This paper describes the growth and etching characteristics of phosphorusdoped tin oxide films, prepared by the simultaneous oxidation of tetramethyltin (TMT) and phosphine gas in the 400°–500°C range. Both the growth and etch rates of these films are found to be relatively constant until the P/Sn ratio exceeds 3.2%, at which point they fall off and eventually become negligible. In addition, films grown by this technique are found to undergo a rapid transition from the polycrystalline to the amorphous state when their P/Sn ratio exceeds 3.2%. Possible mechanisms for this behavior are outlined, based on the relative strength of the P‒O and Sn‒O bonds and on the network former properties of
P2O5
. It is proposed that the mechanism of film growth and dopant incorporation is the direct (and independent) reaction of phosphine and TMT with oxygen adsorbed on the substrate surface. The transport properties of these films are discussed in a companion paper.
EFFECT OF PHOSPHORUS DOPING1595 Z_2oo .2 m "= -r ~ioo (PH3/TMT) I , ! 15 z RATIO I 0 0 .... ~ 163 161 Fig. 5. Etch rate vs. PH3/TMT mole ratio on the basis of the relative strengths of the P--O and Sn--O bonds. These arguments also explain the rapid transition of these films from the crystalline to the amorphous state at low phosphorus incorporation levels. Finally, a relatively simple model for the film growth is proposed, based on the direction reaction of the phosphorus and tin species with the surface adsorbed oxygen.
AcknowledgmentsThe authors wish to thank R. Rafun and A. Hayner for assistance in manuscript preparation.on the order of 1.0 (12-cm) -1. This conductivity can be further increased by doping with Group V elements, such as phosphorus (1), antimony (2-6), and arsenic (7). This paper describes the effect of phosphorus doping upon the conductivity of tin oxide films. An anomalous feature of this doping behavior is that the conductivity ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.237.29.138 Downloaded on 2015-03-08 to IP ABSTRACT
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