The shape and alignment of silver nanoparticles embedded in a glass matrix is controlled using silicon ion irradiation. Symmetric silver nanoparticles are transformed into anisotropic particles whose larger axis is along the ion beam. Upon irradiation, the surface plasmon resonance of symmetric particles splits into two resonances whose separation depends on the fluence of the ion irradiation. Simulations of the optical absorbance show that the anisotropy is caused by the deformation and alignment of the nanoparticles, and that both properties are controlled with the irradiation fluence. *

In this work we have studied the elongation of silver nanoparticles irradiated with 40 MeV Bromine ions by means of in situ optical measurements, transmission electron microscopy and molecular dynamics simulations. The localized surface plasmon resonance of silver nanoparticles has a strong dependence on the particle shape and size, which allowed us to obtain the geometrical parameters with remarkable accuracy by means of a fit of the optical spectra. Optical results have been compared with transmission electron microscopy images and molecular dynamics simulations and the agreement is excellent in both cases. An important advantage of in situ measurements is that they yield an extremely detailed information of the full elongation kinetics. Final nanoparticle elongation depends on a complex competition between single-ion deformation, Ostwald ripening and dissolution. Building and validating theoretical models with the data reported in this work should be easier than with the information previously available, due to the unprecedented level of kinetic details obtained from the in situ measurements.

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High-energy metallic ions were implanted in silica matrices, obtaining spherical-like metallic nanoparticles (NPs) after a proper thermal treatment. These NPs were then deformed by irradiation with Si ions, obtaining an anisotropic metallic nanocomposite. An average large birefringence of 0.06 was measured for these materials in the 300-800 nm region. Besides, their third order nonlinear optical response was measured using self-diffraction and P-scan techniques at 532 nm with 26 ps pulses. By adjusting the incident light's polarization and the angular position of the nanocomposite, the measurements could be directly related to, at least, two of the three linear independent components of its third order susceptibility tensor, finding a large, but anisotropic, response of around 10(-7) esu with respect to other isotropic metallic systems. For the nonlinear optical absorption, we were able to shift from saturable to reverse saturable absorption depending on probing the Au NP's major or minor axes, respectively. This fact could be related to local field calculations and NP's electronic properties. For the nonlinear optical refraction, we passed from self-focusing to self-defocusing, when changing from Ag to Au.

A large optical birefringence of oriented Ag nanoellipsoids embedded in silica was measured using an ellipsometric technique. The two main surface plasmon resonances associated with the axes of the ellipsoid were tuned, allowing us to quantify the light transmission through the samples when placed and rotated between crossed and parallel polarizers. This birefringence can be physically associated with the selective optical absorption of one component of the linear polarization of the incident light with respect to the anisotropic axis of the sample, depending on the wavelength used to perform the measurement.

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Plasma polymerization and deposition of linear, cyclic and aromatic fluorocarbons on (100)-oriented single crystal silicon substrates Interfacial force microscopy ͑IFM͒ is used to measure the electrical contact properties of electroplated gold thin films of the type used in microelectromechanical system relays. Force and current levels consistent with those present in metal-metal contact switches are examined in an atmospheric-pressure, dry-nitrogen ambient at room temperature, and the nature of a nonmetallic contamination layer which limits contact resistance and lifetime is explicitly examined mechanically, electrically and chemically. The electrical and mechanical properties of the contamination layer on the gold substrate are observed by IFM both before and after being exposed to ozone for an extended period of time. The contamination film is characterized by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, and found to consist mostly of hydrocarbons; the film remains relatively stable in both composition and thickness following ozonation. However, some subtle chemical changes in the contamination layer induced by the ozonation process are found to profoundly affect the electrical properties of the gold-gold contact, reducing the resistance by more than 3 orders of magnitude and considerably reducing variability in the contact resistance between contact events. These results clearly demonstrate the critical role both positive and negative of the latent contamination present on the contact surfaces.