[en] X-ray scattering has long been used to investigate the atomic structure of materials. Two relatively recent developments, however, have strongly influenced modern applications of this technique. The first is the advent of the modern microelectronics age in which materials in thin film geometries are of critical importance. The second is the development of synchrotron radiation-an extremely bright source of tunable wavelength x-rays which has dramatically broadened the scope of possible investigations. The natural coupling between these developments is reflected in this thesis, in which synchrotron radiation is used to study the structure of thin films and interfaces. This thesis is divided into two parts. Part I describes novel in situ investigations, in which the film is examined in its growth environment. Part II describes more conventional ex situ studies carried out on multilayer films or open-quotes superlatticesclose quotes. The in situ work involved extensive technical development, and a description of the physical principles, design challenges, and resulting experimental apparatus is presented. In situ investigations using this apparatus involved the study of strain relaxation in the epitaxial Cu(001)/Fe(001) system. Through observations made in this work, a modified theory of strain relaxation in ultra-thin films is developed. The ex situ studies concern the influence of interface roughness on antiferromagnetic coupling in Fe/Cr superlattices. The magneto-optic techniques used in measuring this coupling are described, and results from exchanged coupled multilayers are presented. This is followed by a theoretical investigation of the physics of x-ray scattering from juxtaposed rough interfaces. Experimental x-ray techniques used to study interfacial roughness are described, and the results of a study of interfacial roughness in Fe/Cr superlattices are presented

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[en] While electron-based structural probes have been extensively applied to low-pressure film growth techniques such as evaporation, similar studies on sputter deposition have been hindered by the relatively high gas pressure (1--10 mT) inherent to the technique. Because x rays scatter more weakly than electrons the absorption in the ambient is not significant and diffraction from the growing film can be observed if a sufficiently bright source of x rays is used. We have developed a chamber which combines features of an ultrahigh-vacuum sputter-deposition system with the goniometric adjustments and the x-ray windows of a scattering chamber. A description of its design and recent results are presented

[en] We have observed a rapid amorphization reaction at ambient temperature in the Gd/Co system by employing grazing incidence x-ray scattering. We find that a 135 A crystalline Gd film is amporhized in less than 30 min by deposition of Co. We postulate that the rapidity of the reaction is due to surface diffusion of Co atoms after deposition to fast diffusion sites such as grain boundaries in the Gd film. Once the interfacial region has been amorphized these fast diffusion paths are sealed off from the surface, rapid diffusion of Co into the Gd crystalline layer is prevented, and the amorphization reaction stops

[en] Using surface x-ray scattering, we have studied a (3x1) Si(111) reconstruction induced by chemisorption of CaF₂. This reconstruction consists of a parallel array of zigzag Si adatom chains oriented along left-angle 1 bar 10 right-angle. The orbitals on the Si chain atoms rehybridize into p_x and p_y along the surface to form σ bonds, and parallel sp_z orbitals perpendicular to the surface to give additional π bonding. This basic structure, with no dangling bonds at only 1/3 monolayer adsorbate coverage, may explain the occurrence of (3x1) reconstructions among a diverse range of Si-adsorbate systems

[en] Conversion electron Moessbauer spectroscopy (CEMS) and X-ray diffraction (XRD) have been used to investigate the structure of Pt/Fe and Cr/Fe multilayers deposited by magnetron sputtering. The Cr/Fe samples consisted of four samples prepared under Ar sputtering pressures of 1.3, 3.0, 5.0, and 10.0 mT, all with the same multilayer structure of 3.5 nm Cr/2.5 nm Fe, repeated 35 times onto c-Si wafer substrates. The quality of the interfaces between Cr and Fe is clearly degraded with increasing sputter pressure, as seen by changes in the relative intensities of four magnetic subspectra in the CEMS and the gradual appearance of a single-line resonance similar to Fe in solution in Cr. The low-angle XRD superlattice peaks also disappear with increasing sputter pressure, while the high-angle XRD shows a tendency for loss of the preferred (110) texture. Two films of Pt/Fe were deposited epitaxially onto MgO single crystals with bilayer periods of 1.3 nm and 2.6 nm and total thickness of 300 nm each. A transition from fcc-PtFe with near-perpendicular magnetic anisotropy to a bcc-Fe/fcc-PtFe mixture with in-plane magnetic texture is observed by CEMS for the factor of two increase in bilayer period. (orig.)