Surface X-ray Diffraction Methods Research Articles

Structure of quasi-free-standing graphene on the SiC (0001) surface prepared by the rapid cooling method

A systematic structural study of epitaxial graphene samples on the SiC (0001) surface has been performed by the surface x-ray diffraction method, which is a non-contact technique. For samples with only a buffer layer, one layer graphene, and multilayer graphene, the distances between the buffer layer and the surface Si atoms were found to be 2.3 Å. This value is the same as reported values. For quasi-free-standing graphene samples prepared by the rapid cooling method [Bao et al., Phys. Rev. Lett. 117, 205501 (2016)], there was no buffer layer and the distance between the quasi-free-standing graphene and the surface Si atoms was 3.5 Å, which is significantly shorter than the value in hydrogen-intercalated graphene and slightly longer than the interplane distance in graphite. The Si occupancy deviated from unity within 1 nm of the SiC surface. The depth profile of the Si occupancy showed little sample dependence, and it was reproduced by a simple atomistic model based on random hopping of Si atoms.

Evaluation of surface decarburization depth by magnetic Barkhausen noise technique

Industrially unfavorable process of steel surface decarburization was induced by annealing in air. Two methods of after-anneal surface treatment were used: an acid pickling and a sand blasting. The obtained decarburized layers were examined by optical microscope, wave dispersive spectrometer, and surface X-ray diffraction method. Magnetic Barkhausen noise technique was tested for applicability of non-destructive characterization of the decarburized layer depth. A newly introduced parameter, Barkhausen noise coercivity, was proposed for practical use due to its sensitivity to decarburization and stability to measurement conditions. Other magnetic parameters, e.g. number of Barkhausen noise counts, were found to be sensitive to the compressive residual stress caused by the sand blasting.

The structure of the V 2O 3(0 0 0 1) surface: A scanned-energy mode photoelectron diffraction study

Scanned-energy mode photoelectron diffraction (PhD), using the O 1s and V 2p photoemission signals, together with multiple-scattering simulations, have been used to investigate the structure of the V 2O 3(0 0 0 1) surface. The results support a strongly-relaxed half-metal termination of the bulk, similar to that found in earlier studies of Al 2O 3(0 0 0 1) and Cr 2O 3(0 0 0 1) surfaces based on low energy electron and surface X-ray diffraction methods. However, the PhD investigation fails to provide definitive evidence for the presence or absence of surface vanadyl (V O) species associated with atop O atoms on the surface layer of V atoms. Specifically, the best-fit structure does not include these vanadyl species, although an alternative model with similar relaxations but including vanadyl O atoms yields a reliability-factor within the variance of that of the best-fit structure.

Temperature dependence of the structure of Langmuir films of normal-alkanes on liquid mercury.

The temperature dependent phase behavior of Langmuir films of n-alkanes [CH3(CH2)(n-2)CH3, denote Cn] on mercury was studied for chain lengths 19< or =n< or =22 and temperatures 15< or =T< or =44 degrees C, using surface tensiometry and surface x-ray diffraction methods. In contrast with Langmuir films on water, where molecules invariably orient roughly surface normal, alkanes on mercury are always oriented surface parallel and show no long-range in-plane order at any surface pressure. A gas and several condensed phases of single, double, and triple layers of lying-down molecules are found, depending on n and T. At high coverages, the alkanes studied here show transitions from a triple to a double to a single layer with increasing temperature. The transition temperature from a double to a single layer is found to be approximately 5 degrees C, lower than the bulk rotator-to-liquid melting temperature, while the transition from a triple to a double layer is about as much below the double-to-single layer transition. Both monolayer and bulk transition temperatures show a linear increase with n with identical slopes of approximately 4.5 degrees C/CH2 within the range of n values addressed here. It is suggested that the film and bulk transitions are both driven by a common cause: the proliferation of gauche defects in the chain with increasing temperature.

Study on pyrite FeS 2 films deposited on Si(1 0 0) substrate by synchrotron radiation surface X-ray diffraction method

Synchrotron radiation with surface X-ray diffraction is conducted to study pyrite FeS 2 films on Si (1 0 0) wafers. The results show that the “strong (2 0 0) reflection” for the FeS 2/Si(1 0 0) sample primarily comes from the stress peak of the silicon substrate, other than the effect of the preferred orientation of pyrite crystal grains which has been assumed previously. On the contrary, the FeS 2/Si(1 0 0) sample actually indicates a strong preferred growth along (3 1 1) orientation, and this preferential growth of pyrite films becomes intenser with the prolonged annealing time.

Langmuir films of normal-alkanes on the surface of liquid mercury

The coverage dependent phase behavior of molecular films of n-alkanes (CH3CHn−2CH3, denote Cn) on mercury was studied for lengths 10⩽n⩽50, using surface tensiometry and surface x-ray diffraction methods. In contrast with Langmuir films on water, where roughly surface-normal molecular orientation is invariably found, alkanes on mercury are always oriented surface-parallel, and show no long-range in-plane order at any surface pressure. At a low coverage a two-dimensional gas phase is found, followed, upon increasing the coverage, by a single condensed layer (n⩽18), a sequence of single and double layers (19⩽n⩽20; n⩾26), or a sequence of single, double, and triple layers (22⩽n⩽24). The thermodynamical and structural properties of these layers, as determined from the measurements, are discussed.

Structure determination of [formula omitted] surface by X-ray diffraction

The structure of the Si(111) 3 × 3  Sb surface was investigated by the surface X-ray diffraction method. A newly designed ultrahigh-vacuum apparatus for surface X-ray diffraction experiments was used. The results of data analysis in the framework of absolute reflectivity confirmed that the Si(111) 3 × 3  Sb system forms the so-called T 4-centered milk-stool structure with the coverage of 1 ML. A technique using Laue geometry diffraction was successfully applied to discriminate between the T 4-centered model and an alternative model, that is, the H 3-centered model.

Both Surface Inequi-thickness Removal-both Surface X-ray Diffraction Method for Residual Stress Measurement in a Plate

The authors have proposed a method to measure the residual stress by X-ray on both surface after removing thin layers of equal thicknesses from both surfaces of a plate. In this paper is derived a new method of X-ray after removing inequithickness from both surfaces of a plate. The theories of the formar Single Surface Removal Method and Both Surface Removal Method are derived from the present theory as special cases. The authors applied this method to a quenched and tempered alloy steel plate of SKS 51 and discussed the influence of neglecting the inequality of removal thickness on both surface.

Both Surface Removal-Both Surface X-Ray Diffraction Method for Residual Stress Measurement in a Hollow Cylinder

The authors proposed in this paper a new method of X-ray diffraction to measure three principal residual stresses in a hollow cylinder. With thin layers of equal thickness removed from both surfaces of a hollow cylinder, surface stresses are measured by X-ray on both surfaces, and then the residual stress distributions can be calculated from both surfaces at the same time. As an application of the new method, the authors measured the residual stresses of a heat treated hollow cylinder of STPT 38.

Both Surface Removal-Both Surface X-Ray Diffraction Method for Residual Stress Measurement in a Hollow Cylinder

内面または外面から逐次薄層除去を行い,両面X線照射による中空円筒の軸対称3主成分残留応力を測定する方法については,すでに発表した.本論文は平板の場合について発表したと同様,内外両面から等量ずつ薄層除去し,両面にX線照射法を適用して得られる両表面応力測定値を用いて内外面からの残留応力分布を同時に計算する測定理論式を提唱するもので,適用例として熱処理した中空鋼管の残留応力分布を測定した.