Comparison between nucleation of pentacene monolayer islands on polymeric and inorganic substrates

Abstract

We present a comparative study of the nucleation and growth of pentacene monolayer islands in the submonolayer regime onto inorganic substrates of SiO 2 and sapphire ͑Al 2 O 3 ͒ and organic substrates of poly͑methyl-metacrylate͒ ͑PMMA͒. We have determined the scaling laws that govern the saturated nucleation density per unit area N as a function of two essential deposition parameters: the deposition rate and the substrate temperature T s . For all substrates, we found N ϰ ␦ , with 0.8ഛ ␦ ഛ 1.2, and the T s dependence of the nucleation density follows a typical activated Arrhenius law. Whereas a critical nucleus size of i = 2 is obtained for all investigated substrates, the activation energy for nucleation depends significantly on the dielectric. The difference in activation energy of nucleation on PMMA and SiO 2 is due to different molecule-substrate interactions.

Controlling charge‐transfer at the gate interface of organic field‐effect transistors

“…Performance has been improved by refining the film growth process [10][11][12][13] and modifying the surface of suitable gate dielectrics [2][3][4]9]. Although high performance has been achieved, the characterization and control of the threshold field and the field-effect mobility have been complicated by competing physical phenomena occurring at the oxide surface.…”

Pentacene thin films on ferromagnetic oxide: Growth mechanism and spintronic devices

“…If the smallest stable nucleus were a dimer, E i à ¼2 $ 1.5 6 0.5 eV, in contrast with the calculated value of 0.67 eV. 35 If we instead assume that the smallest stable nucleus is a trimer, E i à ¼ E 2 þ E 3 $ 1.5 6 0.6 eV. This seems reasonable and a similar trend in formation energies was reported for the benzene molecule, which comes from the same family to that of pentacene.…”

“…40 C, in the latter because desorption started to play a significant role. From the Arrhenius plot in Figure 4(a), we extracted E N ¼ 0.65 6 0.05 eV for 40 T 60 C. This energy scale is confirmed by ultra-violet photoemission spectroscopy measurements of a 0.4 eV energy dipole between pentacene and LSMO, 27 which is low if compared to the 1 eV found for pentacene deposited on Co. 33,34 The E N value for pentacene on LSMO can be compared with the nucleation energy found for pentacene grown on SiO 2 over the same temperature range: E N ¼ 0.78 6 0.05 eV was found for a growth rate of 0.007 nm/s, 35 which is similar to the one used in the present experiment. At higher growth rates (0.03 nm/s) P i à m¼2 E m þ i à E D ¼ 1.13 6 0.04 eV and i* ¼ 3 were reported, 36 hence E N ¼ 0.23 6 0.01 eV.…”

“…Considering that E N varies with the growth rate, 31 the value we extracted for pentacene on LSMO is compatible with the one for SiO 2 substrates (Figure 4(b)), assuming that at lower rates E N levels off rather than diverging. 35,37 Pentacene nucleation and growth on LSMO are much closer to those on SiO 2 than those on Co. 34 The diffusion mechanism was analysed in order to disentangle the contributions of diffusion and nucleation in E N . The surface diffusion length is defined as x s ¼ ffiffiffiffiffiffiffi ffi D s s p , where D s is the diffusion coefficient and s is the residence time, i.e., the time the molecule moves on the substrate before attaching or desorbing.…”

Key role of molecular kinetic energy in early stages of pentacene island growth

“…In the past few years, several studies based on OMBD grown pentacene layers have demonstrated that the pentacene grain size can be modulated via changing the deposition rate, the substrate temperature or modifying the substrate surface with organic self assembled layers [13][14][15][16][17]. However, for SuMBD grown pentacene thin films, it is more straightforward to change the grain size by tuning the pentacene kinetic energy (E k ) within the molecular beam.…”