449,813 research outputs found
Band Alignment and Electrical Investigations of Ultra-Thin Al2O3 on Si by E-beam Evaporation
No full textThe continuous downscaling leads the search of high-gate dielectrics. The films amorphous in nature offered good mechanical flexibility, smooth surfaces and better uniformity associated with low leakage current density. In this work, 16 nm thick amorphous Al2O3 films on silicon substrate are fabricated by E-beam evaporation. The high value of refractive index (1.76) extracted from ellipsometry analysis directs the deposition of compact film. The AFM analysis reveal a flat surface with small RMS surface roughness 1.5 angstrom. The band gap is extracted from O-1s electron loss spectra and was found 6.7 eV and band alignment of Al2O3/Si is derived from the UPS measurements. The films are incorporated in Metal Insulator -Semiconductor (MIS) capacitor to perform the electrical measurement. The flat band voltage (V-FB), dielectric constant () and oxide trapped charges (Q(ot)) extracted from high frequency (1 MHz) C-V curve are - 0.4 V, 8.4 and 2 x 10(11) cm(-2), respectively. The small flat band voltage - 0.4 V, narrow hysteresis and very little frequency dispersion suggest an exceptional good Al2O3/Si interface with small quantity of trapped charges in the oxide. The leakage current density was 4.27 x 10(-8) A/cm(2) at 1 V. The moderate dielectric constant and low leakage current density with ultra-smooth surface is quite useful towards its application in future CMOS and memory devices
Probing of Barrier Induced Deviations in Current-Voltage Characteristics of Polymer Devices by Impedance Spectroscopy
No full textTemperature dependent current-voltage measurements have been performed on poly(3-methylthiophene) based devices in metal/polymer/metal geometry in temperature range 90-300 K. Space charge limited current (SCLC) controlled by exponentially distributed traps is observed at all the measured temperatures at intermediate voltage range. At higher voltages, trap-free SCLC is observed at 90 K only while slope less than 2 is observed at higher temperatures which is quiet unusual in polymer devices. Impedance measurements were performed at different bias voltages. The unusual behavior observed in current-voltage characteristics is explained by Cole-Cole plot which gives the signature of interface dipole on electrode/polymer interface. Two relaxation mechanisms are obtained from the real part of impedance vs frequency spectra which confirms the interface related phenomena in the devic
Na2Ti6O13 Thin films as Anode for Thin Film Sodium Ion Batteries
No full textThe pulsed laser deposition was employed to produce Na2Ti6O13 (NTO) thin films, which were applied as an anode material for Sodium-Ion batteries (SIBs). X-ray diffraction made it clear that the film is crystalline in single phase. Morphology and elemental composition studies were done using FESEM. Grain size and surface roughness was measured from atomic force microscopy. The electrochemical measurements were performed at 0.5 - 3V range and it exhibited the initial discharge capacity was 49.7 mu Ah/mu m-cm(2) with coulombic efficiency 69.8%
Seminário sobre aquacultura 14 a 16 de dezembro de 1983
No full textA necessidade de desenvolver a aquacultura em Portugal obriga à escolha das espécies mais indicadas para tal finalidade. A propósito o autor chama a atenção para as graves consequências que podem advir das introduções e/ou transferências de animais aquáticos, quer para as espécies locais e meio ambiente, como para a para a saúde pública.Concerning the need to choose the most convenient species to cultivate in order to implement aquaculture in Portugal, the author draws the attention to the deleterious consequences of introductions and transfers of aquatic animals.Caixa Geral de Depósito
Impact of Time-dependent Annealing on TiO2 Films for CMOS application
No full textPost-deposition annealing (PDA) is the inherent part of sol-gel fabrication process to achieve the optimum device performance, especially in CMOS applications. The annealing removes the oxygen vacancies and improves the structural order of dielectric films. The process also reduces the interface related defects and improves the interfacial properties. In this work, we have integrated the sol-gel spin-coating deposited high-TiO2 films in MOS. The films are fired at 400 degrees C for the duration of 20, 40, 60 and 80 min. The thicknesses of the films were found to be of similar to 30 nm using ellipsometry. The (Al/TiO2/p-Si) devices were examined with current-voltage (I-V) and capacitance-voltage (C-V) at room temperature to understand the influence of firing time. The C-V and I-V characteristic showed a significant dependence on annealing time such as variation in dielectric constant and leakage current. The accumulation capacitance (Cox), dielectric constant (kappa) and the equivalent oxide thickness (EOT) of the film fired for 60 min were found to be 458 pF, 33, and 4.25nm, respectively with a low leakage current density (1.09 10(-6) A/cm(2)) fired for 80 min at + 1 V
Nanocomposite Films on Mylar for Temperature Sensing Applications
No full textHere in, we are reporting the fabrication of graphene oxide (GO) Platinum (Pt) nanocomposite films on Mylar substrate for temperature sensor application on the basis of negative temperature coefficient (NTC) resistive element. The nanocomposite was successfully prepared by the solution mixing of GO nanosheets and Pt metal nanoparticles in N-Methyl-2-Pyrrolidone (NMP) using ultra sonication process. It was found that, the as-formed nanocomposite shows the Pt nanoparticles were dispersed no homogeneously on the surface of the GO nanosheets. The as-synthesized GO nanosheets and nanocomposite were characterized by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD) for their surface analysis and structural properties respectively. `file sensing film formation is carried out onto the flexible Mylar membrane for the fabrication of temperature sensor using drop casting method. The thickness of the sensing film is around 50 mu m. As cab be observed that, the resistivity of nanocomposite sensing film decreased with the increase of temperature resulting in NTC behavior. The measured NTC and sensitivity of the sensor were found to be -4.26 x 10(-3) Omega/Omega/K and 1.5231 Omega/K respectively. Therefore, the synthesized graphene oxide-Platinum nanocomposite film is an attractive candidate for making temperature sensors. Since the output is linear with respect to temperature variation, the electronic readout circuitry will be simpler. However, the change of electrical resistance of nanocomposite films can also be used in sensing environmental parameters such as chemical, biological, moisture and mechanical for their gas, glucose, humidity and strain/pressure sensor applications respectively
Na-23 and Si-29 NMR Investigation of Na-SrSiO3 Superior Ion Conductor
No full textPresent work reports the Na-23, Si-29 NMR studies on the Sr0.55Na0.45SiO2.775 along with PXRD and ionic conductivity studies. NMR results indicate that Sr0.55Na0.45SiO2.775 consists of two phases, one being insulating alpha-SrSiO3 and other being a Na+ conducting amorphous Na2Si2O5. High temperature heat treatment of Sr0.55Na0.45SiO2.775 leads to the crystallization of amorphous phase into different polymorphs of Na2Si2O5 phase
Impedance studies on PF6- doped Poly(3,4 ethylenedioxythiophene) Devices
No full textCarrier density, substrate and synthesis temperature dependent impedance measurements have been performed on Poly(3,4-ethylenedioxythiophene) PEDOT] based devices in metal/polymer/metal geometry at room temperature. The relaxation mechanism of carries in these devices can be varied as per the growth condition. It is observed that in stainless steel (SS)/PEDOT/Silver (Ag) devices, as the carrier density decreases the interface related mechanism takes control over bulk transport, but as the synthesis temperature is lowered the bulk transport dominates over interface related mechanism. The substrate dependent studies have shown that the electrode potential can alter the growth of polymer chains, which affects the relaxation mechanism of the carriers
Alluaudite Class of High Voltage Sodium Insertion Materials: An Interplay of Polymorphism and Magnetism
No full textThe research and development with sodium ion batteries has geared up manifold in last one decade, owing to their abundance, non-toxicity, uniform geographical distribution and electrochemical performance complimentary to lithium counterpart. This research often leads to various novel material discoveries such as Na2Fe2(SO4)(3) sodium insertion material, which has recently registered the highest-ever Fe3+/Fe2+ redox potential (3.8 V vs. Na) having excellent cyclability and rate kinetics. This basically belongs to a family of materials-Alluaudites Na2M2(SO4)(3) (M: Fe, Mn, Co, Ni). Such cathode insertion compounds are basically functional materials, involving redox active 3d transition metals that are often magnetic in nature. We have investigated the magnetic structure and properties of - Alluaudites Na2M2(SO4)(3). These alluaudite shows wide structural diversity and polymorphism. Employing various experimental methods involving diffraction, magnetic susceptibility, Mossbauer spectroscopy and low temperature neutron powder diffraction data we have explored the magnetic properties exhibited by the Alluaudite class of insertion materials
Growth and Characterization Studies of ZnS Thin Films Prepared by Single Source Evaporation Technique
No full textZinc sulfide thin films are deposited on glass substrates using thermal evaporation technique. Effect of thickness on the properties of as-deposited ZnS films is studied. ZnS films exhibited cubic structure with preferential orientation along (111) plane. All the films exhibited n-type conductivity with resistivity ranging in the order of 10(5) to 10(6) Omega-cm. The transmittance in the visible region is in the range of 80 to 89% and the band gap of the material varied from 3.65 to 3.52 eV. The as-deposited films can be used as window layer for fabrication of hetero-junction solar cell
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