Stick-slip transition at the nanometer scale

We report the first observation of a stick-slip transition of surfactant solution flow through nanopores. From the experimental data, we were able to determine both the slip length and the critical wall shear stress from which slip occurs. Whereas the latter is found to increase linearly with the concentration, the former remains constant and approximately equal to 20 nm over the studied range of concentrations. We model slip to occur in the surfactant bilayer adsorbed at the nanopore wall. The stick-slip transition is then related to a reorganization of the surfactant bilayer from an entangled structure into independent layers flowing past one another, as evidenced by independent surface plasmon resonance experiments. We conclude from our analysis that surfactant solutions are always slipping in larger tubes. However, the larger the tube diameter, the smaller the relative slip contribution to the total flow.     

Contact angle hysteresis at the nanometer scale

Using atomic force microscopy with nonconventional carbon tips, the pinning of a liquid contact line on individual nanometric defects was studied. This mechanism is responsible for the occurrence of the contact angle hysteresis. The presence of weak defects which do not contribute to the hysteresis is evidenced for the first time. The dissipated energy associated with strong defects is also measured down to values in the range of kT, which correspond to defect sizes in the order of 1 nm.     

From reciprocal space to real space in surface science

This issue is dedicated to Karl-Heinz Rieder on the occasion of his 70th birthday. It contains contributions written by his former students and colleagues from all over the world. Experimental techniques based on free electrons, such as photoelectron spectroscopy, electron microscopy and low energy electron diffraction (LEED), were foundational to surface science. While the first revealed the band structures of materials, the second provided nanometer scale imagery and the latter elucidated the atomic scale periodicity of surfaces. All required an (ultra-)high vacuum, and LEED illustrated impressively that adsorbates, such as carbon monoxide, hydrogen or oxygen, can markedly and periodically restructure surfaces from their bulk termination, even at pressures ten orders of magnitude or more below atmospheric. Yet these techniques were not generally able to reveal atomic scale surface defects, nor could they faithfully show adsorption of light atoms such as hydrogen. Although a complete atom, helium can also be regarded as a wave with a de Broglie wavelength that allows the study of surface atomic periodicities at a delicateness and sensitivity exceeding that of electrons-based techniques. In combination, these and other techniques generated insight into the periodicity of surfaces and their vibrational properties, yet were limited to simple and periodic surface setups. All that changed with the advent of scanning tunneling microscopy (STM) roughly 30 years ago, allowing real space access to surface defects and individual adsorbates. Applied at low temperatures, not only can STM establish a height profile of surfaces, but can also perform spectroscopy and serve as an actuator capable of rearranging individual species at atomic scale resolution. The direct and intuitive manner in which STM provided access as a spectator and as an actor to the atomic scale was foundational to today's surface science and to the development of the concepts of nanoscience in general. The cover image of this issue honors this achievement. It shows 27 chiral heptahelicene molecules arranged by one of the guest editors (KHE) with the very same STM at IBM Almaden Research Center, San José that was used for moving xenon atoms more than 20 years ago. Karl-Heinz Rieder's career, as briefly outlined in the biography by G Benedek in this issue, reflected this paradigm shift in surface science from reciprocal to real space investigations: initially focusing on helium scattering as a superior technique for the investigation of delicate surfaces, his group at the Freie University in Berlin became the second in the world to rearrange atoms and molecules at surfaces in a controlled way and they generated much of the foundational work of low temperature STM investigations. Besides his saxophone skills and many other hobbies, Karl-Heinz is a real poet and loves composing funny limericks and spoonerisms. He wrote the following poem (passed on to us by W-D Schneider) at the International School of Solid State Physics in 1998 in Erice, Italy. It is a real masterpiece, beautifully summarizing us all, the 'Surface Science Society'. The top atom sheetSome become real slaves is important and neat.looking at standing waves. Therefore there is a strong raceThe producers of coatings in the science of surface.get really good quotings. To clean it you needStill others use new ways ions and heat.with electrons and x-rays. Then the atoms arrangeAnd all has to be in some ways that are strange,in good UHV-except theory, they relax, reconstructwhich thinks on extensions as a matter of fact.to still lower dimensions, And reacting with gasesand with lots of computing they form quite new phasestries to get solid footing. with large unit cellsSo everybody with joy as diffraction tells.plays his own special toy. Some people use lightAnd all think they are better from a synchrotron brightshould get published a letter. and claim it is bestBut before there's more cluster to do this in Triest.let's finish-aus basta Some move atoms around to hear how they sound.Karl-Heinz Rieder, Erice, 6 April 1998 From reciprocal space to real space in surface science contents From reciprocal space to real space in surface scienceLudwig Bartels and Karl-Heinz Ernst Karl-Heinz Reider: the quiet pioneerGiorgio Benedek Scattering of CO and N(2) molecules by a graphite surfaceJunepyo Oh, Takahiro Kondo, Keitaro Arakawa, Yoshihiko Saito, Junji Nakamura, W W Hayes and J R Manson Helium, neon and argon diffraction from Ru(0001)M Minniti, C Díaz, J L Fernández Cu?ado, A Politano, D Maccariello, F Martín, D Farías and R Miranda Enhanced charge transfer in a monolayer of the organic charge transfer complex TTF-TNAP on Au(111)T R Umbach, I Fernandez-Torrente, J N Ladenthin, J I Pascual and K J Franke Extended pattern recognition scheme for self-learning kinetic Monte Carlo simulationsSyed Islamuddin Shah, Giridhar Nandipati, Abdelkader Kara and Talat S Rahman Acetylene on Cu(111): imaging a molecular surface arrangement with a constantly rearranging tipYeming Zhu, Jonathan Wyrick, Kamelia D Cohen, Katie Marie Magnone, Connor Holzke, Daniel Salib, Quan Ma, Dezheng Sun and Ludwig Bartels Coulomb attraction during the carpet growth mode of NaClFriederike Matthaei, Sarah Heidorn, Konrad Boom, Cord Bertram, Ali Safiei, J?rg Henzl and Karina Morgenstern Molecular self-assembly on an insulating surface: interplay between substrate templating and intermolecular interactionsMarkus Kittelmann, Philipp Rahe and Angelika Kühnle Vertical manipulation of native adatoms on the InAs(111)A surfaceJ Yang, C Nacci, J Martínez-Blanco, K Kanisawa and S F?lsch Charge transfer between isomer domains on n(+)-doped Si(111)-2 × 1: energetic stabilizationR M Feenstra, G Bussetti, B Bonanni, A Violante, C Goletti, P Chiaradia, M G Betti and C Mariani Probing the properties of metal-oxide interfaces: silica films on Mo and Ru supportsLeonid Lichtenstein, Markus Heyde, Stefan Ulrich, Niklas Nilius and Hans-Joachim Freund Mapping the first electronic resonances of a Cu phthalocyanine STM tunnel junctionW-H Soe, C Manzano, H S Wong and C Joachim Epitaxial Bi allotropes on quasicrystal surfaces as templates for adsorption of pentacene and fullereneH R Sharma, J A Smerdon, K M Young and R McGrath Island formation and manipulation of prochiral azobenzene derivatives on Au(111)Sofia Selvanathan, Maike V Peters, Stefan Hecht and Leonhard Grill.     

Characterization of thin films on the nanometer scale by Auger electron spectroscopy and X-ray photoelectron spectroscopy

We describe two NIST databases that can be used to characterize thin films from Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) measurements. First, the NIST Electron Effective-Attenuation-Length Database provides values of effective attenuation lengths (EALs) for user-specified materials and measurement conditions. The EALs differ from the corresponding inelastic mean free paths on account of elastic-scattering of the signal electrons. The database supplies “practical” EALs that can be used to determine overlayer-film thicknesses. Practical EALs are plotted as a function of film thickness, and an average value is shown for a user-selected thickness. The average practical EAL can be utilized as the “lambda parameter” to obtain film thicknesses from simple equations in which the effects of elastic-scattering are neglected. A single average practical EAL can generally be employed for a useful range of film thicknesses and for electron emission angles of up to about 60°. For larger emission angles, the practical EAL should be found for the particular conditions. Second, we describe a new NIST database for the Simulation of Electron Spectra for Surface Analysis (SESSA) to be released in 2004. This database provides data for many parameters needed in quantitative AES and XPS (e.g., excitation cross-sections, electron-scattering cross-sections, lineshapes, fluorescence yields, and backscattering factors). Relevant data for a user-specified experiment are automatically retrieved by a small expert system. In addition, Auger electron and photoelectron spectra can be simulated for layered samples. The simulated spectra, for layer compositions and thicknesses specified by the user, can be compared with measured spectra. The layer compositions and thicknesses can then be adjusted to find maximum consistency between simulated and measured spectra, and thus, provide more detailed characterizations of multilayer thin-film materials. SESSA can also provide practical EALs, and we compare values provided by the NIST EAL database and SESSA for hafnium dioxide. Differences of up to 10% were found for film thicknesses less than 20 Å due to the use of different physical models in each database.     

Dynamics of water confined on a nanometer length scale in reverse micelles: ultrafast infrared vibrational echo spectroscopy

The dynamics of water, confined on a nanometer length scale (1.7 to 4.0 nm) in sodium bis-(2-ethylhexyl) sulfosuccinate reverse micelles, is directly investigated using frequency resolved infrared vibrational echo experiments. The data are compared to bulk water and salt solution data. The experimentally determined frequency-frequency correlation functions show that the confined water dynamics is substantially slower than bulk water dynamics and is size dependent. The fastest dynamics (approximately 50 fs) is more similar to bulk water, while the slowest time scale dynamics is much slower than water, and, in analogy to bulk water, reflects the making and breaking of hydrogen bonds.     

Two-dimensional diffusion model for the biopolymers dynamics at nanometer scale

In this paper the driven transport of linear polymers through a nanopore is presented. Biopolymer physical behavior in an external electric field is modeled and its motion is simulated using the Langevin impulse integrator method. Within fairly large limits, the polymer translocation time is inversely proportional with the electric field intensity and directly proportional with the polymer chain length.      

Glass breaks like metal,but at the nanometer scale

We report in situ atomic force microscopy experiments which reveal the presence of nanoscale damage cavities ahead of a stress-corrosion crack tip in glass. Their presence might explain the departure from linear elasticity observed in the vicinity of a crack tip in glass. Such a ductile fracture mechanism, widely observed in the case of metallic materials at the micrometer scale, might be also at the origin of the striking similarity of the morphologies of fracture surfaces of glass and metallic alloys at different length scales.     

Optical spectroscopy of electronic surface states

In this paper a number of optical spectroscopic methods for investigating surface electronic structure are discussed, including reflectance techniques, ellipsometry, surface photoconductivity and surface photovoltage spectroscopy. In addition to electron scattering techniques and UV-photoemission, optical spectroscopic methods have contributed much in recent times to the understanding of electronic surface states on solids. A discussion and comparison is given of the nature and significance of information obtained by these methods and exemplary experimental results are presented to illustrate the contribution of the optical techniques to the present knowledge about surface states. The relation between information obtained from optical measurements and electron spectroscopy is considered.     

基态非简并导电聚合物——坐标空间研究

通过引入简并破缺项,建立了非等势垒Kronig-Penney方势阱模型,在实坐标空间中研究了基态非简并聚合物——顺式聚乙炔的基态及其激发态,并与紧束缚模型所得到的结果进行了比较.给出了体系的电子态、电荷密度等在实坐标空间的分布特征.发现在坐标空间研究可以更加准确地反映体系的电子态密度、电子空间密度分布等特征. 关键词： 聚合物 方势阱 基态 极化子     

Chemical-specific imaging of multicomponent metal surfaces on the nanometer scale by scanning tunneling spectroscopy

The topographic and chemical surface structure of a submonolayer iron film on a W(110) substrate has been studied by combined scanning tunneling microscopy and spectroscopy. Local tunneling spectra revealed a pronounced difference in the electronic structure between nanometer-scale iron islands of monolayer height and the bare W(110) substrate. In particular, a pronounced empty-state peak at 0.2 eV above the Fermi level has been identified for the iron islands. Based on the pronounced difference in the local tunneling spectra measured above the iron islands and the tungsten substrate, chemical-specific imaging was achieved by performing spatially resolved measurements of the differential tunneling conductivitydl/dU (x, y) at selected sample bias voltages.     

Optical spectroscopy of the surface of nanoporous diamond films

We have studied the IR absorption spectra of samples of porous ultrananocrystalline diamond (UNC diamond) obtained by selective etching of the sp ² phase in UNC diamond films. We show that the surface of porous UNC diamond is polyfunctional. We have studied the behavior of surface hydride, carbonyl, carboxyl, and hydroxyl groups as a function of annealing temperature in air and the time kept under normal conditions for UNC diamond films previously oxidized at 430°C–450°C. In the range from a few minutes to a few months, we studied the kinetics for establishment of the steady state for the functional adsorbed layer on the diamond surface under normal conditions. The observed growth in the intensity of the transmission bands due to hydride (CH _x ) and other hydrogen-containing functional groups is explained by dissociation of water molecules on the surface of the UNC diamond films.     

Optical absorption of isolated silver cluster-tryptophan: A joint experimental and theoretical study

We present a joint experimental and theoretical gas phase study of photoabsorption and photofragmentation of silver cluster-biomolecule complexes. We demonstrate on the example of [ Trp.Ag₃] ⁺ that binding of the metal cluster to a biomolecule leads to a significant enhancement of the photoabsorption in comparison with [Trp.H]⁺ and [Trp.Ag]⁺. This enhancement arises due to the coupling between the excitations in the metallic subunit with charge transfer excitations between silver cluster and tryptophan. Our experimental studies show that silver clusters up to eleven atoms can be bound to tryptophan and we present first results on the photofragmentation of the Trp.Ag₁₁ ⁺ complex cation, in which properties of cluster subunit remain preserved.     

Spin-polarized surface states on Fe-deposited Au(111) surface: A theoretical study

We have studied electronic structure of Fe-deposited Au(111) by performing ab initio density functional theory calculations. We find that the magnetic moment on the deposited Fe layer is enhanced as compared to that in bulk iron. We observe a large number of new states on the Fe-deposited surface — one of which is in the majority spin channel having similar dispersion to that on the clean surface, and others in the minority spin channel. The effective mass of electrons in surface states near the Fermi level increases on Fe deposition. The electronic properties are found to be insensitive to the stacking of near-surface layers. We need to use very thick slabs in our calculations to avoid splitting of surface states due to spurious interactions between the two surfaces of the slab. Using the local density of states profiles for different surface states, we conclude that in scanning tunneling microscope experiments one can detect two of the surface states — one in the majority channel below the Fermi level, and another in the minority channel appearing just above the Fermi energy. We compare our results to those from scanning tunneling spectroscopy experiments.     

Optical charging of real surface of germanium over a wide range of temperatures

A study is made of the charging of a real germanium surface under the effect of light. Mechanisms of electron and hole transport from germanium to the oxide layer are discussed. Conclusions are drawn as to the nature of the deep electron and hole traps in the oxide.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 36–41, May, 1979.In conclusion the authors wish to thank V. F. Kiselev for his discussion of the paper and his useful comments.     

Experimental determination of the viscosity at the nanometer scale on a block copolymer with an oscillating nanotip

: This work is an attempt to investigate viscosities at the nanometer scale. To do so, the tapping mode atomic force microscopy is used on a triblock copolymer exhibiting a well-defined periodic structure at the nanometer scale. Variations of the oscillator amplitude and phase delay as a function of the tip-sample distance are recorded on the glassy and rubbery domains of the copolymer. The experimental data are compared to analytical expressions derived from Stokes law. In the present study, among the different possible expressions of the viscous forces depending on the tip shape and on the experimental length scale, only a force proportional to the indentation depth is able to describe the experimental data. In this particular case, quantitative measurements are possible. Finally, the oscillator is shown to be sensitive to local variations of the viscosity within few nanometers.     

Experimental determination of the viscosity at the nanometer scale on a block copolymer with an oscillating nanotip

The European Physical Journal E - This work is an attempt to investigate viscosities at the nanometer scale. To do so, the tapping mode atomic force microscopy is used on a triblock copolymer...     

Localization of light energy on the nanometer scale in a silicon cone

The spatial structure of light fields in a metallized cone filled with a medium with complex dielectric function was studied on the basis of the exact solution of the eigenwave problem. It is suggested that silicon can be used as a core of optical probe in the visible spectral region. It is shown that the density of light energy at the output of optical probe can be drastically increased if silicon is used instead of glass fiber.     

A real space approach to study the effect of off-diagonal disorder on superconductivity

We present an efficient numerical methodology to study the effect of off-diagonal randomness on superconductivity. This is a real space approach using Bogoliubov-de-Gennes (BdG) method coupled with augmented space vector recursion (ASVR) technique for disorder averaging. We find in the presence of off-diagonal randomness s-wave superconductivity is favoured by greater hopping integral strength between similar species as compared to that between dissimilar ones and d-wave superconductivity is suppressed by off-diagonal randomness much like diagonal randomness. Combined diagonal and off-diagonal randomness leads to asymmetry in both the normal as well as the superconducting densities of states.