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Zhang, Hanmin; Gustafsson, Jörgen; Johansson, Lars

doi:10.1016/j.cplett.2009.11.070

Cited by 20 publications

(7 citation statements)

References 30 publications

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“…The formation of the H and L states at 1 ML PTCDI coverage has previously been assigned as the results from a HOMO-LUMO split of the molecular orbitals, 11 similarly to what was observed for the herringbone phase of PTCDA on Ag/Si(111)- 23 The HOMO-LUMO split in the case of PTCDI was explained to be due to two different adsorption sites for the molecules. This results in these two types having different electronic structures and consequently different frontier orbitals.…”

mentioning

confidence: 53%

Delicate interactions of PTCDI molecules on Ag/Si(111)-3×3

Emanuelsson

Johansson

Zhang

2018

The Journal of Chemical Physics

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PTCDI molecules were evaporated onto a Ag/Si(111) √ 3× √ 3 surface and studied using scanning tunneling microscopy (STM) and angular resolved ultraviolet photoelectron spectroscopy (ARUPS). High resolution STM images are used to identify the delicate molecule/molecule and molecule/substrate interactions and the shapes of the molecular orbitals. The results show that the substrate/molecule interaction strongly modifies the electronic configuration of the molecules as their orbital shapes are quite different at 1 and 2 monolayer (ML) coverage. Simple models of molecular HOMO/LUMO levels and intermolecular hydrogen-bondings have been made for 1 and 2 ML PTCDI coverages to explain the STM images. Changes due to the interaction with the substrate are also found in ARUPS as extra states above the regular HOMO level at 1 ML PTCDI coverage. The ARUPS data also show that the electronic structure of the substrate remains unchanged after the deposition of molecules as the dispersion of the substrate related bands is unchanged. The changes in electronic structure of the molecules are discussed based on a HOMO/LUMO split.

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confidence: 53%

Delicate interactions of PTCDI molecules on Ag/Si(111)-3×3

Emanuelsson

Johansson

Zhang

2018

The Journal of Chemical Physics

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“…The √3 × √3-Ag surface is chemically inert for many adsorbed molecules, hence on this surface the intermolecular interaction typically prevails over molecular-substrate interaction. As a result, the Si(111)√3 × √3-Ag template is widely used for observing self-assembly of the various organic molecules − and fullerenes − into the ordered arrays.…”

Section: Resultsmentioning

confidence: 99%

“…Due to a high reactivity of the Si(111)7 × 7 surface, the molecule−substrate interaction there typically prevails over molecule−molecule interaction. Among variety of metal-induced Si(111) reconstructions, the Si(111)√3 × √3-Ag surface has appeared to be the most popular template for growing molecular layers. − This surface is atomically smooth and chemically inert, hence there adsorbing molecules are free to move and self-assembly into the ordered two-dimensional nanostructures. Other metal-induced reconstructions (e.g., Si(111)√3 × √3-Au, Si(111)5 × 2-Au, , Si(111)3 × 2-Sm, and Si(111)4 × 1-In) have been used for this purpose much seldom.…”

Section: Introductionmentioning

confidence: 99%

Effect of Surface Potential Relief on Forming Molecular Arrays: Tryptanthrin Adsorbed on Various Si(111) Reconstructions

et al. 2010

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To explore the effect of the substrate surface potential relief on the self-assembly of the adsorbed organic molecules, adsorption of tryptanthrin molecules on the various reconstructed Si(111) surfaces has been studied using scanning tunneling microscopy. The set of the Si(111) surface reconstructions under consideration includes atomically clean adsorbate-free Si(111)7 × 7 and metal-induced Si(111)4 × 1-In, Si(111)’5.5 × 5.5’-Cu, and Si(111)√3 × √3-Ag surfaces, each having specific surface potential relief. It has been found that on the Si(111)7 × 7 surface, which is characterized by a high density of dangling bonds, the tryptanthrin molecules are randomly trapped by dangling-bond Si adatoms without forming any ordered array. On the quasi-one-dimensional Si(111)4 × 1-In surface, the tryptanthrin molecules are self-assembled into the meandering molecular chains aligned along the In-atom rows of the 4 × 1-In reconstruction. On the Si(111)’5.5 × 5.5’-Cu surface, having a honeycomb-like potential relief associated with its discommensurate structure, the tryptanthrin molecules form an array of the supramolecular complexes displaying a ring-shaped STM appearance and containing presumably two molecules each. On the atomically smooth and inert Si(111)√3 × √3-Ag surface with very shallow potential relief, the adsorbed tryptanthrin forms at room temperature a two-dimensional gas of highly mobile molecules, which condensates into random disordered molecular islands upon cooling sample to 110 K.

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“…PTCDA has been extensively studied as a candidate for organic devices [10–15] and its adsorption geometry and binding mechanism is well-known on several surfaces. Furthermore the electronic structure and growth of PTCDA on the Ag/Si(111) √3 × √3 surface is well understood [10,16–17]. In the submonolayer range the PTCDA molecules grow on the Ag/Si(111) √3 × √3 surface in three different phases, namely the herringbone, square and hexagonal phases.…”

Section: Introductionmentioning

confidence: 99%

A measurement of the hysteresis loop in force-spectroscopy curves using a tuning-fork atomic force microscope

Lange¹,

Vörden²,

Möller³

2012

Beilstein J. Nanotechnol.

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SummaryMeasurements of the frequency shift versus distance in noncontact atomic force microscopy (NC-AFM) allow measurements of the force gradient between the oscillating tip and a surface (force-spectroscopy measurements). When nonconservative forces act between the tip apex and the surface the oscillation amplitude is damped. The dissipation is caused by bistabilities in the potential energy surface of the tip–sample system, and the process can be understood as a hysteresis of forces between approach and retraction of the tip. In this paper, we present the direct measurement of the whole hysteresis loop in force-spectroscopy curves at 77 K on the PTCDA/Ag/Si(111) √3 × √3 surface by means of a tuning-fork-based NC-AFM with an oscillation amplitude smaller than the distance range of the hysteresis loop. The hysteresis effect is caused by the making and breaking of a bond between PTCDA molecules on the surface and a PTCDA molecule at the tip. The corresponding energy loss was determined to be 0.57 eV by evaluation of the force–distance curves upon approach and retraction. Furthermore, a second dissipation process was identified through the damping of the oscillation while the molecule on the tip is in contact with the surface. This dissipation process occurs mainly during the retraction of the tip. It reaches a maximum value of about 0.22 eV/cycle.

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STM study of the electronic structure of PTCDA on Ag/Si(1 1 1)-3×3

Cited by 20 publications

References 30 publications

Delicate interactions of PTCDI molecules on Ag/Si(111)-3×3

Delicate interactions of PTCDI molecules on Ag/Si(111)-3×3

Effect of Surface Potential Relief on Forming Molecular Arrays: Tryptanthrin Adsorbed on Various Si(111) Reconstructions

A measurement of the hysteresis loop in force-spectroscopy curves using a tuning-fork atomic force microscope

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