IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Thin Films Tuesday Sessions
       Session TF-TuM

Paper TF-TuM2
Linear Combinatorial Synthesis of Cadmium Tin Oxide Films by Low-pressure Chemical Vapor Deposition

Tuesday, October 30, 2001, 8:40 am, Room 123

Session: Optical Thin Films
Presenter: X. Li, National Renewable Energy Laboratory
Authors: X. Li, National Renewable Energy Laboratory
T. Gessert, National Renewable Energy Laboratory
T. Coutts, National Renewable Energy Laboratory
Correspondent: Click to Email
Recent work on transparent conducting oxides (TCOs) such as tin oxide (SnO@sub 2@) and cadmium stannate (CTO) has been of great interest because of the relevance of these materials to important technological applications. The electrical and optical properties of these materials are relevant to low-emissivity glass, flat-panel displays, and thin-film solar cells. SnO2 is very durable and appropriate for coatings on low-emissivity windows whereas CdO has exhibited mobilities over 200 cm@super 2@ V@super -1@ s@super-1@. The intermediate alloy, CTO, may be either orthorhombic or spinel, although thin-films are typically spinel. This material has also exhibited high mobilities of 80 cm2 V-1 s-1, although requiring rather specific deposition and annealing conditions. This paper will discuss our early efforts to make this material using a technique that is potentially more suitable for large-scale manufacture. We have deposited films of the individual materials using low-pressure metal organic chemical vapor deposition (LPMODVD) and have also combined the precursors to make films of CTO. We used tetramethyltin (TMT), dimethylcadmium and oxygen as the precursors. The concentrations of the two organic precursors varied along the length of the substrate because of their varying rates of decomposition. In effect, we had established conditions that enabled us to perform linear combinatorial synthesis experiments. Our objective was to make CTO films but the films varied from near-CdO (at the leading edge of the substrate) to near-SnO2 (at the trailing edge). The mobilities varied from less than 1 cm2 V-1 s-1 to about 60 cm2 V-1 s-1. Optical data indicated that the bandgaps varied from 2.75 eV (somewhat characteristic of CdO) to about 3.65 eV (more characteristic of SnO2). We also measured the compositional and structural variations along the length of the substrate and found consistent behavior. Within a limited range of distances, we established material similar to spinel CTO.