Modular High-Intensity Monochromatic In Situ Illumination Set-Up for Investigating ESR Photoactive Centers in Semiconductors

Nistor, S. V.; Joita, Alexandra C.

doi:10.1007/s00723-019-01183-z

Cited by 3 publications

(5 citation statements)

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“…ESR spectroscopy, which has been extensively employed in investigating the properties of unpaired electrons trapped at lattice point defects in solids, ,, has also been used to study the conduction electron spin resonance of metal colloids incorporated in insulating or semiconductor crystals. ,,, To understand the electron properties of the α-Sn NCs identified by TEM in the dark cBN crystallites, we performed ESR measurements over a broad temperature range, with the results being further analyzed in correlation with the microstructure and microanalysis data obtained from the same samples, as well as with published results of first principle quantum calculations of the α-Sn NCs structure and electronic properties.…”

Section: Resultsmentioning

confidence: 99%

“…One of the factors contributing to this behavior, previously observed for certain localized paramagnetic centers in semiconductors, is an increase in the N population of electrons responsible for the ESR spectrum due to the thermal excitation of the electrons from a lower donor energy level. 41 , 65 Δ low / k B from eq 9 is, therefore, the energy separation between the lower donor level, source of the thermally excited electrons, and the CESR magnetic doublet level responsible for the Sn1 line.…”

Section: Resultsmentioning

confidence: 99%

“…The ESR spectra were recorded in the X (9.8 GHz) and Q (34.1 GHz) microwave frequency bands using an ELEXSYS E580 Bruker spectrometer equipped with an ER4118X-MD5 X-band dielectric resonator and an ELEXSYS–E500Q Bruker spectrometer equipped with an ER5106QT/W Q-band probe head, respectively. Both spectrometers from NIMP-CetRESav (Magurele, Romania) were equipped with cryostats for low temperature ESR measurements, adapted for in situ monochromatic illumination using either laser diodes or light-emitting diodes as light sources . The ESR spectral parameters were determined by numerical line deconvolution and fitting procedures using EasySpin v. 5.2.28 software …”

Section: Methodsmentioning

confidence: 99%

“…Both spectrometers from NIMP-CetRESav (Magurele, Romania) were equipped with cryostats for low temperature ESR measurements, adapted for in situ monochromatic illumination using either laser diodes or light-emitting diodes as light sources. 41 The ESR spectral parameters were determined by numerical line deconvolution and fitting procedures using EasySpin v. 5.2.28 software. 42 …”

Section: Methodsmentioning

confidence: 99%

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Microstructure and Conduction Electron Quantum Properties of Small Diamond Cubic α-Sn Nanocrystals Embedded in Cubic Boron Nitride Crystals

Nistor

Stefan

et al. 2022

ACS Omega

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The morphology, structure, composition, and conduction electron properties of quasi-spherical tin nanocrystals (NCs) of 2.5 nm average diameter, with unstrained, bulk-like α-Sn diamond cubic structure, observed in dark cubic boron nitride (cBN) crystallites, were determined by correlated analytical high-resolution scanning transmission electron microscopy and multifrequency electron spin resonance (ESR) investigations. The narrow Lorentzian ESR line with g = 2.0028 is attributed to the conduction ESR of the α-Sn NCs, consistent with the temperature-and frequency-independent small g-shift and intensity reduction under high temperature (950 °C) vacuum annealing when the α-Sn NCs are thermally dissolved in the host cBN crystallites. The ESR linewidth and line intensity vs temperature dependences recorded in the 20 to 295 K range are quantitatively described considering the presence of discrete, quantum confinement-induced conduction electron energy levels with Δ QC /k B = 125 K separation, close to the theoretical value for conductive α-Sn NCs of 2.5 nm in diameter. The observed properties are tentatively explained with the predicted nanosize induced band-gap opening and change of band ordering from bulk α-Sn to small unstrained α-Sn NCs, resulting in a topological phase transition that also explains the predominantly s-like character of the conduction band electron orbitals.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Microstructure and Conduction Electron Quantum Properties of Small Diamond Cubic α-Sn Nanocrystals Embedded in Cubic Boron Nitride Crystals

Nistor

Stefan

et al. 2022

ACS Omega

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“…Examples of this type of illumination typically include illumination through an optical window, [4][5][6] or via optical fibre. 7,8 Here, the limiting time scale is the time taken for the measurement to be recorded, which can be on the order of ns to ms for time resolved transient EPR (trEPR) methods, which use a pulsed laser as the light source. 9 Alternatively for species with longer lifetimes, on the order of seconds to hours, a time course of continuous wave (CW) EPR experiments can be used to record the formation and decay of the species.…”

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confidence: 99%