Thickness Of Transition Layer Research Articles

Improvement of the SiO 2/Si interface characteristics by two-step deposition with intermediate plasma treatment using N 2/He or O 2/He gas

Two-step deposition using O 2/He or N 2/He intermediate plasma treatment was studied to improve the characteristics of SiO 2/Si interfaces. Under this method plasma damage on the Si surface could be minimized and the interface characteristics such as intermediate oxidation states, causing P b center, and V fb shift could be improved. In the case of the intermediate plasma treatment on 6 nm 1st oxide, the improvement of the interface characteristics was best. N 2/He plasma intermediate treatment showed better interface characteristics than O 2/He plasma treatment. The number of Si atoms (N SiO x ) in the sub-oxide region was decreased by approximately 27% after N 2/He plasma intermediate treatment compared with the sample without plasma treatment. Also, the transition layer thickness was decreased to 1.34 monolayers. P b center density decreased from 4.7×10 12/eV cm 2 to 2.29×10 11/eV cm 2 due to nitrogen incorporation in the transition region. The moderate nitrogen incorporation near the SiO 2/Si interface reduced the V fb shift due to the decrease in the fixed oxide charge.

High-quality cBN thin films prepared by plasma chemical vapor deposition with time-dependent biasing technique

Cubic boron nitride thin films were deposited on silicon (111) wafers by inductively coupled plasma-enhanced chemical vapor deposition. The influences of Ar flow rate and the time-dependent substrate biasing condition on the composition and the transition layer's thickness of cBN films were systematically investigated. By using the time-dependent biasing technique, with decreasing the substrate bias voltage gradually from sputtering mode to a final appropriate value for cBN deposition mode, 600 nm thick high quality and stoichiometric cBN films consisting of more than 98% cubic phase were successfully deposited with the deposition rate of 1.5 nm/s. The transition layer consisted of an amorphous layer and a turbostratic boron nitride layer that could be reduced less than 10 nm, which proved that, by using proper deposition technique, high-quality cBN films similar to those prepared by physical vapor deposition methods can be prepared even by chemical vapor deposition.

Electron-Irradiation-Induced Amorphization in Mo/Si Nano-Multilayer Material

In the Mo–Si system, there are three typical intermetallic compounds. In order to get insight into the phase stability under irradiation, interface structure and non-equilibrium phase formation in multilayer materials with several nanometers scale were investigated by means of high-voltage electron microscope. The initial structure was composed of crystalline Mo and amorphous Si layers, and transition layer existed at the interfaces. The thickness of transition layers is thicker at the Mo-on-Si than at the Si-on-Mo interface. While those structures were basically stable after thermal annealing up to 773 K, two types of amorphous layers developed during electron irradiation at room temperature: one is an amorphous-Si layer and the other is a Mo–Si mixing layer. And the radiation-induced amorphization was accompanied by anomalous shrinkage in the thickness of layers. It is suggested that those phenomena are related to non-equilibrium phase formation and biased diffusion process during irradiation.

Plasma-Enhanced Chemical Vapor Deposition of High Quality Cubic BN Films with an Intermediate Layer of Turbostratic BN Thinner than 3 nm

ABSTRACTCubic boron nitride (cBN) thin films were deposited on silicon wafers by low-pressure inductively coupled plasma-enhanced chemical vapor deposition (ICP-CVD). By using special substrate pre-treatment processes including positive biasing treatment in H2 plasma or 1200 K pre-heating in H2 atmosphere followed by an N2 plasma treatment, turbostratic BN (tBN) intermediate layer was revealed to directly grow on Si substrates without an initial amorphous layer. The thickness of the tBN transition layer can be reduced to less than 3 nm.

Penetration of electronic states from silicon substrate into silicon oxide

The depth profiling of O 1s energy loss in silicon oxide near the SiO 2/Si interface was performed using extremely small probing depth. As a result, the energy loss of O 1s photoelectrons with threshold energy of 3.5 eV was found. This value of 3.5 eV is much smaller than the SiO 2 bandgap of 9.0 eV, but quite close to direct interband transition at Γ point in energy band structure of silicon. This can be explained by considering the penetration of electronic states from silicon substrate into silicon oxide up to 0.6 nm from the interface. In addition, the penetrating depth is larger than the thickness of the compositional transition layer.

The use of preliminary ion implantation and heating on the substrate for modifying TiN coating properties and TiN/substrate interface

The influence of preliminary implantation of argon ions on a carbon steel substrate and deposition temperature on the texture and adhesion of TiN coatings deposited by cathodic arc plasma deposition has been investigated. The samples have been evaluated by glancing X-ray diffraction, Auger-electron spectroscopy and scratch adhesion testing. Strengthening of the (220) TiN texture with increasing ion implantation dose on the substrate has been revealed. An increment of deposition temperature (from 450 up to 720 K) leads to a more chaotic orientation of TiN crystallites. An increase of transitional layer thickness (by 60% for the Ti profile) is only observed when depositing the coating at high temperature (720 K). However, both the preliminary implantation process and the heating of the substrate lead to an adhesion improvement of TiN coatings.

Initial oxidation process on Si(001) studied by high-resolution Rutherford backscattering spectroscopy

We have observed the initial oxidation process on Si(001) at $20\char21{}700\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ in ${10}^{\ensuremath{-}7}\char21{}{10}^{\ensuremath{-}4}$ Torr ${\mathrm{O}}_{2}$ pressure by high-resolution Rutherford backscattering spectroscopy. The oxygen coverage saturates at $1.45\ifmmode\pm\else\textpm\fi{}0.2$ ML (1 $\mathrm{ML}=6.78\ifmmode\times\else\texttimes\fi{}{10}^{14}$ ${\mathrm{cm}}^{\ensuremath{-}2})$ and $2.3\ifmmode\pm\else\textpm\fi{}0.3$ ML at room temperature (RT) and $640\ifmmode^\circ\else\textdegree\fi{}\mathrm{C},$ respectively. The oxidation of the second layer is found to start before the first layer oxidation is completed even at RT. Further oxidation proceeds basically in the layer-by-layer mode, although there is a compositional transition layer of sub-nm thickness in the interface.

Oxide thinning percolation statistical model for soft breakdown in ultrathin gate oxides

An existing cell-based percolation model with parameter correlation can find its potential applications in assessing soft-breakdown (BD) statistics as long as the oxide thinning due to the localized physical damage near the SiO2/Si interface is accounted for. The resulting model is expressed explicitly with the critical trap number per cell nBD and the remaining oxide thickness tox′ both as parameters. Reproduction of time-to-bimodal (soft- and hard-) breakdown statistical data from 3.3-nm-thick gate-oxide samples yields nBD of 3 and 4 for soft and hard breakdown, respectively. The extracted tox′ of 1.0 nm for soft breakdown, plus the transition layer thickness of 0.5 nm in the model, is fairly comparable with literature values from current–voltage fitting. The dimension and area of the localized physically damaged region or percolation path (cell) are quantified as well. Based on the work, the origins of soft and hard breakdown are clarified in the following: (i) soft breakdown behaves intrinsically as hard breakdown, that is, they share the same defect (neutral trap) generation process and follow Poisson random statistics; (ii) both are independent events corresponding to different tox′ requirements; and (iii) hard breakdown takes place in a certain path located differently from that for the first soft breakdown.

SAXS examination of the water evaporation process from silica materials coated with a polysaccharide–polyimine copolymer layer

We present small-angle X-ray scattering (SAXS) studies of the water evaporation process from controlled porosity glass (CPG) coated with a polysaccharide–polyimine copolymers layer. The comparison of SAXS data with power law scattering and the level of scattering intensity for the material from which water is evaporated shows that SAXS is useful in defining a stage of evaporation or its degree. The results show the applicability of the SAXS method regarding the observation of changes in the thickness of the surface polymer layer during water evaporation. The possibility of estimating the polymer transition layer thickness in dried and wetted samples is an additional advantage of the SAXS method employment in the investigation of polymer–porous material systems.

Vibrational spectra of a plasma-polymerized coating on the surface of a silicon single crystal

The composition and structure of plasma-polymerized coatings on the surface of a silicon single crystal are studied using methods of mass spectrometry and vibrational spectroscopy. It is established that the coating on the side of the surface is a set of ordered and unordered regions of branched chains of halogenocarbons and halogenohydrocarbons. A significant thickness of the coating-substrate transition layer contains silicon carbide and nitrogen dissolved in carbon. A great bulk of the coating is made up of amorphous carbon. The coating mass contains adsorbed gases that block reactive centers. Consideration is given to the special features of recording of vibrational spectra, the coating structure, its differences over the depth, the structural difference between the coating and a polymer film, and aging of the polymer material.

Evaluation of Interface SiOx Transition Layer in Ultrathin SiO2 Film by Oscillatory Tunneling Current-Voltage Characteristics in Photo-CVD SiO2-Si Diode

The interface transition layer in ultrathin SiO2 film is characterized by analyzing the oscillatory tunneling current. SiO2 thin films are deposited on atomically flat Si at low temperature (300°C) by photo-induced chemical vapor deposition (photo-CVD) and their electrical characteristics are investigated. The electrical characteristics of the SiO2/Si diode are improved by annealing in O2 atmosphere under ultraviolet irradiation, and the current becomes small and equivalent to that of a thermally grown oxide. Tunneling current through the ultrathin gate oxide is observed to exhibit oscillatory behavior in the Fowler-Nordheim (FN) tunneling region, which results from the interference of the incident and reflected electron waves at the SiO2/Si interface. It is clarified from theoretical calculation of the tunneling current that the amplitude and phase of the oscillatory current are strongly affected by the transition layer thickness. It is concluded that the interface transition layer of photo-CVD SiO2 film is thinner than that of thermally grown SiO2 film from analysis of the amplitude of the oscillatory profile.

Asymptotic derivation of the glued-wetting-layer model and contact-angle condition for Stranski-Krastanow islands

We derive a generic mathematical model for Stranski-Krastanow island morphologies in strained solid films. We show that a class of boundary-layer transition models for the material properties across the film/substrate interface reduce to the ``glued-wetting-layer'' model in the limit of small transition-layer thickness. Our results provide an explicit derivation of the zero-contact angle condition for Stranski-Krastanow islands with isotropic properties. The glued-wetting-layer model is used to calculate a typical Stranski-Krastanow morphology and these results are combined with a specific boundary-layer transition model to determine a detailed solution for the wetting layer and the corner region. A consequence of our results is the equivalence of Stranski-Krastanow morphologies calculated from boundary-layer models in the limit of vanishing boundary-layer thickness.

Surface area investigation of materials with transition layers of continuously changing electron density

The paper examines the comparison of the surface areas of siliceous materials with the surface polymer layer, measured by means of SAXS and BET methods. The investigated materials possessed the transition layer at the air–surface polymer layer interface border in which the electron density changes in a continuous manner. The results show that the equation [ I( q)= k 1/ q+ k 2/ q 3] gives SAXS surface areas comparable with those from BET measurements. However, the former are lower. In addition, the difference between them depends on the transition layer thickness, as well as on the composition of the surface polymer layer. In case of the surface area investigation of rigid materials with soft surface polymer layer and not sharply defined interface border, the SAXS method seems to be more convenient than the BET one due to the low temperature (−196°C) during BET measurements.

Crustal Structure of the Baltic Shield Along the Pechenga–Kostomuksha–Lovisa Geotraverse

Results of geologic and geophysical modeling are presented, based on detailed seismic studies along two profiles—Pechenga-Kostomuksha and Lieksa-Lovisa. Density, geothermal, magnetic, and geoelectric models were obtained from the interpretations of various geophysical fields and correlated with the reference seismic sections. All the models were combined in order to compile a geologic-geophysical crustal section. The crustal thickness along the Pechenga-Kostomuksha-Lovisa geotraverse varies from 38 to 65 km. Two anomalous structures have been observed that are referred to as the Belomorian-Karelian and Ladoga-Bothnian zones. These zones are characterized by enhanced values of magnetic fields, presence of seismic foci and wave attenuation, and variation of the depth and magnitude of modern crustal movements. These zones are distinguished by the discontinuity M reconstruction, an increase in transitional layer thickness (to 25 km) at the base of the crust, and an increase in depth down to the discontinuity M (50 to 65 km). On average, the crust is thinner (40 km) in the ancient part of the shield than in the younger Svecofennian province (45 km). The velocity differences also are important: for example, the crust of the ancient shield is characterized by lower velocities and the transitional high-velocity layer is absent or thinner. The Karelian granite-greenstone area (a fragment of the Archean craton) has the most simple and balanced deep structure. Within the Karelian area, the layers are nearly horizontal and their thickness is rather constant. The northeastern part of a fragment of the Murmansk block has similar crustal characteristics within the Kola area, where it has undergone Early Proterozoic deformation. Geological and geophysical data for the Pechenga-Varzuga zone suggests that there was intracontinental rifting and a subsequent construction regime during the Svecofennian orogeny that involved a considerable part of the shield. The deep-crustal structure is more complicated to the south. An increase in volume of material with the properties of granulites and basic rocks is observed in the upper crust. The rocks form an inclined alternation of high-density and high-velocity plates and lenses. The packet of tectonic clustering of supracrustal rocks is most conspicuous in the Lapland-Kolvitsa granulite belt. The packet thickness does not exceed 13 km.

Optical and electronic characterization of transition layer in thin film Au-GaAs Schottky barrier

The possibility of determination of optical parameters and thickness of interfacial oxide (IO) layer by multiple-angle-of-incidence (MAI) ellipsometry has been studied for Au-IO-GaAs structures with different oxide thickness. The films parameters have been calculated by the original program of inverse ellipsometric problem solution. Parameters of oxide layer have been determined both for free GaAs surface and for that covered by Au film. Gold film was prepared by vacuum evaporation on the heated n-n+GaAs substrate. Its parameters have been determined by MAI ellipsometry and transparency measurements of Au-quartz satellite system. The investigation showed the change of optical parameters of GaAs oxide layer after the Au evaporation. In the assumption of invariable thickness of IO layer its optical parameters are : n = 1.0±0.1, k = 0.4 ÷ 0.6. The mechanism of current transport and electrical parameters of Au-IO-GaAs structures have been determined from I-V and C-V characteristics of Schottky diodes. The results of the determination of transition layer thickness to its dielectric constant ratio (d\\εi)) from electrical characteristics of barrier also indicate its difference from initial parameters of oxide layer probably due to interdiffusion of Au, Ga, and As.

Determination of the transition region thickness in polymer blends by the SAXS method

The width of domain boundaries is an important parameter for the characterization of microphase separation in polymers. This parameter is often obtained by measurements of small-angle X-ray scattering (SAXS) in the range of validity of Porod's law, according to which X-ray intensity scattered by an ideal two-phase system decreases with the scattering vector h as h-4. Here h is defined as h = (4π sin)/λ, where is half the scattering angle and λ the wave-length of the X-ray. If the interface boundary is diffuse, i.e. the electron density does not change stepwise between separated phases but changes continuously in certain transition regions with a finite thickness, the intensity of scattering decreases more rapidly than predicted by Porod's law. In the present paper we have used the SAXS method in order to determine the supermolecular structure parameters, including the transition layer thickness, of polypropylene/polyamide-6 (PP/PA) blends. The transition layer thickness has been obtained by two methods elaborated by Koberstein and co-workers [4] and by Ruland [1], respectively. Both these methods assume that changes of the electron density in the transition region can be described by a Gaussian function with a standard deviation σ. The parameter σ have been determined graphically from the appropriate plots. Then, the thickness of the phase boundary, E, was estimated as √12σ. The investigated PP/ PA blends are multiphase systems and the problem of determination of the boundary width is more complicated because the meaning of Porod's law must be considered with caution. This problem is discussed based on a wide range of investigated samples prepared over various pressure and crystallization temperature conditions.

The slender solar tachocline: a magnetic model

AbstractA model for the sharp transition from differential rotation in the solar convection zone to rigid rotation in the radiative interior is presented. Differential rotation in the radiative zone is shown to be quenched efficiently by an internal magnetic field. The poloidal field amplitude, B0, is the input parameter for our model which determines the transition layer thickness and the toroidal field strength. It is illustrated analytically and confirmed numerically that a rather small field, B0 = 10−4 Gauss, suffices to satisfy the helioseismological restrictions on the depth of the differential rotation penetration below the convection zone. The transition layer thickness decreases further with increasing B0. The toroidal field amplitude B ≃ 200 Gauss is almost independent of B0.

On exciton luminescence of ZnO/Al 2O 3 epitaxial thin films

Exciton luminescence of non-doped and newly prepared gallium-doped ZnO epitaxial thin films deposited onto sapphire substrates in a low-pressure system within a single chemical vapor deposition cycle is studied depending on films thickness as well as the doping degree. It is shown that the thickness dependence of the ratio between the integral intensities of single-phonon and double-phonon lines allows one to estimate the transition layer thickness.

Microstructural features of dissimilar MMC/AISI 304 stainless steel friction joints

The microstructure and mechanical properties of dissimilar friction joints between aluminium-based MMC and AISI 304 stainless steel base materials were investigated. The microstructural features which occur in the stainless steel substrate comprise deformation twinning, formation of a fine-grained dislocation substructure in austenite, and plastic deformation. The stainless steel substrate was plastically deformed in the region close to the mid-radius of the dissimilar joint. In a similar manner, 5–10 μm thick transition layers, comprising regions of locally plasticized MMC-base material, were formed close to the mid-radius location in dissimilar joints. The interlayer formed at the dissimilar joint interface comprised a mixture of oxide (Fe(Al,Cr)2O4 or FeO(Al,Cr)2O3) and FeAl3 intermetallic phases. The notch tensile strength of dissimilar MMC/AISI 304 stainless steel joints increased when the rotational speed increased from 500 r.p.m. to 1000 r.p.m., and at higher rotation speeds, there was no effect on notch tensile strength properties.

The influence of the Ti intermediate layer on TiN coated on an iron substrate by plasma-enhanced magnetron sputtering ion plating

The influence of the titanium intermediate layer on the TiN coatings achieved by plasma-enchanced magnetron sputtering ion plating has been studied by means of Auger electron spectroscopy and transmission electron microscopy. The results indicate that there exists a transition layer of thickness 50 nm in the interface between the coating and substrate. It was also found that there are crystallographic orientations among α-Fe, FeTi, α-Ti, Ti 2N and TiN.