Channel formation in single-monolayer pentacene thin film transistors

Abstract

The geometrical arrangement of single-molecule-high islands and the contact between them have large roles in determining the electrical properties of field effect transistors (FETs) based on monolayer-scale pentacene thin films. As the pentacene coverage increases through the submonolayer regime there is a percolation transition where islands come into contact and a simultaneous rapid onset of current. At coverages just above the percolation threshold, the electrical properties vary with geometrical changes in the contacts between the pentacene islands. At higher coverages, the FET mobility is much lower than the mobility measured by the van der Pauw method because of high contact resistances in monolayer-scale pentacene film devices. An increase in the van der Pauw mobility of holes as a function of pentacene coverage shows that second layer islands take part in charge transport.

Molecular Self‐Assembled Monolayers and Multilayers for Organic and Unconventional Inorganic Thin‐Film Transistor Applications

“…[290,291] This phenom- enon opens the possibility of using SAMs and SAMTs as the active channel in TFTs. [292][293][294] In 2005, Pilkuhn and co-workers studied ODTS SAMs with different end group functionalizations, such as methyl, thiol, thiophene, phenoxy, and biphenyl.…”

Precise Structure of Pentacene Monolayers on Amorphous Silicon Oxide and Relation to Charge Transport

“…[2][3][4][5][6][7][8][9] The charge transport in organic TFT devices predominantly occurs in the first few monolayers above the dielectric layer. [10,11] The molecular packing motif in the first monolayer determines the degree of the overlap of the frontier orbitals between neighboring molecules, which in turn is determinant for the intrinsic charge-carrier mobility. While many other factors are known to impact the performance of thin-film transistors -such as density, size, and shape of the grains, the structural compliance at the interfaces between thin film and electrodes/substrate, and the chemical properties of substrate and electrode surfaces -knowledge of the exact packing motif in the first monolayer is crucial to the discussion of the pentacene TFT performance.…”

Solution‐Processable Septithiophene Monolayer Transistor

“…[4] Often, the mobility in monolayer transistors is orders of magnitude lower than in the corresponding multilayer film. [5,6] The major problems of polycrystalline films, as obtained usually, is the existence of structural defects and grain boundaries, which act as traps for the charge carriers and therefore considerably reduce mobilities. [5][6][7] Liquid crystalline (LC) π-conjugated mole cules may alleviate these restrictions.…”

“…[5,6] The major problems of polycrystalline films, as obtained usually, is the existence of structural defects and grain boundaries, which act as traps for the charge carriers and therefore considerably reduce mobilities. [5][6][7] Liquid crystalline (LC) π-conjugated mole cules may alleviate these restrictions. [8,9] Their capability to self-heal structural defects and form large structurally homogeneous domains is well documented.…”