A novel deep submicron SiGe-on-insulator (SGOI) MOSFET with modified channel band energy for electrical performance improvement

In this paper, we present the unique features exhibited by a novel nanoscale SiGe-on-insulator metal-oxide-semiconductor field-effect transistor (MOSFET) with modified channel band energy. The key idea in this work is to modify the band energy in the channel for improving electrical performances. Graded Ge composition profile is employed in the channel that leads to call the proposed structure as GC-SGOI structure. Using two-dimensional two-carrier simulation we demonstrate that the GC-SGOI structure has higher saturation velocity in comparison with stepped (SC-SGOI) and uniform (UC-SGOI) germanium composition due to the high conduction and valence bands slopes by using graded Ge composition profile. Also, our results show that the GC-SGOI exhibit excellent properties not only higher mobility, drain current and saturation velocity but also hot electron degradation improvement and better reliability. Therefore, refer to the results, the GC-SGOI structure has superior performances in comparison with the SC- and UC-SGOI structures which leads to be a good candidate for VLSI circuits.     

A Short and Efficient Synthesis of Novel N-(2,3-dihydro-2-oxo-5-phenyl-1 H -1,4-benzodiazepin-3-yl)-2-carboxamides

 Several novel N-(2,3-dihydro-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl)-2-carboxamides were prepared by acyl coupling of 2-aminobenzophenones with α-(benzotriazol-1-yl)-N-acylglycines followed by displacement of the benzotriazole ring with ammonia and cyclization of the resulting monoacyl aminals. In addition to high yields and shorter reaction sequences due to avoiding deprotection and acylation of the protected 3-amino-1,4-benzodiazepin-2-one intermediates, the present approach did not involve the use of toxic and odoriferous materials as is the case with other methods.     

A vertical heat pipe: an experimental and statistical study of the thermal performance in the presence of low-frequency vibrations

New experimental results present the effects of low-frequency vibrations in a vertical heat pipe. The thermal resistance was investigated under different heat transfer rates, filling ratios and frequencies, increase of which improved the thermal performance. The vibrations were effective 33.83 % on the performance, and the best performance was estimated using the L16 array of Taguchi method, and it was achieved with the thermal resistance 0.064 K/W in the frequency 30 Hz.     

Combined effects of holes and winglets on chevron plate-fins to enhance the performance of a plate-fin heat exchanger working with nanofluid

ABSTRACT

The current work reports an experimental study on hydrothermal improvement in a chevron plate-fin heat exchanger combined with holes and winglets. The experiments are performed for water flow through a test square duct fitted with enhanced chevron plate-fins for the Reynolds number from 4000 to 10000. Characteristics of the enhanced chevron plate-fins include three waviness aspect ratios and four different arrangements of holes and winglets at a constant diameter of holes and width/height of winglets. An overall performance factor is applied to obtain the optimal geometry. Then, only the optimal geometries are applied to find out the effect of Al₂O₃/water nanofluid flow on the performance of a plate-fin heat exchanger. In comparison to simple chevron plate-fins, the enhanced ones would increase the Nusselt number by a factor between 1.05% and 1.6%. In addition, simultaneous application of the optimal enhanced chevron plate-fins and the nanofluid could increase the Nusselt number. The best working conditions of this system are detected for the nanofluid at a weight fraction of 0.3%.     

Exact Solutions of the Equilibrium Shape Equations in a General WLC Model for DNA Forms

In this letter,we are going to use a geometrical approach to describe the free energy of DNA structures.The exact solutions of the equilibrium shape equations in a general WLC model for DNA forms by using the Feoli's formalism [A.Feoli,et al.,Nucl.Phys.B 705(2005) 577] are studied.Then,the free energy of transition between Band Z-DNA is calculated in this formalism.     

Dual material insulator SOI-LDMOSFET: A novel device for self-heating effect improvement

The silicon-on-insulator (SOI) power devices show good electrical performance but they suffer from inherent self-heating effect (SHE), which limits their operation at high current levels. The SHE effect is because of low thermal conductivity of the buried oxide layer. In this paper we propose a novel silicon on insulator lateral double diffused MOSFET (SOI-LDMOSFET) where the buried insulator layer under the active region consists of two materials in order to decrease the SHE. The proposed structure is called dual material buried insulator SOI-LDMOSFET (DM-SOI). Using two-dimensional and two-carrier device simulation, we demonstrate that the heat dissipation and the SHE can be improved in a conventional SOI-LDMOSFET by replacement of the buried oxide with dual material buried insulator (silicon nitride and silicon oxide) beneath the active region. The heat generated in the active silicon layer can be flowed through the buried silicon nitride layer to the silicon substrate easily due to high thermal conductivity of silicon nitride. Furthermore, the channel temperature is reduced, negative drain current slope is mitigated and electron and hole mobility is increased during high-temperature operation. The simulated results show that silicon nitride is a suitable alternative to silicon dioxide as a buried insulator in SOI structures, and has better performance in high temperature.     

Phonon‐polariton entrapment in homogenous surface phonon cavities

Surface phonon cavities that are homogenous in both mechanical and dielectric properties are reported. The cavities are formed by the placement of a defect of a single domain within periodic domain inversion of single crystal piezoelectric lithium niobate that exhibits surface phononic bandgap through the phonon‐polariton coupling. Surface cavity resonances are observed within the bandgap, which manifest in entrapment of phonon‐polariton within the defect. In addition to demonstrating that the observed resonances are non‐radiative and decoupled to bulk radiation, which is critical for high Q cavities, it is also shown the possibility to tune the surface cavity resonance spectra simply by varying the defect width. Such an ability to excite surface cavity resonance that is non‐radiative with simultaneous localization of the electric field together with the advantage of a cavity that is physically formed from a completely monolithic and uniform material offers unique opportunities for widespread applications for example in actuation, detection, and phonon lasing that can be fully integrated with other physical systems such as quantum acoustics, photonics, and microfluidics.

     

Red luminescence from potassium feldspar for dating applications: a study of some properties relevant for dating

Aspects of the red thermoluminescence (RTL) and IR (833±5 nm) stimulated red (λ_emission=600–750 nm) luminescence (orange-red IRSL) of potassium feldspar from different origins are described. Anomalous fading of RTL (300–500°C) from a selection of potassium feldspar samples was tested. High temperature RTL (300–450°C) exhibits less anomalous fading in comparison to UV luminescence, for the samples under study. The result supports the contention of Zink and Visocekas (1997) that the red TL emission from feldspar does not fade. It was found that RTL is bleachable due to IR exposure, and the relationship between RTL lost and orange-red IRSL produced is linear. It is shown that around one third of the trapped charge responsible for the orange-red IRSL signal gives rise to an RTL signal, indicating that some traps and luminescence centres are shared for RTL and orange-red IRSL.

Specific characteristics of orange-red IRSL from feldspar were identified. It was found that the orange-red IRSL decay curve is bleachable by IR and daylight and can be described by the sum of three exponential components. Orange-red IRSL fading was tested. Short-term storage tests (up to 2 weeks) showed no fading. Longer-term (ca. months) storage of orange-red IRSL do in fact indicate fading, though at levels considerably lower than for the UV emission. The contradictory result is possibly due to the detection wavelength. As such, it is highly likely that the long-term fading experiment is strongly influenced by the feldspar emission centred at ca. 570 nm, which exhibits anomalous fading, while the short-term fading experiment is more greatly influenced by the far red emission centred at ca. 710 nm that in comparison to UV emission shows no or less fading.     

The effect of carrier gas flow on structural and optical properties of TiO2 nanowires

Optical properties and photoluminescence of TiO₂ nanowires, synthesized by two-step thermal evaporation process, under different Ar gas flow as carrier have been studied. The gas flow was varied from 50 to 150 sccm in order to find the optimum gas flow to growth TiO₂ nanowires. As evidenced by X-ray diffraction patterns, our synthesized nanowires, were found to be crystalline rutile TiO₂. Our results indicated a convenient gas flow for controlling diameter size of nanowires was about 100 sccm. In this case, diameters and lengths were, respectively, within the ranges of 40–100 and 400–1800 nm. The experimental data of the reflectance of TiO₂ nanowires have been obtained through using spectrometer of wavelength 250–800 nm that has been indicated reflectance decreasing with increasing the gas flow, due to the scattering from the surface of the nanowires and also an increase in voids’ roughness. Under excitation 370 nm, the TiO₂ nanowires can emit light peaked at 435 nm. It is believed that peak 435 may be due to free excitons emission.