Ganesh N. Raikar

Spectroscopic characterization of passivated titanium in a physiologic solution

Titanium (Ti) has been used for many biomedical applications. Surface characteristics of titanium devices are critical to their success. In this study, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to analyse Ti surfaces prior to immersion in alpha-modification of Eagles medium (α-MEM). The ionic constituents deposited onto Ti surfaces after in vitro exposure to α-MEM were investigated using XPS and Fourier transform infrared spectroscopy (FTIR). Surface studies revealed an amorphous oxide layer on the Ti surface, with a chemistry similar to TiO2. However, after exposure to the physiologic solution for 12 days, dynamic changes in surface chemistry were observed. Ions such as phosphorus (P) and calcium (Ca) were increasingly deposited as amorphous fine crystalline calcium-phosphate (Ca−P) compounds, having a Ca/P ratio of 1.2 and a chemistry similar to brushite.

Electrochemical corrosion analyses and characterization of surface-modified titanium

Titanium (ASTM F76) samples received three different surface treatments after which the resulting oxides were characterized and the corrosion behavior was evaluated. No differences in the corrosion potential (Ecorr) were observed for the non-passivated and passivated Ti samples. However, the anodized Ti samples exhibited a significantly more noble Ecorr. At potentials higher than Ecorr, significant differences in current densities were observed for all three different Ti surfaces, with lower current densities observed for anodized Ti samples as compared to the non-passivated and passivated Ti samples. X-ray photoelectron spectroscopy indicated predominantly TiO2 on all Ti surfaces, with a higher concentration of carboxyl species for the anodized Ti surfaces as compared to the non-passivated Ti surfaces. Auger electron spectroscopy revealed a 10-fold thicker oxide layer for anodized Ti surfaces as compared to non-passivated and passivated Ti surfaces.

Surface characterization of titanium implants

The initial biocompatability of titanium (Ti) implants is associated with surface and not bulk properties; hence surface characterization of these implants is critical for their clinical success. A goal of this study was to characterize the Ti (ASTM F67) samples after conducting three different surface treatments. In this article, the results of x‐ray photoelectron spectroscopy, Auger electron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy performed on surface‐modified Ti samples, and also samples immersed in alpha‐modification of Eagle’s medium and in phosphate buffered saline solution after different surface treatments, are presented. Surface analysis prior to immersion revealed an amorphous oxide layer on all the samples similar in composition to TiO2. No significant difference in oxide thicknesses was observed. After exposure to the two media an amorphous or finely crystalline Ca–P layer was exhibited on all Ti surfaces, having a chemistry similar to brushite.The initial biocompatability of titanium (Ti) implants is associated with surface and not bulk properties; hence surface characterization of these implants is critical for their clinical success. A goal of this study was to characterize the Ti (ASTM F67) samples after conducting three different surface treatments. In this article, the results of x‐ray photoelectron spectroscopy, Auger electron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy performed on surface‐modified Ti samples, and also samples immersed in alpha‐modification of Eagle’s medium and in phosphate buffered saline solution after different surface treatments, are presented. Surface analysis prior to immersion revealed an amorphous oxide layer on all the samples similar in composition to TiO2. No significant difference in oxide thicknesses was observed. After exposure to the two media an amorphous or finely crystalline Ca–P layer was exhibited on all Ti surfaces, having a chemistry similar to brushite.

Surface characterization of ion-beam sputter-deposited Ca-P coatings after in vitro immersion

Abstract The surface properties of ion-beam sputter-deposited calcium phosphate (Ca-P) coatings on titanium (Ti) substrates were investigated using atomic force microscopy (AFM), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The Ca-P coatings showed columnar growth with AFM. Although FTIR analyses revealed structural changes as a result of the coating process, negligible changes in the structural integrity of the coatings were observed after immersion in an alpha-modification of Eagles Medium (α-MEM). This finding was confirmed by XPS and AES analyses, indicating constant binding and kinetic energies for P 2p and O 1s spectra, and O KLL and P LVV Auger lines, respectively, for all controls and samples immersed in α-MEM solutions. Although XPS analyses indicated no significant change in the P concentration, a reduction in the Ca concentration was observed, thereby resulting in a decrease in the Ca/P ratio from 2.3 to 1.5 after 12 days of immersion.

Hydroxyapatite Characterized by XPS

Hydroxyapatite [Ca10(PO4)6(OH)2] is commonly used as a coating material on orthopedic and dental implants. Hydroxyapatite is the major inorganic component of bone and is biocompatible with tissues when used on implants. Quality control tests are critical for the proper calcium to phosphorous ratio and also for checking for the presence of impurities. Being an important surface analytical tool used in the field of biomaterials, x-ray photoelectron spectroscopy was used to examine as-received hydroxyapatite pressed powders.

Oxidation of copper by fast atomic oxygen

The surface composition of the oxide formed on thin-film and solid OFHC copper samples exposed to a fast-atomic-oxygen environment in a low-earth orbit on NASAs Long Duration Exposure Facility (LDEF) was investigated using X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), thin-film X-ray diffraction (TF-XRD), high-resolution profilometry, and reflectance measurements. The results confirm that it is easier to form thick copper oxide layers in the atomic oxygen ambient than is normally possible with other laboratory-based techniques.

Auger line shape analysis of Zn3P2

The technique of Auger line shape analysis is applied to Zn3P2 single crystal. Zn3P2 is a semiconductor that has some potential as a material suitable for solar energy conversion. The measured line shapes are band-like and so are amenable to analysis and comparison with theory. The line shapes are recovered from the spectra by background subtraction followed by the Van Cittert deconvolution. This technique is first applied to the L3VV line of copper and the results checked against those already in the literature. The line shapes for Zn3P2 are compared with band structure calculations. In general, there is good agreement between the theory and our measured valence band structure.

Surface processing of semiconductor materials with fast atomic oxygen

In a series of space flight experiments and laboratory simulations of the hyperthermal oxygen atom environment of space, we have investigated several oxidation reactions occurring on materials of major significance to the semiconductor manufacturing industry. The materials on which we have reaction rate data and chemical composition measurements under various conditions include: Cu, Si, Ge, GaAs, GaP and SiC. In general, we observe accelerated growth of oxide films of thickness far greater than those obtainable at low temperatures (300 K to 600 K) with molecular oxygen or thermal atomic oxygen. Furthermore, the oxides are usually of good stoichiometry and involve the metals in their highest normal oxidation state. Some representative results we have obtained on the formation and characterization of these oxide films will be reviewed and references to more complete descriptions are cited.

CVV Auger line shapes in FeS2

Abstract We have measured the CVV Auger spectra of Fe and S from FeS 2 and compared them, after deconvoluting, with results from other techniques and with band structure calculations. These Auger spectra exhibit a number of interesting features, including a strong feature similar to that found in metallic Fe, previously assigned to an ‘autoionisation’ process. The effective hole-hole interaction energy ( U eff ) was calculated for each of the three Auger lines investigated. We found in each case that U eff was less than twice the width of the valence band, so that these spectra could be considered as ‘bandlike’ and compared with the theoretical calculations of the density of states. The corrected Fe Auger spectra were compared with calculations made by Bullet [ J Phys C15 , 6163 (1982)] and were found to be in broad agreement.

Determination of the Reactivity of Copper with Atomic Oxygen

In low Earth orbit (LEO), the composition of the atmosphere is dominated by atomic oxygen which is a major determinant of material degradation of external surfaces and a critical determining factor of spacecraft life. To simulate the effects of atomic oxygen in LEO, thin films of copper were exposed to a laboratory atomic oxygen beam. Copper films were characterized both before and after exposure by a variety of surface sensitive techniques including thin film x-ray diffraction, optical reflectance measurements, high resolution profilometry, and x-ray photoelectron spectroscopy. The results of these ground based experiments were compared to actual flight data acquired from the Space Shuttle based CONCAP-II experiment which exposed various materials in LEO on ambient and 320°C hot plates. The similarity of results generated from exposure of copper in an atomic oxygen beam to actual flight results prove that ground based atomic oxygen experiments can be good simulations of the LEO environment.