Hydrogenated amorphous silicon deposited under accurately controlled ion bombardment using pulse-shaped substrate biasing

Journal article (2010)

Authors

M.A. Wank Photovoltaic Materials and Devices - EEMCS
R.A.C.M.M. van Swaaij Photovoltaic Materials and Devices - EEMCS
P Kadlacek External organisation
MCM van de Sanden External organisation
M. Zeman Photovoltaic Materials and Devices - EEMCS
Research Group
Photovoltaic Materials and Devices (EEMCS) (TU Delft)
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Published Date

2010

Language

English

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Faculty

Electrical Engineering, Mathematics and Computer Science

Department

Electrical Sustainable Energy

Research Group

Photovoltaic Materials and Devices

Abstract

We have applied pulse-shaped biasing to the expanding thermal plasma deposition of hydrogenated amorphous silicon at substrate temperatures ~ 200¿°C and growth rates around 1 nm/s. Substrate voltage measurements and measurements with a retarding field energy analyzer demonstrate the achieved control over the ion energy distribution for deposition on conductive substrates and for deposition of conductive materials on nonconductive substrates. Presence of negative ions/particles in the Ar¿H2¿SiH4 plasma is deduced from a voltage offset during biasing. Densification of the material at low Urbach energies is observed at a deposited energy 4.8¿eV/Si atom is attributed to bulk atom displacement in subsurface layers. We make the unique experimental abservation of a decreasing Tauc band gap at increasing total hydrogen concentration¿this allows to directly relate the band gap of amorphous silicon to the presence of nanovoids in the material.