Enhancement of interconnectivity in the channels of pentacene thin-film transistors and its effect on field-effect mobility

With the aim of improving the field-effect mobility of transistors by promoting the interconnectivity of the grains in pentacene thin films, deposition conditions of the pentacene molecules using one-step (total thickness of layer 50 nm: 0.1 Ås^-1) and two-step (first layer 10 nm: 0.1 Ås^-1, second layer 40 nm: 4.0 Ås^-1) depositions are controlled. Significantly, it is found that the continuities of the pentacene thin films vary with the deposition conditions of the pentacene molecules. Specifically, a smaller number of voids is observed at the interface for the two-step deposition, which results in field-effect mobilities as high as 1.2 cm² V^-1 s^-1; these are higher by more than a factor of two than those of the pentacene films deposited in one step. This remarkable increase in field-effect mobility is due in particular to the interconnectivity of the pentacene grains near the insulator substrate.