Giant suppression of shot noise as signature of coherent transport in double barrier resonant diodes

Shot noise suppression in double barrier resonant tunnelling diodes with a Fano factor well below the value of 0.5 is theoretically predicted. This giant suppression is found to be a signature of the coherent transport regime and can occur near zero temperature as a consequence of the Pauli principle or above about 77 K as a consequence of long range Coulomb interaction. These predictions are validated by experimental data

Coherent approach to transport and noise in double-barrier resonant diodes

We implement a quantum approach which includes long range Coulomb interaction and investigate current voltage characteristics and shot noise in double-barrier resonant diodes. The theory applies to the region of low applied voltages up to the region of the current peak and considers the wide temperature range from zero to room temperature. The shape of the current voltage characteristic is well reproduced and we confirm that even in the presence of Coulomb interaction the shot noise can be suppressed with a Fano factor well below the value of 0.5. This feature can be an indication of coherent tunneling since the standard sequential tunneling predicts in general a Fano factor equal to or greater than the value 0.5. This giant suppression is a consequence of Pauli principle as well as long range Coulomb interaction. The theory generalizes previous findings and is compared with experiments

Giant suppression of shot noise in double barrier resonant diode: a signature of coherent transport

Shot noise suppression in double barrier resonant tunnelling diodes with a Fano factor well below the value of 0.5 is theoretically predicted. This giant suppression is found to be a signature of coherent transport regime and can occur at zero temperature as a consequence of the Pauli principle or at sufficiently high temperatures above 77 K as a consequence of a long-range Coulomb interaction. These predictions are in agreement with experimental data

Photo-detectors integrated with resonant tunneling diodes

We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 m in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD's NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.FCT under the project WOWi [PTDC/EEA-TEL/100755/2008]; programme POCTI/FEDER [REEQ/1272/EEI/2005]; FCT Portugal [SFRH/BPD/84466/2012]info:eu-repo/semantics/publishedVersio

Through vial impedance spectroscopy (TVIS): A novel approach to process understanding for freeze-drying cycle development

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Through vial impedance spectroscopy (TVIS) provides a new process analytical technology for monitoring a development scale lyophilization process, which exploits the changes in the bulk electrical properties that occur on freezing and subsequent drying of a drug solution. Unlike the majority of uses of impedance spectroscopy, for freeze-drying process development, the electrodes do not contact the product but are attached to the outside of the glass vial which is used to contain the product to provide a non-sample-invasive monitoring technology. Impedance spectra (in frequency range 10 Hz to 1 MHz) are generated throughout the drying cycle by a specially designed impedance spectrometer based on a 1 GΩ trans-impedance amplifier and then displayed in terms of complex capacitance. Typical capacitance spectra have one or two peaks in the imaginary capacitance (i.e., the dielectric loss) and the same number of steps in the real part capacitance (i.e., the dielectric permittivity). This chapter explores the underlying mechanisms that are responsible for these dielectric processes, i.e., the Maxwell-Wagner (space charge) polarization of the glass wall of the vial through the contents of the vial when in the liquid state, and the dielectric relaxation of ice when in the frozen state. In future work, it will be demonstrated how to measure product temperature and drying rates within single vials and multiple (clusters) of vials, from which other critical process parameters, such as heat transfer coefficient and dry layer resistance, may be determined

Cyclic compression of a multi-layer multi-span corrugated package with plastic deformation of its tapes

In this article we present our solution of the problem of cyclic compression of a single-layer and multi-layer corrugation, as well as of a single-layer multi-span corrugation by the FEM method using Ansys. This problem can be considered as the first part of the general complex nonlinear problem of cyclic compression of a multi-layer multi-span corrugated package with dry friction on the contact surfaces. We conducted an analysis of the known published solutions to this problem, and we discovered inaccuracy of some of them and the physical reason resulting in this unacceptable error. A very large number of published solutions to this problem are generally explained by the presence of successful examples of their practical application in the field of aircraft and rocket engine manufacturing, by the wide possibilities of their use as damping devices in both of these areas, and, for example, in the automotive industry, by their high elastic-friction, strength and performance characteristics. All the known published solutions to this problem were obtained for cyclic compression of a multilayer multi-span package in the region of its elastic deformations and for the same geometric shape of the corrugation. The task of improving the mass characteristics of an engineering unit is quite relevant for the development of shock-proof single-shot damping devices that increase the passive safety of the car bumper protective devices. This can be solved by using single-layer or two-layer, multi-span packages with an optimally selected geometric shape of the corrugation, deformable in the elastic-plastic region. Therefore, the above-mentioned problems are solved taking into account the elastic-plastic deformation of the corrugations for any of their geometric shapes. The obtained solutions make it possible to construct any loading processes in the field of elastic-hysteresis package loops. We also investigated the influence of the parameters of the corrugated package on its elastic-friction characteristics (including the shape of the corrugation and the presence of gaps between the tapes of the package at the tops of their corrugations)