A method of producing electronic plasmons by applying a bias to a molecular tunnel junction to excite plasmons, in which the molecular tunnel junction contains a top metallic electrode formed of a eutectic metal alloy and a metal oxide, a bottom metallic electrode formed of a transition metal, and a self-assembled monolayer formed of a plurality of organic molecules disposed between the top metallic electrode and the bottom metallic electrode. Also disclosed are a molecular tunnel junction for producing electronic plasmons and a method for preparing such a molecular tunnel junction.