Light emission from molecular layers has been induced by inelastically
tunneling electrons in a tunneling junction. The fast quenching of mo
lecular emission on metal surfaces was suppressed by use of the ''tran
sparent conductor'' indium-tin-oxide for the junction electrodes. The
emission measurements have been made in squeezable tunneling junctions
as small as 10(-9) square centimeters, coated with 9-10 dichloro-anth
racene layers. At a bias of 2.5 to 3.5 volts, yields of 5000 photons p
er microcoulomb were observed. Evidence for the molecular origin of th
e emission is given. This method shows good prospects for use in the i
maging of chromophores on surfaces with atomic resolution.