Formation and Properties of ITO Films Produced on Silicon for Applications in Solar Cells
Аннотация
ITO films were obtained on n- and p-type silicon substrates by an improved CVD method in a quasi-closed volume at normal atmospheric pressure without the participation of a carrier gas. To elucidate the dependence of the properties of ITO films on the substrate temperature and the ratio x = SnO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/In<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>, the layers were synthesized in the temperature range 170–500°C by thermal decomposition of vapors of alcohol solutions of indium chloride and tin chloride, taken in various x ratios. The modes were set by controlling the temperatures of the substrate and the evaporator, to which water-alcohol solutions of indium and tin chlorides are supplied, as well as the ratio of the solution components and the solution supply rate. The film growth rate was about 0.5–1.0 μm/h, which is several times higher than in the case of spray pyrolysis under similar conditions. The thicknesses of the ITO films were determined using an MII-4 interference microscope; the results showed that the films obtained under such conditions have a thickness of ~3 μm. The dependence of the specific resistances of ITO films on the substrate temperature has been established, and it has been shown that films obtained at substrate temperatures of 240–260°C have a sufficiently low resistivity acceptable for use in microelectronic devices and solar cells. The X-ray diffraction spectrum of ITO films was identified in comparison with map 00-006-0416 (In<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>, cubic) from the database (JCPDS). The average value of the lattice constant of the obtained ITO film was 10.1273 Å. This is larger than the lattice parameter of 10.1195 Å of pure In<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>, which is explained by the presence of Sn, which changes the behavior of oxygen ions.