We report on Scanning Thermal Lithography (SThL), a recently introduced lithographic tool, for local thermochemistry on tert-butyl acrylate based polymer films featuring chemical cross links. The tailored polymer films afford platforms for controlled high molecular density coupling and surface immobilization of biologically relevant molecules, such as proteins. The thermally labile tert-butyl ester groups in tert-butyl acrylate based polymer films can be cleaved in air at temperatures above 150 °C to yield carboxylic acid functional groups for further (bio)- conjugation. The films were optimized to avoid plastic deformation at the elevated temperatures used during SThL. Exploiting these properties patterns with length scales as small as 35 ± 6 nm have been successfully thermally activated with SThL. Hence SThL comprises an attractive approach for the development of e.g. (bio)sensors and platforms for cell surface interaction studies with nanoscale patterns.

We study theoretical aspects of step fluctuations on vicinal surfaces by adding conservative white noise to the Burton-Cabrera-Frank model in one spatial dimension. We consider material deposition from above, as well as entropic and elastic-dipole step repulsions. Two approaches are discussed: (i) the linearization of stochastic equations when fluctuations are small, which captures correlations; and (ii) a mean field approach, which leaves out correlations but captures nonlinearities. Comparisons to kinetic Monte-Carlo simulations are presented.

Nano-scale superlattice (SL) based devices, such as quantum cascade lasers QCLs, have recently become very important due to their capability to identify toxic and explosive chemicals. In manufacturing these Mid-IR photonic devices, atomic-level scanning tunneling microscopes (STM) and transmission electron microscopes (TEM) have been used to characterize the growth quality of superlattice wafers. However, these methods yield observations that are localized and cannot view the entire structure and even now we have not been able to correlate these measured crystal lattice images with device performance. The x-ray scanning technique has greater likelihood of success given that it can observe not only the localized, but also the entire superlattice structure. By extracting special features and key parameters in x-ray diffraction (XRD) patterns, the epitaxial quality of QCL superlattices can be evaluated and correlated to the performance of fabricated QCL devices. We can then differentiate and classify different grades of wafers before starting device fabrication and testing.

Such an example of the usefulness of XRD can be found with strain-balanced superlattices, such as InGaAs/InAlAs, where there is notable decrease in laser performance after relaxation. It can also be found with type-II InAs/GaSb strained layer superlattice, which is currently the best candidate for room temperature mid-IR detectors and focal plane arrays. Experimentally measured x-ray patterns are compared to simulation results and problem sources are identified.

Neutron imaging as a method to perform in situ studies of hydrogen fuel cells, hydrogen storage devices, heat pipes, and batteries has made tremendous progress in recent years. Neutrons are useful to study light elements mixed with heavy Z elements where penetration by other forms of radiation is either impossible or incapable of contrasting the light elements. Useful spatial resolution available at neutron imaging facilities is now approaching 10 micrometers. Complimentary time resolution of 30 fps or greater is also possible with a spatial resolution approaching 300 micrometers. Here we will provide an overview of the technique of neutron imaging and experimental studies with neutrons at the National Institute of Standards and Technology. Examples of in situ studies of fuel cells, hydrogen storage devices, heat pipes and batteries will be discussed.

The spreading of a smectic nanodrop (8CB liquid crystal) on a solid surface was investigated by direct and real time imaging using the Surface Enhanced Ellipsometric Contrast (SEEC) microscopy [1-2]. The spreading ends with two molecular terraces (made of one monolayer and a bilayer). Two different behaviors were observed. In the first one the upper layer stays dense while shrinking. At the end of the process, the last molecules to disappear are located at the center of the initial disk. In the second one, nucleation and growth of holes is observed in the upper layer, in addition to shrinking. A model is proposed to describe the time evolution of the late stage structure. This model gives exact solutions of the kinetic equations, it covers strongly layered liquids such as smectic liquid crystals, it introduces the two dimensional Laplace pressure as an essential motor for spreading and it takes into account the liquid/gas transition in the surface layer that was consistently reported in experiments with 8CB. This model is in remarkable agreement with the experimental data and can explain the two observed behaviors [3].

The oxygen reduction reaction (ORR) mechanism of non-Pt catalysts was elucidated by investigating electronic structures of carbon alloy catalysts (CACs) for polymer electrolyte membrane fuel cells (PEMFC). For metal phthalocyanine-based carbon alloy catalysts with 1-2% of nitrogen and less than 0.1% of Co or Fe, photoelectron spectroscopy, X-ray absorption spectroscopy (XAS), and X-ray Absorption Fine Structure (XAFS) have revealed that Co or Fe metal sites are not the ORR active site, whereas the carbon atoms adjacent to graphitic nitrogens at a zigzag edge of graphite may act as the ORR active site, which is in good agreement with first principles calculations. These studies have also revealed that the zigzag edges, detected as a XAS shoulder component, are well evolved for catalysts pyrolyzed at 600°C, which show the maximum ORR activity. Based on these analyses, we have realized significantly improved carbon alloy based ORR performance, up to about 70 % of that with Pt catalysts. Further, to analyze the electronic structure of CACs during operation, we constructed a new in situ soft X-ray emission spectroscopy system with very high energy resolution (ΔE) of 120 meV at 640 eV at the University of Tokyo beamline BL07LSU in SPring-8.

Adsorption and desorption kinetics of thin film formation on metal surfaces has been directly monitored in real-time by optically measuring the deflection of activated atomic force microscope microcantilevers. Microcantilever deflection is caused by stress generated during the formation of an adsorbate layer on one side of the microcantilever. In this work, rapid adsorption of carboxylic acid in hydrocarbon solvent onto a gold surface was directly observed as a compressive stress developed on the microcantilever substrate. Upon exposure to alkylthiol, acid desorbed and was displaced by alkylthiol; this process was continuously monitored in real-time. Experiments suggest that some film organization and intermolecular interaction are required before substantial surface stress can be detected.

The results obtained by direct nano-patterning demonstrate the potential of the SPM-based techniques that include surface scratching to create 3D nanostructures. Such techniques became known as tribo-nanolithography and have prospects of being successfully implemented in the future nanofabrication industry. An important obstacle to this, however, is the effect of wear at the nanometer scale which is critical to the stability of tribo-nanolithoraphic processes. Such stability is achievable via in-depth theoretical and experimental studies of friction at the nanoscale along with the development of pioneering equipment. Our work presents the results of experimental fabrication of nanostructures formed by nanoscratching with the use of the multifunctional scanning tunneling microscopy previously developed by the authors. The authors attempted scratching the silicon surface by using a boron-doped diamond tip. This operation was undertaken in the same direction sequentially with the tip sliding a side of the groove by one of the tip’s facets and the consequent surface scanning. Although not being applicable to non-conductive surfaces, the proposed technique has significant advantages. One advantage is related to the high stiffness of the tunneling probe as compared to the stiffness of the AFM cantilever. High stiffness and perpendicularity of the tip to the surface during surface processing eliminates bending beam effects on the typical AFM and ensures machining effectiveness. Purposely synthesized boron-doped single-crystal diamonds were used as a tip material. The results of experimental fabrication of nanostructures formed by nanoscratching with the use of the multifunctional scanning probe are demonstrated and discussed.

An automated technique for the mapping of nanocrystal phases and orientations in a transmission electron microscope (TEM) is briefly described. It is primarily based on the projected reciprocal lattice geometry that is extracted automatically from precession electron diffraction (PED) enhanced spot patterns. The required hardware allows for a scanning-precession movement of the primary electron beam on the crystalline sample and can be interfaced to any newer or older mid-voltage TEM. Comprehensive open-access crystallographic databases that may be used in support of this technique are mentioned.

This study describes a low-energy atom scattering system that was combined with a time-of-flight spectrometer for insulator surface structural analysis. We show one example. MgO(001) crystal was used to study the surface analysis technique and is illustrated here. Insulator surface structure is difficult to study because of the charging effects during electron or ion-beam bombardment. Nevertheless, structural analysis of insulator surfaces is very important in fundamental research as well as in technology fields.

An organic molecular beam deposition system coupled to a soft x-ray excitation source has been developed to monitor the growth of organic semiconductor thin films in-situ and in real-time. Rapid collection of photoelectron spectra has been enabled using a multichannel array detector coupled to a hemispherical analyzer. The organic semiconductor tin phthalocyanine (SnPc) exhibits a Stranski-Krastanov growth mode on a polycrystalline gold substrate where the transition thickness between layered and clustered growth has been determined to be comparable to the thickness of a single molecular layer within which the molecules are standing on edge relative to the substrate plane.

A new technique in microscopy is demonstrated in which the domain of Atomic Force Microscopy (AFM) is extended to optical spectroscopy at the nanometer scale. Molecular resonance of feature sizes down to the single molecular level were detected and imaged purely by mechanical detection of the force gradient between the interaction of the optically driven object molecular dipole and its mirror image in a Platinum coated scanning probe tip. We provide full experimental details including a basic theory for this new technique. The microscopy and spectroscopy technique is extendable to frequencies ranging from radio to infrared and the ultra violet.

A wide information gap exists between our present atomic-scale knowledge of metal oxidation derived from conventional ultrahigh vacuum (UHV) surface science experiments and the oxidation mechanisms obtained from the growth of bulk oxide thin films under technologically relevant realistic (or near-) atmospheric conditions. To bridge this pressure gap, we present an in-situ transmission electron microscopy (TEM) study of the initial oxidation stage of Cu(100) and Cu-Au(100) surfaces where the oxygen partial pressure varies from 5x10-4 to 150 Torr. For Cu(100), with increasing oxygen partial pressure (pO2), the nucleation density of the oxide islands increases and so does the growth rate of the oxide islands. As the pO2 continues to increase, a transition from epitaxial cube-on-cube Cu2O islands to randomly oriented oxide islands is observed. A kinetic model based on the classic heterogeneous nucleation theory is developed to explain the effect of oxygen partial pressure on the oxide orientation. It is shown that such a transition in the oxide nucleation orientation is related to the effect of oxygen pressure on the nucleation barrier and atom collision rate. The Cu-Au(111) alloy revealed the same oxygen pressure dependency of the oxide nucleation orientation as pure Cu oxidation.

In the work presented here atomic force microscopy (AFM) based mechanical mapping techniques - HarmoniX imaging and Peak Force Tapping - were applied to determine the surface elastic modulus of phase separated polyurethanes and silica reinforced rubbers across the length scales. Segmented polyether polyurethanes (PUs) were prepared with varying stoichiometric ratio of the isocyanate and hydroxyl groups. The effect of molar mass, as well as the type and number of end-groups on their morphology was investigated. Smooth PU samples for AFM imaging were prepared by ultramicrotonomy. The micro phase separated morphology of the phase separated PUs showed characteristic “fingerprint” AFM phase images. Surface modulus values obtained by AFM were compared to bulk modulus values obtained by tensile testing. The moduli were mapped quantitatively with nanoscale resolution and were in excellent agreement for both AFM modes. Surface mean moduli values do not coincide with bulk values obtained via tensile testing which is attributed to fundamentally different averaging procedures and effects that lead to the respective modulus values obtained via surface and volume averaging. EPDM and SBR rubbers and rubber blends thereof were prepared with varying concentrations of silica nanoparticles and studied in order to investigate the effect of different composition on the resulting morphology (filler distribution) and elastic moduli on a specific rubber or rubber blend sample. Elastic moduli of the rubber and rubber blend samples were first measured by bulk tensile testing. The morphology of the rubber samples was visualized by height and phase imaging. Surface elastic moduli of silica reinforced rubbers and rubber blends were mapped quantitatively and compared with bulk tensile test results. AFM allowed the determination of modulus distributions at the sections imaged. As potential reasons for the observed differences between bulk and surface modulus different averaging procedures like surface and bulk averaging of AFM vs. tensile testing, different filler distributions in SBR and EPDM and the AFM modulus calibration procedures can be named.

The surface potential (SP) undulation on the surfaces of tris(8-hydroxyquinolinato) aluminum (III) (Alq3) films has been investigated with Kelvin probe force microscopy (KFM) and scanning near-field optical microscope (SNOM)-KFM. The SP undulation observed on the amorphous Alq3 films with thicknesses of up to 300 nm showed a cloud-like morphology of 200–300 nm in lateral size. The temporal change of SP undulation was traced through cyclic measurement with KFM observation with intermittent photoexposure, as well as in situ localized photoexcitation with SNOM-KFM. We concluded that the origin of the SP undulation is the nonuniform distribution of charged traps and drift mobility in the Alq3 films.

Electrical conduction in Fe, Pd, Nb, W and Mo cluster-assembled films was investigated in-situ, during their growth by supersonic cluster beam deposition. We observed for clusterassembled films resistivity values several orders of magnitude larger than corresponding bulk, as well as an increase of resistivity by increasing the film thickness, in contrast to the behaviour of atom-assembled metallic films. This suggests that nanoscale morphology arising by growth dynamics of cluster-assembled films, such as the minimal cluster-cluster interconnection and the evolution of surface roughness with thickness, may play a crucial role in the observed behaviour. Theoretical models based on non-isotropic 3D distributions of clusters into the film would help for a deeper understanding of the behaviour of cluster-assembled films compared to atomassembled ones. Benefits are expected in the technological field of devices performing electrical read-out on active nanostructured layers, as in the case of chemoresistive sensors.

We present a method for performing nanoscale wet chemistry on single carbon nanotubes as well as spectroscopic characterization of the functionalized molecules using a coupled atomic force microscope (AFM) and optical microscope. An AFM probe was functionalized with a single multiwalled carbon nanotube and then locally oxidized by dipping it into nitric acid (HNO3) in situ using AFM manipulation. Raman scattering was collected from the carbon nanotube functionalized probe before and after the oxidation reaction. An increase in the Raman D band was observed after the acid treatment, demonstrating that oxidation had occurred. This is the first step towards developing a real-time technique for dynamic studies of chemical reactions on single nanoparticles/molecules.

The actual transverse and longitudinal displacement of PZT thick film was measured using a newly developed atomic force microscopy (AFM). The AFM is attached a feedback circuit named “torsion feedback”. The torsion and Z-height feedback circuits control an AFM cantilever to follow piezoelectric deformation of the sample. To measure transverse displacement, the cantilever contacts the edge of sample. The transverse displacement is determined from the torsion feedback signal absolutely. To measure longitudinal displacement, the cantilever contacts the center of sample. The longitudinal displacement is determined from Z-height feedback signal absolutely. A 5-μm-thick PZT film was prepared on Pt/Ti/SiO2/Si substrates. The film sample was shaped square pillar. The side electrode length (L) of square pillar shaped sample was ranged from 1000 μm to 10 μm. The relation between side electrode length and the transverse or the longitudinal displacements were investigated. With decreasing L, the transverse displacement decreased nonlinearly, and the longitudinal displacement increased nonlinearly. The finite element method (FEM) simulation suggests that the substrate clamped PZT film behaved nonlinearly. The effective -d31 and d33 were calculated from the measured displacement, and these values increase with decreasing L. The effective d33 and -d31 showed correlation, and the ratio was d33 : -d31 = 5.3 : 1 , whereas the bulk ratiois d33 : -d31 = 2.4 : 1.This result suggests that the substrate clamping effect of the transverse displacement was larger than that of the longitudinal displacement.

For the first time, a new AFM mode is presented that simultaneously allows the measuring of adhesion and friction forces at different constant and continuous sliding velocities. Our methodology consists of implementing a circular relative displacement of the contact to reach a constant sliding velocity, with no stop periods. Some of the main advantages of performing a circular displacement is that continuous and high sliding velocities (more than 1 mm/s) can be reached compared to the low sliding velocities (up to 10 μm/s) available when using commercial AFM. Also, a stationary state is reached when doing measurements. Moreover, the circular mode can be coupled with the classical operating mode, for instance, force spectrum. Main applications of this circular mode are related to metrological measurements in physics that require high speed displacements. As an example, we report the evolution of friction and adhesive forces measured in air at different high sliding velocities.