MATERIALS FOR NANOTECHNOLOGIES

1. ComputationalMaterials Science MATERIALS FOR NANOTECHNOLOGIES CMAST (ComputationalMAterials Science & Technology) VirtualLab www.afs.enea.it/project/cmast Adhesion of organicmolecules on inorganicsurfaces • Projects: • META - Materials Enhancement for Technological Applications (FP7-PEOPLE-2010-IRSES) C.- Arcangeli (ENEA), F. Buonocore (ENEA), M. Celino (ENEA) Pulling of the proteinstocompute the adhesionforce Classicalmoleculardynamics of the entireprotein on the TiO2 surface META project aimstodevelop a DNA nanogridfixed via aptamerproteinstospecificinorganicsurfaces. Thiscouldbe the first step of a newclass of devices Problem: Itisknown in nature that some animals , likegecko, can haveanextraordinaryadhesion on surfaces. Thisadhesion can beselective and very strong. Thisis due tosurfaceproteins and theirspecificconformationalproperties. Open questions: Why some proteins are so adhesive on inorganicsurfaces ? Whichis the recipetoengineersuchproteins ? Which are the criticalaminoacids ? Organic-inorganicadhesion can beusedtodevelopnew microelectronic devices ? Method: Atomic scale moleculardynamics of proteins in contactwith the (110) anatase TiO2 surfaces . Quantum approaches are usedtostudy the adhesion fo singlesaminoacids. Classicalmoleculardynamicsisusedtocharacterize the adhesion of the entireprotein. • Results: • the aminoacidsinvolved in the adhesion are identified. Argseems to play the major role • the adhesionismainlydriven by the electrostaticinteracions and by the interfacial water moleculeswhichform a stable and oriented a hydrogen • bonding network induced by the surface Quantum total energycalculationsselectbindingsites and charge transfer betweenaminoscides and surface Classicalmoleculardynamicsfindsfolding of anengineeredprotein in water C. Arcangeli et al. (2013) Nanosci. Nanotech.Lett5(11):1147-1154 Graphene production • Projects: • European Future and EmergingTechnology (FET) Iniziative on Graphene F. Buonocore (ENEA) Graphene-Copper Band Structure Graphene Band Structure Problem: The production of graphene on large scale and high purity is still a challenging problem. Experiments indicate that CVD growth mechanism on copper could be a very promising process. However quality of the graphene should be improved. Open questions: Which are the adhesion energies of graphene on liquid copper ? Which is the growth mechanism of graphene ? Method: Quantum molecular dynamics simulations are used to model a graphene –liquid copper interface. Total energy calculations are used to compute electronic density of state and charge transfers. Quantum molecular dynamics is used to simulate the effect of temperature on the adhesion properties. Model of graphene on crystalline copper Dirac cone Work Function Calculation of Copper Functionalized with Graphene Charge density and interface dipole Model of graphene on liquid copper Graphene-Copper Adhesion Energy ChemicalVapourDepositiongrowth of graphene (ENEA, UTTMAT-SUP lab) • Results: • Electron transfer from copper substrate to graphene was found and an interface dipole is generated • In graphene Fermi level is shifted upwards due to the interface dipole so that graphene is electrostatically n-doped Adhesionofself-assembled alkylsilane coatings of a (111) silicon surface Problem Self-assembled monolayers (SAMs) octadecyltrichlorosilanefilms (CH3(CH2)17SiCl3, OTS) depositedon Si or SiO2 exhibit high insulating properties, provided that a good control of film quality is achieved, making this system highly appealing for the fabrication of efficient field emitting transistors (FETs) or organic thin film transistors (OTFTs) at the nanoscale, where silicon dioxide (SiO2) behaves as a poor insulator with high leakage currents. SAM coatings of semiconductor surfaces have been also employed in organic light-emitting diodes (OLED) as “adapting” dipolar thin films that may greatly improve the device performance by modifying the work function at the gate/substateinterface. F. Gala (Univ. La Sapienza), G. Zollo (Univ. La Sapienza) Fully relaxed configurations of the OTS adhesion on the hydrogenated (111) Si surface Partial dipole as a function of z, for the H:Si slab (black line) and 1 × (1:1) structure (red line). The surface dipoles have been evaluated at zs, which is one of the special planes dividing the whole structure into two neutral subunits Open questions: Is the adhesion chemistry related to the uniformity of the SAM? What are the basic phenomena causing self-assembling? At which extent OTS SAM improves the isolation properties of Si (i.e. how the work function depend on the adhesion chemistry and SAM uniformity)? Method: OTS multiple adsorptions onto the (111) Si surface have beenvmodeled by ab initio density functional theory (DFT), with a generalized gradient approximation (GGA), using the Perdew−Burke−Ernzerhof formula19 (PBE) for the electron exchange and correlation energy, together with norm-conserving pseudopotentials, constructed using the Troullier−Martins scheme,20 and a plane wave basis set expansion scheme. First-principles calculations have been performed using the QUANTUM-ESPRESSO package, Work function shifts ΔΦ with respect to the hydrogenated (111) Si surface as a function of Δds for the various configurations studied. • Results: • SAM are formed via hydrogen bonds formedbetween the silane adhesiongroupsonlyif OTS adhere with just one bond per molecule. • A simple model hasbeenadopted to calculate the work functionat full coverageinvolvingpartial dipoles. • structural information are providedtoavoid a decrase in the device performance.