Thin Barium Research Articles

Determination of the stoichiometry and trace impurities in thin barium strontium titanate perovskite layers by inductively coupled plasma-mass spectrometry

The determination of the stoichiometry in semiconducting and non-conducting thin layers is of importance for the study of growth mechanisms and for the control of defects during development and production. An analytical procedure using inductively coupled plasma-mass spectrometry (ICP-MS) was developed, employing different ICP-MS instruments [one double-focusing sector field ICP-MS (DF-ICP-MS) and two quadrupole ICP-MS without and with a hexapole collision cell (ICP-QMS and HEX-ICP-QMS, respectively)] for the determination of the stoichiometry and trace impurities in thin BaxSryTiO3 perovskite films (BST) on silicon substrates after the dissolution of layers. The maximum sensitivity (138Ba+, 1720 MHz ppm−1; 88Sr+, 1330 MHz ppm−1; 48Ti+, 560 MHz ppm−1), lowest detection limit (Ba, 0.004 ng l−1; Sr, 0.007 ng l−1; Ti, 0.08 ng l−1) and best precision down to 0.11% relative standard deviation (RSD, at an analyte concentration of 1 µg l−1) were achieved in DF-ICP-MS. HEX-ICP-QMS yielded a better sensitivity (HEX-ICP-QMS, 100–240 MHz ppm−1; ICP-QMS, 23–50 MHz ppm−1) and lower detection limit (HEX-ICP-QMS, 0.09–3.4 ng l−1; ICP-QMS, 0.8–19 ng l−1) in comparison with conventional ICP-QMS. Precision values of 0.3 and 0.2% RSD were observed for Ba/Sr and (Ba + Sr)/Ti ratios, respectively, by ICP-QMS and HEX-ICP-QMS at an analyte concentration of 10 µg l−1. Besides ICP-MS, inductively coupled plasma-optical emission spectroscopy (ICP-OES) and X-ray fluorescence (XRF) analysis were used for the validation of the experimental results. The stoichiometric compositions measured by different methods are in good agreement taking into account the local inhomogeneity of element distribution in thin layers and the diffusion of elements in the substrate. Due to the high sensitivity of ICP-MS, the determination of 38 trace elements was performed in thin BaxSryTiO3 films (with a thickness less than 60 nm) with detection limits in the low ng g−1 range.

Microstructures in BaTiO 3 thin films by hydrothermal growth and lift-off technique

Barium titanate microstructures with minimum feature sizes of 2.5 μm are fabricated on silicon substrates coated with platinum by a combination of hydrothermal growth and lift-off. Polycrystalline, cubic barium titanate is grown at a temperature of 80°C. Microstructures are obtained by positive and negative patterning processes, where the former leads to the better lift-off results due to the thicker resist layer. The minimum feature size of 2.5 μm refers to the minimum line width and separation between structures. It is limited by the optical lithography used in this work. The resolution of the pattern edges is estimated to be approximately 80 nm and would allow the fabrication of even smaller patterns. Additionally, it is shown that the use of electrochemistry for growth of thin barium titanate films is compatible with lift-off and leads to similar pattern definition.

X-ray and neutron diffraction of yttrium–barium–copper–oxide: Modeling diffraction intensity variations produced by surface leaching

High normal current fluences have long been reported to produce major changes in the x-ray diffraction pattern of YBa2Cu3O7−x (YBCO). These x-ray diffraction effects have now been shown to result from the removal of barium from the YBCO near-surface lattice together with the formation of a thin barium oxide overlayer. Neutron diffraction reveals that the bulk crystallographic structure remains unaltered by charge fluences of more than 40 million C/cm2, and Auger electron spectroscopy confirms the presence of surface barium enrichment.

Domain-Wall Motion under Mechanical Stresses and Giant Piezoresistivity in Thin Barium Titanate Ceramic Bars

Extremely large piezoresistance (stress-sensitive resistance), equivalent to a value of the gage factor (the magnitude of resistance change per strain) of > 107 was observed in single grain boundaries formed in thin semiconducting barium titanate ceramic bars at room temperature. The samples were produced to have a grain structure consisting of single grains joined together in series and a diameter in the range 10-20,um. In this study, observation of ferroelectric domain structures and measurements of resistance were simultaneously carried out for some samples under cyclic mechanical stresses to closer look at the influence of the morphological change of ferroelectric domain structures on the grain boundary resistance in the materials. In a bar sample with a single grain boundary, a 90° domain wall was observed to appear and move from one end of the sample to the other during one cycle of the stress applied. It has been found that the observed large piezoresistance is closely connected with a drastic change of the domain structure in the vicinity of grain boundaries in the samples.

Very thin barium ferrite particles prepared by a novel technique: Ion exchange resin method

Very thin hexagonal barium ferrite particles have been prepared by a new method—ion exchange resin method. The exchanged resin when heated to 850 °C, transformed to the hexagonal ferrite BaFe12O19 as confirmed by x-ray diffraction. These particles show single-domain behavior with average diameter D̄=220 nm, average aspect ratio D̄/t̄=13, specific magnetization σ=71 emu/g and coercivity Hc=3800 Oe.

A Lung Abscess Combined with Mediastinal Air Shadow

A 55-year-old-female was admitted for the evaluation of mass shadow on chest film. She complained of fever, chilling, cough, and whitish sputum. She did not give any history of choking or coughing when she ate. The chest CT showed lung aoocess in right lower lobe with extension of infiltration and air shadow in mediastinum. The esophagoscopy and esophagography were performed to find the cause of mediastinal infiltration, and bronchoesophageal fistula was detected in esophagography. The patient complained of severe chilling and febrile sensation after esophagography, mediastinitis aggravated by thin barium was suggested clinically. So, surgical drainage of lung abscess and thin barium was done urgently. One month after operation, follow-up of esophagoscopy and esophagography were done, the bronchoesophageal fistula was not detected.

X-Ray Diffraction Study of Barium Titanate Thin Films

Sychrotron diffraction study of barium titanate films grown by molecular beam epitaxy method were performed in grazing incidence geometry. Thin barium titanate film with 8 nm thick was psudomorphic nature. Upper part of the film with 40 nm showed that c-axis lay parallel to the substrate surface and in the middle of the film a-axis lay along the surface. The region, where c-axis lies parallel to the substrate, is quite possible to be 90° domain of BT film.

Giant Piezoresistive Effects in Single Grain Boundaries of Semiconducting Barium Titanate Ceramics

Extremely large piezoresistive effects with a gage factor (elastoresistance) of > 1 × 106 in single grain boundaries of thin ceramic bars of semiconducting barium titanate have been observed at room temperature. Thin barium titanate ceramic bars with a diameter in the range of 10 to 20 μm were prepared to consist of single grains joined together in series. Large piezoresistive effects were observed for some of the single grain boundaries in the present samples under compressive stresses, but no distinct piezoresistance was observed in the grain bulk. A giant piezoresistive effect with a gage factor of 3 × 107 was observed for a single grain boundary which exhibited a saw-tooth type PTCR (positive temperature coefficient of resistivity) characteristic with a significantly large bias dependence of it. This demonstrates that the piezoresistive phenomenon may be interpreted in terms of the change of the potential barrier height due to the change of ferroelectric domain morphologies in the vicinity of grain boundaries under mechanical and electric stresses.

Oxygen vacancy mobility determined from current measurements in thin Ba0.5Sr0.5TiO3 films

The current density is measured as a function of time for thin (⩽1000 Å) barium strontium titanate (BST) capacitors with platinum electrodes. The current density curve shows a peak prior to the onset of resistance degradation. The peak position on the time axis varies with applied voltage and temperature. The data are explained by the theory for space-charge-limited (SCL) current transients, and the measured current is identified as ionic current associated with oxygen vacancies. Using the SCL analysis, the mobility of the oxygen vacancies is measured as a function of temperature. The mobility obtained from current measurements is shown to be compatible with the Einstein relation for mobility and diffusivity. In summary, the ionic current associated with oxygen vacancies is shown to be an important component of the measured current in thin BST films.

Phase characterization of dysprosium barium copper oxide thin films grown on strontium titanate by molecular beam epitaxy

X-ray diffraction, transmission electron microscopy, and /ital in/ /ital situ/ reflection high energy electron diffraction studies of thin epitaxial dysprosium barium copper oxide films grown by oxygen plasma molecular beam epitaxy (MBE) on strontium titanate substrates are presented. A remarkable variety of structure is revealed, making clear both the possibilities and challenges for this growth technique as applied to the cuprate superconductors. The films studied are highly epitaxial, obtained through the use of shuttered molecular beams to encourage the layered structure characteristic of superconducting DyBa/sub 2/Cu/sub 3/O/sub 7/minus//ital x// (''123''). While some of these films are superconducting as deposited, more often they are semiconducting or insulating. The 123-like material in these films has a lengthened c-axis, perhaps due to nonstoichiometry. Phases related to DyBa/sub 3/Cu/sub 2/O/sub /ital x// (the other perovskite) are also very important for epitaxial growth, and display a distinctive signature in the RHEED patterns. Other epitaxial impurity phases including BaCuO/sub 2/ and a new orthorhombic phase are also characterized.

Peristalsis in Pharyngeal Constrictor Musculature in Relation to Positioning and Gravity

The motor activity of the pharyngeal constrictors in terms of peristalsis and protrusion depths was studied cineradiographically in 15 non-dysphagic volunteers in three positions: sitting, right decubitus horizontal, and head-down 30 degrees, during swallowing of a 10 ml bolus of thin liquid barium. Using a frame rate of 50/s the speed of peristalsis was calculated by frame counting. The speed of peristalsis and the depth of protrusion of the constrictor wall did not depend on the direction of gravity force in relation to the long axis of the pharynx. Neither the position of the hyoid bone nor its movement during pharyngeal swallowing changed in relation to position and gravity. Pharyngeal activity during swallowing in normal individuals is fairly stable and does not change in relation to gravity.

The radiological demonstration of vessels in embryos and foetuses. Comparative radiological studies of the venous system of the neck, head and brain in domestic animals. Paper 3 (author's transl)

A method was developed for prenatal, post-mortem angiography, post-mortem angiography of the venous system of the brain, head and neck; its development was studied in the embryos and foetuses of 80 cattle, 20 sheep and 20 pigs with a crown-rump lenght of 19 to 155 mm. Radiological and corrosion preparations were studied. The embryonic and foetal venous systems were filled with thin barium sulphate through the umbilical and omphalic veins. The development and transformation of the cerebral veins and sinuses are compared and are related to the corresponding vascular anatomy of the adult animal and to man. The radio-embryological method for demonstrating cerebral vessels is also applicable to live foetuses.

Photoionization of barium clouds via the [formula omitted] metastable levels

The photoionization of optically thin barium clouds is analyzed and shown to occur primarily by a two-step process involving the 3D metastable term as the ntermediate state. The equilibrium populations of the 1D and 3D metastable levels are calculated and found to differ significantly from the values now in the literature. These populations are combined with our newly available photoionization data to calculate the resulting photoionization rate in the upper atmosphere.

Photoemission from thin barium films: V N Lyasnikov and A N Arseneva-Geyl, Uch Zap LGU, No 354, 1970, 30–33 ( in Russian)

Photoemission from thin barium films: V N Lyasnikov and A N Arseneva-Geyl, Uch Zap LGU, No 354, 1970, 30–33 ( in Russian)

Diverticula of colon.

DIvERTicuLA occur in the large bowel and are herniations of the mucous membrane through acquired defects in -the muscular coats-the small pouches being covered by serosa; exicept in the smallest sacs muscle fibres are only found in the neck. When first 'formed the necks are wide and the diverticula globular-later the necks become attenuated and the pouches flask shaped. The appendices epiploicae when heavily fat laden tend to obscure the diverticula. The diverticula iarise between the mesenteric and antimesenteric taeniae near the site of entry of the small perforating vessels, consequently diverticula are not found in the rectum where the longitudinal muscle is complete. The commonest site is the pelvic colon and in many cases is the only part involved. Diverticula in the caecum and ascending colon are rare, tend to be solitary and when inflamed simulate appendicitis. Under 40 years diverticula are uncommon but after the 4th decade 5-10% of adults have diverticulosis. mostly asymptomatic. Painter (1964) has investigated intracolonic pressure in volunteer subjects by means of three open-ended water-filled polythene tubes with metal tips, inserted through a sigmoidoscopethe tips being 3 inches apart from each other. He did not find any intraluminal hypertension in diverticulosis under resting conditions but after injection of morphine, tracings recorded from the immediate vicinity of diverticula showed very high pressures compared with those from normal bowel after morphine. Continuing his investigations with cine-radiography Painter outlined the colon with thin barium injected through one of the polythene tubes; he demonstrated that diverticula are reducible and vary in size according to local pressure in the bowel. Following an injection of morphine the bowel, bearing diverticula, narrowed, the diverticular necks contracted whilst the diverticula enlarged as barium was forced into therm. Colonic movements were generally increased. Jf probanthine was 'then given, this caused paralysis of the bowel muscle, the colon dilated, !the diverticular necks reopened, barium drained back into the relaxed bowel and the intrasigmoid pressure fell. Painter found after morphine the colon in diverticulosis localised pressure by altering the configuration of its wall, as it was seen to 'be segmented in the vicinity of any tip which was recording changes of pressure. The segments were defined by interhaustral contraction rings which narrowed and at times completely occluded the colonic lumen, so the colon functioned as a series of bladders and not as a tube. Very high pressures resulted if one segment, isolated from its fellows, contracted forcibly as its contents could not escape. As segments of colon bearing diverticula produce pressures after morphine differing from those recorded from their neighbours, and from segments of healthy colon, it is possilble that the diseased segments also react excessively to natural stimuli such as eating, drinking and emotion which are known to activate the colon. Painter is uncertain whether this ability of affected segments to behave differently precedes the appearance of diverticulosis and is iesponsible for its causation or whether it is result of the disease. Most probably the differential response is present in the early stages of the disease process and is responsiible for the progressive nature of diverticulosis. The ripple-edge border of the sigmoid colon seen on barium enema examination 'has been regarded as a prediverticular state but Marcus and Watt (1964) consider it indicates established diverticula at an early stage. Bilateral irregularities of contour indicate small but definite diverticula in the lateral .intertaenia areas. When the sawtooth outline is unilateral it is due to diverticula in the antimesenteric intertaenia area.

CINERADIOGRAPHY OF SWALLOWING. OBSERVATION IN PATIENTS WITH LESIONS OF BRAIN STEM, LOWER CRANIAL NERVES, OR BULBAR MUSCULATURE.

The act of swallowing is a complex sequence of anatomical and physiological phenomena, which, although often influenced by neurologic disease, has rarely been studied by neurologists. Detailed manometric studies of esophageal motility have previously been reported in neurologic patients, 1-3 and a variety of abnormalities have been described. The purposes of this communication are to introduce another technique, cinefluorography, for the study of swallowing in neurologic illness and to report and discuss the findings observed in 35 patients. Materials and Methods All observations were performed with the cinefluoroscopic equipment of the Radiology Department. Almost all patients were studied while they stood erect, although a few were investigated while supine or in either lateral decubitus position. Barium paste was utilized as contrast medium, except for patients who were known to aspirate liquids. Thin barium suspensions or meglumine diatrizoate (Gastrografin) were used in these patients. Fluoroscopic observations of swallowing were made of

Preparation and Properties of Thin Barium Titanate Films

Thin films of barium titanate were synthesized by the simultaneous deposition of the barium and titanium oxides evaporated by electron bombardment. The oxides were reacted on a substrate to form barium titanate during deposition. The reaction was carried out in an oxygen atmosphere at a substrate temperature in excess of 600°C. Experiments were performed to determine the range of conditions under which barium titanate was formed during deposition and to evaluate the potential of the films for electronic applications. The thickness of the films was in the range from 0.1 to Iμ. Effects of heat treatment on films deposited at room temperature are given. X‐ray spectroscopy and x‐ray diffraction were used to determine the composition and structure of the films. The maximum dielectric constant at room temperature is 1330, close to the value for polycrystalline barium titanate. Leakage current and frequency dependence of the dielectric properties are given. Films with high structural order show the characteristic phase transition, indicated by a peak in capacitance at 120°C.

Ion Density Measurement in a Barium Plasma by Scattering of Resonance Radiation

A method for measuring local atom or ion densities, based on the scattering of resonance line radiation, is discussed for the case of an optically thin barium plasma confined by a strong magnetic field. The anisotropy of the flux of scattered resonance radiation due to anisotropic illumination and the presence of a magnetic field is examined. Barium ion density measurements on a laboratory plasma are described. It is noteworthy that this method is capable of high spatial resolution, and that light intensity ratio measurements suffice to obtain absolute ion densities. No absolute photometric measurements are required.

Barium enema reduction of gallstone ileus

A recommendation is made for the use of therapeutic colonic and ileal distention with thin barium as a therapeutic measure in a patient presenting with gallstone ileus. Two cases treated successfully by this method are included.

The roentgenologist as a consultant.

The rendition of a signed report to the referring physician is an important part of the practice of diagnostic roentgenology. This report, based upon examination of the patient, presents the findings of the roentgenologist and expresses his medical judgment or diagnosis. Because definite responsibilities have been assumed in the performance of such an examination, no matter how simple it may be, the report should show that these commitments have been honored. What exactly are these responsibilities? In what manner are they best discharged? Evaluation: In most cases the evaluation of an x-ray examination as to suitability, completeness, and technic requires no direct mention by the roentgenologist. This holds true particularly for the simpler and more standardized procedures. Occasionally, however, it is necessary that a statement be included pertaining to one or another of these three conditions any one of which can be of real significance to the patient and the referring physician. In order to pass on the suitability of any examination that the roentgenologist may be called upon to interpret, a clear statement is required from the referring physician as to the information sought or, in other words the purpose of the roentgen study that has been requested. Unless such information is provided, one is unable to determine whether or not the examination chosen was the one best suited to the purpose. If doubt exists in the mind of the referring physician as to the correct x-ray procedure in a particular situation, then a consultation with the roentgenologist is in order. Usually, however, it is simpler if the patient is turned over to the roentgen diagnostician who, being informed of the problem to be answered, is left free to choose the most efficient way to proceed with his work-up. Should it transpire that an inappropriate examination has been carried out, then the report must define its ill conception and state the correct method of approach to the problem. In this manner the patient's interest will be protected and similar errors may be prevented in the future. The second part of the evaluation concerns the presence of any restrictions on the conduct or execution of the roentgen examination. Restrictions which can lead to an examination that is less than complete, may emanate from the referring physician or from the patient himself. Stipulations imposed by the referring physician, although well intended, are often unwise and founded upon commonly held misconceptions. The failure to permit adequate preparation of a patient, the insistence on the use of certain types of radiopaque material, such as “thin barium,” and the rigid designation of technical matters can seriously undermine the usefulness of the roentgen method. To the extent that an x-ray study is compromised in these ways are the chances for a successful result diminished.