Z. U. Rek

X-ray depth profiling of iron oxide thin films

A nominally γ-Fe 2 O 3 thin film (oxidized from an Fe 3 O 4 film) has been structurally depth profiled using x-ray scattering in a grazing incidence, asymmetric Bragg geometry. By varying the grazing incidence angle, the x-ray penetration depth is varied from tens of Angstroms to several thousand Angstroms, slightly larger than the film thickness. At small incidence angles a diffraction pattern characteristic of α-Fe 2 O 3 is observed, while at larger angles the pattern is predominantly from γ-Fe 2 O 3 , showing that there is a surface layer of α-Fe 2 O 3 . These results are quantified and the thickness of the α phase found to be 90 A. The presence of the α phase explains a nonferromagnetic layer observed previously. These data together with magnetic and chemical data suggest that the nonferromagnetic layer forms during oxidation of the Fe 3 O 4 film due to outward diffusion of Fe ions and their subsequent oxidation to form α-Fe 2 O 3

STRAIN GRADIENTS AND NORMAL STRESSES IN TEXTURED MO THIN FILMS

The high-resolution x-ray-diffraction technique was used to explore strain variations in sputtered Mo films with thicknesses of 170, 260, and 800 nm that possess a (110) out-of-plane texture. The strains in crystallographic planes perpendicular to the surface of each film were found to be nominally constant and compressive at all x-ray penetration depths. Near the surface of each film, the inclined-plane strains were compressive, and then relaxed as the penetration depths approached each entire film thickness. The strain tensor in a laboratory reference frame for each film, as a function of penetration depth, revealed that the normal strain ezz was tensile near the surface of each film, and then relaxed to a nominally constant value as the penetration depths approached the entire film thickness. The penetration depth over which the normal strain decayed to a nominally constant value increased as the total film thickness increased. A consequence of the large normal strains near the free surface of each fil...

Effects of high carbon concentration upon oxygen precipitation and related phenomena in CzSi

Effects of high carbon concentration upon oxygen precipitation and related phenomena in Czochralski (Cz) silicon have been investigated by combining various furnace and rapid thermal anneals. Our data show that oxide precipitate (OP) density, estimated from changes in interstitial oxygen concentration (ΔOi), increases with increasing substitutional carbon concentration, Cs, while thermal donor (TD) formation is inhibited at high Cs. Even though ΔOi increases monotonically with Cs, synchrotron radiation section topographs of processed high carbon content wafers (Cs∼4 ppma) exhibit Pendellosung fringes, indicating a strain‐free bulk state. Our transmission electron microscope and optical microscopic data also show very few resolvable structural defects associated with precipitates inside the bulk Si. Using a thermodynamic and kinetic model, we attempt to explain: (1) reduced thermal donor formation, (2) lack of bulk stress notwithstanding high ΔOi, and (3) predominantly polyhedral precipitate morphologies i...

Analysis of cobalt-doped iron oxide thin films by synchrotron radiation☆

Abstract Surface and bulk structures of as-deposited Fe 3 O 4 and post-oxidized γ-Fe 2 O 3 thin films were successfully identified by synchrotron diffraction analysis. A new synchrotron diffraction method which combines the Seemann-Bohlin and the grazing incidence techniques was used to record polycrystalline diffraction patterns for structure depth profiling analysis. The post-oxidized film was found to have an α-Fe 2 O 3 layer at the surface and γ-Fe 2 O 3 in the bulk of the film. The formation of a thermodynamically stable antiferromagnetic α-Fe 2 O 3 surface caused the magnetically dead layer previously detected by neutron reflection analysis. Synchrotron diffraction results also showed that the structure of the as-deposited film remains constant throughout the thickness of the film. The presence of a superlattice (300) peak indicates the film has been oxidized beyond Fe 3 O 4 .

Characterization of Si‐TaSi2 in situ composites by synchrotron white beam topography and by double axis diffractometry

In situ Si‐TaSi2 composites are studied by synchrotron white beam topography and by double axis diffractometry. These results show that the single crystal Si matrix is of excellent quality: Rocking curve widths are between 40 and 60 s of arc, and the topographs do not exhibit asterism. Diffuse radial streaks in the Laue patterns originate from diffraction by the TaSi2 rods in the matrix: The K‐absorption edge of filters placed in the incident x‐ray beam produces a sharp change in contrast in the streaks, and this is used to determine the d spacings present in the streaks and to show that considerable preferred orientation exists between the TaSi2 rods and the Si matrix.

High pressure structural phase transition in AgGaTe2

From in situ diffraction measurements of synchrotron produced x radiation, we have found that AgGaTe2 transforms from the tetragonal, chalcopyrite structure to a face‐centered cubic structure at 4.0±0.5 GPa. The resistivity shows a minimum near this pressure, but the material retains its semiconducting nature.

Characterization of TaSi2–Si composites for use as wide‐bandpass optical elements for synchrotron radiation

The wide rocking curves of matrix reflections of the in situ eutectic composite TaSi2–Si make wafers of this material attractive for use as wide‐bandpass monochromators for synchrotron radiation, and characterization of wafers of TaSi2–Si for use with energies normally accessible at storage rings (i.e., 5–40 keV) is the focus of the present report. A wafer with [111]Si orientation and a wafer with [110]Si orientation are studied. The high degree of preferred orientation of the TaSi2 rods relative to the Si matrix is examined using synchrotron Laue patterns, and the 100TaSi2, 003TaSi2, 101TaSi2, and 102TaSi2 reflections are used to establish the orientation relationship and to determine that the spread of rod orientations is at least 5° and probably no greater than 6°. Double‐axis diffractometry with Cu Kα radiation reveals matrix reflections with rocking curve widths that are about 20 times broader than those from perfect Si and with peak reflectivities approaching 20%. The rocking curves widths are found...

The evolution of texture in thin films and multilayers via synchrotron transmission Laue and grazing-incidence X-ray scattering

Sputter-deposited films and multilayers are used for a wide variety of applications including protective coatings on turbine engine blades, magnetic recording heads, optical elements, electronic packaging, X-ray filters and monochromator components to name a few examples. This wide range of interest requires growth thicknesses from a few nanometres to tens of micrometres depending on the product. In many applications, specific film textures in the growth direction as well as in the plane of growth are required. The control and manipulation of these textures can be accomplished by using advanced characterization techniques to select particular processing conditions. A variety of X-ray methods including grazing-incidence X-ray scattering, conventional pole figure studies and synchrotron white-beam transmission Laue scattering were used to study texture evolution for the thinnest films up to the thickest multilayer coatings.

Structure determination of B{sub 4}C and SiC thin films via synchrotron high-resolution diffraction

Thin films of B{sub 4}C and SiC deposited by magnetron sputtering as components of multilayers have the potential to provide significant property improvements over current wear resistant coating technology. B{sub 4}C and SiC have previously been found to be amorphous and possibly nanocrystalline under the deposition conditions used. This study reports results of synchrotron x-ray scattering experiments providing information on the degree of crystallinity, /strain, average density, and coordination number in 2000 {angstrom} films of these compounds on Si substrates. Radial distribution functions from B{sub 4}C and SiC thin films were obtained and used to model the structure. Strain results are compared with Double Crystal x-ray Diffraction Topography (DCDT) results as a means for establishing a standard strain state.

Evolution of in-plane texture in reactively sputtered CrN films

The microstructure and texture of chromium nitride films reactively sputtered on silicon substrates were investigated using x-ray scattering, pole figures, transmission electron microscopy, and atomic force microscopy. Under the given deposition geometry, the CrN films were shown to develop a in-plane texture. The three preferred crystallographic orientations of the CrN films approximately coincided with the characteristic directions associated with the deposition geometry. There appear to be two regimes that govern the microstructural evolution and texture development for reactively sputtered chromium films. The first one involves the deposition conditions that lead to the formation of a single, stable phase such as stoichiometric CrN (above certain level of nitrogen partial pressure). In this regime, the film growth appears to be controlled by local epitaxy in individual columns, competitive grain growth, and kinetic roughening. The film characteristics resulted from this regime include the development ...