Morphology and Current–Voltage Characteristics of Nanostructured Pentacene Thin Films Probed by Atomic Force Microscopy (original) (raw)

Atomic force microscopy was used to study the growth modes (on SiO 2 , MoS 2 , and Au substrates) and the current-voltage (I-V) characteristics of organic semiconductor pentacene. Pentacene lms grow on SiO 2 substrate in a layer-by-layer manner with full coverage at an average thickness of 20 Å and have the highest degree of molecular ordering with large dendritic grains among the pentacene lms deposited on the three different substrates. Films grown on MoS 2 substrate reveal two different growth modes, snow ake-like growth and granular growth, both of which seem to compete with each other. On the other hand, lms deposited on Au substrate show granular structure for thinner coverages (no crystal structure) and dendritic growth for higher coverages (crystal structure). I-V measurements were performed with a platinum tip on a pentacene lm deposited on a Au substrate. The I-V curves on pentacene lm reveal symmetric tunneling type character. The eld dependence of the current indicates that the main transport mechanism at high eld intensities is hopping (Poole-Frenkel effect). From these measurements, we have estimated a eld lowering coef cient of 9077 10 ƒ6 V ƒ1=2 m 1=2 and an ideality factor of 18 for pentacene.