Interfacial reactions in Mo-Zr multilayer structure: an X-ray reflectivity study

The effect of elevated temperature on the structural stability and alloy formation in Mo-Zr multilayers is investigated. Mo-Zr multilayers deposited by the electron beam evaporation technique under ultra-high vacuum conditions are annealed up to 650 °C. The changes induced due to thermal treatment are observed using X-ray reflectivity (both specular and off-specular) and X-ray diffraction techniques. The Mo-Zr multilayers remained as an insoluble layered structure even after annealing as revealed from X-ray reflectivity measurements. The interfacial roughness is found to be very similar at all interfaces and decreases on annealing. The multilayer structure remains intact on annealing with expansion of the multilayer period and a marginal increase in X-ray reflectivity.     

Dielectric properties of sol–gel synthesized SrTiO3/(Ba0.7Sr0.3)TiO3 and SrTiO3/Ba(Zr0.3Ti0.7)O3 thin film heterostructures

The paper presents synthesis of Ba_0.7Sr_0.3TiO₃ (BST), BaZr_0.3Ti_0.7O₃ (BZT) and SrTiO₃ (ST) thin films and their heterostructures using modified Pechini method. The La_0.7Sr_0.3MnO₃ has been used as a conducting bottom layer to form metal ferroelectric metal capacitor. The thin films are spin coated on SiO₂/n-Si(100) substrates. The thin films thus deposited are characterized for crystal structure, morphology, dielectric, complex impedance and admittance properties. Deposition of surface layer ST is observed to reduce loss tangent tan δ of BST and BZT thin films, still maintaining equivalent magnitude of figure of merit γ. The results on dielectric properties are analyzed in terms of the Maxwell–Wagner model and Koop’s phenomenological theory.     

Effect of 200 MeV Ag ion irradiation on structural and electrical transport properties of Fe3O4 thin films

Thin films of Fe₃O₄ have been deposited on single crystal MgO(1 0 0) and Si(1 0 0) substrates using pulsed laser deposition. Films grown on MgO substrate are epitaxial with c-axis orientation whereas, films on Si substrate are highly 〈1 1 1〉 oriented. Film thicknesses are 150 nm. These films have been irradiated with 200 MeV Ag ions. We study the effect of the irradiation on structural and electrical transport properties of these films. The fluence value of irradiation has been varied in the range of 5 × 10¹⁰ ions/cm² to 1 × 10¹² ions/cm². We compare the irradiation induced modifications on various physical properties between the c-axis oriented epitaxial film and non epitaxial but 〈1 1 1〉 oriented film. The pristine film on Si substrate shows Verwey transition (T_V) close to 125 K, which is higher than generally observed in single crystals (121 K). After the irradiation with the 5 × 10¹⁰ ions/cm² fluence value, T_V shifts to 122 K, closer to the single crystal value. However, with the higher fluence (1 × 10¹² ions/cm²) irradiation, T_V again shifts to 125 K.     

Irradiation induced texturing in the Mg0.95Mn0.05Fe2O4 ferrite thin film

We present a study on the effect of swift heavy ions irradiation on the structural and magnetic properties of Mg_0.95Mn_0.05Fe₂O₄ ferrite thin film grown by pulsed laser deposition technique. X-ray diffraction (XRD) pattern of the as-deposited film reveals a cubic spinel structure with an intermediate phase of α-Fe₂O₃. This impurity phase completely dissolves upon irradiation with 200 MeV Ag¹⁵⁺-ions and it exhibits a strong crystallographic texture along the (440) plane. The magnetization values start increasing systematically with irradiation at lower fluence values, whereas decrease for higher one. This decrease in magnetic signal can be attributed to partial amorphization caused by irradiation in agreement with XRD and atomic/magnetic force microscopic images.     

Microstructural study of iron nitride thin films deposited by ion beam sputtering

An amorphous iron nitride thin film was deposited using reactive ion beam sputtering of iron by a beam of argon and nitrogen ions. Nitrogen content in the film as determined from conversion electron Mössbauer spectroscopy (CEMS) and X-ray photoelectron spectroscopy (XPS) was FeN_0.7. The mass density of the film was calculated using energy-dispersive X-ray reflectivity (EDXRR) measurements and is found to be 6.0 gm/cm³. CEMS shows that the film is nonmagnetic in nature. Morphology of the film is obtained from atomic force microscopy (AFM). The surface roughness of the film does not increase appreciably beyond that of the substrate even after a deposition of 131 nm of material with these qualities the film is a good candidate for the multilayer superstructure of a nuclear Bragg monochromator of the type ⁵⁶FeN_0.7/⁵⁷FeN_0.7.     

Cyclic oxidation behavior of some plasma-sprayed coatings in Na2SO4-60%V2O5 environment

Cyclic oxidation behavior of plasma-sprayed NiCrAlY, Ni-20Cr, Ni₃Al, and Stellite-6 coatings was investigated in an aggressive environment of Na₂SO₄-60%V₂O₅ by thermogravimetric techniques for 50 cycles. These coatings were deposited on a Ni-base superalloy, namely Superni 600; 10Fe-15.5Cr-0.5Mn-0.2C-Bal Ni (wt.%). X-ray diffraction, scanning electron microscopy/energy dispersive x-ray (SEM/EDX), and electron probe microanalyzer (EPMA) techniques were used to analyze the oxidation products. The uncoated superalloy suffered accelerated oxidation in the form of intense spallation of its oxide scale. After deposition of the NiCrAlY coating, the superalloy showed a minimum mass gain, whereas after application of the Stellite-6 coating, a maximum mass gain was observed among the coatings studied. All of the coatings were found to be useful in reducing the spallation of the substrate superalloy. Moreover, the coatings were successful in maintaining continuous surface contact with the base superalloy during the cyclic oxidation. The phases revealed for the oxidized coatings were mainly the oxides of chromium and/or aluminum and the spinels containing nickel-chromium/cobalt-chromium/nickel-aluminum mixed oxides, which are reported to be protective against high-temperature oxidation/hot corrosion.     

睡莲（优秀奖）

1.睡莲方案 一个设计的初始概念通常很简单，但又往往是最纯粹的。本设计的最初意向一睡莲即是如此。睡莲象征着纯净与和谐。它们生长在水中，花朵向着太阳。     

Synthesis and characterization of Ba0.7Sr0.3TiO3, BaZr0.3Ti0.7O3 thin film heterostructures

The paper presents synthesis of Ba_0.7Sr_0.3TiO₃ (BST), Ba_0.7Sr_0.3TiO₃ (BZT) thin films and BZT/BST heterostructures using modified Pechini method. The La_0.7Sr_0.3MnO₃ has been used as a conducting bottom layer to form metal ferroelectric metal capacitor. The thin films are spin coated on SiO₂/n-Si (100) substrates. The thin films thus deposited are characterized for crystal structure, morphology, dielectric and complex impedance properties. The results show that BZT/BST heterostructures show reduced loss tangent tan δ and useful value of figure of merit γ in RF range of frequencies. The results on dielectric properties could be analyzed in terms of the Maxwell–Wagner Model and contribution due to superlattice effects.