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Organic nanowires with unusual transport properties: a theoretical study

English title Organic nanowires with unusual transport properties: a theoretical study
Applicant Pignedoli Carlo Antonio
Number 135435
Funding scheme Project funding (Div. I-III)
Research institution Eidg. Materialprüfungs- und Forschungsanstalt (EMPA)
Institution of higher education Swiss Federal Laboratories for Materials Science and Technology - EMPA
Main discipline Condensed Matter Physics
Start/End 01.07.2011 - 30.06.2014
Approved amount 162'706.00
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All Disciplines (2)

Discipline
Condensed Matter Physics
Material Sciences

Keywords (7)

nanotechnology; ab initio simulations; surface effects; transport ; organic nanowires; defects; 1D nanostructures

Lay Summary (English)

Lead
Lay summary

The development of experimental techniques capable of manipulation and analysis at the nanoscale has determined in the last years the enormous fortune of nanotechnology. One of the most fascinating aspects is the manifestation in realistic systems of theoretically predicted (but often unexpected) quantum effects that lead to remarkable and unusual properties of matter at the 10-100 nm scale.

In particular, the technology for the fabrication of organic nanostructures designed to become microelectronic devices is now mature, and the concepts governing the growth and stability of nano-derivatives of molecular crystals are now accessible. The range of forecasted applications is broad: catalysis, solar cells, nanosensors, lasers, device miniaturization, etc.

The choice of p-conjugated molecules as building blocks for such organic nanostructures is central in the definition of this emerging new field and has clear advantages: ease of synthesis at low cost and big scale, processing in solution and possibility to control the properties of the devices by molecular design.

In our laboratory at Empa a methodology was recently developed to fabricate single-crystalline 1D nanostructures with high density, quality and purity. The growth method is based on a plasma vapor deposition process of organic molecules on tailored-roughness substrate surfaces.  Such substrate-supported nanowires are ideal systems for fundamental studies such as: understanding of complex self-assembly mechanisms for organic molecules into crystalline structures, elucidating transport mechanisms, addressing the role of nanoscale domains in microstructures, defining of the relationship between molecular/crystalline structure and corresponding electronic properties. 

The generalization of this growth methodology to different molecules provides a straightforward way to study the relation between the chemical structure of the molecules and the final morphology and structure of the wires.

atomistic simulations, in connection to the experiments that are being conducted in our laboratory. ab initio The aim of the present project is to understand the structural and electronic properties of selected nanowires belonging to different molecular precursors by means of

The project will be focused towards two main goals:

  • The investigation of the geometric and electronic properties of ideal models of nanowires based on Cu-phtalocyanines and Co-phtalocyanines.
  • Understanding of the transport properties of the nanowires

 

The successful outcome of the present project will represent a considerable step forward in the understanding of the electronic properties of molecular nanowires. Although transport theories are developed since several years, due to their complexity in relation to systems such as molecular nanowires, there are no detailed investigations of the transport properties of similar systems. The results obtained within our project will represent a step forward in the understanding of complex transport phenomena. Moreover, the collaboration with developers of transport theory codes will allow to tune and develop future instruments, more suitable for application in direct connection with experiments.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Exciton-dominated optical response of ultra-narrow graphene nanoribbons
Denk Richard (2014), Exciton-dominated optical response of ultra-narrow graphene nanoribbons, in nature communications, 5, 4253.
Graphene nanoribbon heterojunctions
J. Cai C. A. Pignedoli L. Talirz P. Ruffieux H. Söde L. Liang V. Meunier R. Berger R. Li X. (2014), Graphene nanoribbon heterojunctions, in Nature Nanotechnology, 9, 896.
Termini of Bottom-Up Fabricated Graphene Nanoribbons
Talirz Leopold (2013), Termini of Bottom-Up Fabricated Graphene Nanoribbons, in Journal of the american chemical society, 135, 2060.

Collaboration

Group / person Country
Types of collaboration
S3-NANO-CNR and Physics Dept, University of Modena and Reggio Emilia, 41125 Modena, Italy Italy (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
ECOSS 30 Talk given at a conference Band gap of atomically precise graphene nanoribbons as a function of ribbon length and termination 08.07.2014 Antalia, Turkey Talirz Leopold;
Molecules at surfaces meeting Talk given at a conference Electronic Structure of decoupled Graphene Nanoribbons 11.06.2014 Bern, Switzerland Pignedoli Carlo Antonio; Talirz Leopold;
International Workshop "On-Surface Synthesis" Talk given at a conference Synthesis of Atomically Precise Graphene-Based Nanostructures: a Simulation Point of View 25.05.2014 Les Houches, France Talirz Leopold; Passerone Daniele; Pignedoli Carlo Antonio;
Heraeus Seminar “Functional molecules on surfaces”, Poster Atomic and Electronic Structure of Graphene Nanoribbons from Scanning Tunneling Microscopy 19.05.2014 Bad Honnef, Germany Talirz Leopold;
Annual meeting “Schweizerische Arbeitsgemeinschaft Oberflächen und Grenzflächen”, Poster -- 24.01.2014 Fribourg, Switzerland Talirz Leopold;
International workshop on computational physics and materials science Talk given at a conference DFT Challenges Following Synthesis Routes for Atomically Precise Graphene Based Heterostructures 09.01.2014 Lausanne, Switzerland Pignedoli Carlo Antonio; Talirz Leopold; Passerone Daniele;
Advanced Quantum ESPRESSO Developer Training Poster -- 09.12.2013 ICTP Trieste, Italy Talirz Leopold;
International Conference on Nanoscience and Technology (ICN+T) Talk given at a conference Termini of Bottom-Up Fabricated Graphene Nanoribbons 09.09.2013 Paris, France Talirz Leopold;
HP2C/PASC Materials Simulation Junior Retreat Poster -- 09.07.2013 Maennedorf, Switzerland Talirz Leopold;
CECAM Yambo tutorial: Yambo Poster -- 08.04.2013 Lausanne, Switzerland Talirz Leopold;
Quantum ESPRESSO Developer Training Poster -- 25.03.2013 Trieste, Italy Talirz Leopold;
Workshop on Computer Programming & Advanced Tools for Scientific Research Work Poster -- 11.03.2013 Trieste, Italy Talirz Leopold;
Workshop: Getting the best out of multicore Poster -- 10.12.2012 Lugano, Switzerland Talirz Leopold;
• ADGLASS Science/Industry Workshop Talk given at a conference -- 14.11.2012 Bremen, Germany Pignedoli Carlo Antonio; Passerone Daniele; Talirz Leopold;
NANOSMAT-2012 Talk given at a conference -- 13.09.2012 Prague, Czech Republic Talirz Leopold; Passerone Daniele; Pignedoli Carlo Antonio;
European Conference on Surface Science (ECOSS-29), Edinburgh (poster presentation) Talk given at a conference -- 03.09.2012 Edinburg, Great Britain and Northern Ireland Talirz Leopold; Pignedoli Carlo Antonio; Passerone Daniele;
CAMD summer school on electronic structure theory and materials design Poster -- 11.08.2012 Technical University of Denmark, Denmark Talirz Leopold;
CECAM work shop: What about U? Corrective approaches to DFT for strongly-correlated systems Poster -- 18.06.2012 EPFL Lausanne, Switzerland Talirz Leopold;
CECAM work shop: Nonadiabatic quantum dynamics with MCTDH and CPMD Poster -- 10.05.2012 EPFL Lausanne, Switzerland Talirz Leopold;
CECAM CPMD tutorial Poster -- 07.05.2012 EPFL Lausanne, Switzerland Talirz Leopold;
Cray XE6 Workshop: "Monte Rosa" Poster -- 07.11.2011 CSCS manno, Switzerland, Switzerland Talirz Leopold;
Empa PhD students’ symposium Talk given at a conference -- 18.10.2011 Empa Duebendorf Switzerland, Switzerland Talirz Leopold; Pignedoli Carlo Antonio; Passerone Daniele;


Awards

Title Year
Outstanding oral presentation award at Empa PhD students’ symposium 2014
• CMSZH travel award 2013

Associated projects

Number Title Start Funding scheme
140812 Applied nanoscience: novel catalysts and bottom-up design of graphene-like nanostructures. Computational insight within a surface science laboratory 01.09.2012 Project funding (Div. I-III)
128754 UP-IPAZIA: “UPgrade and full deployment of the Empa/Eawag computational cluster IPAZIA: towards an interdisciplinary on-site resource for computational sciences” 01.04.2010 R'EQUIP
153661 Predicting properties of realistic zigzag like graphene nanoribbons, a DFT challenge 01.07.2014 Project funding (Div. I-III)

Abstract

The development of experimental techniques capable of manipulation and analysis at the nanoscale has determined inthe last years the enormous fortune of nanotechnology. One of the most fascinating aspects is the manifestation in realistic systems of theoretically predicted (but often unexpected) quantumeffects that lead to remarkable and unusual properties of matter at the 10-100 nm scale.In particular, the technology for the fabrication of organic nanostructures designed to become microelectronic devices is now mature, and the concepts governing the growth and stability of nano-derivatives of molecular crystals are now accessible. The range of forecasted applications is broad: catalysis, solar cells, nanosensors, lasers, device miniaturization, etc. The choice of p-conjugated molecules as building blocks for such organic nanostructures is central in the definition of this emerging new field and has clear advantages: ease of synthesis at low cost and big scale, processing in solution and possibility to control the properties of the devices by molecular design. In our laboratory at Empa a methodology was recently developed to fabricate single-crystalline 1D nanostructures with high density, quality and purity. The growth method is based on a plasma vapor deposition process of organic molecules on tailored-roughness substrate surfaces. Such substrate-supported nanowires are ideal systems for fundamental studies such as: understanding of complex self-assembly mechanisms for organic molecules into crystalline structures, elucidating transport mechanisms, addressing the role of nanoscale domains in microstructures, defining of the relationship between molecular/crystalline structure and corresponding electronic properties. The generalization of this growth methodology to different molecules provides a straightforward way to study the relation between the chemical structure of the molecules and the final morphology and structure of the wires.The aim of the present project is to understand the structural and electronic properties of selected nanowires belonging to different molecular precursors by means of ab initio atomistic simulations, in connection to the experiments that are being conducted in our laboratory. The project will be focused towards two main goals:The investigation of the geometric and electronic properties of ideal models of nanowires based on Cu-phtalocyanines and Co-phtalocyanines. For the model geometries the starting point will be the data collected from experimental measurements; van der Waals corrections, based on the Grimme parameterization will be included in our model. For the electronic properties the role played by surface effects and possible defects (as suggested by experiments) in the molecular crystal will be discussed;The evaluation of transport properties in the band conductance regime and in the hopping regime. On the one hand, we will simply rely on the band structure determined from our first goal; on the other hand we will also compute transfer integrals and reorganization energies to be included in proper Monte Carlo simulations.The methodology developed in the present project will be of fundamental relevance for the future research activity of our laboratory in the field of molecular based nanostructures.Summary of the research tasks1)Characterization of the geometrical and electronic properties of MPcs crystals.For two representative systems of interest, given the crystalline structure obtained by XDS measurements, we will compare theoretical and measured equilibrium geometries, compute the band structure of the corresponding crystalline phase and the correct Hubbard parameter U. We will perform phonon calculations for isolated molecules and, if possible, evaluate the effects of molecule-molecule interactions on the phonon spectra.The outcome of this task will be of general relevance for the scientific community: the correct Hubbard parameters will represent a reference value for future calculations.The final objective of the first task will be the investigation of surface effects, confinement effects and the inclusion of defects in the bulk and at the surface of the model nanowires.2)Transport properties: evaluation of transfer integrals, reorganization energy and evaluation of carriers mobilityThe second task is devoted to characterize the transport properties of the systems investigated in task 1. Carriers mobility for band-like conduction mechanism will be evaluated from the band structure calculations completed in the first task. The second step will be the evaluation of quantities necessary to compute mobility in the hopping regime as requested by Marcus-Hush formula (Marcus 1956, Hush 1958): transfer integrals as well as the reorganization energywill be computed.The final step will be collection of all the information to compute the charge carriers mobility in the incoherent regime of conductivity via Monte Carlo approaches. The results obtained from this task should allow understanding the origin of the unexpected conductibility of the nanowires obtained at Empa. The methodology developed within the first two tasks will be fundamental for future applications to the graphene based devices engineered at Empa. 3)Carriers mobility for a macroscopic nanowireIn case that the first two tasks are completed successfully the final efforts will be devoted to compute stress effects on the electronic properties of the systems and to transfer the results to a realistic model for a nanowire. By means of large scale molecular dynamics simulations the stress field in a realistic model of nanowire will be computed. Integrating the mobility across the wire will provide information on the macroscopic properties of the system. The additional methodology that could be developed in this last task is extremely appealing in view of its transfer to other sys-tems that will be investigated at Empa.
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