His work has opened new lines of research and has stimulated innovative theoretical and experimental lines of work in very diverse fields of condensed matter physics such as electron and tunnel microscopy, physical chemistry on the femtosecond scale, electronic surface localization, reverse photo-emission, atomic collisions, the interaction of ions with plasma particles, ion implantation and surface excitations in superfluid helium.

[7] Many works, starting with his PhD thesis in Cambridge study the interaction of electrons, atoms, and ions with surfaces.

An important concept introduced and developed by Etxenike are image-potential states at metal surfaces [8] in which electrons can be trapped in the potential of their own image charge.

[12] In 1980 he gave up his professorship in Barcelona to join the first government of the Basque Autonomous Community after the Francoist dictatorship.

[citation needed] After leaving government politics, Etxenike continues to play an important role in the science policy of the Basque country.

[22] He played a similar role for the Cooperative Research Centre CIC nanoGUNE (founded 2009)[23] and was until 2019 chairman of its governing board.

[24] In 2007, he was among the founders of the Academy of Sciences, Arts and Letters of the Basque Country Jakiunde and served as its first president until 2012.