X-ray Reflectivity Method Research Articles

Strain-drived giant flexoelectric field and its efficient modulation in (111) BiFeO3 films

Flexoelectric effect in ferroelectric epitaxy films has attracted significant attention due to its theoretical and application potentials. However, the origin and control of flexoelectric field is not yet fully understood. In this study, we investigated the surface structure of single-domain epitaxial BiFeO3 films with a (111) orientation using grazing incidence X-ray diffraction and X-ray reflection methods. We observed large strain gradient on the surface of the BiFeO3 films, which produces a giant flexoelectric field up to 82.55 MV/m at the surface of 15 nm thick BiFeO3 film. Additionally, we discovered the presence of a surface layer with lower electron density than that of the underlying BiFeO3 layer, which is related to the flexoelectric field. Moreover, with increased film thickness, we found the strain distribution along growth direction of the film is changed, thereby leads to the decreased flexoelectric field and increasing thickness of the surface layer respectively. These findings convinced the coupling between the strain state and surface structure, changing the thickness of the ferroelectric film and consequently the strain state is an efficient way to adjust the flexoelectric field and the surface structure.

Near substrate surface plasma characteristics of ZnO film deposition in DC reactive magnetron sputtering with water vapor

The effect of varying the water vapor content in a DC magnetron sputtering process was investigated for zinc oxide film formation. The plasma parameters near the substrate surface were measured using a single Langmuir probe, and the deposited films were characterized using X-ray diffraction, X-ray reflectivity, optical transmittance, and 4-point probe methods. In the region near the substrate surface, the addition of water changes the plasma properties, and the measured plasma parameters showed the changes corresponding to the transition in the film growth mechanism from Zn to ZnO. Depositing at 40% water content resulted to a highly transparent film with a ρ of 1.20 Ω cm. The band gap of films deposited at 40%–100% water content ranged from 3.36 to 3.34 eV, which matches the expected shallow hydrogen donor doping in ZnO.

Stellar-mass black hole spinning and its relation to transient jets

Despite the vast research on spinning black holes and jets, little is known about details of jet formation. This paper is aimed to study whether Penroses prediction that black hole spin power jets can be verified. Once proved, a deeper understanding of energy/momentum transfer near event horizon is to be achieved. This paper compares two dominant spin measuring methods. Thermal continuum fitting method makes use of thermal emission to measure the spin, where a theoretical flux profile is created by inputting parameters (inclination of X-ray binaries, distance of X-ray binaries from the earth, mass of black hole, etc). X-ray reflection method uses broadened Fe-line to measure the spin, and that corona geometry is often required. This paper also compares various definitions of jet power and spin-jets relation. In conclusion, transient jets are highly possible to be powered by black hole spin, but more evidence is required to confirm this. Steady jets remain in a vague relation with spin. It has also been found that different measuring methods of both spin and jets can affect the spin-jets relation.

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Structural Analysis of DLC Thin Film Using X-Ray Reflectivity and Raman Spectroscopy Techniques

The characteristics of sputtered amorphous diamond-like carbon-containing copper (DLC: Cu films) films deposited on Si (100) substrates and Si (111) in argon gas-filled chamber using carbon target under different substrates deposition time, and RF power. The samples were deposited by RF magnetron sputtering and analyzed using Raman spectroscopy and X-ray reflectivity (XRR) methods. Different parameters of depositions were used to study the structure, thickness, roughness, and density of the samples. The Cu preliminary layer act as a catalyst to growth the DLC thin-film analyzed using XRR analysis to measure thickness, roughness, and density of the thin films. The film structures of the samples were analyzed using Raman spectroscopy with a 532nm laser source. Gaussian peak shapes were used in Raman spectrum fitting to analyzed to measure the D band and G band for both samples. The Films thickness, roughness, and mass density were studied by XRR techniques using XRD to acquire the multilayer structure of thin films grown by magnetron sputtering.

Study of silicon-to-silicon carbide transformation stages in the process of atomic substitution by the methods of total external X-ray reflection and X-ray diffractometry

X-ray diffraction and total external reflection of X-rays (X-ray reflectometry) methods were used to study the successive stages of synthesis of epitaxial SiC films on Si (100) X-ray diffraction and total external X-ray reflection (XRD) methods were used to study successive stages of synthesis of epitaxial SiC films on Si (100) surfaces, (110) and (111) surfaces by the atom substitution method. The data on the transformation evolution of (100) surfaces were studied, (110) and (111) Si, into SiC surfaces. A comparative analysis of the X-ray structural quality of the SiC layers grown on Si by the atom substitution method with the quality of SiC layers grown by Advanced Epi by the standard CVD method. A modified technique for the total outer X-ray reflection method, based on measurements of the intensity of the reflected X-rays using a special parabolic mirror. It is shown that the method of total external reflection method makes it possible to obtain important information about the degree of surface roughness of SiC layers, the evolution of their crystal structure and plasmon energy in the process of Si to SiC conversion. Keywords: total external reflection, X-ray reflectometry, silicon carbide, plasmons.

Исследование этапов превращения кремния в карбид кремния в процессе атомного замещения методами полного внешнего отражения рентгеновских лучей и рентгеновской дифрактомерии

X-ray diffraction and total external reflection of X-rays (X-ray reflectometry) methods were used to study the successive stages of synthesis of epitaxial SiC films on Si (100) X-ray diffraction and total external X-ray reflection (XRD) methods were used to study successive stages of synthesis of epitaxial SiC films on Si (100) surfaces, (110) and (111) surfaces by the atom substitution method. The data on the transformation evolution of (100) surfaces were studied, (110) and (111) Si, into SiC surfaces. A comparative analysis of the X-ray structural quality of the SiC layers grown on Si by the atom substitution method with the quality of SiC layers grown by Advanced Epi by the standard CVD method. A modified technique for the total outer X-ray reflection method, based on measurements of the intensity of the reflected X-rays using a special parabolic mirror. It is shown that the method of total external reflection method makes it possible to obtain important information about the degree of surface roughness of SiC layers, the evolution of their crystal structure and plasmon energy in the process of Si to SiC conversion.

Study of silicon-to-silicon carbide transformation stages in the process of atomic substitution by the methods of total external X-ray reflection and X-ray diffractometry

X-ray diffraction and total external reflection of X-rays (X-ray reflectometry) methods were used to study the successive stages of synthesis of epitaxial SiC films on Si (100) X-ray diffraction and total external X-ray reflection (XRD) methods were used to study successive stages of synthesis of epitaxial SiC films on Si (100) surfaces, (110) and (111) surfaces by the atom substitution method. The data on the transformation evolution of (100) surfaces were studied, (110) and (111) Si, into SiC surfaces. A comparative analysis of the X-ray structural quality of the SiC layers grown on Si by the atom substitution method with the quality of SiC layers grown by Advanced Epi by the standard CVD method. A modified technique for the total outer X-ray reflection method, based on measurements of the intensity of the reflected X-rays using a special parabolic mirror. It is shown that the method of total external reflection method makes it possible to obtain important information about the degree of surface roughness of SiC layers, the evolution of their crystal structure and plasmon energy in the process of Si to SiC conversion. Keywords: total external reflection, X-ray reflectometry, silicon carbide, plasmons.

Nanostructured Ga doped ZnO thin films prepared by Sol-Gel spin-Coating / Filmes finos de ZnO NanoestruturadoS Ga doped preparados por sol-Gel spin-Coating

ZnO nanostructures are used in device systems such as photodetectors, gas sensors,photoemission devices, UV-photosensors and many others in Optoelectronics.In the present work we studied nanocrystalline ZnO:Ga thin films prepared by the sol–gel dip-coating technique. Samples were characterized by Grazing Incidence X-ray Diffraction(GIXD), X-ray Reflectivity (XR) and Grazing Incidence Small-Angle X-ray Scattering(GISAXS) methods and Field Effect Scanning Electronic Microscopy (FESEM). Characterization of the samples shows that the obtained films were uniform, continuous, with a crystallite size around 12 nm, an average pores size of around 3.5nm, and a volume fraction of nanoporosity between 0.18 and 0.3. Comparison of densities between doped and undoped films is discussed.

Measurement method of black hole spin and its application in jet

Spin is an important property of black holes. The formation of jet and black hole is related to spin. At present, there are two commonly used spin measurement methods, the X-ray reflection method, and the continuum-fitting method. By analyzing the distribution of black hole spin in black hole binary system measured by these two methods, we find that in high-mass X-ray binaries, black holes have high spin, this is because the companion stars have a large mass and short lifetime, the black holes don’t have enough time to accelerate the spin by accretion so must be bored with high spin. However, in low-mass X-ray binaries, the spin will be widely distributed because they have enough time to increase spin by accreting gas. And according to the existing data, we can also get the relationship between spin and jet. However, both methods are affected by the complex physics of the accretion disk, in the future, gravitational waves will become another effective tool to measure the spin of black holes.

The spin measurement of black holes in active galactic nucleus

Spin as one of the two parameters describing black holes. Measuring the spin of black holes is very important in black holes research. In this paper, we introduce the method to measure the spin of AGNs which is the X-ray reflection method, including both specific content and precautions. Based on this method, we select 25 aim objects and give the spin number. The spins mainly focus on 0.5~1. The selection effect is shortly discussed in this paper. Gravitational waves may be next major technology to measure the spin of AGNs. Gravitational waves method is also briefly introduced in this paper.

Measurement of Black Hole Spin via X-ray Reflection Spectra

The measurement of black hole spin is of great significance. The methods of measuring the spin have been discussed for a long time. For this important astrophysical problem, the paper begins with the significance of measuring a black hole spin and focuses on the theory of measuring the spin via the X-ray reflection recognized as iron line spectrum method. The paper also discusses the popular reflection models and explains the important parameters. Besides, the other methods of spin measurement are introduced, mainly comparing them with the X-ray reflection method. Finally, the advantages and disadvantages of the X-ray reflection method are summarized.

Influence of Glass Surface Modification on Thin Film Copper Electrodes

We investigate the impact of the glass surface on the structural and electrical properties of Ti/Cu film stacks as well as single Ti adhesion layer, by modifying Corning® Eagle XG® glass surfaces using four acids common in TFT-LCD microfabrication processes. Atomic force microscopy results indicate significant change of the surface topography of Ti and Cu, particularly found on hydrofluoric acid treated glass surfaces. The film microstructures are characterized by a comprehensive analysis using Bragg, grazing incidence and in-plane X-ray diffraction, and X-ray reflectivity methods as well as the transmission electron microscopy. The sheet resistance was measured using the four-point probe method. We demonstrate the role of the glass surface state through its impact on the structural and electrical properties of Ti/Cu electrodes emanating from glass surface treatments.

Evaluation of microstructure and residual stress in W/B4C multilayer optics

The microstructure and residual stress are investigated in W/B4C x-ray multilayer (ML) mirrors as a function of the number of layer pairs (N) varying from 20 to 400 at a fixed period, d ≈ 1.9 nm. The microstructure is analyzed using the x-ray reflectivity (XRR) and rocking scan methods. The total residual stress in the ML film is derived using the substrate curvature measurement method, whereas the stress in W layers of MLs is separately determined by grazing incidence x-ray diffraction measurements based on the sin2 χ method using synchrotron. The successive order Bragg peaks in XRR measured curves indicate good quality of the ML structure in terms of interface roughness and thickness errors. As N increases, the interface width of B4C and W varies in the range of 0.15–0.22 nm and 0.26–0.44 nm, respectively. The contribution of physical roughness to the interface width is significantly lower (∼sub-angstrom) compared to interfacial diffuseness (angstrom level) along with a small (few nanometers) correlation length in the ML structures as observed by rocking scan measurements. The residual stresses both in the W layers and in the ML film are compressive in nature. The total stress in the ML film decreases from −1.444 GPa to −0.389 GPa with increasing N. Measured residual stress in the ML film and W layers is correlated considering a net combined tensile stress arising from B4C layers and interfaces. The ML film with N = 400 shows the least residual stress and is suitable for large layer pair ML optics. Microstructure and stress are correlated considering the mechanism of film growth at the early stage and is discussed.

Vanadium and vanadium nitride thin films grown by high power impulse magnetron sputtering

Thin vanadium and vanadium nitride films were grown on SiO2 by non-reactive and reactive high power impulse magnetron sputtering (HiPIMS), respectively. The film properties were compared to films grown by conventional dc magnetron sputtering (dcMS) at similar conditions. We explored the influence of the stationary magnetic confinement field strength on the film properties and the process parameters. The deposition rate is much lower for non-reactive sputtering by HiPIMS than for dcMS. Furthermore, for both dcMS and HiPIMS the deposition rate is lower for strong magnetic confinement. Structural characterization was carried out using x-ray diffraction and reflection methods as well as atomic force microscopy and scanning electron microscope. Both dcMS and HiPIMS grown vanadium films are polycrystalline with similar grain size regardless of magnetic field strength. For dcMS grown vanadium films the surface roughness is higher when a strong magnetic field is used. For both non-reactive growth of vanadium and reactive growth of vanadium nitride the HiPIMS process produces denser films with lower surface roughness than dcMS does. Lowering the magnetic field strength increases the deposition rate significantly for reactive HiPIMS while it increases only slightly in the reactive dcMS case. The films grown by HiPIMS with strong magnetic confinement exhibit higher density and lower roughness. We find that the operating pressure, growth temperature, discharge voltage and film thickness has influence on the properties of HiPIMS grown vanadium nitride films. The films are denser when grown at high temperature, high discharge voltage and low pressure. The density of those films is lower for thicker films and thicker films consist of larger grain size. For all the films explored, higher density coincides with lower surface roughness. Thus, the deposition method, magnetic field strength, growth temperature, discharge voltage, film thickness and growth pressure have a significant influence on the film quality and structural properties, including the grain size for the various orientations.

Carbon coatings with high concentrations of silicon deposited by RF PECVD method at relatively high self-bias

This paper presents properties of a-C:H:Si coatings as a function of incorporated silicon atoms. The chemical composition of the examined coatings was controlled by tetramethylsilane (Si(CH3)4) to methane (CH4) flow ratio during RF PECVD (Radio Frequency Plasma Enhanced Chemical Vapour Deposition) process conducted at two values of negative substrate bias. The results have shown two stages in behavior of hardness, refractive index and density of deposited coatings, measured using the nanoindentation, ellipsometry and X-ray reflectivity techniques, respectively. The critical concentration of incorporated silicon, dividing the two stages, was established to about 15at.%. Below this concentration the analyzed parameters decrease with the increasing amount of dopant, whereas above this value, just after reaching the minimum, further increase in silicon concentration results in increase of hardness, refractive index and density. We also registered a high consistency of results from both ellipsometry and X-ray reflectivity methods.

Integration of electrochemical and synchrotron-based X-ray techniques for in-situ investigation of aluminum anodization

Anodization of aluminum alloys AA 6082 and AA 7075 was investigated in-situ with integrated electrochemical and synchrotron-based X-ray reflectivity (XRR) methods providing complementary information about the anodic processes taking place on the alloys. The stepwise potentiostatic polarization measurements reveal dynamic processes of the anodic oxide formation and dissolution, and the following electrochemical impedance spectroscopy measurements detect the break of the native oxide and the growth of typical two-layer anodic oxide film, while the XRR measurements show the growth of entire anodic oxide film whose thickness increases linearly with the increasing applied potential. The results indicate that while a stable anodic oxide can be formed on the both alloys with a similar growth factor, AA 7075 shows a thinner thickness of the barrier layer and a lower resistance of the oxide film. The electrochemical results suggest both localized and uniform anodic dissolution processes, which are more pronounced on AA 7075, demonstrating the effect of alloying elements on the growth of anodic oxides.

A Comparison of Two Methods for Estimating Black Hole Spin in Active Galactic Nuclei

Abstract Angular momentum, or spin, is a fundamental property of black holes (BHs), yet it is much more difficult to estimate than mass or accretion rate (for actively accreting systems). In recent years, high-quality X-ray observations have allowed for detailed measurements of the Fe Kα emission line, where relativistic line broadening allows constraints on the spin parameter (the X-ray reflection method). Another technique uses accretion disk models to fit the AGN continuum emission (the continuum-fitting, or CF, method). Although each technique has model-dependent uncertainties, these are the best empirical tools currently available and should be vetted in systems where both techniques can be applied. A detailed comparison of the two methods is also useful because neither method can be applied to all AGN. The X-ray reflection technique targets mostly local (z ≲ 0.1) systems, while the CF method can be applied at higher redshift, up to and beyond the peak of AGN activity and growth. Here, we apply the CF method to two AGN with X-ray reflection measurements. For both the high-mass AGN, H1821+643, and the Seyfert 1, NGC 3783, we find a range in spin parameter consistent with the X-ray reflection measurements. However, the near-maximal spin favored by the reflection method for NGC 3783 is more probable if we add a disk wind to the model. Refinement of these techniques, together with improved X-ray measurements and tighter BH mass constraints, will permit this comparison in a larger sample of AGN and increase our confidence in these spin estimation techniques.

Pore size evaluation of mesoporous organosilicate films by non-destructive X-ray reflectivity methods

200-nm-thick organosilicate films deposited by mixture of tetraethyl orthosilicate (TEOS) and methyltrimethoxysilane (MTMS) dissolving in different cetrimonium bromide (CTAB)/ethanol ratios were characterized in terms of pore size determination and its distribution. Under the toluene ambient, the pores would adsorb the gas hence elevating the whole film density. The X-ray reflectivity (XRR) equipped with mass flow control was utilized to detect the film density increasing. By fitting with Gaussian function and conversing with Kelvin’s equation, the pore size was increased from 6.2 to 10.8 Å as the CTAB/ethanol ratio increasing to 0.075. It was attributed to the ethanol and CTAB enhanced the TEOS hollow droplets stability and dissolvability. As the CTAB/ethanol ratio is further increased, the pore size is reversely decreased, owing to the formation of solid microspheres. The non-destructive XRR measurement can evaluate the sub-nano pore sizes and its size distribution, which would fascinate the development and characterization of back-end of line process.

Morphology of Tantalum Nitride Thin Films Grown on Fused Quartz by Reactive High Power Impulse Magnetron Sputtering (HiPIMS)

ABSTRACTThin tantalum nitride films were grown on fused quartz by reactive high power impulse magnetron sputtering (HiPIMS) while varying the fractional N2 flow rate at fixed substrate temperature of 400°C. The film properties were compared to films grown by conventional dc magnetron sputtering (dcMS) at similar conditions. Structural characterization was carried out using X-ray diffraction and reflection methods. The HiPIMS process produces slightly less dense films than does dcMS and the surface roughness is similar for both the HiPIMS and dcMS grown films. The deposition rate for HiPIMS is up to 80 % lower than for dcMS but it can be roughly doubled by lowering the magnetic field strength by 30 %.