The first direct comparison of self-assembly and Langmuir–Blodgett deposition techniques: Two routes to highly organized monolayers

Gyepi-Garbrah, Samuel H.; Šilerová, Roberta

doi:10.1039/b201698b

Cited by 19 publications

(19 citation statements)

References 19 publications

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“…The capability to control either the chemistry of the subphase, the area per molecule and the extraction surface pressure of the layers is an alternative over other preparation techniques of supported monolayers such as Self-Assembled Monolayer deposition (SAMs) [16]. The control of the film transfer to the substrate and the possible relaxation of the extraction surface pressure of the supported film over time are still subject to controversy.…”

Section: Introductionmentioning

confidence: 99%

Lateral force microscopy study of Langmuir–Blodgett films of a macrocyclic compound

2006

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Langmuir-Blodgett films of 4-phenyl-4-sulfide-11-(1-oxodecyl)-1,7-dithia-11-aza-4-phosphacyclotetradecane, a thiomacrocyclic compound used as a Cu(II) ions sensor, were extracted over mica at several surface pressure values from two subphases: pure water and a 0.01 M Cu(II) aqueous solution. Atomic Force Microscopy and Force Spectroscopy (Lateral Force Microscopy) were used to study both the morphology and the nanomechanical response of Langmuir-Blodgett films. A correlation between extraction pressure and monolayer mechanical properties was observed, so an increase in the extraction pressure of the monolayers corresponds with an increase in the vertical force at which the monolayer breaks while doing lateral force experiments. Experimental data proves that Langmuir-Blodgett extraction technique truly obtains monolayers with different nanotribological properties as a function of the extraction surface pressure. The formation of islands on top of the monolayers was studied and a model mechanism of formation is proposed. A higher friction value was measured on the islands than on the monolayer and friction asymmetry was observed in the latest stage of island formation.

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Section: Introductionmentioning

confidence: 99%

Lateral force microscopy study of Langmuir–Blodgett films of a macrocyclic compound

2006

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“…[17,18] The Langmuir-Blodgett (LB) technique is an effective tool for transferring well-ordered molecular films at the airwater interface onto a solid support, permitting a degree of control over the molecule-surface interaction or contact, as it is applicable for forming both chemisorbed and physisorbed films. [19] Therefore, the use of the LB metal-organic assembly technologies provides diverse opportunities for the exploration of different metal-molecule contacts that, so far, have been limited to a few interfaces formed by the traditional self-assembly (SA) method. The thiol moiety has been used extensively to attach molecules to gold surfaces using such SA methods.…”

Section: Introductionmentioning

confidence: 99%

Metal–Molecule–Metal Junctions in Langmuir–Blodgett Films Using a New Linker: Trimethylsilane

Pera

Martı́n

Ballesteros

et al. 2010

Chemistry A European J

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Herein trimethylsilane (TMS) is demonstrated to be an efficient binding group suitable for construction of metal-molecule-metal (M-mol-M') junctions, in which one of the metal contacts is an atomically flat gold surface and the other a scanning tunnelling microscopy (STM) tip. The molecular component of the M-mol-M' devices is an oligomeric phenylene ethynylene (OPE) derivative Me(3)Si C≡C{C(6)H(4)C≡C}(2)C(6)H(4)NH(2), featuring both Me(3)SiC≡C and NH(2) metal contacting groups. This compound can be assembled into Langmuir-Blodgett (LB) films on Au--substrates by surface binding through the amine groups. Alternatively, low coverage (sub-monolayer) films are formed by adsorption from solution. In the case of condensed monolayers top electrical contacts are formed to STM tips through the TMS end group. In low coverage films, single molecular bridges can be formed between the gold surface and a gold STM tip. The similarity in the I-V response of a one-layer LB film and the single molecule conductance experiments reveals several points of critical importance to the design of molecular components for use in the construction of M-mol-M' junctions. Firstly, the presence of neighbouring π systems does not have a significant effect on the conductance of the M-mol-M' junction. Secondly, in the STM configuration, intermolecular electron hopping does not significantly enhance the junction transport characteristics. Thirdly, the symmetric behaviour of the I-V curves obtained, despite the different metal-molecule contacts, indicates that the molecule is simply an amphiphilic electron-donating wire and not a molecular diode with strong rectifying characteristics. Finally, the conductance values obtained from the amine/TMS-contacted OPE described here are of the same order of magnitude as thiol anchored OPEs, making them attractive alternatives to the more conventionally used thiol-contacting chemistry for OPE molecular wires.

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“…The nature of the substrate-molecule interaction depends on both the nature of the surface and the functional group of the organic material. Thus, the monolayer can be either physisorbed onto the substrate surface or chemisorbed [172,173]. Therefore, by making use of the large variety of functional groups that can be physically or chemically adsorbed onto different electrodes, it is possible to use the LB technique to fabricate molecular junctions featuring any one of a large number of organic-electrode interfaces [174].…”

Section: Reaction Referencementioning

confidence: 99%

Nanofabrication techniques of highly organized monolayers sandwiched between two electrodes for molecular electronics

2014

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Molecular electronics [1,2] is a promising field of research based on the idea that a single molecule or two dimensional assemblies of molecules (monomolecular films) can work as wires, switches, rectifiers, etc. Molecules are the smallest functional units and therefore it is expected that the use of molecules will permit to catch up with the limits of miniaturization (MM: more Moore), with an increase in device density by a factor of several orders of magnitude compared to today's state of the art. At the same time due to quantum effects novel and remarkable properties of organic and organometallic compounds at the nanoscale devices will result in increased performance (MtM: more than Moore) together with the appearance of new functions not possible with conventional semiconductors, and also cheaper devices due to the non-dependence of expensive materials used today in CMOS (complementary metal-oxide semiconductor) technology such as hafnium oxide. Nowadays, the number of research groups from different disciplines of science contributing to molecular electronics is gradually growing, and this field is becoming of great scientific and technological interest [1,3-8]. Since the seminal work of Aviram and Ratner in 1974 who firstly suggested that a single molecule could function as a rectifier [9], molecules have been experimentally demonstrated to work as switches, molecular wires or rectifiers, and a new field of opportunities is opened due to the understanding of electron transport through single entities or assemblies of molecules and expansion towards work on molecular spintronics, vibronic effects, excitation of the molecular junction with polarized light, quantum interference and decoherence, molecular chirality, molecular stretching and distortion as well as work on thermoelectric response in molecular junctions.Abstract: It is expected that molecular electronics, i.e., the use of molecules as critical functional elements in electronic devices, will lead in the near future to an industrial exploitable novel technology, which will open new routes to high value-added electronic products. However, despite the enormous advances in this field several scientific and technological challenges should be surmounted before molecular electronics can be implemented in the market. Among these challenges are the fabrication of reliable, robust and uniform contacts between molecules and electrodes, the deposition of the second (top) contact electrode, and development of assembly strategies for precise placement of molecular materials within device structures. This review covers advances in nanofabrication techniques used for the assembly of monomolecular films onto conducting or semiconducting substrates as well as recent methods developed for the deposition of the top contact electrode highlighting the advantages and limitations of the several approaches used in the literature. This contribution also aims to define areas of outstanding challenges in the nanofabrication of monomolecular layers sandwiched between two electro...

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The first direct comparison of self-assembly and Langmuir–Blodgett deposition techniques: Two routes to highly organized monolayers

Cited by 19 publications

References 19 publications

Lateral force microscopy study of Langmuir–Blodgett films of a macrocyclic compound

Lateral force microscopy study of Langmuir–Blodgett films of a macrocyclic compound

Metal–Molecule–Metal Junctions in Langmuir–Blodgett Films Using a New Linker: Trimethylsilane

Nanofabrication techniques of highly organized monolayers sandwiched between two electrodes for molecular electronics

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