Nanoscience and nanotechnology are tremendously increasing fields of research that aim at producing, characterizing and understanding nanoobjects and assemblies of nanoobjects. Their new physical or chemical properties, which arise from confinement effects, intimately depend on their morphological properties, i.e. their shapes, their sizes and their spatial organization. This calls for dedicated morphological characterization tools, among which is the Grazing Incidence Small Angle X-Ray Scattering (GISAXS). This reciprocal space technique has emerged in the last two decades as a powerful tool that allows investigating in a non-destructive way the morphological properties from one to billions of nanoparticles, either on a surface, or embedded in a matrix, with sizes ranging from 1 nm to several microns. The advantages of the technique are that it is non-destructive; it yields statistical information averaged on a large number of nanoparticles; it allows probing both the surface or deep below it, by changing the incident angle of the X-ray beam; it can be used in very different sample environments, in particular in situ in the course of a given process such as growth, annealing, gas exposure; and it may be given chemical sensitivity by use of anomalous scattering.

The behaviour of the NiO(111) surface has been investigated by grazing incidence X-ray scattering (GIXS). We show on single crystals with an improved crystalline quality that NiO(111) is always p(2×2) reconstructed. After air annealing the structure is close to the predicted octopolar reconstruction; after in situ annealing and oxidation it is very different. The transformation of the surface is continuous with temperature but seems to be only based on two possible atomic configurations.

The mechanism of thermal pore generation in organosilicate thin films loaded with a six-armed star-shaped poly(-caprolactone) porogen was quantitatively investigated by using in-situ grazing-incidence small-angle X-ray scattering and thermogravimetry. These analyses found that the blend components have a limited miscibility that depends on the composition; for porogen loadings up to only 20 wt%, molecularly miscible blend films were obtained. Even for the miscible blend films, heating the films produced a curing reaction of the precursor matrix component, leading to the phase separation of the porogen component. This phase separation was found to begin at 393 K for 10 wt% porogen loaded films and at 373 K for 20 wt% porogen loaded films, and to continue for temperatures up to 423 K. The porogen aggregates remained and were confined within the matrix film without any further growth or movement until complete thermal decomposition above 564 K. ‡ K. S. Jin and K. Heo contributed equally to this work.

The structure of MgO(001) single crystal surfaces that are of very high crystalline quality, extremely flat, clean and stoichiometric, was investigated by grazing incidence X-ray scattering. A new procedure for preparing these surfaces is described, which includes hightemperature annealing in air followed by high-temperature ion bombardment, and annealing under partial oxygen pressure. The relaxation, −0.56±0.35%, and rumpling, 1.07±0.5%, were determined with a much better accuracy than in any previous experimental study. These values are compared with those given in previous experimental and theoretical studies. The atomic structure of the Ca-segregated MgO(001) surface was also investigated. The most likely structure is the theoretically predicted (ǰ2×ǰ2)R45°r econstruction. Atomic displacements within this unit cell were determined.

The structure of ultrathin silicon layers obtained by molecular hydrophobic bonding is investigated. The twist and tilt angles between the two crystals are accurately controlled. The buried Si Si interface is observed by transmission electron microscopy and by grazing incidence X-ray techniques. For low twist angle values (

A general formalism of X-ray scattering from different kinds of surface morphologies is described. Based on a description of the surface morphology at the atomic scale through the use of the paracrystal model and discrete distributions of distances, the scattered intensity by non-periodic surfaces is calculated over the whole reciprocal space. In one dimension, the scattered intensity by a vicinal surface, the two-level model, the N-level model, the faceted surface and the rough surface are addressed. In two dimensions, the previous results are generalized to the kinked vicinal surface, the two-level vicinal surface and the step meandering on a vicinal surface. The concept of Crystal Truncation Rod is generalized considering also the truncation of a terrace by a step (yielding a Terrace Truncation Rod) and a step by a kink (yielding a Step Truncation Rod).

The structure and morphology of Ag deposits grown at room temperature on high-quality MgO͑001͒ surfaces have been investigated in situ, from 0.2 to 300 equivalent monolayers ͑ML͒ of Ag deposited. Surface x-ray diffraction and grazing incidence small angle x-ray scattering parallel and perpendicular to the surface were combined. Nucleation, growth, and coalescence of islands are found from 0.2 ML. The average in-plane width, height, and in-plane separation of growing islands are deduced and are found to reproduce well the Mg 1s x-ray photoemission spectroscopy spectrum previously reported by other authors. The height over width ratio of the islands is ϳ0.37Ϯ0.05 at all stages of the deposit. Ag grows in cube-on-cube epitaxy with respect to the MgO͑001͒ substrate. A very unusual evolution of the state of strain in Ag with increasing amount of Ag deposited is observed. Below 4-6 ML ͑island width smaller than 90 Å͒, the small Ag islands are coherent with the MgO. Below 1 ML ͑island width smaller than 35 Å͒, they have their bulk lattice parameter, and between 1 and 4 ML they become more and more strained by the MgO substrate, with an average lattice parameter intermediate between those of Ag and of MgO. Around 4-6 ML, the islands reach a critical size and misfit dislocations are introduced at the edges. Above 30 ML, the film is almost continuous, and the interfacial misfit dislocations reorder to form a square network, oriented along ͗110͘ directions. Stacking faults appear in Ag at this stage. A small amount of twinned Ag also starts to grow around 4 ML. This unusual evolution of the strain in the Ag islands and the following introduction of misfit dislocations are interpreted on the basis of a one-dimensional Frenkel-Kontorova model involving a very weak Ag-MgO interaction and a weak corrugation of the interatomic potential. Quantitative measurements and analysis of the MgO crystal truncation rods ͑CTR's͒ during growth were shown to provide different structural parameters of the interface that are important for theoretical calculation, especially the epitaxial site, above oxygen atoms of the substrate, and the interfacial distance (2.52Ϯ0.1 Å). The origin of the interference along the CTR's is discussed according to the strain state of the epitaxial Ag. ͓S0163-1829͑99͒14131-6͔ PHYSICAL REVIEW B 15 AUGUST 1999-II VOLUME 60, NUMBER 8 PRB 60 0163-1829/99/60͑8͒/5858͑14͒/$15.00 5858

The self-organized growth of Co nanoparticles with 10 nm periodicity was achieved at room temperature on a Ag(001) surface patterned by an underlying dislocation network, as shown by real time, in situ Grazing Incidence Small and Wide Angle X-ray Scattering. The misfit dislocation network, buried at the interface between a 5nm-thick Ag thin film and a MgO(001) substrate, induces a periodic strain field on top of the surface. Nucleation and growth of Co on tensile areas are found as the most favorable sites as highlighted by Molecular Dynamic simulations.

Grazing incidence anomalous x-ray scattering was used to monitor in situ the molecular beam epitaxy growth of GaN/AlN quantum dots (QDs). The strain state was studied by means of grazing incidence Multi-wavelength Anomalous Di raction (MAD) in both the QDs and the AlN during the progressive coverage of QDs by AlN monolayers. Vertical correlation in the position of the GaN QDs was also studied by both grazing incidence MAD and anomalous Grazing Incidence Small Angle Scattering (GISAXS) as a function of the number of GaN planes and of the AlN spacer thickness. In a regime where the GaN QDs and the AlN capping are mutually strain influenced, a vertical correlation in the position of QDs is found with as a side-e ect an average increase in the QDs width.

A new mirror device has been implanted on the station EXAFS IV at LURE-DCI This harmonic refection assembly is made of two glass mirrors which ensure an output beam parallel to the entrance one. This easy operating device efficiently rejects the unwanted higher orders, and new experiments performed at the sulfur K-edge are presented.