1,338 research outputs found
Flux dependent 1.5 MeV self-ion beam induced sputtering from Gold nanostructured thin films
We discuss four important aspects of 1.5 MeV Au2+ ion-induced flux dependent
sputtering from gold nanostrcutures (of an average size 7.6 nm and height 6.9
nm) that are deposited on silicon substrates: (a) Au sputtering yield at the
ion flux of 6.3x10^12 ions cm-2 s-1 is found to be 312 atoms/ion which is about
five times the sputtering yield reported earlier under identical irradiation
conditions at a lower beam flux of 10^9 ions cm-2 s-1, (b) the sputtered yield
increases with increasing flux at lower fluence and reduces at higher fluence
(1.0x10^15 ions cm-2) for nanostructured thin films while the sputtering yield
increases with increasing flux and fluence for thick films (27.5 nm Au
deposited on Si) (c) Size distribution of sputtered particles has been found to
vary with the incident beam flux showing a bimodal distribution at higher flux
and (d) the decay exponent obtained from the size distributions of sputtered
particles showed an inverse power law dependence ranging from 1.5 to 2.5 as a
function of incident beam flux. The exponent values have been compared with
existing theoretical models to understand the underlying mechanism. The role of
wafer temperature associated with the beam flux has been invoked for a
qualitative understanding of the sputtering results in both the nanostructured
thin films and thick films.Comment: 25 pages, 5 figures, 1 table To be Appeared in J. Phys. D: Appl. Phy
Magnetic Field and Displacement sensor based on Giant Magneto-impedance effect
A two-core transducer assembly using a Fe73.5Nb3Cu1Si13.5B9 ribbon to detect
a change of magnetic field is proposed and tested for displacement (linear and
angular) and current sensor. Two identical inductors, with the ribbon as core,
are a part of two series resonance network, and are in high impedance state
when excited by a small a.c field of 1MHz in absence of d.c biasing field
(Hdc). When the magnetic state of one inductor is altered by biasing field,
produced by a bar magnet or current carrying coil, an ac signal proportional to
Hdc is generated by transducer. The results for the sensitivity and linearity
with displacement (linear and angular) of a magnet and with field from the
current carrying coil are presented for two particular configurations of the
transducer. High sensitivities of voltage response as much as
12micro-volt/micro-meter and 3mV/degree have been obtained for the transducer
as a linear and angular displacement sensor respectively in the transverse
configuration of exciting a.c and biasing d.c fields.Comment: 16 pages,7 figure
Anisotropic Dependence of Giant Magneto-Impedance of Amorphous Ferromagnetic Ribbon on Biasing Field
The magneto-impedance (MI) in amorphous ribbon of nominal composition
Fe73.5Nb3Cu1Si13.5B9 has been measured at 1MHz and at room temperature for
different configurations of exciting a.c and biasing d.c. fields. A large drop
in both resistance and reactance is observed as a function of d.c magnetic
field. When the d.c and a.c fields are parallel but normal to the axis of
ribbon, smaller magnetic field is needed to reduce the impedance to its small
saturated value compared to the situation when fields are along the axis of
ribbon. Larger d.c. field is required to lower the impedance when the d.c field
acts perpendicular to the plane of the ribbon. Such anisotropy in
magneto-impedance is related to the anisotropic response of the magnetization
of ribbon. The large change of impedance is attributed to large variation of
a.c permeability on the direction and magnitude of the dc biasing field.Comment: 12 pages, 7 figures, to be published in "International Journal of
Modern Physics B
Ion beam induced enhanced diffusion from gold thin films in silicon
Enhanced diffusion of gold atoms into silicon substrate has been studied in
Au thin films of various thicknesses (2.0, 5.3, 10.9 and 27.5 nm) deposited on
Si(111) and followed by irradiation with 1.5 MeV Au2+ at a flux of 6.3x10^12
ions cm-2 s-1 and fluence up to 1x10^15 ions cm-2. The high resolution
transmission electron microscopy measurements showed the presence of gold
silicide formation for the above-mentioned systems at fluence greater than
equal to 1x1014 ions cm-2. The maximum depth to which the gold atoms have been
diffused at a fluence of 1x10^14 ions cm-2 for the cases of 2.0, 5.3, 10.9 and
27.5 nm thick films has been found to be 60, 95, 160 and 13 nm respectively.
Interestingly, at higher fluence of 1x1015 ions cm-2 in case of 27.5 nm thick
film, gold atoms from the film transported to a maximum depth of 265 nm in the
substrate. The substrate silicon is found to be amorphous at the above fluence
values where unusually large mass transport occurred. Enhanced diffusion has
been explained on the basis of ion beam induced, flux dependent amorphous
nature of the substrate, and transient beam induced temperature effects. This
work confirms the absence of confinement effects that arise from spatially
confined structures and existence of thermal and chemical reactions during ion
irradiation.Comment: 15 pages, 3 figure
Confinement induced instability of thin elastic film
A confined incompressible elastic film does not deform uniformly when
subjected to adhesive interfacial stresses but with undulations which have a
characteristic wavelength scaling linearly with the thickness of the film. In
the classical peel geometry, undulations appear along the contact line below a
critical film thickness or below a critical curvature of the plate.
Perturbation analysis of the stress equilibrium equations shows that for a
critically confined film the total excess energy indeed attains a minima for a
finite amplitude of the perturbations which grow with further increase in the
confinement.Comment: 11 pages, 6 figure
Peeling from a patterned thin elastic film
Inspired by the observation that many naturally occurring adhesives arise as
textured thin films, we consider the displacement controlled peeling of a
flexible plate from an incision-patterned thin adhesive elastic layer. We find
that crack initiation from an incision on the film occurs at a load much higher
than that required to propagate it on a smooth adhesive surface; multiple
incisions thus cause the crack to propagate intermittently. Microscopically,
this mode of crack initiation and propagation in geometrically confined thin
adhesive films is related to the nucleation of cavitation bubbles behind the
incision which must grow and coalesce before a viable crack propagates. Our
theoretical analysis allows us to rationalize these experimental observations
qualitatively and quantitatively and suggests a simple design criterion for
increasing the interfacial fracture toughness of adhesive films.Comment: 8 pages, To appear in Proceedings of Royal Society London, Ser.
Fibrillar Elastomeric Micropatterns Create Tunable Adhesion Even to Rough Surfaces
Acknowledgements V.B., N.K.G., and E.A. contributed with conception and experimental design. V.B. performed the experiments. V.B., R.H., A.G., and R.M.M. carried out analysis and interpretation of data. V.B., R.H., A.G., and E.A. wrote the manuscript. V.B. and R.H. contributed equally to this work. V.B. acknowledges funding by SPP 1420 of the German Science Foundation DFG. E.A., N.K.G., and R.H. acknowledge funding from the European Research Council under the European Union/ERC Advanced Grant “Switch2Stick,” Agreement No. 340929.Peer reviewedPublisher PD
Exploiting entanglement in communication channels with correlated noise
We develop a model for a noisy communication channel in which the noise
affecting consecutive transmissions is correlated. This model is motivated by
fluctuating birefringence of fiber optic links. We analyze the role of
entanglement of the input states in optimizing the classical capacity of such a
channel. Assuming a general form of an ensemble for two consecutive
transmissions, we derive tight bounds on the classical channel capacity
depending on whether the input states used for communication are separable or
entangled across different temporal slots. This result demonstrates that by an
appropriate choice, the channel capacity may be notably enhanced by exploiting
entanglement.Comment: 9 pages, 5 figure
Entangled Quantum State Discrimination using Pseudo-Hermitian System
We demonstrate how to discriminate two non-orthogonal, entangled quantum
state which are slightly different from each other by using pseudo-Hermitian
system. The positive definite metric operator which makes the pseudo-Hermitian
systems fully consistent quantum theory is used for such a state
discrimination. We further show that non-orthogonal states can evolve through a
suitably constructed pseudo-Hermitian Hamiltonian to orthogonal states. Such
evolution ceases at exceptional points of the pseudo-Hermitian system.Comment: Latex, 9 pages, 1 figur
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