (from-to)421-429
Number of pages9
JournalIEEE Journal of Photovoltaics
Volume7
Issue number2
DOIs
Publication statusPublished - 2 Mar 2017

Keywords

  • Annealing
  • defects
  • hydrogenated amorphous silicon (a-Si:H)
  • nanostructure
  • vacancies

Fingerprint Dive into the research topics of 'Migration of open volume deficiencies in hydrogenated amorphous silicon during annealing'. Together they form a unique fingerprint.

  • Cite this

    Melskens, J., Eijt, S. W. H., Schouten, M., Vullers, A. S., Mannheim, A., Schut, H., Macco, B., Zeman, M., & Smets, A. H. M. (2017). Migration of open volume deficiencies in hydrogenated amorphous silicon during annealing. IEEE Journal of Photovoltaics, 7(2), 421-429. [7828138]. https://doi.org/10.1109/JPHOTOV.2016.2646421