Contactless doping characterization of Ga_2O_3 using acceptor Cd probes

Finding suitable p-type dopants, as well as reliable doping and characterization methods for the emerging wide bandgap semiconductor beta-Ga_2O_3 could strongly influence and contribute to the development of the next generation of power electronics. In this work, we combine easily accessible ion implantation, diffusion and nuclear transmutation methods to properly incorporate the Cd dopant into the beta-Ga_2O_3 lattice, being subsequently characterized at the atomic scale with the Perturbed Angular Correlation (PAC) technique and Density Functional Theory (DFT) simulations. The acceptor character of Cd in beta-Ga_2O_3 is demonstrated, with Cd sitting in the octahedral Ga site having a negative charge state, showing no evidence of polaron deformations nor extra point defects nearby. The possibility to determine the charge state of Cd will allow assessing the doping type, in particular proving p-type character, without the need for ohmic contacts. Furthermore, a possible approach for contactless charge mobility studies is demonstrated, revealing thermally activated free electrons for temperatures above similar to 648 K with an activation energy of 0.54(1) and local electron transport dominated by a tunneling process between defect levels and the Cd probes at lower temperatures

Ultra sensitive quantification of Hg2+^{2+} sorption by functionalized nanoparticles using radioactive tracker spectroscopy

We present an ultra sensitive method to quantify the uptake of Hg by dithiocarbamate functionalized magnetic nanoparticles using radioactive tracker spectroscopy. We show a lower limit of detection of about 10 fg L-1, much lower than any other known techniques used to determine the uptake of Hg (about 104 more sensitive), without the need of digesting or processing the sorption agent. Such high sensitivity enables the characterization of Functionalized Nanoparticles as Hg sorbents in natural waters, where the low Hg concentration is very difficult to detect using current analytical methods such as absorption/fluorometry methods (namely Cold Vapour Atomic Absorption/fluorescence spectroscopy). Radioactive trackers also give the ability to track the sorbed element, allowing the reconstruction of the path made by the sorbed element during the uptake process, unveiling further information about the impact of toxic metals in the environment and living beings

Free molecule studies by perturbed γ-γ angular correlation:A new path to accurate nuclear quadrupole moments

Accurate nuclear quadrupole moment values are essential as benchmarks for nuclear structure models and for the interpretation of experimentally determined nuclear quadrupole interactions in terms of electronic and molecular structure. Here, we present a novel route to such data by combining perturbed γ-γ angular correlation measurements on free small linear molecules, realized for the first time within this work, with state-of-the-art ab initio electronic structure calculations of the electric field gradient at the probe site. This approach, also feasible for a series of other cases, is applied to Hg and Cd halides, resulting in $Q(^{199}\mathrm{Hg}, 5/2^−) = +0.674(17)b$ and $Q(^{111} \mathrm{Cd}, 5/2^+) = +0.664(7) b$

Ultra sensitive quantification of Hg 2+ sorption by functionalized nanoparticles using radioactive tracker spectroscopy

We present an ultra sensitive method to quantify the uptake of Hg by dithiocarbamate functionalized magnetic nanoparticles using radioactive tracker spectroscopy. We show a lower limit of detection of about 10 fg L-1, much lower than any other known techniques used to determine the uptake of Hg (about 104 more sensitive), without the need of digesting or processing the sorption agent. Such high sensitivity enables the characterization of Functionalized Nanoparticles as Hg sorbents in natural waters, where the low Hg concentration is very difficult to detect using current analytical methods such as absorption/fluorometry methods (namely Cold Vapour Atomic Absorption/fluorescence spectroscopy). Radioactive trackers also give the ability to track the sorbed element, allowing the reconstruction of the path made by the sorbed element during the uptake process, unveiling further information about the impact of toxic metals in the environment and living beings