Contact atomic force microscopy

Abstract Aqueous biocompatible tribosystems are desirable for a variety of tissue-contacting medical devices. L-3,4-dihydroxyphenylalanine (DOPA) and lysine (K) peptide mimics of mussel adhesive proteins strongly interact with surfaces and may be useful for surface attachment of lubricating polymers in tribosystems. Here, we describe a significant improvement in lubrication properties of poly (dimethylsiloxane) (PDMS) surfaces when modified with PEG-DOPA-K. Surfaces were characterized by optical and atomic force microscopy, contact angle, PM-IRRAS, and X-ray photoelectron spectroscopy. Sudi surfaces, tested over the course of 200 rotations ( 8 m in length), maintained an extremely low friction coefficient (p) (0.03 0.00) compared to bare PDMS (0.98 0.02). These results indicate... 

SAMs of allgrlphosphonic acids (butylphosphonic acid, octylphosphonic acid, undecylphosphonic acid and octadecylphosphonic acid) on native niekel oxide allow substrates to be functionalized easily. Monolayer formation has been investigated by diffuse reflectance Fourier transform infrared spectroscopy, non-contact mode atomic force microscopy, contact angle measurements and matrix-assisted laser desorption ionization mass spectrometry. Cyclic voltammetry and electrochemical impedance spectroscopy studies showed that the monolayer increased surface resistance to oxidation. 

Raza H, Pang C L, Haycock S A and Thornton G 1999 Non-contact atomic force microscopy imaging of 7102(100) surfaces Appl. Surf. Sc/. 140 271... 

Carpick, R.W., The study of contact, adhesion, and friction at the atomic scale by atomic force microscopy. University of Califomia-Berkeley, Berkeley, CA, 1997. 

Non-contact atomic force microscopy (NC-AFM) Magnetic force microscopy (MFM)... 

Nevertheless, it is possible to obtain truly atom-by-atom measurements from suitable surfaces. Iwasawa and coworkers reported atom-resolved images of the TiO2(110) surface by non-contact atomic force microscopy, revealing the correct... 

Contact dermatitis, from nickel, 17 119 Contact dryers, coatings, 7 29 Contact drying, 9 105-107 Contact icing, of food, 21 561 Contacting, differential, 10 760-762 Contact mechanics, 1 515-517 Contact mode atomic force microscopy, 3 320-325 17 63 Contact nucleation, 8 105 Contactors ozone, 17 801-802 selection of, 10 767-768... 

The technique of atomic force microscopy (AFM) has permitted the direct observation of single polysilane molecules. Poly[//-decyl-(high molecular weight (4/w = 5,330,000 and Mn = 4,110,000), PSS, helicity, and rigid rod-like structure due to the aliphatic chiral side chains, was deposited from a very dilute (10-10 Si-unit) dm-3] toluene solution onto a (hydrophobic) atomically flat (atomic layer steps only present) sapphire (1012) surface. After drying the surface for a few minutes in a vacuum, AFM images were taken at room temperature in air in the non-contact mode.204,253 An example is shown in Figure 22, in which the polymer chain is evident as a yellow trace. 

We reported the synthesis of Si/Si02//PS-h-poly(acrylate) tethered diblock copolymer brushes [31,32,46,47]. The properties of these diblock brushes were studied using water contact angles, ellipsometry. X-ray photoelectron spectroscopy (XPS), FTIR spectroscopy and atomic force microscopy (AFM). For a sample with a 26 nm PS layer and a 9 nm PMMA layer, the advanc-... 

A number of methods are available for the characterization and examination of SAMs as well as for the observation of the reactions with the immobilized biomolecules. Only some of these methods are mentioned briefly here. These include surface plasmon resonance (SPR) [46], quartz crystal microbalance (QCM) [47,48], ellipsometry [12,49], contact angle measurement [50], infrared spectroscopy (FT-IR) [51,52], Raman spectroscopy [53], scanning tunneling microscopy (STM) [54], atomic force microscopy (AFM) [55,56], sum frequency spectroscopy. X-ray photoelectron spectroscopy (XPS) [57, 58], surface acoustic wave and acoustic plate mode devices, confocal imaging and optical microscopy, low-angle X-ray reflectometry, electrochemical methods [59] and Raster electron microscopy [60]. 

The dominant role of asperity contact is also apparent from analysis of the texture of polished surfaces. Figure 9 illustrates a typical post CMP surface as examined via atomic force microscopy (AFM). Surface texture is composed of innumerable randomly oriented nanogrooves of a width and depth consistent with traveling Hertzian loaded contact [12] particle bombardment during turbulent liquid flow produces profoundly different texture. All classes of semiconductor materials examined show similar textures, indicating the general nature of the process. From the data to date, it appears that asperity contact is the dominant wear mechanism in CMP. 

Fig. 3 Pentacene grown by supersonic molecular beam deposition to form near monolayer p-type FETs with thiolate monolayer modified Au source and drain contacts (a) visualized by atomic force microscopy and with well-behaved (b) /d-Eds and (c) -Eg characteristics...

The force microscope, in general, has several modes of operation. In the repulsive-force or contact mode, the force is of the order of 1-10 eV/A, or 10 -10 newton, and individual atoms can be imaged. In the attractive-force or noncontact mode, the van der Waals force, the exchange force, the electrostatic force, or magnetic force is detected. The latter does not provide atomic resolution, but important information about the surface is obtained. Those modes comprise different fields in force microscopy, such as electric force microscopy and magnetic force microscopy (Sarid, 1991). Owing to the limited space, we will concentrate on atomic force microscopy, which is STM s next of kin. 

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