Composition Of Interface Layer Research Articles

A Review of Bonding Immiscible Mg/Steel Dissimilar Metals.

The challenge of joining immiscible Mg/Steel dissimilar metals lies in the absence of an Fe-Mg intermetallic or Fe-Mg solid solution in an Mg-Fe system, and differences in their physical and chemical properties. Promoting interfacial reaction and regulating the composition of interface layer are beneficial for the formation of an Mg/steel interface layer and to obtain an effective Mg/steel joint. This research work focusses on the bonding of immiscible Mg/steel dissimilar metals: First, an Mg/steel interface layer was designed by controlling the composition of added alloy elements and trace elements in the base metal. Second, the Mg/steel dissimilar metals welding methods were divided into three parts—solid state welding, welding-brazing and fusion welding. The main distinctions between them were difference in interfacial temperature, thickness of interface layer, and type of compound. Third, the orientation relationships (OR) of the Mg/interface layer system and the interface layer/steel system was investigated. In this review, the effect of welding processing parameters, addition of alloy elements, base metal, and different welding methods on the joint’s performance was studied. The mechanical property, microstructure, interface layer and metallurgical reactions of the joint were also examined. The most recent progress in joining immiscible Mg/Steel dissimilar metals and future research prospects are presented at the end of the paper.

Morphology of thick film metallization on aluminum nitride ceramics and composition of interface layer

Surface metallization of aluminum nitride is performed by a reactively thick film method. A layer of copper film is deposited on the surface of AlN ceramics. The morphology and composition of the metalized copper layer on ceramic substrate were investigated via scanning electron microscope (SEM) and X-ray diffraction (XRD). The interface layer between copper film and AlN substrate was examined through SEM, XRD and EDS. Reaction phases, Cu2O and intermediate phases (CuAlO2 and CuAl2O4), were detected at the interface layer. Subsequently, the formation process of these phases at the interface layer was discussed. And consequently, the relation within reaction phases and bonding strength was observed. Reaction phases play a key role in increasing bonding strength. The effect of these phases such as Cu2O and intermediate phases (CuAlO2 and CuAl2O4) on the mechanical property was discussed. Results show that the presence of Cu2O particles are detrimental to bonding strength. However, spinel CuAl2O4 and isolated CuAlO2 laminates at the interface layer can increase the bonding strength. The experimental results suggest that this thick film method is a useful technology for various metal-ceramics bonding.

Rutherford Backscattering Spectrometry Analysis of Self-Formed Ti-Rich Interface Layer Growth in Cu(Ti)/Low-k Samples

A new fabrication technique to prepare ultrathin barrier layers for nanoscale Cu wires was proposed in our previous studies. Ti-rich layers formed at Cu(Ti)/dielectric layer interfaces consisted of crystalline TiC or TiSi and amorphous Ti oxides. The primary control factor for the Ti-rich interface layer composition was C concentration in the dielectric layers rather than the formation enthalpy of the Ti compounds. To investigate Ti-rich interface layer growth in Cu(Ti)/dielectric layer samples annealed in ultrahigh vacuum, Rutherford backscattering spectrometry (RBS) was employed in the present study. Ti peaks were obtained only at the interfaces for all samples. Molar amounts of Ti atoms segregated to the interfaces (n) were estimated from Ti peak areas. Log n values were proportional to log t values. Slopes were similar for all samples, suggesting similar growth mechanisms. The activation energy (E) for Ti atoms reacting with the dielectric layers containing carbon (except SiO2) tended to decrease with decreasing C concentration (decreasing k), while those for the SiO2 layers were much higher. Reaction rate coefficients [Z · exp(−E/RT)] were insensitive to C concentration in the dielectric layers. These factors lead to the conclusion that growth of the Ti-rich interface layers is controlled by chemical reactions, represented by the Z and E values, of the Ti atoms with the dielectric layers, although there are a few diffusion processes possible.

Rutherford Backscattering Spectrometry Analysis of Growth Rate and Activation Energy for Self-formed Ti-rich Interface Layers in Cu(Ti)/Low-k Samples

AbstractA new fabrication technique to prepare ultra-thin barrier layers for nano-scale Cu wires was proposed in our previous studies. Ti-rich layers formed at the Cu(Ti)/dielectric-layer interfaces consisted of crystalline TiC or TiSi and amorphous Ti oxides. The primary control factor for Ti-rich interface layer composition was the C concentration in the dielectric layers rather than the formation enthalpy of the Ti compounds. To investigate Ti-rich interface layer growth in Cu(Ti)/dielectric-layer samples annealed in ultra high vacuum, Rutherford Backscattering Spectrometry (RBS) was employed in the present study. Ti peaks were obtained only at the interface for all the samples. Molar amounts of Ti atoms segregated to the interface (n) were estimated from Ti peak areas. Thenvalue was defined byn=Z·exp(-E/RT) · tm, whereZis a preexponential factor andEthe activation energy for the reaction. TheZ,E, andmvalues were estimated from plots of lognvs logtand lognvs 1/T. Themvalues are similar in all the samples. TheEvalues for Ti atoms reacting with the dielectric layers containing carbon (except SiO2) tended to decrease with decreasing C concentration (decreasingk), while reaction rate coefficients (Z·exp(-E/RT)) were insensitive to C concentration in the dielectric layers. These factors lead to conclusion that growth of the Ti-rich interface layers is controlled by chemical reactions of the Ti atoms with the dielectric layers represented by theZandEvalues, rather than diffusion in the Ti-rich interface layers.

Engineering the interface between epitaxial lanthanide oxide thin films and Si substrates: a route towards tuning the electrical properties

The impact of interface layer composition on electrical properties of epitaxial Gd 2O 3 thin films on Si(001) substrates have been investigated. The electrical properties of epitaxial Gd 2O 3 thin films were improved significantly by controlled modification of interface layer composition. The minimum capacitance equivalent thickness estimated for Pt/Gd 2O 3/Si MOS structures was as low as 0.76 nm with leakage current density of 15 mA/cm 2 at ( V g- V FB) = 1 V. The corresponding density of interface states was found to be 2.3*10 12cm −2eV −1. We also find that a change in the interface layer composition significantly alters band alignment of Gd 2O 3 layer with respect to Si substrates.

Influence of interface layer composition on the electrical properties of epitaxial Gd2O3 thin films for high-K application

The authors report on the impact of interface layer composition on electrical properties of epitaxial Gd2O3 thin films on Si(001) substrates. The electrical properties of epitaxial Gd2O3 thin films were improved significantly by controlled modification of interface layer composition. The minimum capacitance equivalent thickness estimated for Pt∕Gd2O3∕Si metal oxide semiconductor structures was as low as 0.76nm with leakage current density of 15mA∕cm2 at (Vg−VFB)=1V. The corresponding density of interface states was found to be 2.3×1012cm−2eV−1. The authors also find that a change in the interface layer composition significantly alters band alignment of Gd2O3 layer with respect to Si substrates.

Electrical and Physical Characterization of Zirconium-Doped Tantalum Oxide Thin Films

Thin films of zirconium-doped tantalum oxide (Zr-doped deposited by reactive sputtering were studied in an effort to replace silicon dioxide as the gate dielectric material for future metal-oxide-semiconductor devices. Influences of process parameters, such as Zr concentration, postdeposition annealing temperature, and film thickness, on the film’s electrical and physical characteristics were investigated. The lightly Zr-doped film (15 nm thick) showed a low current density, e.g., at −1 MV/cm in the accumulation regime. The current conduction mechanism of the Zr-doped films was analyzed and compared with mechanisms of Poole-Frenkel and Schottky emissions. In comparison with pure tantalum oxide and zirconium oxide films, the Zr-doped films had higher dielectric constants. A high-temperature annealing step reduced the film’s hysteresis and fixed charge density. The interface layer composition changed from to zirconium silicate when the Zr concentration in the film was increased. The binding energies of Ta 4f, Zr 3d, and O 1s of the bulk shifted to lower values as the Zr concentration increased due to the charge transfer among elements. In summary, the Zr-doped films showed many advantages over pure and films for the gate dielectric application. © 2004 The Electrochemical Society. All rights reserved.

Engineering the nm-thick Interface Layer Formed Between a High-k Film and Silicon

ABSTRACTThe interface layer between thin sputter-deposited tantalum oxide (TaOx) high-k film and silicon substrate was engineered with the Hf doping method and the insertion of a thin 5Å TaNx interface. The following results have been obtained: 1) the Hf dopant in the TaOx film was involved in the interface formation process, e.g., forming a new, thinner high-k HfSixOy interface layer rather than the SiOx layer, 2) when the TaNx interface was inserted, the interface layer composition was even more complicated, e.g., including TaOxNy and HfSixOy structures. No hafnium nitride or oxynitride was detected, 3) the interface layer structure was changed, e.g., from single-zone to multi-zone with different compositions, 4) when a low concentration of Hf existed in the TaOx film, the high-k dielectric properties, such as the k value, fixed charge density, dielectric strength, were improved, and 5) when the thin TaNx interface layer was inserted, the above electric properties were further improved. However, the fixed charge density and interface states were increased due to the insertion of the TaNx interface layer. These results were contributed by factors such as the charge-trapping characteristics in the interface layer and the some damage repairing mechanisms. In summary, this research proved that the high-k film's interface layer and bulk properties could be were improved with the doping process as well as the insertion of an ultra-thin TaNx interface film.

The growth start on the heterovalent GaAsZnSe interface under Te, Se and Zn termination

To improve the properties of ZnSe related devices grown on GaAs substrates or ZnSeGaAs heterostructures a deeper understanding of the II–VIIII–V interface is necessary. In particular island growth within the first few monolayers will influence the properties of such devices drastically. Because theory predicts an enhanced stability for a special interface layer composition (Kley and Neugebauer, Phys. Rev. B 50 (1993) 8616 [1]), we have varied the starting growth conditions by utilizing Zn, Se or Te termination of the GaAs (100) surface with different coverages. Only the layers grown on TeGaAs which has a coverage of approximately half a monolayer (ML) Te showed a two dimensional (2D) growth start, pseudomorphic growth up to 400 nm, good crystal quality and reproducible electrical behavior. From all this we can conclude that an initial layer with the theoretically proposed coverage should allow growth to remain in the 2D mode and thus result in an improved crystal quality. Further we have shown that it is possible to double the thickness of pseudomorphic layers compared to values reported by other groups using conventional MBE.

Effects of interface stoichiometry on the structural and electronic properties of Ga1−xInxSb/InAs superlattices

We report an investigation of the effects of interface layer composition on the structural and electronic properties of Ga1−xInxSb/InAs superlattices, which are of interest for infrared detector applications. Shutter sequencing during growth of a series of Ga0.75In0.25Sb (8 ML)/InAs (13 ML) superlattices by molecular-beam epitaxy has been employed to select structures with GaInAs-like interfaces, InSb-like interfaces, and intermediate choices of interfacial composition. Comparison of x-ray diffraction scans from the superlattices confirms that a superlattice with GaInAs-like interfaces has a 1.6% smaller average interatomic spacing in the growth direction than a sample with InSb-like interfaces, in near agreement with expected interfacial bond length differences. Hall measurements of intrinsic carrier concentrations at high temperatures indicate an increase in superlattice energy gap when interfaces are switched from InSb-like to GaInAs-like, consistent with intuitive expectations. Low temperature Hall measurements suggest that both the type and the level of background doping in Ga1−xInxSb/InAs superlattices may depend upon interfacial composition.

Simulation of x-ray diffraction intensity variation of W/Si multilayer after annealing

A computer simulation of small-angle diffraction intensities is performed for a W/Si amorphous multilayer structure. The different models which are related to different interface structures after annealing are set up. Calculated results show that the existence of silicide interface layers which induces a change of both direction and magnitude of the diffraction amplitude is not always accompanied by a decrease of the diffraction intensity. In some cases, proper thickness and composition of interface layers may increase the diffraction intensity. However, the existence of systematic and random deviations of layer thicknesses always induces a decrease of x-ray diffraction intensity.