Segregation Layer Research Articles

Impact of Segregation Layer on Scalability and Analog/RF Performance of Nanoscale Schottky Barrier SOI MOSFET

In this paper, the impact of segregation layer density (NDSL) and length (LDSL) on scalability and analog/RF performance of dopant-segregated Schottky barrier (DSSB) SOI MOSFET has been investigated in sub-30 nm regime. It has been found that, although by increasing the NDSL the increased off-state leakage, short-channel effects and the parasitic capacitances limits the scalability, the reduced Schottky barrier width at source-to-channel interface improves the analog/RF figures of merit of this device. Moreover, although by reducing the LDSL the increased voltage drop across the underlap length reduces the drive current, the increased effective channel length improves the scalability of this device. Further, the gain-bandwidth product in a commonsource amplifier based on optimized DSSB SOI MOSFET has improved by ~40% over an amplifier based on raised source/drain ultrathin-body SOI MOSFET. Thus, optimizing NDSL and LDSL of DSSB SOI MOSFET makes it a suitable candidate for future nanoscale analog/RF circuits

Interface Stress-Induced Degradation of the Performance of Electrically Conductive Adhesives

Electrically conductive adhesives are of increasing importance as a powerful alternative to eutectic bonding. In the use of electrically conductive adhesives in soldering applications, a lack of conductivity of the adhesive bond between surface mounted devices (SMD) and the printed circuit board was frequently observed. This lack of conductivity caused failure of the unit because of an unacceptable series resistivity in the circuit. A failure analysis proved that the resistance of the contact between the adhesive and device depends on the stress situation in the bonded interface induced by the shrinkage of the adhesive during curing. Under stress, the formation of a resin segregation layer of low conductivity results. The outer shape of the electrical component as well as the SMD assembly process has strong influence on the electrical performance.

In situ atomic force microscopy studies of reversible light-induced switching of surface roughness and adhesion in azobenzene-containing PMMA films

Thin films in the range 40–80 nm of a blend of PMMA with an azobenzene derivative have been studied directly during UV and blue light irradiation by atomic force microscopy (AFM), revealing highly reversible changes in the surface roughness and the film adhesion. UV light induces an ≈80% increase in surface roughness, whereas illumination by blue light completely reverses these changes. Based on the observed surface topography and transition kinetics a reversible mass flow mechanisms is suggested, where the polarity changes upon switching trigger a wetting-dewetting transition in a surface segregation layer of the chromophore. Similar AFM measurements of the pull-off force indicate a decrease upon UV and an increase after blue light illumination with a complex kinetic behavior: a rapid initial change, attributed to the change in the cis isomer fraction of the azobenzene derivative, and a more gradual change, indicative of slow structural reorganization.

Grain Boundary Segregation and Amount of Bulk Carbides in Severely Deformed Fe–C Alloys

The microstructure, phase composition, Mössbauer spectra, grain boundary segregation and magnetic properties of binary Fe–C alloys with carbon concentration of 0.05, 0.10, 0.20, 0.25, 0.45, 0.60, 1.3, 1.5 and 1.7 wt. % were studied in the as-cast state, after a long annealing at 725°C and after high-pressure torsion (HPT) at the ambient temperature and 5 GPa with 5 anvil rotations (shear strain about 6). The grain size after HPT was in the nanometer range. Only Fe3C (cementite) and -Fe remain in the alloys after HPT. It was also shown that the less stable Hägg carbide (Fe5C2) and retained austenite disappear, and phase composition closely approaches the equilibrium corresponding to the HPT temperature and pressure. Measurements of saturation magnetization and Mössbauer effect reveal that the amount of cementite decreases after HPT. The reason for partial cementite dissolution is the formation of the carbon-rich segregation layers in the ferrite grain boundaries.

Effects of Low Frequency Electromagnetic Field on Segregation Layer during Hot-Top Casting of Aluminium Alloy

Surface segregation layer are frequently encountered during aluminium alloy direct chill casting process, and the removal of the surface segregation layer before further processing of the ingot decreases the ingot yield. In this work, the low frequency electromagnetic field was applied to study the effects of low frequency electromagnetic field on segregation layer during the direct chill casting process. The results show that under the effect of the low frequency electromagnetic field, the surface quality of ingot is improved, the structure of the ingot is refined, and the thickness of segregation layer is decreased.

Research on Friction and Wear Properties of Annealed 5052 Al-Mg Alloy

At annealing temperature, Al-Mg alloys have grain boundary and surface magnesium segregation and their strength are also impossibly enhanced by heat treatment. Friction and wear properties of cold-rolled 5052 aluminum alloy annealed at different temperature were studied in this paper. X-ray diffract analysis(XRD) indicates that metallurgical phase has no obvious transformation with different annealing temperature. Auger electron (AE) fines that magnesium segregation and oxide layer thickness of surface are different along the plate thickness direction at different annealing temperatures. Results show that the higher oxide layer of the surface, the smaller wear can be got. Friction and wear testing shows that 5052 aluminum alloy annealed at different temperatures almost have the same coefficient of friction under the same experimental condition , but the coefficient friction of the same sample will increase while temperature rises.

Chemical Trend of Schottky-Barrier Change by Segregation Layers at Metal/Si Interfaces: First-Principles Study

Chemical trend of segregation-induced Schottky-barrier modulation and the stability of segregation layers are studied for Au/Si interfaces, using the first-principles calculations. The Schottky barrier for electrons monotonously decreases as increasing the valency of segregated atoms. This variation is shown closely related to how the Si atoms are terminated at the interface.

Ferromagnetic properties of the Mn-doped nanograined ZnO films

Dense nanograined pure and Mn-doped Zn1−xMnxO polycrystals with x ranging between 0.1–34 at. % were synthesized by the wet chemistry method from butanoate precursors. Pure and Mn-doped ZnO possesses ferromagnetic properties only if the ratio of grain boundary (GB) area to grain volume sGB exceeds a certain threshold value sth. The polycrystals in this work satisfy these conditions and, therefore, reveal ferromagnetic properties. The observed dependence of saturation magnetization on the Mn concentration shows an unexpected nonmonotonous behavior. The increase in saturation magnetization at low Mn concentration is explained by the injection of divalent Mn2+ ions and charge carriers into pure ZnO. The decrease in saturation magnetization between 0.1 and 5 at. % Mn can be explained by the increase in the portion of Mn3+ and Mn4+ ions. The second increase in saturation magnetization above 5 at. % Mn is explained by the formation of multilayer Mn segregation layer in ZnO GBs. The shape of the dependence of saturation magnetization on Mn concentration is different for the Mn-doped nanograined ZnO manufactured by different methods. It is most probably controlled by the topology of GB network (ferromagnetic GB foam) in the ZnO polycrystals.

Twinning-induced kinking of Sb-doped ZnO nanowires

Sb-doped ZnO nanowires with kinking structures have been synthesizedby a catalyst-free thermal evaporation method with the addition ofSb2O3. Transmission electron microscopy (TEM) observations revealed that the kinks of thenanowires are induced by twinning structures. , twins and heavy stacking faults in the (0001) plane were observed in these kinkednanowires. High-resolution TEM and energy dispersive x-ray spectroscopy showed thatthere exists an Sb-rich segregation layer in the twin boundaries of some nanowires. Aformation mechanism of the kinked nanowires was proposed. The optical property of thesynthesized nanowires was investigated by room-temperature photoluminescence.

Chemical Trend of Schottky-Barrier Change by Segregation Layers at Metal/Si Interfaces: First-Principles Study

not Available.

Dopant-segregated Schottky barrier MOSFETs with an insulated dielectric oxide

An insulated dielectric oxide (IDO) is presented for the dopant-segregated Schottky barrier MOSFETs (DS-SBMOS) to suppress the unwanted on- and off-state leakage currents in short-channel DS-SBMOS. The effects of the IDO on DS-SBMOS are investigated using two-dimensional device simulations. Although the dopant segregation technique can efficiently modify a Schottky barrier to improve Schottky barrier MOSFETs, the performance of scaled DS-SBMOS suffers from degraded short-channel behavior and ambipolar conduction from the extension of a heavily doped segregation layer. With sidewall IDO insulators between the heavily doped N+ segregation layer and P+ halo region, band-to-band and ambipolar leakage currents are simultaneously minimized. Thus, an optimal halo can be utilized to control the short-channel effect without any constraints in problematic leakage currents. Using the IDO architecture, DS-SBMOS can be successfully scaled as a promising candidate for next-generation CMOS devices.

EFFECT OF HIGH MAGNETIC FIELD ON THE TRANSITION BEHAVIOR OF Cu–RICH PARTICLES IN Cu–80%Pb HYPERMONOTECTIC ALLOY

将含有大量富Cu颗粒的Cu-80%Pb（质量分数）过偏晶合金在强磁场作用下进行不同温度的保温实验,研究了富Cu颗粒在液固混合区的迁移行为.结果表明,无磁场作用时,富Cu颗粒在800℃以上出现迁移而上浮,900℃以上在试样顶部形成致密的富Cu分层,颗粒尺寸及迁移速率随温度升高而增加;富Cu颗粒在迁移过程中可通过热化长大或合并,其机制与富Cu液滴不同;富Cu颗粒群整体向上迁移,颗粒区与枝晶区有明显边界,颗粒间相互作用可使其迁移速率降低.强磁场具有降低颗粒迁移速度,抑制颗粒熟化及合并的作用,降低了富Cu颗粒的偏析程度,抑制致密富Cu分层的形成.考虑颗粒间相互作用,对有无磁场作用下颗粒所受的作用力和运动终端速度进行了分析和计算.

Study on the Microstructure of Micro Laser Welded Joint of TiNi Shape Memory Alloy Sheet

Butt welding of 0.2mm thick TiNi shape memory alloy sheet was successfully realized by using micro impulse laser whose average power is 80W and the microstructure of welded joint was study in this paper. The results show that, the welded joint of micro laser welding can be divided into four zones according to grain size and microstructure. The microstructure in base metal zone is rolled structure and the grains are coarse and heterogeneous. The microstructures of welded seam center zone are fine equiaxed crystals and the microstructures of both lower surface and upper surface edge zone are columnar crystals. There is almost no obvious coarse grain heat-affected zone at the edge between welded seam and base metal. There is obvious segregation layer in local area of welded seam because the content of Ti and Ni elements is changed and different with base metal during the crystallizing course of welding pool.

10.1007/s11453-008-1010-4

Formation of InSb quantum dots grown in an InAs matrix by molecular-beam epitaxy that does not involve forced deposition of InSb is studied. Detection of intensity oscillations in the reflection of high-energy electron diffraction patterns was used to study in situ the kinetics of the formation of InSb quantum dots and an InAsSb wetting layer. The effects of the substrate temperature, the shutter operation sequence, and the introduction of growth interruptions on the properties of the array of InSb quantum dots are examined. Introduction of a growth interruption immediately after completing the exposure of the InAs surface to the antimony flux leads to a reduction in the nominal thickness of InSb and to an enhancement in the uniformity of the quantum-dot array. It is shown that, in the case of deposition of submonolayer-thickness InSb/InAs quantum dots, the segregation layer of InAsSb plays the role of the wetting layer. The Sb segregation length and segregation ratio, as well as their temperature dependences, are determined.

On The Formation of Extruded Surface Segregation Layer in Aluminum Direct Chill Casting Process

The aim of this research work was to develop a mathematical model to study the formation of extruded surface segregation phenomenon during the early stages of solidification in an aluminum direct chill casting process. The mathematical analyses contain a one dimensional mathematical model of heat flow, solidification, interdendritic strain and macrosegregation. Some typical cases in conventional direct chill casting processes related to increase surface segregation and fluctuation in macrosegregation with distance from the ingot surface were simulated. Good agreement was found by previous measurements and simulated results. Model results were discussed to explain the effects of different thermal solidification factors and interdendritic strain on the extruded surface segregation layer phenomenon. The results show that this phenomenon is sensitive to alloy composition and forms in the gap between the ingot surface and mould wall. Also, the model results point out that this phenomenon appears as a direct effect of the extrusion mechanism of interdendritic solute liquid associated with the interdendritic strain distribution in the coherent region in the mushy zone.

The Influence of Liquid Surface Segregation on the Pitting Corrosion Behavior of Semi-Solid Metal High Pressure Die Cast Alloy F357

Semi-solid metal processing results in liquid segregation at the surface of the components. The pitting behavior of this surface layer of semi-solid metal processed alloy F357 was compared with the centre (or bulk) of cast plates in 3.5% NaCl aqueous solution. It is shown that pitting attack occurs preferentially in the eutectic regions at the interface between silicon particles and the alpha phase in the eutectic. Since the surface liquid segregation layer consists of mainly eutectic, this makes semi-solid metal processed components specially susceptible to pitting corrosion attack.

Characterization of Arsenic segregation at Si/SiO 2 interface by 3D atom probe tomography

Dopant loss due to the segregation and dopant pile up at the Si/SiO 2 interface are crucial phenomena in the scaling trend of MOSFET devices for the 22-nm technology node. Arsenic segregation and pile-up at the Si/SiO 2 interface have been studied by the atom probe tomography (APT) technique which allows the 3D observation and the chemical analyses of dopant distribution with the atomic scale resolution. Arsenic (10 16 at/cm², 32 keV) was implanted in mono-crystalline silicon and then annealed at 900 °C for 6 h after a cleaning step and an oxide growing. The thickness of the segregation layer was determined at 2.3 nm containing 9.36 × 10 14 at/cm² dose of segregated arsenic. Finally, the obtained arsenic segregated dose has been compared to the resistivity profile performed by spreading resistance profiling technique.

Antiferromagnetic iridium-manganese intermediate layers for perpendicular recording media (invited)

Current generation of cobalt-oxide-based perpendicular magnetic recording media uses single or dual ruthenium intermediate layers in order to grow crystallographically textured, and magnetically isolated granular media. In this work, the potential advantages of an antiferromagnetic iridium-manganese intermediate layer directly under the recording layer are highlighted. Owing to its close lattice matching with hexagonal cobalt, iridium-manganese which has the L12, or AuCu3-type crystal structure, can support the heteroepitaxial growth of the cobalt-based recording layer. In one of the media schemes described here, (111) textured iridium-manganese thin film was grown on 7.5 nm thick ruthenium layer. On the iridium-manganese as segregation layer, the Co-oxide-based magnetic recording layer showed perpendicular texture with Δθ50 below 4°, coercivity of over 4000 Oe alongside magnetic exchange decoupling, average grain sizes of 6 nm with distributions under 14%, and improved thermal stability. Measurements of the anisotropy constant did not show any significant change and even an IrMn capping layer was observed to improve the thermal stability. The possible mechanisms through which the IrMn layer could affect the thermal stability are hypothesized. The initial layers of the magnetic recording layer on IrMn segregation layers also showed exchange-decoupled and segregated grains, which is unlike that observed on Ru segregation layers. In a second media scheme, (111) textured iridium-manganese thin film was grown on a crystalline soft magnetic underlayer belonging on top of amorphous soft underlayers. In this scheme, partial pinning of the soft underlayer due to exchange-bias interaction with the IrMn layer was observed. This scheme offers the possibility to reduce the intermediate layer thickness, thus improve media writability, and with further optimization, could potentially facilitate the approach toward 1 Tbits/in.2.

Device considerations and design optimizations for dopant segregated Schottky barrier MOSFETs

This work thoroughly explores the considerations and optimizations of dopant segregated Schottky barrier MOSFETs (DS-SBMOS) using two-dimensional device simulations. The dependences of the device characteristics on the dopant segregated layer are clarified in the DS-SBMOS. The heavier and wider dopant segregation layer efficiently modifies the Schottky barriers to suppress the off-state ambipolar conduction and simultaneously to enhance the on-state driving current. However, DS-SBMOS devices have slightly worse short-channel effects than conventional MOSFETs, because of additional segregation extensions into the silicon substrate. Importantly, apparent degradations of DS-SBMOS in ambipolar conduction are observed when a thinner gate-insulator or a heavier halo profile is used for the scaled short-channel DS-SBMOS. Dual workfunction gate (DWG) architecture is first proposed to optimize DS-SBMOS by tailoring Schottky barrier distributions through vertical gate engineering. An optimal design of DS-SBMOS devices can be achieved using the DWG structure with enhanced driving current, minimized ambipolar conduction and a suitable short-channel effect as the gate-insulator is scaled down.

Fe–C nanograined alloys obtained by high-pressure torsion: Structure and magnetic properties

The microstructure, phase composition, Mössbauer spectra and magnetic properties of nine binary Fe–C alloys with carbon concentrations between 0.05 and 1.7 wt.% were studied in the as-cast state, after a long annealing at 725 °C and after high-pressure torsion (HPT) at ambient temperature and 5 GPa with five anvil rotations (shear strain about 6). The grain size after HPT was in the nanometer range. Only Fe 3C (cementite) and α-Fe remain in the alloys after HPT. It was also shown that the less stable Hägg carbide (Fe 5C 2) and retained austenite disappear, and phase composition closely approaches the equilibrium corresponding to the HPT temperature and pressure. Measurements of saturation magnetization and Mössbauer effect reveal that the amount of cementite decreases after HPT. The reason for partial cementite dissolution is the formation of the carbon-rich segregation layers in the ferrite grain boundaries.