.In order to deposit films of the alloy YBa2Cu3, the metals Y, Ba, and Cu are evaporated from three point
sources. The latter are situated at the corners of an equilateral triangle whose side is 20 cm. Directly above
the centroid of the source array, and parallel to it, lies a small substrate; the deposition system geometry is
effectively a tetrahedron, each side being 20 cm long.
a. If the Y source is heated to 1740 K to produce a vapor pressure of 10-3 torr, to what temperature must
the Cu source be heated to maintain film stoichiometry?
b. Rather than a point source, a surface source is used to evaporate Cu. How must the Cu source
temperature be changed to ensure deposit stoichiometry?
c. If the source configuration in part (a) is employed, what minimum O2 partial pressure is required to
deposit stoichiometric superconducting oxide YBa2Cu3O7 films by a reactive evaporation process?
The atomic weights are Y = 89, Cu = 63.5, Ba = 137, and O = 16.