Natalia Erina

Organogel Formation by a Cholesterol-Stoppered Bistable [2]Rotaxane and Its Dumbbell Precursor

The switching properties, gelation behavior, and self-organization of a cholesterol-stoppered bistable [2]rotaxane containing a cyclobis(paraquat-p-phenylene) ring and tetrathiafulvalene/1,5-dioxynaphthalene recognition units situated in the rod portion of the dumbbell component have been investigated by electrochemical, spectroscopic, and microscopic means. The cyclobis(paraquat-p-phenylene) ring in the [2]rotaxane can be switched between the tetrathiafulvalene and 1,5-dioxynaphthalene recognition units by addressing the redox properties of the tetrathiafulvalene unit. The organogels can be prepared by dissolving the [2]rotaxane and its dumbbell precursor in a CH2Cl2/MeOH (3:2) mixed solvent and liquified by adding the oxidant Fe(ClO4)3. Direct evidence for the self-organization was obtained from AFM investigations which have shown that both of the [2]rotaxane and its dumbbell precursor form linear superstructures which we propose are helical in nature.

Parametrization of atomic force microscopy tip shape models for quantitative nanomechanical measurements

The uncertainty of the shape of the tip is a significant source of error in atomic force microscopy (AFM) based quantitative nanomechanical measurements. Using transmission electron microscopy, scanning electron microscopy, or tip reconstruction images, it is possible to parametrize the models of real AFM tips, which can be used in quantitative nanomechanical measurements. These measurements use algorithms described in this article that extend classical elastic, plastic, and adhesive models of contact mechanics. Algorithms are applicable to the tips of arbitrary axisymmetric shapes. Several models of AFM tip have been utilized. The goal of tip model parameterization is to develop AFM tip-independent quantitative mechanical measurements at the nanometer scale. Experimental results demonstrate independence of the AFM measurements from tips and their closeness to bulk measurements where available. In this article the authors show the correspondence between microtensile, nanoindentation, and AFM based indenta...

Theoretical modelling and implementation of elastic modulus measurement at the nanoscale using atomic force microscope

Quantitative studies of mechanical behaviour and primarily elastic modulus are essential for material science at the nanometer scale. AFM nanoindentation is the most promising approach to address the problem. In our study we perform AFM-based nanoindentation (deflection-versus-distance curves) on a set of polymer materials with microscopic moduli ranging from 1 MPa to 10 GPa. The measurements were done with probes of different tip shapes and force levels from 100 nN to 3 μN. The tip geometry was evaluated from TEM and SEM micrographs and piecewise linearly interpolated for the use of analysis software; probe spring constant was determined from thermal tune data. The comparative analysis of nanoindentation data was carried out using models of Sneddon and Oliver-Pharr. We derived Sneddons integrals in closed form for any practical tip shape using a piecewise linear interpolation. Oliver-Pharrs method to account for plasticity for the unloading curve was adapted for Sneddons integrals. An interactive software implementation with both models was developed and applied.

Interplay between an experiment and theory in probing mechanical properties and phase imaging of heterogeneous polymer materials

The analysis of experimental amplitude and phase curves and phase images of polymer blends was performed in combination with KBM (Krylov-Bogoliubov- Mitropolsky) modelling of tapping mode atomic force microscopy (AFM). Different phase and dissipation contrast of images of multilayer polymer blends suggests that phase imaging is better for compositional mapping whereas understanding of the dissipative processes will facilitate a quantitative description of tip-sample force interactions in this mode. The KBM model describes tapping mode amplitude and phase curves in terms of three stationary solutions (two stable nodes, one saddle) verified by the experiment. A simple model of energy dissipation (adhesion avalanche) was also considered.

Interplay between H-bonding and alkyl-chain ordering in self-assembly of monodendritic L-alanine derivatives.

This paper reports on the synthesis and self-organizing properties of monodendrons consisting of L-alanine at the focal point and alkyl chains with different length at the periphery. The structures of thin films and monolayers are studied by temperature-resolved grazing-incidence X-ray diffraction and scanning force microscopy. The interplay between H-bonding and ordering of the alkyl chains results in a rich temperature-dependent phase behavior. The monodendrons form H-bonded stabilized clusters with the number of molecules depending on the length of the aliphatic chains and temperature. The clusters play the role of constitutive units in the subsequent self-assembly. Short alkyl chains allow the material to form thermodynamically stable crystalline phases. The molecules with longer side groups exhibit additional transitions from the crystalline phase to thermotropic columnar hexagonal or columnar rectangular liquid-crystalline phases. In monolayers deposited on highly ordered pyrolytic graphite, the materials show ordering similar to thin films. However, for the compound bearing hexadecyl chains the affinity of the alkyl groups to graphite dominates the self-assembly and thereby allows epitaxial growth of a 2D lattice with flat-on oriented molecules.

High-speed atomic force microscopy and peak force tapping control

ITRS Roadmap requires defect size measurement below 10 nanometers and challenging classifications for both blank and patterned wafers and masks. Atomic force microscope (AFM) is capable of providing metrology measurement in 3D at sub-nanometer accuracy but has long suffered from drawbacks in throughput and limitation of slow topography imaging without chemical information. This presentation focus on two disruptive technology developments, namely high speed AFM and quantitative nanomechanical mapping, which enables high throughput measurement with capability of identifying components through concurrent physical property imaging. The high speed AFM technology has allowed the imaging speed increase by 10-100 times without loss of the data quality. Such improvement enables the speed of defect review on a wafer to increase from a few defects per hour to nearly 100 defects an hour, approaching the requirements of ITRS Roadmap. Another technology development, Peak Force Tapping, substantially simplified the close loop system response, leading to self-optimization of most challenging samples groups to generate expert quality data. More importantly, AFM also simultaneously provides a series of mechanical property maps with a nanometer spatial resolution during defect review. These nanomechanical maps (including elastic modulus, hardness, and surface adhesion) provide complementary information for elemental analysis, differentiate defect materials by their physical properties, and assist defect classification beyond topographic measurements. This paper will explain the key enabling technologies, namely high speed tip-scanning AFM using innovative flexure design and control algorithm. Another critical element is AFM control using Peak Force Tapping, in which the instantaneous tip-sample interaction force is measured and used to derive a full suite of physical properties at each imaging pixel. We will provide examples of defect review data on different wafers and media disks. The similar AFM-based defect review capacity was also applied to EUV masks.