  A rigorous analytical study of the eigenmodes supported by a charge
accumulation layer within a transparent conductive oxide (TCO) is presented.
The new class of surface plasmons termed Accumulation-Layer Surface Plasmon
(ASP) is introduced. Near resonance ASP are tightly bound and display a vast
effective index tunability that could be of great practical interest. The
suppression of ASP in the presence of epsilon-near zero regions is discussed.
