Ryna B. Marinenko

Epitaxial growth of BaTiO3 thin films at 600 °C by metalorganic chemical vapor deposition

BaTiO3 thin films were grown epitaxially on (100) MgO substrates by metalorganic chemical vapor deposition (MOCVD) at a temperature of 600 °C. This substrate temperature is the lowest reported temperature for the growth of epitaxial BaTiO3 films by an MOCVD process. The films had a cube–cube orientation relationship with the substrate and were oriented with an a‐axis perpendicular to the substrate plane. Nanoscale energy dispersive x‐ray spectrometry measurements showed no evidence of interdiffusion between the film and substrate.

Sputtered amorphous carbon nitride films

The recent announcement of the synthesis of C 3 N 4 has increased interest in this unique material. Carbon nitride may have several useful applications as wear and corrosion resistant coatings, electrical insulators, and optical coatings. We have produced amorphous carbon nitride coatings containing up to 40% nitrogen using planar magnetron RF sputtering with and without an ion beam in a nitrogen atmosphere. Both wavelength dispersive x-ray spectrometry (WDX) and x-ray photoelectron spectroscopy (XPS) indicate this composition. Coatings up to 2 μm thick were produced on alumina, silicon, SiO 2 , and glass substrates using a graphite target. Films with transparency greater than 95% in the visible wavelengths and harder than silicon have been produced. The properties of these films are correlated with composition, fabrication, conditions, and subsequent heat treatments. A scanning tunneling microscope (STM) and transmission electron microscopy (TEM) were used to characterize the morphology of the films. XPS studies confirm the stability of a carbon nitrogen phase up to 600 °C. Compositional variations were determined with secondary ion mass spectrometry (SIMS) depth profiling, and the Raman spectra are compared with those of carbon and carbon nitride films prepared by other methods.

High-accuracy determination of the dependence of the photoluminescence emission energy on alloy composition in AlxGa1−xAs films

In an effort to improve the accuracy of photoluminescence (PL) measurements of the Al mole fraction (x) of AlxGa1−xAs alloys, the PL peak emission energy, EPL,peak, was measured at room temperature for molecular-beam epitaxy-grown AlxGa1−xAs films with 0⩽x<0.37, and correlated with independent measurements of x by in situ reflective high-energy electron diffraction (RHEED) and also by ex situ wavelength-dispersive x-ray spectroscopy in an electron microprobe analyzer (WDS/EMPA). The measurement uncertainty of EPL,peak was minimized through the following procedures: Accurate calibration of the photon energy (or wavelength) scale, correction of the measured spectra for the spectrometer response function, fitting the data with a well-chosen line shape function, and compensation for the effect of ambient temperature drift. With these procedures, the 2σ measurement uncertainty of EPL,peak was of the order 5×10−4 eV for most samples. From correlation of the PL and WDS/EMPA composition data, the slope ∂EPL,peak/...

Compositional Homogeneity of Ferroelectric (Pb,La)(Ti,Zr)O-3 Thick Films

Quantified wavelength dispersive spectroscopy (WDS) x-ray element maps were used to characterize active (Pb,La)(Ti,Zr) O 3 (PLZT) layers on Pt/PLZT/Al 2 O 3 substrates, one fired at 1050 °C and the other at 1150 °C. In the layer fired at 1050 °C, randomly distributed micrometer-sized compositional irregularities were observed as La-rich regions that were in most cases enriched also with Ti and deficient in Pb and Zr compared to the matrix. Such compositional imperfections were not observed in the PLZT layer fired for the same duration at 1150 °C. The level of microheterogeneity for all elements in the specimen fired at 1150 °C and for Pb, Ti, and Zr in the specimen fired at 1050 °C was below 1% relative at confidence level of 99% while for La it was as much as 2.5% relative. In point-beam line profiles across the active layer starting from the Pt electrode toward the outer surface of the cross-section of the PLZT film, the Pb concentration decreased continuously in both samples, confirming the importance of providing a properly equilibrated partial pressure of Pb around the sample during the entire firing process. Better dielectric and ferroelectric characteristics of the specimen fired at 1150 °C compared to the sample fired at 1050 °C were attributed to the differences in compositional heterogeneity between these samples. The study of the micro-compositional characteristics of these ceramic materials with quantitative WDS mapping has contributed to the optimization of processing parameters and hence to the understanding of the properties of ferroelectric PLZT materials.

Intensity Measurement of Wavelength Dispersive X-Ray Emission Bands: Applications to the Soft X-Ray Region

Line shapes of atomic lines and soft X-ray emission bands are described using pseudo-Voigt profiles accounting for the presence of non-diagram features (low and high energy satellites) and instrumental distortions. Peak shape changes of soft X-ray emission bands as a function of the excitation conditions and the matrix composition are related with self-absorption phenomena. Implications of spectral deconvolution of WDS X-ray intensity measurement for quantitative analysis of complex spectra and for studying valence states are reviewed.

Quantitative Compositional Mapping with the Electron Probe Microanalyzer

Of all the techniques of electron probe microanalysis, the one that has undergone the least change over the history of the field is the technique of producing an image of the distribution of the elemental constituents of a sample, which can be termed compositional mapping. Even today with the dominance of computers for digital data collection and processing in the microprobe laboratory, most compositional mapping is still carried out with an analog procedure that is little changed from the “dot mapping” or “area scanning” technique described by Cosslett and Duncumb in 1956 [1]. The dot mapping procedure can be summarized as follows: (1) As in conventional scanning electron imaging, the beam on the cathode ray tube (CRT) is scanned in synchronism with the beam on the specimen. (2) When the beam is at a particular position on the specimen and an x-ray photon is detected with either a wavelength-dispersive (WDS) or an energy dispersive spectrometer (EDS), the corresponding beam location on the CRT is marked by adjusting the current to excite the phosphor to full brightness. (3) The white dots produced on the CRT display are continuously recorded by photographing the screen to produce the dot map.

Uncertainties in electron probe microanalysis

We determined uncertainties for WDS-EPMA (wavelength-dispersive X-ray spectroscopy – electron probe microanalysis) data using the globally accepted ISO/GUM (International Standards Organization/Guide to the Expression of Uncertainty in Measurement). For each calculation, such as the current drift correction and deadtime correction that precede the calculation of a k-value (net corrected X-ray counts of unknown/net corrected X-ray counts of standard), uncertainties were calculated from contributing factors and combined until a final combined standard uncertainty for the k-value was calculated. Our example used data from the analysis of the Ge Lα X-ray line in a SiGe alloy. Additional contributions to uncertainties in EPMA results, such as the matrix correction procedure and mass absorption coefficients (MACs) are considered. All statistical calculations used in the process of arriving at the combined uncertainty are included, and the basic steps of the ISO/GUM are described.

Growth of Epitaxial BaTiO 3 Thin Films at 600°C by Metalorganic Chemical Vapor Deposition

Presented at Ferroelectric thin films IV : symposium held November 29-December 2, 1994, Boston, Massachusetts, U.S.A.

Characterization of SiGe films for use as a National Institute of Standards and Technology Microanalysis Reference Material (RM 8905).

Bulk silicon-germanium (SiGe) alloys and two SiGe thick films (4 and 5 microm) on Si wafers were tested with the electron probe microanalyzer (EPMA) using wavelength dispersive spectrometers (WDS) for heterogeneity and composition for use as reference materials needed by the microelectronics industry. One alloy with a nominal composition of Si0.86Ge0.14 and the two thick films with nominal compositions of Si0.90Ge0.10 and Si0.75Ge0.25 on Si, evaluated for micro- and macroheterogeneity, will make good microanalysis reference materials with an overall expanded heterogeneity uncertainty of 1.1% relative or less for Ge. The bulk Ge composition in the Si0.86Ge0.14 alloy was determined to be 30.228% mass fraction Ge with an expanded uncertainty of the mean of 0.195% mass fraction. The thick films were quantified with WDS-EPMA using both the Si0.86Ge0.14 alloy and element wafers as reference materials. The Ge concentration was determined to be 22.80% mass fraction with an expanded uncertainty of the mean of 0.12% mass fraction for the Si0.90Ge0.10 wafer and 43.66% mass fraction for the Si0.75Ge0.25 wafer with an expanded uncertainty of the mean of 0.25% mass fraction. The two thick SiGe films will be issued as National Institute of Standards and Technology Reference Materials (RM 8905).

Heterogeneity Evaluation of Research Materials for Microanalysis Standards Certification

Electron microprobe testing and evaluation procedures to determine the extent of within- and between-specimen heterogeneity of reference materials and the experimental uncertainty are described. These procedures have been developed and used at NIST in the certification of several NIST Standard Reference Materials (SRMs). In this article, they have been simplified and updated for general use. Suggestions for experimental testing of specimens are described and a detailed description of the statistical evaluation process is included with an example of a data spreadsheet and instructions for its preparation.