ELECTRONIC PROPERTIES OF THIN FILMS SUBLIMED FROM La@C82 AND Li@C60

La@C82 and Li@C60 thin films obtained by sublimation in vacuum are studied using four-probe current–voltage measurements and atomic force microscopy. In situ electrical measurements show semiconducting behavior of both films with room-temperature resistivity of 21 ± 8 and 1230 ± 50 Ω · cm for the La@C82 and Li@C60, respectively. A variable range hopping mechanism of conductance is suggested from the temperature dependences of resistance. The activation energies for electron transport are calculated for both metallofullerenes. Irreversible changes to the Li@C60 film structure increasing the film resistivity to values typical for C60 are found at elevated temperatures. The effect of exposure to ambient atmosphere on the conductance of the films is discussed.