Work function modification of the (111) gold surface covered by long alkanethiol-based self-assembled monolayers.

Many recent experimental studies have demonstrated that the deposition of self-assembled monolayers on a metal electrode can significantly modulate its work function and hence charge injection properties in organic-based devices. In this context, we model here by means of Density Functional Theory (DFT) calculations the deposition of long saturated and partially fluorinated alkanethiol chains on the gold (111) surface and explore the shift in the work function while changing the size and degree of fluorination of the molecular backbone in order to contribute to the definition of design rules. Among all the derivatization schemes, only the introduction of a terminal fluoromethyl unit leads to an appreciable change in the work function shift, further accompanied by a reversal of its sign. The results show pronounced odd-even effects with different origins.

[1]  Amy L. Graham,et al.  Tuning the Effective Work Function of Gold and Silver Using ω-Functionalized Alkanethiols: Varying Surface Composition through Dilution and Choice of Terminal Groups , 2009 .

[2]  G. M. Lazzerini,et al.  Photoinduced work function changes by isomerization of a densely packed azobenzene-based SAM on Au: a joint experimental and theoretical study. , 2011, Physical chemistry chemical physics : PCCP.

[3]  J. Brédas,et al.  Interface energetics and level alignment at covalent metal-molecule junctions: pi-conjugated thiols on gold. , 2006, Physical review letters.

[4]  R. Rousseau,et al.  Metal work-function changes induced by organic adsorbates: a combined experimental and theoretical study. , 2005, Physical review letters.

[5]  R. Salvarezza,et al.  Self-assembled monolayers of thiols and dithiols on gold: new challenges for a well-known system. , 2010, Chemical Society reviews.

[6]  A. C. Jamison,et al.  The impact of fluorination on the structure and properties of self-assembled monolayer films , 2013 .

[7]  M. Grunze,et al.  The effect of sulfur–metal bonding on the structure of self-assembled monolayers , 2000 .

[8]  Richard L. Martin,et al.  CONTROLLING CHARGE INJECTION IN ORGANIC ELECTRONIC DEVICES USING SELF-ASSEMBLED MONOLAYERS , 1997 .

[9]  Andreas Hirsch,et al.  The Potential of Molecular Self‐Assembled Monolayers in Organic Electronic Devices , 2011, Advanced materials.

[10]  M. Ratner,et al.  Molecular Self‐Assembled Monolayers and Multilayers for Organic and Unconventional Inorganic Thin‐Film Transistor Applications , 2009 .

[11]  George M. Whitesides,et al.  Structures of self-assembled monolayer films of organosulfur compounds adsorbed on gold single crystals: electron diffraction studies , 1988 .

[12]  S. Perry,et al.  Characterization of the surface structure of CH3 and CF3 terminated n-alkanethiol monolayers self assembled on Au{111} , 1998 .

[13]  P. Dirac.  Note on Exchange Phenomena in the Thomas Atom , 1930, Mathematical Proceedings of the Cambridge Philosophical Society.

[14]  D. Ceperley.  Ground state of the fermion one-component plasma: A Monte Carlo study in two and three dimensions , 1978 .

[15]  Z. Shuai,et al.  Is there a Au-S bond dipole in self-assembled monolayers on gold? , 2010, Physical Chemistry, Chemical Physics - PCCP.

[16]  D. F. Ogletree,et al.  AN UNEXPECTED PACKING OF FLUORINATED N-ALKANE THIOLS ON AU(111) : A COMBINED ATOMIC FORCE MICROSCOPY AND X-RAY DIFFRACTION STUDY , 1994 .

[17]  Y. Olivier,et al.  Depolarization Effects in Self‐Assembled Monolayers: A Quantum‐Chemical Insight , 2007 .

[18]  B. de Boer,et al.  Tuning of Metal Work Functions with Self‐Assembled Monolayers , 2005 .

[19]  Nancy S. Ferris,et al.  Self-Assembled Monolayers of Alkanethiols Containing a Polar Aromatic Group: Effects of the Dipole Position on Molecular Packing, Orientation, and Surface Wetting Properties , 1991 .

[20]  A. Zunger,et al.  Self-interaction correction to density-functional approximations for many-electron systems , 1981 .

[21]  H. Monkhorst,et al.  SPECIAL POINTS FOR BRILLOUIN-ZONE INTEGRATIONS , 1976 .

[22]  A. Ulman,et al.  Self-assembled monolayers of semifluorinated alkaneselenolates on noble metal substrates. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[23]  B. Alder,et al.  THE GROUND STATE OF THE ELECTRON GAS BY A STOCHASTIC METHOD , 2010 .

[24]  J. Hsu,et al.  Molecular monolayer modification of the cathode in organic light-emitting diodes , 2006 .

[25]  S. Franzen.  Density functional calculation of a potential energy surface for alkane thiols on Au(1 1 1) as function of alkane chain length , 2003 .

[26]  Daniel Sánchez-Portal,et al.  Density‐functional method for very large systems with LCAO basis sets , 1997 .

[27]  M. Zharnikov.  High-resolution X-ray photoelectron spectroscopy in studies of self-assembled organic monolayers , 2010 .

[28]  Q. Ge,et al.  Steric Effects on the Adsorption of Alkylthiolate Self-Assembled Monolayers on Au (111) † , 2003 .

[29]  F. Tao,et al.  Understanding odd-even effects in organic self-assembled monolayers. , 2007, Chemical reviews.

[30]  Hsiao-Wen Zan,et al.  Concomitant tuning of metal work function and wetting property with mixed self-assembled monolayers , 2011 .

[31]  N. Crivillers,et al.  Tuning the charge injection of P3HT-based organic thin-film transistors through electrode functionalization with oligophenylene SAMs , 2010 .

[32]  G. Brocks,et al.  Work functions of self-assembled monolayers on metal surfaces by first-principles calculations , 2006, cond-mat/0606663.

[33]  G. Pourtois,et al.  Work-function modification of Au and Ag surfaces upon deposition of self-assembled monolayers: influence of the choice of the theoretical approach and the thiol decomposition scheme. , 2013, Chemphyschem : a European journal of chemical physics and physical chemistry.

[34]  A. T. Blumenau,et al.  Steric and chain length effects in the (√(3)×√(3))R30° structures of alkanethiol self-assembled monolayers on Au(111). , 2011, Chemphyschem : a European journal of chemical physics and physical chemistry.

[35]  J. Soler,et al.  Efficient implementation of a van der Waals density functional: application to double-wall carbon nanotubes. , 2008, Physical review letters.

[36]  W. Hofer,et al.  Self-assembly of semifluorinated n-alkanethiols on {111}-oriented Au investigated with scanning tunneling microscopy experiment and theory. , 2007, The Journal of chemical physics.

[37]  A. Shluger,et al.  Intramolecular Dipole Coupling and Depolarization in Self‐Assembled Monolayers , 2008 .

[38]  G. Whitesides,et al.  Self-assembled monolayers of thiolates on metals as a form of nanotechnology. , 2005, Chemical reviews.

[39]  M. Porter,et al.  Atomic force microscopic characterization of a fluorinated alkanethiolate monolayer at gold and correlations to electrochemical and infrared reflection spectroscopic structural descriptions , 1993 .

[40]  G. M. Lazzerini,et al.  Large Work Function Shift of Gold Induced by a Novel Perfluorinated Azobenzene‐Based Self‐Assembled Monolayer , 2013, Advanced materials.

[41]  Emilio Artacho,et al.  The SIESTA method; developments and applicability , 2008, Journal of physics. Condensed matter : an Institute of Physics journal.

[42]  Amy L. Graham,et al.  Interface Dipoles Arising from Self-Assembled Monolayers on Gold: UV−Photoemission Studies of Alkanethiols and Partially Fluorinated Alkanethiols , 2003 .

[43]  R. Hsung,et al.  Tuning the Work Function of Gold with Self-Assembled Monolayers Derived from X−[C6H4−C⋮C−]nC6H4−SH (n = 0, 1, 2; X = H, F, CH3, CF3, and OCH3) , 1999 .

[44]  Y. Tao,et al.  Continuous modulation of electrode work function with mixed self-assembled monolayers and its effect in charge injection. , 2009, Langmuir : the ACS journal of surfaces and colloids.