Surface chemically-switchable ultraviolet luminescence from interfacial two-dimensional electron gas

\noindent We report intense, narrow-linewidth, surface chemisorption-activated and reversible ultraviolet (UV) photoluminescence from radiative recombination of the two-dimensional electron liquid with photo-excited holes at the LaAlO$_3$/SrTiO$_3$ interface. The switchable luminescence arises from an electron transfer-driven modification of the electronic structure via H-chemisorption onto AlO$_2$-terminated LaAlO$_3$, at least 2 nm away from the interface. Control of the onset of emission and its intensity are functionalities that go beyond the luminescence of compound semiconductor quantum wells. Connections between reversible chemisorption, fast electron transfer, and quantum-well luminescence suggest a new model for surface chemically reconfigurable solid-state UV optoelectronics and molecular sensing.\\ Work supported by NSF under DMR 1124696, DoE BES under DE-FG02-07ER46453, DE-FG-2-07ER15920, and DE-SC0004764, and by ONR under N00014-12-1-1033 and N00014-11-1-0664.