Abstract:The application of grazing incidence X-ray reflectivity measurements to the characterization of metallic multilayers is described. Use of simulation permits interface roughness to be determined to a precision of about 0.1 nm r.m.s. from the specular reflectivity profile. Measurement of the diffuse scatter permits interdiffusion to be distinguished in principle from interface roughness. Localization of strong diffuse scatter around the Bragg peaks of superlattices provides evidence for coherency in the roughnes… Show more
“…The narrow breadth of the Bragg reflections is indicative of uniformity in the subunit thickness, that is, the thickness of each bilayer within the multilayer is well-matched. Bragg peak broadening is observed in higher order peaks in multilayers exhibiting multiple orders of Bragg diffraction …”
Section: Resultsmentioning
confidence: 99%
“…This observation is consistent with atomic force microscopy studies of single-component ALD ZnO films which indicate a correlation between increased ZnO surface roughness and ZnO layer thickness . It should be noted that off-specular reflectivity ,,, may be used to deconvolve roughness and composition gradient effects, though the interpretation of these data is less straightforward and will not be presented here. 3 Overlay of X-ray reflectivity curves for multilayers A−C as defined in Table .…”
Section: Resultsmentioning
confidence: 99%
“…Bragg peak broadening is observed in higher order peaks in multilayers exhibiting multiple orders of Bragg diffraction. 17 Reflectivity curves for the second set of samples, labeled alphabetically in Table 1, are given in Figure 3. Bragg peak positions are well-matched from sample to sample, indicating well-matched repeat unit thicknesses as intended.…”
Section: Resultsmentioning
confidence: 99%
“…The accuracy of indirect characterization methods such as ellipsometry rely on the accuracy of user-defined material parameters such as refractive index, which are often assumed or entirely unknown. X-ray reflectivity (XRR), or low-angle X-ray diffraction, provides nondestructive, accurate characterization of thin films and multilayers. ,, X-ray reflectivity probes the intensity of scattered X-rays at small angles, providing information about film thickness, roughness, and density. The fundamental framework for quantitative interpretation of X-ray reflectivity data was derived in the 1950s by Parratt, though the task of carrying out the necessary recursion calculation by hand limited its application initially to simple systems. , The advent of high-performance desktop PCs drastically reduced the requisite calculation time, allowing simulated reflectivity for complicated multilayer systems to be carried out in a matter of seconds…”
Specular X-ray reflectivity (XRR) has been employed in the characterization of a novel
series of ZnO/Al2O3 multilayer materials prepared by atomic layer deposition in a custom-built hot-wall reactor. All multilayers studied are approximately 1200 Å thick and consist
of 1−128 ZnO/Al2O3 bilayer subunits. Reflectivity data are treated both qualitatively and
quantitatively by computer-aided simulation and modeling. Surface roughness is observed
to increase dramatically with increasing ZnO layer thickness. ZnO density is determined to
be within 5% of bulk values, while the Al2O3 layers exhibit densities less than 80% of that
expected for crystalline alumina. Thickness parameters determined by computer simulation
correspond to deposition rates of 1.71 and 1.28 Å/reaction cycle for ZnO and Al2O3,
respectively. XRR-determined thickness and density parameters are in clear quantitative
agreement with analyses of single-component films by other techniques. Conventional and
grazing-incidence X-ray diffraction show the ZnO layers to be polycrystalline above a critical
layer thickness of approximately 10 Å. The Al2O3 layers are amorphous.
“…The narrow breadth of the Bragg reflections is indicative of uniformity in the subunit thickness, that is, the thickness of each bilayer within the multilayer is well-matched. Bragg peak broadening is observed in higher order peaks in multilayers exhibiting multiple orders of Bragg diffraction …”
Section: Resultsmentioning
confidence: 99%
“…This observation is consistent with atomic force microscopy studies of single-component ALD ZnO films which indicate a correlation between increased ZnO surface roughness and ZnO layer thickness . It should be noted that off-specular reflectivity ,,, may be used to deconvolve roughness and composition gradient effects, though the interpretation of these data is less straightforward and will not be presented here. 3 Overlay of X-ray reflectivity curves for multilayers A−C as defined in Table .…”
Section: Resultsmentioning
confidence: 99%
“…Bragg peak broadening is observed in higher order peaks in multilayers exhibiting multiple orders of Bragg diffraction. 17 Reflectivity curves for the second set of samples, labeled alphabetically in Table 1, are given in Figure 3. Bragg peak positions are well-matched from sample to sample, indicating well-matched repeat unit thicknesses as intended.…”
Section: Resultsmentioning
confidence: 99%
“…The accuracy of indirect characterization methods such as ellipsometry rely on the accuracy of user-defined material parameters such as refractive index, which are often assumed or entirely unknown. X-ray reflectivity (XRR), or low-angle X-ray diffraction, provides nondestructive, accurate characterization of thin films and multilayers. ,, X-ray reflectivity probes the intensity of scattered X-rays at small angles, providing information about film thickness, roughness, and density. The fundamental framework for quantitative interpretation of X-ray reflectivity data was derived in the 1950s by Parratt, though the task of carrying out the necessary recursion calculation by hand limited its application initially to simple systems. , The advent of high-performance desktop PCs drastically reduced the requisite calculation time, allowing simulated reflectivity for complicated multilayer systems to be carried out in a matter of seconds…”
Specular X-ray reflectivity (XRR) has been employed in the characterization of a novel
series of ZnO/Al2O3 multilayer materials prepared by atomic layer deposition in a custom-built hot-wall reactor. All multilayers studied are approximately 1200 Å thick and consist
of 1−128 ZnO/Al2O3 bilayer subunits. Reflectivity data are treated both qualitatively and
quantitatively by computer-aided simulation and modeling. Surface roughness is observed
to increase dramatically with increasing ZnO layer thickness. ZnO density is determined to
be within 5% of bulk values, while the Al2O3 layers exhibit densities less than 80% of that
expected for crystalline alumina. Thickness parameters determined by computer simulation
correspond to deposition rates of 1.71 and 1.28 Å/reaction cycle for ZnO and Al2O3,
respectively. XRR-determined thickness and density parameters are in clear quantitative
agreement with analyses of single-component films by other techniques. Conventional and
grazing-incidence X-ray diffraction show the ZnO layers to be polycrystalline above a critical
layer thickness of approximately 10 Å. The Al2O3 layers are amorphous.
“…It is one of the non-destructive techniques used to assess multilayer structure properties. [1][2][3] It measures film thickness, interfacial roughness and density of films. It can be used to assess the physical properties of both single and multilayer structures.…”
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