Currents Induced by Moving Charges

Sirkis, M.D.; Holonyak, N.

doi:10.1119/1.1972306

Cited by 27 publications

(12 citation statements)

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“…Similar to the concept of image charges, this redistribution induces a current in the external circuit which is measured as J ( t ). The amount of mobile or free charges N F is determined via the Shockley-Ramo theorem 39 – 41 : where e denotes the elementary charge and x mean the average distance the carriers have to travel during the charge redistribution process (here half of the total superlattice thickness, i.e., ~40 nm). Figure 4b shows the N F values of all samples as function of E. For samples P3 to P5 we observe a saturation behaviour at carrier densities in the low 10 17 cm −3 range.…”

Section: Resultsmentioning

confidence: 99%

Defect-Induced Luminescence Quenching vs. Charge Carrier Generation of Phosphorus Incorporated in Silicon Nanocrystals as Function of Size

Hiller

López-Vidrier

Gutsch

et al. 2017

Sci Rep

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Phosphorus doping of silicon nanostructures is a non-trivial task due to problems with confinement, self-purification and statistics of small numbers. Although P-atoms incorporated in Si nanostructures influence their optical and electrical properties, the existence of free majority carriers, as required to control electronic properties, is controversial. Here, we correlate structural, optical and electrical results of size-controlled, P-incorporating Si nanocrystals with simulation data to address the role of interstitial and substitutional P-atoms. Whereas atom probe tomography proves that P-incorporation scales with nanocrystal size, luminescence spectra indicate that even nanocrystals with several P-atoms still emit light. Current-voltage measurements demonstrate that majority carriers must be generated by field emission to overcome the P-ionization energies of 110-260 meV. In absence of electrical fields at room temperature, no significant free carrier densities are present, which disproves the concept of luminescence quenching via Auger recombination. Instead, we propose non-radiative recombination via interstitial-P induced states as quenching mechanism. Since only substitutional-P provides occupied states near the Si conduction band, we use the electrically measured carrier density to derive formation energies of ~400 meV for P-atoms on Si nanocrystal lattice sites. Based on these results we conclude that ultrasmall Si nanovolumes cannot be efficiently P-doped.Since the first reports about (heavy) P-doping of silicon nanocrystals (Si NCs), luminescence quenching was often attributed to non-radiative exciton recombination with P-induced free carriers (Auger recombination) 1 . Only few works addressed alternative quenching mechanisms like defects 2-4 . We note that a direct proof of successful P-doping is nontrivial since a true free carrier is not generated due to its confinement in the quantum dot (QD). One important parameter in the investigation of P-doped, oxide-embedded Si NCs is the excess Si concentration that determines the size and separation of NCs as well as the degree of agglomeration. While isolated and mainly spherical NCs are formed at low Si concentrations, excess Si contents above the percolation threshold form highly irregular agglomerated Si NC networks. The threshold that separates these regimes is SiO x≈0.6 for very thin films in a superlattice (SL) and SiO x≲1 for thick bulk films [5][6][7] . While the investigation of P-doping of small and well-separated Si NCs remains a challenging task, it does not come as a surprise that extended Si NC networks can be doped successfully 8,9 . Another important parameter is the dopant concentration and the term doping itself. The latter requires a disambiguation for crystallites at the bottom end of the nanoscale where it is often used deceptively for: (i) the bare incorporation of P-atoms into nanocrystals, (ii) the observation of optical or electrical effects caused by P-incorporation, and (iii) the actual generation of free majority charge carr...

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Section: Resultsmentioning

confidence: 99%

Defect-Induced Luminescence Quenching vs. Charge Carrier Generation of Phosphorus Incorporated in Silicon Nanocrystals as Function of Size

Hiller

López-Vidrier

Gutsch

et al. 2017

Sci Rep

View full text Add to dashboard Cite

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“…For simplicity, we assume the geometry in Fig. 2(a), where two electrodes form the two plates of a parallel plate capacitor, separated by a distance d. An important example (analyzed in [29,33]) is that of a single charged particle with charge q resulting in F = qV /d, i.e. β = q/d.…”

Section: Electrical Equivalent Of Mechanical Motionmentioning

confidence: 99%

“…The effect of ∆F can therefore be lumped into a (usually but not necessarily) small change of the system's mechanical properties, e.g. its spring constant in the case of a harmonic oscillator (for a rigorous derivation see [29,33]). Now assume that the mechanical system is harmonic, i.e.…”

Section: Electrical Equivalent Of Mechanical Motionmentioning

confidence: 99%

Hybrid quantum systems with trapped charged particles

2017

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Trapped charged particles have been at the forefront of quantum information processing (QIP) for a few decades now, with deterministic two-qubit logic gates reaching record fidelities of 99.9% and single qubit operations of much higher fidelity. In a hybrid system involving trapped charges, quantum degrees of freedom of macroscopic objects such as bulk acoustic resonators, superconducting circuits or nano-mechanical membranes, couple to the trapped charges and ideally inherit the coherent properties of the charges. The hybrid system therefore implements a "quantum transducer", where the quantum reality (i.e. superpositions and entanglement) of small objects is extended to include the larger object. Although a hybrid quantum system with trapped charges could be valuable both for fundamental research and for QIP application, no such system exists today. Here we study theoretically the possibilities of coupling the quantum mechanical motion of a trapped charged particle (e.g. ion or electron) to quantum degrees of freedom of superconducting devices, nano-mechanical resonators and quartz bulk acoustic wave resonators. For each case, we estimate the coupling rate between the charged particle and its macroscopic counterpart and compare it to the decoherence rate, i.e. the rate at which quantum superposition decays. A hybrid system can only be considered quantum if the coupling rate significantly exceeds all decoherence rates. Our approach is to examine specific examples, using parameters that are experimentally attainable in the foreseeable future. We conclude that those hybrid quantum system considered involving an atomic ion are unfavorable, compared to using an electron, since the coupling rates between the charged particle and its counterpart are slower than the expected decoherence rates. A system based on trapped electrons, on the other hand, might have coupling rates which significantly exceed decoherence rates. Moreover it might have appealing properties such as fast entangling gates, long coherence and flexible electron interconnectivity topology. Realizing such a system, however, is technologically challenging, since it requires accommodating both trapping technology and superconducting circuitry in a compatible manner. We review some of the challenges involved, such as the required trap parameters, electron sources, electrical circuitry and cooling schemes in order to promote further investigations towards the realization of such a hybrid system. CONTENTS

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“…The resulting oscillation of the plasma induces a current in the pick-up electrode [17,18,19] and a voltage V r = v r (ω)e jωt is detected across the resistance R r [ Fig. 1(a)].…”

Section: Methodsmentioning

confidence: 99%

Non-Destructive Positron Plasma Diagnostics for Antihydrogen Production

Amoretti¹,

Amsler²,

Bonomi³

et al. 2003

AIP Conference Proceedings

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Production of antihydrogen atoms by mixing antiprotons with a cold, confined, positron plasma depends on parameters such as the plasma density and temperature. We discuss a nondestructive diagnostic, based on an analysis of excited, low-order plasma modes, that provides comprehensive characterization of the positron plasma in the ATHENA antihydrogen apparatus. The dipole and quadrupole modes of a spheroidal positron plasma are interpreted in the framework of a cold fluid theory. In particular, the excitation and detection of the dipole mode are analytically modeled considering the response of the center-of-mass to a resonant driving perturbation. The model is compared to, and validated by, numerical simulations with a particle-in-cell code. Measurements of the positron plasma properties are discussed.

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Currents Induced by Moving Charges

Cited by 27 publications

References 0 publications

Defect-Induced Luminescence Quenching vs. Charge Carrier Generation of Phosphorus Incorporated in Silicon Nanocrystals as Function of Size

Defect-Induced Luminescence Quenching vs. Charge Carrier Generation of Phosphorus Incorporated in Silicon Nanocrystals as Function of Size

Hybrid quantum systems with trapped charged particles

Non-Destructive Positron Plasma Diagnostics for Antihydrogen Production

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