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Enhancement of the power factor in two‐phase silicon–boron nanocrystalline alloys
Author(s) -
Narducci Dario,
Lorenzi Bruno,
Zianni Xanthippe,
Neophytou Neophytos,
Frabboni Stefano,
Gazzadi Gian Carlo,
Roncaglia Alberto,
Suriano Francesco
Publication year - 2014
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201300130
Subject(s) - materials science , nanocrystalline material , boride , silicon , boron , grain boundary , microstructure , seebeck coefficient , precipitation , nanocrystalline silicon , interphase , thermoelectric effect , metallurgy , composite material , nanotechnology , thermal conductivity , crystalline silicon , chemistry , thermodynamics , physics , organic chemistry , amorphous silicon , meteorology , biology , genetics
In previous publications it was shown that the precipitation of silicon boride around grain boundaries may lead to an increase of the power factor in nanocrystalline silicon. Such an effect was further explained by computational analyses showing that the formation of an interphase at the grain boundaries along with high boron densities can actually lead to a concurrent increase of the electrical conductivity σ and of the Seebeck coefficient S . In this communication we report recent evidence of the key elements ruling such an unexpected effect. Nanocrystalline silicon films deposited onto a variety of substrates were doped to nominal boron densities in excess of 10 20 cm −3 and were annealed up to 1000 °C to promote boride precipitation. Thermoelectric properties were measured and compared with their microstructure. A concurrent increase of σ and S with the carrier density was found only upon formation of an interphase. Its dependency on the film microstructure and on the deposition and processing conditions will be discussed.