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D. L. Bhattacharya

Bio: D. L. Bhattacharya is an academic researcher from Banaras Hindu University. The author has contributed to research in topics: Thin film & Aluminium oxide. The author has an hindex of 3, co-authored 5 publications receiving 26 citations.

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TL;DR: In this article, an effective relaxation time is deduced from the variation of the Hall coefficient with the concentration which is found to be proportional to the mean free path of the electrons.
Abstract: Measurements on Hall constant and magnetoresistance of thin films (350 A-800 A) of Ag-Au alloys with concentrations up to 20% gold have been made. An effective relaxation time is deduced from the variation of the Hall coefficient with the concentration which is found to be proportional to the mean free path of the electrons. The mean free path of the film decreases by about a factor of 3 from the bulk value for silver on the addition of gold to silver. The results are consistent with those of other workers who have used different methods and also indicate that the relaxation time is anisotropic in thin films of alloy. Size effects have also been discussed.

12 citations

Journal ArticleDOI
TL;DR: In this article, a tunnelling mechanism has been proposed at low voltages and at higher voltages Scottky and space charge mechanisms are reported, which can explain conduction on the basis of different current voltage and current temperature curves.
Abstract: Electron transport mechanisms for current flow in very thin (about 50 A) Al2O3 sandwiched film has been studied. At low voltages a tunnelling mechanism has been proposed and at higher voltages Scottky and space-charge mechanisms are reported. The mechanisms of conduction have been explained on the basis of different current voltage and current–temperature curves.

7 citations

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TL;DR: In this paper, a technique for measuring contact potential differences using single junction breakdown has been developed from evidence that recovery of a broken-down junction takes place after breakdown has occurred, and experiments have been performed with Al-Al 2 O 3 -metal thin film sandwiches.

4 citations

Journal ArticleDOI
TL;DR: In this article, a trap cross-section of the order 10−28 cm2 is estimated for the traps and it is found that the (identified) traps are uniformly distributed within an energy of 0009 eV below the conduction band edge of aluminium oxide.
Abstract: Oxide layers of thicknesses less than 100 A have been prepared by thermal-oxidation of a base metal electrode film of aluminium. These films were then neutron-irradiated from a laboratory Ra–Be source to a fluence of ∼ 1011 neutrons cm−2 and the sandwich structure. Al–Al2O3–Au. was completed bv depositing a thin metal film of gold over the irradiated oxide layer. DC. steady and transient flow through the sandwich structures have been studied. Results obtained in our experiments with irradiated sandwiches have been compared with unirradiated ones to show that traps are introduced because of the damage caused by the incident, neutrons. Transient voltage measurement across the junction gives a trap density of ∼ 1018 cm−3. A capture cross-section of the order 10−28 cm2 is estimated for the traps. It is found that the (identified) traps are uniformly distributed within an energy of 0009 eV below the conduction band edge of aluminium oxide. The physical nature of the trap is discussed by comparing the capture c...

3 citations


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TL;DR: The review ends with the current status of RRAMs in terms of stability, scalability and switching speed, which are three important aspects of integration onto semiconductors.
Abstract: The resistance switching behaviour of several materials has recently attracted considerable attention for its application in non-volatile memory (NVM) devices, popularly described as resistive random access memories (RRAMs). RRAM is a type of NVM that uses a material(s) that changes the resistance when a voltage is applied. Resistive switching phenomena have been observed in many oxides: (i) binary transition metal oxides (TMOs), e.g. TiO(2), Cr(2)O(3), FeO(x) and NiO; (ii) perovskite-type complex TMOs that are variously functional, paraelectric, ferroelectric, multiferroic and magnetic, e.g. (Ba,Sr)TiO(3), Pb(Zr(x) Ti(1-x))O(3), BiFeO(3) and Pr(x)Ca(1-x)MnO(3); (iii) large band gap high-k dielectrics, e.g. Al(2)O(3) and Gd(2)O(3); (iv) graphene oxides. In the non-oxide category, higher chalcogenides are front runners, e.g. In(2)Se(3) and In(2)Te(3). Hence, the number of materials showing this technologically interesting behaviour for information storage is enormous. Resistive switching in these materials can form the basis for the next generation of NVM, i.e. RRAM, when current semiconductor memory technology reaches its limit in terms of density. RRAMs may be the high-density and low-cost NVMs of the future. A review on this topic is of importance to focus concentration on the most promising materials to accelerate application into the semiconductor industry. This review is a small effort to realize the ambitious goal of RRAMs. Its basic focus is on resistive switching in various materials with particular emphasis on binary TMOs. It also addresses the current understanding of resistive switching behaviour. Moreover, a brief comparison between RRAMs and memristors is included. The review ends with the current status of RRAMs in terms of stability, scalability and switching speed, which are three important aspects of integration onto semiconductors.

950 citations

Journal ArticleDOI
TL;DR: In this paper, a flight-drift model and an iterative computer simulation of the self-consistent charge transport in bulk insulating samples are described by means of a new flight drift model.
Abstract: Electron beam irradiation and the self-consistent charge transport in bulk insulating samples are described by means of a new flight-drift model and an iterative computer simulation. Ballistic secondary electron and hole transport is followed by electron and hole drifts, their possible recombination and/or trapping in shallow and deep traps. The trap capture cross sections are the Poole-Frenkel-type temperature and field dependent. As a main result the spatial distributions of currents j(x,t), charges ρ(x,t), the field F(x,t), and the potential slope V(x,t) are obtained in a self-consistent procedure as well as the time-dependent secondary electron emission rate σ(t) and the surface potential V0(t). For bulk insulating samples the time-dependent distributions approach the final stationary state with j(x,t)=const=0 and σ=1. Especially for low electron beam energies E0<4keV the incorporation of mainly positive charges can be controlled by the potential VG of a vacuum grid in front of the target surface. For...

94 citations

Journal ArticleDOI
TL;DR: In this paper, the selfconsistent charge transport in bulk alumina samples during electron beam irradiation is described by means of an iterative computer simulation, and the time-dependent secondary electron emission rate σ(t) and the spatial distributions of currents j(x,t), charges ρ(x,t), the field F(x and t), and the potential slope V(x.t) are obtained.
Abstract: The self-consistent charge transport in bulk alumina samples during electron beam irradiation is described by means of an iterative computer simulation. Ballistic electron and hole transport as well as their recombination and trapping are included. As a main result the time-dependent secondary electron emission rate σ(t) and the spatial distributions of currents j(x,t), charges ρ(x,t), the field F(x,t), and the potential slope V(x,t) are obtained. For bulk insulating samples, the time-dependent distributions approach the final stationary state with j(x,t)=const=0 and σ=1. Especially for low electron beam energies E0=1 keV, the incorporation of charges can be controlled by the potential VG of a vacuum electrode in front of the target surface. Finally, for high electron beam energies, the real negative surface potential V0<0 is measured by x-ray bremsstrahlung spectra and the shift of the short wavelength edge. For the initial beam energy E0=30 keV, the experimental value V0=−16 kV is still in good agreemen...

87 citations

Journal ArticleDOI
TL;DR: It was found that topologically disordered 3D nanoporosity leads to extremely low magnetoresistance and anomalous temperature dependence as the characteristic length of nanoporous gold is tuned to be approximately 14 nm.
Abstract: We report the electric conductivity of three-dimensional (3D) nanoporous gold at low temperatures and in strong magnetic fields. It was found that topologically disordered 3D nanoporosity leads to extremely low magnetoresistance and anomalous temperature dependence as the characteristic length of nanoporous gold is tuned to be approximately 14 nm. This study underscores the importance of 3D topology of a nanostructure on electronic transport properties and has implications in manipulating electron transport by tailoring 3D nanostructures.

77 citations

Journal ArticleDOI
TL;DR: A series of poly(imidesiloxane) (SIM) copolymers have been synthesized from α,ω-aminopropylpoly(dimethylsiloxane), (PDMS) of varying lengths, 2,2-bis(4-[4-aminophenoxyl]phenyl)propane (BAPP), and 4,4‘-oxydiphthalic anhydride (ODPA) as mentioned in this paper.
Abstract: A series of poly(imidesiloxane) (SIM) copolymers have been synthesized from α,ω‘-aminopropylpoly(dimethylsiloxane) (PDMS) of varying lengths, 2,2-bis(4-[4-aminophenoxyl]phenyl)propane (BAPP), and 4,4‘-oxydiphthalic anhydride (ODPA). In this series, the total composition of PDMS was maintained at 10 wt % with multiple PDMS segment lengths of different relative compositions (e.g., 5% PDMS containing 1 repeat unit, designated G-1, and 5% PDMS containing an average repeat unit of 9, designated G-9, incorporated into the same polymer vs 1% G-1 and 9% G-9 in the same polymer). Two main polymer series were synthesized: one containing G-1 and G-9 in varying ratios and the other containing G-5 and G-9. Both of these series have been analyzed using angle-dependent X-ray photoelectron spectroscopy (XPS). The Si/N ratios as measured by XPS from all members of the G-9/G-1 series were statistically equivalent to that of the polymer containing pure 10% G-9, while that of the polymer containing 10% G-1 had a significant...

68 citations