Growth of long range ordered pentacene/benzenethiol/Cu(100) heterostructure

Abstract

We present a method of producing a long-range ordered pentacene ultra-thin film on a benzenethiol organic buffer layer at saturation coverage, deposited on a cleaned. single crystalline Cu(100) surface, by means of ultra-high-vacuum organic molecular beam epitaxy. The growth morphology is investigated using in-situ low-energy electron-diffraction (LEED) and high-resolution UV photoelectron spectroscopy (HR-UPS). The change in Surface symmetry from c(4x4) at low coverage to c(2 x 6)/c(2 x 2) at saturation coverage of benzenethiol has been examined by LEED. The corresponding valence band modifications have been found by HR-UPS. Pentacene layers Lip to a thickness of 0.6nni possess exactly the same symmetry of the beneath organic buffer layer at saturation coverage, but with more intense and sharper spots as observed in the LEED patterns

Interaction strength and molecular orientation of a single layer of pentacene in organic-metal interface and organic-organic heterostructure

“…11,12,26 Exposures inside the prechamber were done with a constant rate of 0.3-0.5 L / min ͑1 L = 1.33ϫ 10 −6 mbar s͒ at room temperature ͑RT͒, maintaining the pressure at 2 ϫ 10 −8 mbar, so that the saturation coverage was reached by exposing to about 33 L. Under these conditions, the RHEED pattern revealed a c͑2 ϫ 6͒ two-domain saturation phase, in agreement with previous results. 11,12,26 Pentacene was thermally evaporated in situ by organic molecular beam deposition from a resistively heated quartz crucible. The evaporation rate, calibrated by a quartz microbalance, was kept constant during each deposition at a few Å/min.…”

“…The pentacene standing-up molecules in the single layer on the Bt-SAM layer are packed with a tilt angle consistent with previous results obtained for pentacene deposited on SAM buffer layers and on inert substrates. [11][12][13]34 The same fitting procedure has been employed for the pentacene/Cu͑119͒ interface, where the overall polarization dependence of the NEXAFS data is reversed with respect to the pentacene/Bt-SAM heterostructure, as shown in the right-bottom panel of Fig. 3.…”

“…2,6 If the C-H interactions dominate, a herringbone structure is generally formed; while, with an increasing relative number of C-C interactions, the structure becomes planar and graphitelike. 6 Recently, the formation of highly ordered single layers ͑SLs͒ of pentacene deposited on metal or inert substrates [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] has been exploited to bring insight into the interaction process and clarify the role of the structural arrangements on the electronic and/or transport properties.…”

“…8,9,13,17,[19][20][21][22][23] Single layer of pentacene molecules deposited on inert substrates, such as silicon dioxide, mimics the bulk phase adopting a near vertical structure with a packing motif resembling the ͑001͒ layers in the herringbone structures. 10 Recently, self-assembled monolayers ͑SAMs͒ have been used as buffer layers to obtain a single layer of pentacene molecules arranged in standing-up orientation [11][12][13][14][15]24 by suppressing the direct interaction between the pentacene molecules and the underlying substrate. Substituting the inorganic dielectric with an organic SAM is a prototypical system to reduce the gate voltage in organic thin film transistors ͑OTFTs͒.…”

Interfacial Organic Layers for Chemical Stability and Crystalline Ordering of Thiophene and Carboxyl Films on a Metal Surface

“…In this work, we demonstrate the use of an interfacial organic layer (IOL) to passivate chemical decomposition of thiophenes and carboxylic acids (Scheme ) at the Cu(001) surface, while also achieving formation of a crystalline layer of the functional molecules on top of the IOL at room temperature. Crystalline ordering in multilayered structures has been reported in single-component systems − as well as multicomponent systems − (some studied only at cryogenic temperatures). However, in those prior studies atomically precise ordering was not reported for chemically fragile species, i.e., those that would decompose if deposited directly on the metal surface.…”