Abstract
Pentacene thin layers were deposited on Si with the native oxide at 80°C by remote-plasma-assisted deposition (RPAD) using hydrogen-plasma cell to supply atomic hydrogen radicals. The deposition rate was increased by RPAD comparing to that by non-excited hydrogen gas supply whereas thermal evaporation rate of pentacene from crucible was same in the both process. DFM and XRD studies showed the grain laterally grew in the thin film phase with the size above 10 μm by RPAD. First-principles molecular orbital calculations suggested pentacene is evaporated from crucible as the trimer or larger cluster but atomic hydrogen penetrated into the cluster enhances cracking of pentacene clusters to the monomer.
Highlights
Pentacene is a candidate for organic semiconductors to fabricate organic thin film transistors (O-TFTs) aiming at mechanically flexible and weight reduced devices [1,2] because of the relatively high carrier mobility [3] (1.5 cm2/Vs) close to amorphous Si
We demonstrate remote-plasma-assisted deposition (RPAD) of pentacene using hydrogen-gas plasma to improve the crystallographic feature comparing to that by non-excited hydrogen gas induced vacuum evaporation (H2-VE)
Remote-plasma assisted deposition (RPAD) using remotehydrogen gas plasma was applied for pentacene growth comparing the growth by non-excited hydrogen supply
Summary
Pentacene is a candidate for organic semiconductors to fabricate organic thin film transistors (O-TFTs) aiming at mechanically flexible and weight reduced devices [1,2] because of the relatively high carrier mobility [3] (1.5 cm2/Vs) close to amorphous Si. Vacuum evaporated pentacene layer consists of two crystallographic-phases (bulk phase and thin film phase) [2,4,5], which is unfavorable for the device operations because of increasing sample-to-sample variation and decreasing carrier mobility. Zhu and Varahramyan demonstrated pentacene deposition on modified SiO2 surface by self-assembled monolayer using poly dimethyldiallylammonium chloride [6] They suggested pentacene with uniform grain size grows on the modified surface comparing to that on SiO2, which results in improvement of FET device performance such as increase of the effective carrier mobility and the On/Off ratio. Yokoyama et al demonstrated hydrogen-gas induced evaporation deposition of pentacene layer with devising the apparatus configuration and optimizing the growth condition, and indicated the grain size is significantly increased with preventing the surface roughness and the notably improved FET performance [7]. The first-principle molecular orbital calculations are used to investigate the evaporation behavior of pentacene and the role of hydrogen for the evaporated pentacene
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