High Rate Deposition of DC Magnetron Sputtered a-Si for Photoreceptors
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HIGH RATE DEPOSITION OF DC MAGNETRON SPUTTERED A-SI FOR PHOTORECEPTORS E.Niemann, R.Herkert, D.Leidich, W.Senske AEGResearch Laboratories, Goldsteinstrasse Frankfurt 71, FRG
235,
D-6000
ABSTRACT High rate deposition of a-Si-layers is an important condition for an economical production of a-Si devices. We have obtained deposition rates of up to 30 pm/h by reactive DC magnetron sputtering from n-type and p-type doped monocrystalline silicon targets. The electrical properties of the films (dark conductivity, photoconductivity, activation energy) were examined as a function of the hydrogen partial pressure for the deposition rate of about 10 jm/h. The film structure is investigated by scanning electron microscope (surface and fracture) and hydrogen evolution method. The high rate deposited films show a homogeneous appearance exhibiting voids. The electrophotographic properties were examined for films on flat substrates. The charge acceptance for positive and negative charging is about 35V/pm with a low dark decay for films of the structure AI/SiO /a-Si/SiO . ESCA-measurements show an a-SiO -layer of 2nm oAhthe top. The spectral sensivitity is examined. INTRODUCTION Xerographic photoreceptors made of amorphous silicon (a-Si:H) have several advantages compared to conventional xerographic materials. A high deposition rate of a-Si-layers is an important condition for an economical production of such a-Si devices. Recently a-Si structures were deposited using ordinary glow discharge method, where deposition rates of up to 15 pm/h were attained [i] . a-Si-photoreceptors are also available by rf-sputtering technique [21, but the deposition rates are too low. Recently deposition rates up to 24 jm/h have been obtained with DC magnetron sputtering technique for a-Si films to be used in a-Si solar cells [3]. We have achieved deposition rates of up to 30 pm/h by DC magnetron sputtering from n-type and p-type doped stalline silicon targets, a technique well suited production. Our a-Si-layers show good properties for as xerographic photoreceptors.
reactive monocryfor mass the use
EXPERIMENTAL The targets used for reactive DC magnetron sputtering are n-type and p-type doped monocrystalline silicon (0150mm, 10cm). The sputtering atmosphere consists of argon and hydrogen in the pressure range of 2-10x10• mbar. The flow rates are 14 sccm and 2-20 sccm for argon and hydrogen, respectively. The substrates are quartz for the conductivity measurements, borosilicate glass for the optical investigation and sapphire for the hydrogen evolution technique. The xerographic Mat. Res. Soc. Symp. Proc. Vol. 118. '1988 Materials Research Society
62
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Fig. 2 Dark conductivity for different hydrogen
of sputtered a-Si
flow rates
The structures are deposited on flat aluminium substrates. 0 substrate
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