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Key engineering materials
Trans Tech Publications Ltd.
Key engineering materials

Trans Tech Publications Ltd.

半月刊

1013-9826

Key engineering materials/Journal Key engineering materials
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    Charge Transport Mechanism and the Effects of Device Temperature on Electrical Parameters of Au/ZnPc/N-Si Structures

    A. HussainP. AkhterA.S. Bhatti
    P.372-380页
    查看更多>>摘要：Gold/Zinc Phthalocyanine/n-Si metal semiconductor contact with organic interfacial layer have been developed and characterized by Current-Voltage-Temperature (I-V-T) measurements, to study its junction and charge transport properties. The junction parameters, of diode ideality factor (n), barrier height (φ_b) and series resistance (R_S), of the device are found to shift with device temperature. The barrier height and the diode ideality factor are found to increase and the series resistance is found to decrease with increasing device temperature. The activation energy of the charge carriers is found to be 44 meV and the peak of interface state energy distribution curves is found to shift in terms of Ess-Ev value from 0.582 eV to 0.776 eV with increasing device temperature. The data analysis implies that the Fermi level of the organic interfacial layer shifts as function of device temperature by 100 meV in the device temperature range of 283K to 343K. In terms of dominant conduction mechanism, the I-V-T data analysis confirms the fit of data to the relationship log (IV~4) ∝ V~(1/2) for higher device temperatures and the Poole-Frenkel type is found to be the dominant conduction mechanism for the hybrid device.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Comparative Study for the Design of Optimal Composite Pressure Vessels

    A.M. ButtS.W. ul Haq
    P.381-388页
    查看更多>>摘要：Composite pressure vessels require special design attention to the dome region because of the varying wind angles generated using the filament winding process. Geometric variations in the dome region cause the fiber to change angels and thickness and hence offer difficulty to acquire a constant stress profile (isotensoid). Therefore a dome contour which allows an isotensoid behavior is the required structure. Two design methods to generate dome profiles for similar dome openings were investigated namely Netting Analysis and Optimal Design method. Both methods assume that loads are carried by the fiber alone (monotropic) ignoring the complete composite behavior. Former method produced a lower dome internal volume and a higher fiber thickness as compared to the later optimal design method when studied against different normalized dome opening radiuses. The optimal dome contour was studied in ANSYS with a trial design. The dome was considered to have transversely isotropic property with a dome contour based on monotropic model. While investigating the dome with non linear large displacement finite element analysis, the dome still exhibited isotensoid behavior with transverse isotropic material assignment. Elliptic integrals were used to generate the optimal dome contours and hence elliptic dome contours were formed which were isotensoid in nature with complete composite representation.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Advanced Reading

    P.389-392页
    查看更多>>摘要：Abrasive technologies are central to modern manufacturing as applied to a wide variety of products covering many disciplines: from nanoscale components to large-scale equipment, and from biomedical devices to aerospace structures.This special issue brings together the latest advances in, and applications of, abrasive technologies. It comprises 122 selected peer-reviewed technical and review articles, and covers a broad range of research topics including: design, fabrication, truing and dressing of grinding wheels, precision grinding, abrasive-jet processing, lapping, honing, polishing and non-conventional finishing, semiconductor processing, micro/nano- machining, fabrication and forming, advanced machining and rock-cutting technologies, tribology in manufacturing, process monitoring and measurement, and other novel techniques and advanced studies related to abrasive technologies.
      原文链接:
    • NETL
    • NSTL

    DLTS Studies of Al Diffused n-Si

    S. SiddiqueM.M. AsimF. SaleemiS. Naseem...
    P.393-397页
    查看更多>>摘要：We have studied the electrical properties of Si p-n junction diodes by deep level transient spectroscopy (DLTS) measurements. The p-n junctions were developed on a Phosphorus doped Si by depositing A1 and annealing at various temperatures. In order to confirm junction formation, current-voltage and capacitance-voltage measurements were made. Two deep levels at E_c-0.17 eV (E1) and E_c-0.44 eV (E2) were observed in the DLTS spectrum. These traps have been characterized by their capture cross-section, activation energy level and trap density. On the basis of these parameters, level E1 can be assigned as V-O complex and E2 as P-V complex. These traps are related to the growth of n-Si wafer and not due to A1 diffusion.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    MOCVD Grown Quantum Dot-in-a-Well Solar Cells

    A. MajidL. FuC. JagadishH. Tan...
    P.398-403页
    查看更多>>摘要：This paper reports the experimental work on the characterization of quantum dot-in-well (DWELL) solar cell grown by metal-organic chemical vapor deposition (MOCVD) without employing any post-growing optimization like antireflection coating and metal grid. The structure of the 10-layer DWELL solar cells is studied by cross-sectional transmission electron microscopy (TEM). Room temperature photoluminescence (PL) spectra show strong quantization at 1178.5 nm with a linewidth of 79.9 nm. External quantum efficiency spectra show enhancement in the spectral response of the photocurrent with respect to the reference quantum dot cell (without DWELL structure). In spite of the reduction in conversion efficiency due to poor collection of current in external circuit compared to reference quantum dot cell it show the improvement in open circuit voltage.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Germanium Quantum Dot Sensitized TiO_2 Solar Cells

    M. AbbasB. AliS.I. ShahP. Akhter...
    P.404-414页
    查看更多>>摘要：The size of Germanium (Ge) Quantum Dots (GQD's) in Titanium Dioxide (TiO_2) can be tailored, using different techniques like sputtering, laser ablation and sol gel. Similarly the absorption range of Ge may also be broadened in visible and NIR range. We report the use of Ge QD's to sensitize meso-porous TiO_2 film to make quantum dot sensitized solar cells (QDSSC) for the next generation photovoltaics. Ge -TiO_2 nano-porous thin films were deposited using rf- planer magnetron sputtering using various ranges of rf-power, Argon pressure and substrate temperature. The fabricated films with various Ge concentrations were studied using X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), High Angle Annular Dark Field Imaging (HAADF) and UV-Visible Spectroscopy (UV-VIS).In the thin film meso-structure the Ge dots were embedded in the TiO_2 matrix. The average particle size of Ge quantum dots was determined by HAADF. The solar cell performance has been checked using sun simulator. Experimental ways to improve cell performance are discussed.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Influence of Atmospheric Annealing on the Conductivity of Mn-Doped PZT Ceramics

    M. ShuaibD.A. Hall
    P.415-421页
    查看更多>>摘要：Conductivity measurements were carried out on Mn-doped PZT ceramics in order to investigate the changes in defect chemistry with annealing, by identifying the charge carriers such as lead or oxygen vacancies. PZT compositions were prepared by sol-gel method in rhombohedral region Pb(Zr_(0.56)Ti_(0.44))O_3 with Mn contents 0.4, 0.8, 1.5 and 2 wt.%. Nano-sized powder (～21nm) was obtained after calcination and bulk density values of > 98% were achieved upon sintering. It was found that nitrogen annealing reduced the electrical conductivity strongly as compared to oxygen and air annealing and the possible charge carriers were single ionised oxygen vacancies V_O~· along with V_O~(··) and V_(pb)~(//)acancies.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Development of Perovskite based Ceramics for Ultrasonic Applications

    M. KhalidM. ShuaibA.A. Khan
    P.422-430页
    查看更多>>摘要：Perovskite crystal structure is found in many ionic solids like CaTiO_3, BaTiO_3 and PZTs. In this structure off-center position of cations in oxygen octahedral causes polarization and produces direct and indirect piezoelectric responses in ceramic materials that are suitable for many ultrasonic applications. Lead Zirconate Titanate (PZT) with formulae Pb_(0.91)Sr_(0.09)(Zr_(0.53)Ti_(0.47))O_3 was prepared by conventional mixed oxide route with an objective to achieve dense piezoelectric sintered components exhibiting adequate properties for sonar applications. Dielectric and ferroelectric/piezoelectric properties of PZT are strongly influenced by composition, homogeneity and porosity in the densified part. To achieve the objective of a good homogenous and dense body, the initial powders and the final product were characterized by SEM equipped with EDX, XRD and Particle Size Analyzer during each processing step. Electrical characterization was carried out by LCR meter and Transducer Analyzer. Planetary Mill instead of a conventional ball mill was employed for initial mixing and grinding of calcined powder. Properties achieved by sintering at 1200℃ for 2 hours in lead rich atmosphere were Dielectric Cosntant (K) = 1440, Tangent Loss (Tanδ) = 0.0062, Charge Coefficient(d_(33)) = 335 pC/N, Coupling Coefficient (k) = 0.37 and density = 7.55 g/cm~3. After sintering the observed grain size was 2-3 μm with clean grain boundaries. To ascertain the effects of accelerated ageing on dielectric and piezoelectric properties, final product was first heated at 50℃ for 5 days and then at 100℃ for 3 days. The results showed that dielectric and piezoelectric properties were stabilized to a large extent by heating at 100℃ for 3 days. The ageing data for 9% Sr doped PZT is not reported earlier, therefore, it would help in great deal in predicting the performance of component in service.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Finite Element Based Design of Piezoelectric Vibration Damper

    J.S. BhattiR.A. Pasha
    P.431-437页
    查看更多>>摘要：Vibration control using combination of piezoelectric material and electrical circuits can remove the vibration energy from the host structure. The need for passive damping techniques arises to avoid the complexities and energy requirements associated with other vibration control techniques. Passive damping technique for reduction of vibration of structures by introduction of shunted piezoelectric patch is presented in this study. Finite element analysis is performed for a cantilever beam with shunted piezoelectric patch on it. The prediction of the model is validated against experimental published results. The obtained results demonstrate the feasibility of using piezoelectric patches with passive shunting as effective means for damping out the vibrations. The aim of this research work is the advancement of the coupled field analysis for structural vibration control with advanced methodology and to promote the design and analysis activities in the field of passive vibration control techniques using smart structures. Results obtained showed up to 86% reduction in the amplitude of the host structure which shows good agreement with published experimental results.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Effects of Material Properties on Soft Contact Dynamics

    A. KhurshidA. GhafoorM.A. Malik
    P.438-444页
    查看更多>>摘要：The superiority of deformable human fingertips as compared to hard robot gripper fingers for grasping and manipulation has led to a number of investigations with robot hands employing elastomers or materials such as fluids or powders beneath a membrane at the fingertips. In this paper, to analyze the stability of dynamic control of an object grasped between two soft fingertips through a soft interface using the viscoelastic material between the manipulating fingers and a manipulated object is modeled through bond graph method (BGM). The fingers are made viscoelastic by using springs and dampers. Detailed bond graph modeling (BGM) of the contact phenomenon with two soft-finger contacts considered to be placed against each other on the opposite sides of the grasped object as is generally the case in a manufacturing environment is presented. The stiffness of the springs is exploited in order to achieve the stability in the soft-grasping which includes friction between the soft finger contact surfaces and the object, The paper also analyses stability of dynamic control through a soft interface between a manipulating finger and a manipulated object. It is shown in the paper that the system stability depends on the viscoelastic material properties of the soft interface. Method of root locus is used to analyze this phenomenon.The paper shows how the weight of the object coming downward is controlled by the friction between the fingers and the object during the application of contact forces by varying the damping and the stiffness in the soft finger.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd