Crystal structure determination for CNHP4 - Institute of Solid State ...

Institute of Solid State PhysicsCrystal structure determination of 2-dimensionalpowdersthe example: CNHP4CNProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP41

Institute of Solid State PhysicsIntroductioncooperation with H.-G. Rubahn 1 and M. Schiek 1• variety of functionalised quaterphenylenes• studied nonlinear optical properties• CNHP4 showed largest second harmonic generation applicable for frequency doubling1 Syddansk University, Soenderborg, DenmarkProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP42

Institute of Solid State PhysicsOverviewwhat is a 2d powder?diffraction prinicplesspecular scansgrazing incidence x-ray diffraction (GID)reciprocal space mapsindexation of CNHP4molecular packing of CNHP4theoretical structure factor / experimental intensitiesProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP43

Institute of Solid State PhysicsOur motivation• thin films are key elements in organic electronics• surface induced phases (SIPs) different from bulk structure• crystal structure physical properties• established procedures exist for single crystals and powders• for thin films it‘s a new topicRecently solved thin film phases:• pentacene (5P): Nabok 1 , Schiefer 2 , Yoshida 3• tetraceno[2,3-b]thiophene: Q. Yuan 4• PTCDI-C8: T.N. Krauss, MPI-Stuttgart1 D. Nabok, P. Puschnig, C. Ambrosch-Draxl, O. Werzer, R. Resel, D.-M. Smilgies, Phys. Rev.B, 762S. Schiefer, M. Huth, A. Dobrinevski, B. Nickel, J. Am. Chem. Soc. 129 (2007) 10316-103173 H. Yoshida, K. Inaba, N. Sato, Appl. Phys. Lett. 90 (2007) 1819304 Q. Yuan, SCB Mannsfeld, ML. Tang, et al., J. Am. Chem. Soc. 130 (2008) 11Professor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP44

Institute of Solid State PhysicsFundamental conditions for x-ray scattering Scattering vector : q = kElastic scattering :k0=− k0k =; d2πλ=n2πqnReciprocal space Condition : q =Laue• orientation of q Tilting sampleG hklReal spaceBragg equation : nλ= 2Symmetry: α = αif= θd hklsinθ• length of q Changing 2θProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP45

Institute of Solid State PhysicsThe reciprocal lattice of …… a single crystal• Point lattice q=G hkl… a powder of crystallites• Spheres |q|=|G hkl|Professor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP46

Institute of Solid State Physics2d powder• controlled vacuum deposition + isotropic substrate often strong preferred orientation• one crystallographic plane || substrate surfaceno in-plane alignment reciprocal lattice rings on cylinder surfaces• q z=G zand q x2+q y2= G x2+G y2has to be fulfilledProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP47

Institute of Solid State PhysicsX-ray diffraction Crystal structureCrystal structure = translational lattice + motifTranslational lattice• Bragg peaks set of G hkl• Indexation Find a base (unit cell) for all G hkl• Positions of Bragg peaks translational latticeMotif• Intensity connected with the atomic positions in the unit cell• I ∝ |F| 2 (structure factor)• structure factor = Fourier Transform of Electron densityF = ρ ( r )exp( −iqr) dr∫UCe• Inverse transformation difficult because of phase problem• Intensity corrections not clear at the momentProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP48

Institute of Solid State PhysicsExperimental methodsProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP49

Institute of Solid State PhysicsSpecular Scans• laboratory equipment is sufficient• Θ and 2θ circle are moved synchronously diffraction conditions lattice planes || substrate surface• test if you have a 2d powder.• existing polymorphs• interplanar distance is determinedProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP410

Institute of Solid State PhysicsThin film samples of CNHP4Nr. Substrate Thickness Temperature1 Si(100)/SiOx 178 [nm] 300-340 [K]2 Si(100)/SiOx 100 [nm] 340 [K]3 Si(100)/SiOx 35 [nm] RT-300 [K]4 Si(100)/SiOx 100 [nm] RT-300 [K]5 Si/SiOx/OTS 120 [nm] R T-300 [K]6 Si/SiOx/OTS 120 [nm] RT-300 [K]7/210 Glass 160 [nm] 300 [K]8/207 Glass 60 [nm] 360 [K]Professor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP411

Institute of Solid State PhysicsSpecular scan - sample 6two phases are present only one dominatMeasured lattice plane distancesd00i’ d00i20.75 Å 23.39 Åd001=n2π| |q nn λ=d sinθ2 hklProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP412

Institute of Solid State Physicsspecular scan - sample 1Even three phases are present strong tendency for polymorphismMeasured lattice plane distancesd00i21.2 Åd00i*22.12 Åd00i‘23.02 Åd001=n2π| |q nn λ=d sinθ2 hklProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP413

Institute of Solid State Physicsspecular scan - sample 4Measured lattice plane distanceOnly one phase Onset of 3d distributiond00i20.37 Åd001=n2π| |q nn λ=d sinθ2 hklProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP414

Institute of Solid State PhysicsSurface DiffractionProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP415

Institute of Solid State PhysicsGrazing incidence diffraction• Is needed for indexationGID advantages• Incidence angle ~ critical angle of total reflection diffracted intensity mainly from the surface• for ultra-thin films (down to a monolayer)• variaton of incidence angle variation penetration depth multilayer systems• Large area is illuminatedI ∝ N 2• non destructiveProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP416

Institute of Solid State PhysicsOur grazing incidence experiment• α i~ 0.2°• diffracted beam α f= 0.2° … 30°, θ f= 10° … 50°Scattering vector in sample coordinate system q = k − kqqqxyz02π= (cos αfcosθf− cosαicosθi)λ2π= (cosαfsin θf+ cosαisin θi)λ2π= (sin αi− sin αf)λLattice planes (nearly) perpendicular tosubstrate surface are measuredProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP417

Institute of Solid State PhysicsReciprocal space maps 2d pseudo color images q zand q pare used as coordinatesProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP418

Institute of Solid State PhysicsHow we indexed• finding the unit cell by comparing calculated positions to the experimental data• q = G hklfor a Bragg reflex; integer coordinates hkl• hkl-combinations can be generated easily• Crystal coordinate system sample coordinate systemA* *⎛ a sin β sin γ⎜* *= ⎜−a sin β cosγ⎜ * *⎝ a cos βbb**0*sinα*cosα00c*⎞⎟⎟⎟⎠• c* is chosen parallel to e zbecause of preferred orientation• powder in plane no assumptions about q pProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP419

Institute of Solid State Physicsq=Ghkl* *⎛ a sin β sin γ⎜* *= ⎜−a sin β cosγ⎜ * *⎝ a cos βbb**0*sinα*cosα0 ⎞⎛h⎞⎟⎜⎟0 ⎟⎜k ⎟*c⎟⎜⎟⎠⎝l ⎠• q is a possible scattering vector• Manually change unit cell parameters coincidence with experimentWhy is this approach reasonable• Some preknowledge exists often• Characteristic patterns exist• But it would be nice to have something automaticalProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP420

Institute of Solid State PhysicsReciprocal space map of sample 6Attenuator = 3 Attenuator = 0• Three left spots belong to the11L, 02L and the 12L rod herringbone structure• This gave the first hint about indexation• c was fixed at the 20L roda = 5.60b = 7.67c = 20.85α = 90.0°β = 97.4°γ = 90.0°Professor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP421

Institute of Solid State PhysicsTowards the crystal structureProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP422

Institute of Solid State PhysicsInternal Geometry optimizationby Dmitrii Nabok and Peter Puschnig (MU Leoben)• Force field calculations• Three possible arrangements of the molecule were found Calculation of structure factors is now possibleProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP423

Institute of Solid State Physics• radius of rings = F• structure factors not correctedCHI = 0 CHI = 16 CHI = -16Professor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP424

Institute of Solid State PhysicsCHI = 0CHI = 16CHI = -16Professor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP425

Institute of Solid State PhysicsThe preliminary resultProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP426

Institute of Solid State PhysicsIntensities Crystal Structure,Example Sexiphenylen• also measured at CHESS• well known baker structurea = 8.09b = 5.57c = 26.24α = 90.0°β = 98.17°γ = 90.0°• structure factors are known• match is quite goodProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP427

Institute of Solid State PhysicsConclusion crystal structure solution for a 2-D powder unit cell determination by specular scans / GID molecular packing by force field calculationsCNHP4: strong tendency of polymorphism onset of 3D distribution in thin film samplesbest 2D powders on OTS surfaces herringbone packing with antiparallel moleculesinterpenetration of layers ?internal torsion of molecules ?Professor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP428

Institute of Solid State PhysicsAcknowledgementtheoretical calculations:D. Nabok, P. Puschnig, MU-LeobenGID:D.-M. Smilgies, G-line CHESS, Ithaca, New Yorksamples:M. Schiek, Sydansk University, SoenderborgI. Wallmann, University of Bonnmy group:O. Werzer, R. Resel, H.-G. Flesch, M. Koini, T. Djuric, K. MargucProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP429

Institute of Solid State PhysicsThank you for your attentionProfessor Armin Moser Horst Cerjak, 19.12.2005Grazing incidence diffraction on CNHP430