AVS 53rd International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS2+TF-WeM

Paper PS2+TF-WeM10
Effects of Clusters and Higher-Order Silane Related Radicals on Stability of a-Si:H Films Deposited by Plasma CVD

Wednesday, November 15, 2006, 11:00 am, Room 2011

Session: Plasma Deposition
Presenter: K. Koga, Kyushu University, Japan
Authors: K. Koga, Kyushu University, Japan
H. Miyahara, Kyushu University, Japan
G. Yuan, Kyushu University, Japan
A. Genot, Kyushu University, Japan
S. Iwashita, Kyushu University, Japan
W.M. Nakamura, Kyushu University, Japan
M. Shiratani, Kyushu University, Japan
Correspondent: Click to Email
Light-induced degradation of hydrogenated amorphous silicon (a-Si:H) is one of the most important issues for a-Si:H solar cells.@footnote 1@ Recently, we have succeeded in depositing highly stable a-Si:H films by using a multi-hollow discharge plasma CVD method.@footnote 2@ We can obtain information about species responsible for degrading stability, because stable a-Si:H films are deposited in the upstream region from the discharges while metastable ones are in the downstream region in the multi-hollow discharge plasma CVD reactor. To identify such species, we detected clusters and higher order silane related radicals both in the upstream and downstream region. The amount of amorphous clusters in the upstream region is by more than two orders of magnitude lower than that in the downstream, whereas densities of Si@sub 2@H@sub 6@ and Si@sub 3@H@sub 8@ in the upstream related radicals is 0.3 - 0.7 times as low as those in the downstream even for a high gas velocity of 52 cm/s. Therefore, the multi-hollow discharge plasma CVD method together with a high gas velocity is effective in suppressing volume fraction of clusters incorporated into the films deposited in the upstream region, while such combination has little effects on those of Si@sub 2@H@sub 6@ and Si@sub 3@H@sub 8@ related radicals. These results suggest that amorphous clusters formed in the discharges are one of the species responsible for degrading stability of films, whereas Si@sub 2@H@sub 6@ and Si@sub 3@H@sub 8@ related radicals are not. @FootnoteText@ @footnote 1@R. E. I. Schropp and M. Zeman, "Amorphous and Microcrystalline Silicon Solar Cells", Kluwer Academic Publishers, Boston, 1998, p. 99.@footnote 2@K. Koga, et al., Jpn . J. Appl. Phys., 48 (2005) L1430.