  Epitaxial growth of single crystalline noble metals on dielectric substrates
has received tremendous attention recently due to their technological
potentials as low loss plasmonic materials. Currently there are two different
growth approaches, each with its strengths and weaknesses. One adopts a
sophisticated molecular beam epitaxial procedure to grow atomically smooth
epitaxial Ag films. However, the procedure is rather slow and becomes
impractical to grow films with thickness > 50 nm. Another approach adopts a
growth process using rapid e-beam deposition which is capable of growing single
crystalline Ag films in the thick regime (> 300 nm). However, the rapid growth
procedure makes it difficult to control film thickness precisely, i.e., the
method is not applicable to growing thin epitaxial films. Here we report a
universal approach to grow atomically smooth epitaxial Ag films with precise
thickness control from a few monolayers to the optically thick regime,
overcoming the limitations of the two aforementioned methods. In addition, we
develop an in-situ growth of aluminum oxide as the capping layer which exhibits
excellent properties protecting the epitaxial Ag films. The performance of the
epitaxial Ag films as a function of the film thickness is investigated by
directly measuring the propagation length of the surface plasmon polaritons
(SPPs) as well as their device performance to support a waveguide plasmonic
nanolaser in infrared incorporating an InGaAsP quantum well as the gain media.
