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STRUCTURE DEPENDENT IRRADIATON-INDUCED DESORPTION OF BIPHENYL ALKANETHIOL SELF-ASSEMBLED MONOLAYERS S.Wyczawska 1 , M.Buck 3 , P. Cyganik 2 , P. Lievens 1 , R. E. Silverans 1 , E. Vandeweert 1 , F. Vervaecke 1 , and Z. Postawa 2 1 Laboratory of Solid State Physics and Magnetism, K.U.Leuven, Celestijnenlaan 200D, B 3001 Leuven, Belgium 2 Institute of Physics, Jagiellonian University, ul. Reymonta 4, PL 30-059 Krakow, Poland 3 School of Chemistry, St Andrews University, North Haugh, St Andrews, KY16 9ST, United Kingdom LAP 2006, 10-15 Sep 2006

S.Wyczawska 1 , M.Buck 3 , P. Cyganik 2 , P. Lievens 1 ,

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LAP 2006, 10-15 Sep 2006. STRUCTURE DEPENDENT IRRADIATON-INDUCED DESORPTION OF BIPHENYL ALKANETHIOL SELF-ASSEMBLED MONOLAYERS. S.Wyczawska 1 , M.Buck 3 , P. Cyganik 2 , P. Lievens 1 , R. E. Silverans 1 , E. Vandeweert 1 , F. Vervaecke 1 , and Z. Postawa 2. - PowerPoint PPT Presentation

Text of S.Wyczawska 1 , M.Buck 3 , P. Cyganik 2 , P. Lievens 1 ,

  • STRUCTURE DEPENDENT IRRADIATON-INDUCED DESORPTION OF BIPHENYL ALKANETHIOL SELF-ASSEMBLED MONOLAYERSS.Wyczawska1, M.Buck3, P. Cyganik2, P. Lievens1, R. E. Silverans1, E. Vandeweert1, F. Vervaecke1, and Z. Postawa21 Laboratory of Solid State Physics and Magnetism, K.U.Leuven, Celestijnenlaan 200D, B 3001 Leuven, Belgium2 Institute of Physics, Jagiellonian University, ul. Reymonta 4, PL 30-059 Krakow, Poland3School of Chemistry, St Andrews University, North Haugh, St Andrews, KY16 9ST, United KingdomLAP 2006, 10-15 Sep 2006

  • OutlineIntroductionExperimental setupPolymorphism in biphenyl-based SAMs4. Odd/even effect in BPn/Au5.Conclusions

  • Introduction

    Self-Assembled Monolayer: (SAM)

    Highly ordered and oriented assemblies that are formed spontaneously by the adsorption of a surfactant with a specific affinity of the headgroup to a substrate.

    Tail : surface propertiesSpacer : intermolecular interactions ordening and orientation moleculesHead : bound to substrate atom

  • Introduction

    Aim: to investigate the fundamental influence of the detailed geometric and electronic structure of SAMs on projectile-induced desorptionInteraction of energetic projectiles with self-assembled monolayers:

    Characterization: damage induced during standard characterization techniques such as SIMS and AES Controlled modification: SAMs are promising to be used as ultrathin resist in lithographic patterning

  • IntroductionWe investigated biphenyl-based SAMs:BPn, n=1, 2, 3, 4, 5, 64,4-biphenyl-substituted alkanethiolS(CH2)nPhenyl chromophoreCH3SCRSCRsp3AuspAu2 stable hybridization:=180=104

  • Experimental setupsubstrateSAM

  • Experimental setupTOF and iondetectorsubstrateSAM

  • Experimental setupIonization of neutral molecules Detection of neutral molecules Photo-ionization but also photofragmentation

  • Experimental setupResonance-enhanced multiphoton ionization Detection of neutral molecules Photo-ionization but also photofragmentation Introduction of a suitable chromophore M* resonance enhanced increase of the ionization efficiency reduction of laser intensity reduction of the photofragmentation

    Aromatic rings act as chromophores1. Vandeweert et al., Nucl. Instrum. and Meth. in Phys. Res. B 164-165 (2000)

  • Experimental setupP = 10-10 Torr15 keV Ar+Fion = 1011ions/cm = 259nmFphoton = 1017ph/cm2(m/Dm)lin = 200(m/Dm)ref = 8001 keV Ar+Fion = 1015electrons/cmSpectra Physics

  • Experimental observables1.Flight-time distributions: probing ion signal in function of flight time ( = difference between ion and laser pulse) kinetic energy of desorbing particles2 ejection mechanisms: [2] 1. Ballistic ejection: direct momentum transfer (~ 1 eV) 2. Thermal-like ejection: bond cleavage byreactive species (~ 0.02 eV)BT2. Riederer et al., J. Am. Chem. Soc. 119 (1997)

  • Experimental observables2.Desorption fragmentation pattern: probing which particles are desorbed parent molecule desorbed desulphurized fragment desorbed m/z = 181 photofragment m/z = 168 desorbed m/z = 165 photofragment

  • Polymorphism in BPn/AuDetailed geometric and electronic structure depends on growth parameters [3]3. Cyganik et al., J. Am. Chem. Soc. 126 (2004)

  • Polymorphism in BPn/Aun = even prepared at 295 K angle C-S-Au > 130-BPn- & -BPn prepared at 423 K angle C-S-Au < 130

  • Polymorphism in BPn/AuIon-induced desorption:Probing desorption mass spectra during 15-keV Ar+ irradiation of a and b/d even BPn/Au

  • Polymorphism in BPn/AuDesorption probability of the parent molecule is larger for a than for b/d even BPn/Au Desorption probability of the BPn-S molecule is larger for b/d than for a even BPn/Au bond scission efficiency of the S-Au bond is larger for a than for b/d even BPn/Au bond scission efficiency of the C-S bond is larger for b/d than for a even BPn/Au Ion-induced desorption:

  • Polymorphism in BPn/AuRT BP5/Au and HT BP5/Au: no change in desorption probability Ion-induced desorption: changes in bond scission efficiency between a and b/d even BPn/Au are related to structural change and not to annealing

  • Polymorphism in BPn/Auf > 130 Discussion:a even BPn/Au:b even BPn/Au:optimization bond geometryoptimization 2 dimensional packingf < 130 f ~ 104

  • Polymorphism in BPn/AuDiscussion:a even BPn/Au:f > 130 b/d even BPn/Au: f < 130

  • Odd/even effect in BPn/AuDetailed geometric and electronic structure depends on growth parameters and alkane chain:3. Cyganik et al., J. Am. Chem. Soc. 126 (2004)[3,4]

  • Odd/even effect in BPn/Aun = oddn = even prepared at 295 K angle C-S-Au ~ 109 prepared at 295 K angle C-S-Au > 130-BPn

  • Odd/even effect in BPn/AuIon-induced desorption: Probing desorption mass spectra during 15-keV Ar+ irradiation of odd and even BPn/Au

  • Odd/even effect in BPn/Au bond scission efficiency of the S-Au bond is larger for even than for odd BPn/Au bond scission efficiency of the C-S bond is larger for odd than for even BPn/Au Desorption probability of BPn-S molecule is larger for odd than for even BPn/Au Desorption probability of the parent molecule is larger for even than for odd BPn/Au Ion-induced desorption:

  • Odd/even effect in BPn/AuOdd BPn/Au:f ~ 109 Discussion:f > 130 Even BPn/Auconflict between interactionsboth interactions result in same structure

  • Conclusionscompetition between molecule-substrate bondand intermolecular interactions

  • THANKYOU