Photoinduced interfacial charging and "explosion" of monolayer pentacene islands.
Electrostatic force microscopy shows that the electric field gradients above pentacene monolayer islands on 2-nm SiO2/Si substrates, in a dark, dry nitrogen environment, display a wide distribution of signs and magnitude that is dependent on sample history. Under 12 mW/cm2 green (532 nm) illumination, pentacene islands accumulate positive charge because of photoexcited electron transfer across the oxide to the Si substrate. At a strong illumination of 60 mW/cm2, pentacene islands reform into small spherical particles, apparently because the positive charge Coulomb repulsion energy becomes comparable to the cohesive energy of the pentacene monolayer.
Chen
Liwei
L
Columbia University, Department of Chemistry, New York 10027, USA. lwchen@helios.phy.ohiou.edu
Cherniavskaya
Oksana
O
Shalek
Alexander
A
Brus
Louis E
LE