Arthur Shapiro

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Shapiro

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Arthur

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0000-0003-0522-7522

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Publications 1 - 10 of 20

Simple fabrication of SWIR detectors based on wet deposition of carbon nanotubes and quantum dots
Raz Saltoun, Lilach; Sachyani Keneth, Ela; Jang, Youngjin; et al. (2019)
Sensors and Actuators A: Physical
Over the last two decades, carbon based materials and especially carbon nanotubes (CNTs), were the subject of many studies, mainly due to their unique electrical, optical and mechanical properties (Ouyang et al., 2002; Dresselhaus et al., 2003; Dresselhaus et al., 1995). CNTs can combine electrical conductivity with wide absorption spectra, and can be produced in large scale (Danafar et al., 2009) [4]. These properties enable to realize CNTs in simple, low-cost detector. Here we present a proof-of-concept for such a detector operating at the short-wave infrared (SWIR) regime. We use a simple spray technique, which allows creating a large matrix of CNT bundles. Semiconducting quantum dots (QDs) were adsorbed on top of the CNTs, enhancing the sensitivity to the infrared regime. This regime is important for numerous applications in the civil, medical, defense and security fields. Controlled coupling between the QDs and the CNT matrix generates gate-like electro-optical response when light is absorbed. This proof-of-concept for a detector in the SWIR region is presented for large surfaces and substrates, while the responsivity and detectivity of the detector in a range of frequencies and wavelengths was evaluated.
Impact of anisotropy in spin-orbit coupling on the magneto-optical properties of bulk lead halide perovskites
Kostadinov-Mutzafi, Alyssa; Tilchin, Jenya; Shapiro, Arthur; et al. (2022)
Physical Review B
The renaissance of interest in halide perovskites, triggered by their unprecedented performance in optoelectronic applications, elicited worldwide efforts to uncover a variety of intriguing physical properties, with a particular interest in spin-orbit effects. The current work presents the first magneto-optical experimental evidence for anisotropic electron-hole interactions arising from bulk orthorhombic MAPbBr3. Magneto-photoluminescence spectra, monitored along with several different crystallographic directions, were dominated by dual exciton emission peaks, while each exhibited a highly nonlinear response to a magnetic field. Moreover, these plots depicted asymmetry from -B0 to +B0, with a strong dependence on the axis of observations. A theoretical model implementing anisotropy in the electron-hole interaction, Rashba effect, Landé g factors, and a lesser contribution from an Overhauser effect, corroborated the experimental results. These research discoveries expand the possible applications of excitons in halide perovskites toward optoelectronic and information devices.
Tuning Optical Activity of IV–VI Colloidal Quantum Dots in the Short-Wave Infrared (SWIR) Spectral Regime
Shapiro, Arthur; Jang, Youngjin; Rubin-Brusilovski, Anna; et al. (2016)
Chemistry of Materials
The achievement of tunable optical properties across a wide spectral range, along with an efficient surface passivation of lead chalcogenide (PbSe) colloidal quantum dots (CQDs), has significant importance for scientific research and for technological applications. This paper describes two comprehensive pathways to tune optical activities of PbSe CQDs in the near-infrared (NIR, 0.75–1.4 μm) and the short-wave infrared (SWIR, 1.4–3 μm) ranges. A one-pot procedure enabled the growth of relatively large PbSe CQDs (with average sizes up to 14 nm) exploiting programmable temperature control during the growth process. These CQDs showed optical activity up to 3.2 μm. In addition, PbSe/PbS core/shell CQDs prepared by an orderly injection rate led to an energy red-shift of the absorption edge with the increase of the shell thickness, whereas a postannealing treatment further extended the band-edge energy toward the SWIR regime. A better chemical stability of the CQDs with respect to that of PbSe core CQDs was attained by shelling of PbSe by epitaxial layers of PbS, but limited to a short duration (<1 day). However, air stability of the relatively large PbSe as well as the PbSe/PbS CQDs over a prolonged period of time (weeks) was achieved after a postsynthesis chlorination treatment.
Optically detected magnetic resonance spectroscopic analyses on the role of magnetic ions in colloidal nanocrystals
Dehnel, Joanna; Harchol, Adi; Barak, Yahel; et al. (2023)
The Journal of Chemical Physics
Incorporating magnetic ions into semiconductor nanocrystals has emerged as a prominent research field for manipulating spin-related properties. The magnetic ions within the host semiconductor experience spin-exchange interactions with photogenerated carriers and are often involved in the recombination routes, stimulating special magneto-optical effects. The current account presents a comparative study, emphasizing the impact of engineering nanostructures and selecting magnetic ions in shaping carrier-magnetic ion interactions. Various host materials, including the II-VI group, halide perovskites, and I-III-VI2 in diverse structural configurations such as core/shell quantum dots, seeded nanorods, and nanoplatelets, incorporated with magnetic ions such as Mn2+, Ni2+, and Cu1+/2+ are highlighted. These materials have recently been investigated by us using state-of-the-art steady-state and transient optically detected magnetic resonance (ODMR) spectroscopy to explore individual spin-dynamics between the photogenerated carriers and magnetic ions and their dependence on morphology, location, crystal composition, and type of the magnetic ion. The information extracted from the analyses of the ODMR spectra in those studies exposes fundamental physical parameters, such as g-factors, exchange coupling constants, and hyperfine interactions, together providing insights into the nature of the carrier (electron, hole, dopant), its local surroundings (isotropic/anisotropic), and spin dynamics. The findings illuminate the importance of ODMR spectroscopy in advancing our understanding of the role of magnetic ions in semiconductor nanocrystals and offer valuable knowledge for designing magnetic materials intended for various spin-related technologies.
Optical and electrical characterizations of a single step ion beam milling mesa devices of chloride passivated PbS colloidal quantum dots based film
Hechster, Elad; Shapiro, Arthur; Lifshitz, Efrat; et al. (2016)
AIP Advances
Colloidal Quantum Dots (CQDs) are of increasing interest, thanks to their quantum size effect that gives rise to their usage in various applications, such as biological tagging, solar cells and as the sensitizing layer of night vision devices. Here, we analyze the optical absorbance of chloride passivated PbS CQDs as well as revealing a correlation between their photoluminescence and sizes distribution, using theoretical models and experimental results from the literature. Next, we calculate the CQDs resistivity as a film. Although resistivity can be calculated from sheet resistance measurement using four point probes, such measurement is usually carried-out on the layer’s surface that in most cases has dangling bonds and surface states, which might affect the charges flow and modify the resistivity. Therefore; our approach, which was applied in this work, is to extract the actual resistivity from measurements that are performed along the film’s thickness (z-direction). For this intent, we fabricated gold capped PbS mesas devices using a single step Ion Beam Milling (IBM) process where we milled the gold and the PbS film continually, and then measured the vertical resistance. Knowing the mesas’ dimensions, we calculate the resistivity. To the best of our knowledge, no previous work has extracted, vertically, the resistivity of chloride passivated PbS CQDs using the above method.
Cation Exchange Combined with Kirkendall Effect in the Preparation of SnTe/CdTe and CdTe/SnTe Core/Shell Nanocrystals
Jang, Youngjin; Yanover, Diana; Čapek, Richard K.; et al. (2016)
The Journal of Physical Chemistry Letters
Controlling the synthesis of narrow band gap semiconductor nanocrystals (NCs) with a high-quality surface is of prime importance for scientific and technological interests. This Letter presents facile solution-phase syntheses of SnTe NCs and their corresponding core/shell heterostructures. Here, we synthesized monodisperse and highly crystalline SnTe NCs by employing an inexpensive, nontoxic precursor, SnCl2, the reactivity of which was enhanced by adding a reducing agent, 1,2-hexadecanediol. Moreover, we developed a synthesis procedure for the formation of SnTe-based core/shell NCs by combining the cation exchange and the Kirkendall effect. The cation exchange of Sn2+ by Cd2+ at the surface allowed primarily the formation of SnTe/CdTe core/shell NCs. Further continuation of the reaction promoted an intensive diffusion of the Cd2+ ions, which via the Kirkendall effect led to the formation of the inverted CdTe/SnTe core/shell NCs.
Fundamental Properties in Colloidal Quantum Dots
Barak, Yahel; Meir, Itay; Shapiro, Arthur; et al. (2018)
Advanced Materials
A multidisciplinary approach for the production and characterization of colloidal quantum dots, which show great promise for implementation in modern optoelectronic applications, is described. The approach includes the design and formation of unique core/shell structures with alloy-composed layers between the core and the shell. Such structures eliminate interfacial defects and suppress the Auger process, thus reducing the known fluorescence blinking and endowing the quantum dots with robust chemical and spectral stability. The unique design enables the generation and sustained existence of single and multiple excitons with a defined spin-polarized emission recombination. The studies described herein implement the use of single-dot magneto-optical measurements and optically detected magnetic resonance spectroscopy, for direct identification of interfacial defects and for resolving exciton fine structure. The results are of paramount importance for a fundamental understanding of optical transitions in colloidal quantum dots, with an impact on appropriate materials design for practical applications.
Uncovering the Influence of Ni2+ Doping in Lead-Halide Perovskite Nanocrystals Using Optically Detected Magnetic Resonance Spectroscopy
Barak, Yahel; Meir, Itay; Dehnel, Joanna; et al. (2022)
Chemistry of Materials
Magnetic doping in halide perovskite semiconductors is of timely interest in the pursuit of new optical and magnetic properties that surpass those of the existing undoped materials. Here, we report a thorough investigation of the optical and magneto-optical properties of Ni2+-doped cesium lead halide perovskite with a chemical formula CsPb(Br1-xClx)3, implementing steady-state and transient photoluminescence (PL), polarized magneto-PL, and optically detected magnetic resonance (ODMR) spectroscopies. The magneto-PL measurements revealed three PL features with different degrees of circular polarization, associated with recombination from band-edge and trapping states. The ODMR measurements probed magnetic resonance transitions of photogenerated electrons and holes with phenomenological g-factors that deviate from those of band-edge states. Simulations of the ODMR spectra suggested carriers’ trapping in shallow traps with a slight anisotropic surrounding and with weak electron-hole exchange coupling. Furthermore, we observed substantial broadening of the hole resonance, due to its spin-exchange coupling with the Ni2+ unpaired spins. Overall, these ODMR measurements uncovered the role of the dopant in localizing photogenerated carriers by stiffening (becoming more rigid by decreasing the structural dynamics) the crystal structure and, for the first time, provide a direct observation of carrier-dopant spin exchange interactions in metal-halide perovskite nanocrystals. These results offer insight into the influence of magnetic dopants on the electronic structures of metal-halide perovskites, with a view toward emerging spin-based devices made from perovskites.
Influence of Interfacial Strain on Optical Properties of PbSe/PbS Colloidal Quantum Dots
Rubin-Brusilovski, Anna; Jang, Youngjin; Shapiro, Arthur; et al. (2016)
Chemistry of Materials
The interface in PbSe/PbS core/shell colloidal quantum dots (CQDs) is subject to strain forces due to a 3% crystallographic mismatch between the constituents. The strain profile in PbSe/PbS CQDs was simulated using the classical linear elasticity model, under the assumption of spherical-symmetric dot and isotropic materials. The derived strain profile was incorporated into a band structure calculation to evaluate the influence on the electronic band-edges of the core/shell CQDs. The electronic energy states evaluated were in close agreement with the absorption edges of various core/shell CQDs with different core diameters and shell thicknesses. Furthermore, the synthesized CQDs underwent thermal annealing at various temperatures, thereby creating the alloying interface; consequently, their absorption and photoluminescence spectra exhibited spectral red-shift compared with the untreated samples. The band gap energy red-shift was simulated by the theoretical model, including smoothing potential at the interface. Measurements of the photoluminescence decays indicated an extension of the radiative lifetime after a controlled annealing process, denoting removal of defect quenchers around the core–shell interface. Thus, the study suggests practical means for mitigating interface strain to leverage the quality of core/shell structures.
Enhancement of near infrared light sensing using side-gate modulation
Neubauer, Avner; Shapiro, Arthur; Yochelis, Shira; et al. (2017)
Sensors and Actuators A: Physical
The integration of nanostructures in electronic devices utilizes their unique quantum properties for realizing discrete measuring systems. Specifically, self-assembled organic monolayers and nanocrystals (NCs), together with bottom-up production methods, can lead to new types of electronic devices. In this work, we present a wavelength-tunable near-infrared detection device in which PbS NCs are used to create an optical gate for an AlGaAs/GaAs high electron mobility device. By integrating side gates, we were able to enhance light detection sensitivity by optimizing the conductivity of the channel. Both DC and AC modulations of the side gate were tested and compared in order to enhance the detector’s signal–to-noise ratio (SNR). Higher harmonic signals of the side gate modulation supply additional information about the detection mechanism.

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