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The effects of discharge radio frequency (RF) power and film thickness were studied on the characteristics of Ca5(P04)30 H (hydroxyapatite) thin films fabricated by RF magnetron sputtering. The structure and chemical compo sition were investigated with a-step (thickness), scanning electron microscopy (SEM), X-ray diffraction (XRD), Ruth erford backscattering spectrometry (RBS), and infrared ab sorption spectrometry (FTIR). The films were analyzed assputtered and after annealing at 550°C under argon flow. SEM showed that the film surfaces had no cracks or other defects. X-ray diffraction showed that the deposited films were amorphous with low-discharge RF power, and crystalline with high-discharge RF power. After annealing, all the films had the same crystalline structure as apatite. However, the RBS measurements revealed that all films had a higher calcium-phosphate ratio than standard syn thetic hydroxyapatite. Furthermore, statistical testing of the RBS data revealed the existence of only a weak correlation between the Ca/P ratio and the discharge power level* Al though all sputtered films showed phosphate bonds in the infrared spectrum, only after annealing did the O H bonds of hydroxyapatite become visible.

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The ~teractions of 02 and N20 in the low pressure range with a Cu(ll1) surface and of CO with adsorbed oxygen have been studied with ellipsometry, Auger electron spectroscopy and LEED. The adsorption of 02 was investigated in the 10-6-104Torr range and at crystal temperatures ranging from 23 to 4OO'C. 02 chemisorbs dissociatively with an initial reaction probability of about 10m3 and an apparent activation energy of 2-4 kcal/mol, which depends on the substrate temperature, up to a saturation coverage of 0.45. The probability of decomposition of N20 is 10ms at 300°C, and the activation energy is 10.4 kcal/mol For 250 < T< 4OO'C. The oxygen coverage saturates at B = 0.45 as well. For both oxidation reactions the kinetics can be described with a precursor state model. With LEED no superstructures were observed. The probability of the reaction of CO with adsorbed oxygen is 4 X lo-' at 250°C and is initially independent of the oxygen coverage. The reaction is assumed to proceed via a Langmuir-Hinshelwood mechanism. The activation energy for the reaction COad + oad -+ CO* is 18-20 kcal/mol.

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Irradiation with swift heavy ions of spherical Au nanoparticles confined within a silica matrix shapes them into prolate nanorods and nanowires whose principal axes are aligned along the beam direction. In the present paper, we investigate the role that is played by the initial nanoparticle size and concentration in this so-called ion-shaping mechanism. We have produced silica films wherein Au nanoparticles with average diameters of 15, 30, and 45 nm were embedded within a single plane and have irradiated these films at 300 K at normal incidence with 18, 25, and 54 MeV Ag ions. We demonstrate the existence of both threshold and saturation fluences for the elongation effects mentioned. The values of these critical fluences depend both on the ion energy and the initial nanoparticle size. Moreover, we show that 45 nm Au particles are not deformed when irradiated with 18 MeV Ag ions, such that this value corresponds to an energy threshold for the deformation process. As far as the influence of the nanoparticle concentration on the shaping characteristics is concerned, we have found that above the critical irradiation fluence, the deformation effect becomes very sensitive to the initial concentration of the nanoparticles.

The authors have studied deposition of plasma silicon nitride layers as a function of gas-phase composition for the SiH4-NH3-x system, where x is N~, Ar, or H2. Most of the depositions were performed at 300~ and at an operating frequency of 50 kHz. The deposited layers were characterized with Anger electron spectroscopy in combination with ion-bombardment, Rutherford backscattering, and infrared spectroscopy. It is shown that the ratio of the amount of atomic hydrogen atoms bonded to silicon and nitrogen atoms is only a function of the silicon-nitrogen ratio of the deposited layers. It is further shown that the etch rate of plasma silicon nitride layers in buffered HF depends primarily on the silicon-nitrogen ratio and the density of the deposited material.