  We propose a novel solid-phase epitaxy technique applicable to high annealing
temperatures up to 1000 C without re-vaporization of alkali metal elements with
high vapor pressures. This technique is demonstrated through the successful
growth of high-quality KFe2As2 epitaxial films. The key factors are employing a
custom-designed alumina vessel/cover and sealing it in a stainless tube with a
large amount of atmospheric KFe2As2 powder in tightly closed sample spaces.
This technique can also be effective for other materials composed of elements
with very high vapor pressures, such as alkali metals, and can lead to the
realization of spintronics devices in the future using KFe2As2.
