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Dascalescu I, Palade C, Slav A, Stavarache I, Cojocaru O, Teodorescu VS, Maraloiu VA, Lepadatu AM, Ciurea ML, Stoica T. Enhancing SiGeSn nanocrystals SWIR photosensing by high passivation in nanocrystalline HfO 2 matrix. Sci Rep 2024; 14:3532. [PMID: 38347024 PMCID: PMC10861535 DOI: 10.1038/s41598-024-53845-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 02/06/2024] [Indexed: 02/15/2024] Open
Abstract
SiGeSn nanocrystals (NCs) in oxides are of considerable interest for photo-effect applications due to the fine-tuning of the optical bandgap by quantum confinement in NCs. We present a detailed study regarding the silicon germanium tin (SiGeSn) NCs embedded in a nanocrystalline hafnium oxide (HfO2) matrix fabricated by using magnetron co-sputtering deposition at room temperature and rapid thermal annealing (RTA). The NCs were formed at temperatures in the range of 500-800 °C. RTA was performed to obtain SiGeSn NCs with surfaces passivated by the embedding HfO2 matrix. The formation of NCs and β-Sn segregation were discussed in relation to the deposition and processing conditions by employing HRTEM, XRD and Raman spectroscopy studies. The spectral photosensitivity exhibited up to 2000 nm in short-wavelength infrared (SWIR) depending on the Sn composition was obtained. Comparing to similar results on GeSn NCs in SiO2 matrix, the addition of Si offers a better thermal stability of SiGeSn NCs, while the use of HfO2 matrix results in better passivation of NCs increasing the SWIR photosensitivity at room temperature. These results suggest that SiGeSn NCs embedded in an HfO2 matrix are a promising material for SWIR optoelectronic devices.
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Affiliation(s)
- Ioana Dascalescu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - Catalin Palade
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - Adrian Slav
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - Ionel Stavarache
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - Ovidiu Cojocaru
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - Valentin Serban Teodorescu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
- Academy of Romanian Scientists, 54 Splaiul Independentei, 050094, Bucharest, Romania
| | | | - Ana-Maria Lepadatu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania.
| | - Magdalena Lidia Ciurea
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania.
- Academy of Romanian Scientists, 54 Splaiul Independentei, 050094, Bucharest, Romania.
| | - Toma Stoica
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania.
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Marri I, Grillo S, Amato M, Ossicini S, Pulci O. Interplay of Quantum Confinement and Strain Effects in Type I to Type II Transition in GeSi Core-Shell Nanocrystals. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:1209-1219. [PMID: 36704663 PMCID: PMC9869394 DOI: 10.1021/acs.jpcc.2c07024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 12/14/2022] [Indexed: 06/18/2023]
Abstract
The electronic properties of hydrogenated, spherical SiGe and GeSi core-shell nanocrystals, with a diameter ranging from 1.8 to 4.0 nm, are studied within density functional theory. Effects induced by quantum confinement and strain on the near-band-edge state localization, as well as the band-offset properties between Si and Ge regions, are investigated in detail. On the one hand, we prove that SiGe core-shell nanocrystals always show a type II band-offset alignment, with the HOMO mainly localized on the Ge shell region and the LUMO mainly localized on the Si core region. On the other hand, our results point out that a type II offset cannot be observed in small (diameter less than 3 nm) GeSi core-shell nanocrystals. In these systems, quantum confinement and strain drive the near-band-edge states to be mainly localized on Ge atoms, i.e., in the core region. In larger GeSi core-shell nanocrystals, instead, the formation of a type II offset can be engineered by playing with both core and shell thickness. The factors which determine the band-offset character at the Ge/Si interface are discussed in detail.
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Affiliation(s)
- Ivan Marri
- Department
of Sciences and Methods for Engineering, University of Modena and Reggio Emilia, 42122 Reggio Emilia, Italy
- Interdepartmental
Center for Research and Services in the Field of Hydrogen Production,
Storage and Use H2 − MO.RE, Via Università 4, 41121 Modena, Italy
- Centro
Interdipartimentale En&Tech, 42122 Reggio Emilia, Italy
| | - Simone Grillo
- Department
of Physics, University of Rome Tor Vergata,
and INFN, Via della Ricerca Scientifica 1, I-00133 Rome, Italy
| | - Michele Amato
- Université
Paris-Saclay, CNRS, Laboratoire de Physique
des Solides, 91405 Orsay, France
| | - Stefano Ossicini
- Department
of Sciences and Methods for Engineering, University of Modena and Reggio Emilia, 42122 Reggio Emilia, Italy
- Centro
Interdipartimentale En&Tech, 42122 Reggio Emilia, Italy
- Centro
S3, Institute of Nanoscience — Italian National Research Council
(CNR-NANO), via Campi
213/A, 41125 Modena, Italy
| | - Olivia Pulci
- Department
of Physics, University of Rome Tor Vergata,
and INFN, Via della Ricerca Scientifica 1, I-00133 Rome, Italy
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Application of infrared thermography for estimating residual stress in ground anchors for maintenance. Sci Rep 2023; 13:36. [PMID: 36593276 PMCID: PMC9807557 DOI: 10.1038/s41598-022-27222-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 12/28/2022] [Indexed: 01/03/2023] Open
Abstract
Characterizing the integrity of ground anchors is essential for examining their usability in the maintenance of soil structure. However, the lift-off test, which is generally used for this purpose, has limitations when applied to covering all installed ground anchors. The objective of this study is to assess the possibility of using infrared thermography to measure the residual stress in ground anchors as a noncontact technique that bypasses the disadvantages associated with existing techniques. A preliminary experiment is performed to determine the exact emissivity of the tested materials. Both passive and active methods, as representative techniques in infrared thermography, are applied. In the large-scale experiment, infrared images of four installed strands with growing stress in the range of 0-400 kPa at 100 kPa intervals are used in the passive method of measurement. For the active method, these same stress ranges are applied to a heated anchor head using a UTM machine. The results of the passive method show that the temperature increased and decreased according to load and unload steps. Values for the cooling rate index are deduced through the active method results, and reliable behavior are observed at 10 and 15 min. The number of pixels with huge temperature changes also changed with the loading step in both passive and active methods. This study demonstrates that infrared thermography is a suitable alternative method for assessing the residual stress in ground anchors as a type of noncontact technique.
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Zhang F, Volodin V, Astankova K, Kamaev G, Azarov I, Prosvirin I, Vergnat M. Determination of the infrared absorption cross-section of the stretching vibrations of Ge–O bonds in GeOx films. RESULTS IN CHEMISTRY 2022. [DOI: 10.1016/j.rechem.2022.100461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022] Open
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Nanocrystallized Ge-Rich SiGe-HfO 2 Highly Photosensitive in Short-Wave Infrared. MATERIALS 2021; 14:ma14227040. [PMID: 34832440 PMCID: PMC8623256 DOI: 10.3390/ma14227040] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/16/2021] [Accepted: 11/18/2021] [Indexed: 11/29/2022]
Abstract
Group IV nanocrystals (NCs), in particular from the Si–Ge system, are of high interest for Si photonics applications. Ge-rich SiGe NCs embedded in nanocrystallized HfO2 were obtained by magnetron sputtering deposition followed by rapid thermal annealing at 600 °C for nanostructuring. The complex characterization of morphology and crystalline structure by X-ray diffraction, μ-Raman spectroscopy, and cross-section transmission electron microscopy evidenced the formation of Ge-rich SiGe NCs (3–7 nm diameter) in a matrix of nanocrystallized HfO2. For avoiding the fast diffusion of Ge, the layer containing SiGe NCs was cladded by very thin top and bottom pure HfO2 layers. Nanocrystallized HfO2 with tetragonal/orthorhombic structure was revealed beside the monoclinic phase in both buffer HfO2 and SiGe NCs–HfO2 layers. In the top part, the film is mainly crystallized in the monoclinic phase. High efficiency of the photocurrent was obtained in a broad spectral range of curves of 600–2000 nm at low temperatures. The high-quality SiGe NC/HfO2 matrix interface together with the strain induced in SiGe NCs by nanocrystallization of both HfO2 matrix and SiGe nanoparticles explain the unexpectedly extended photoelectric sensitivity in short-wave infrared up to about 2000 nm that is more than the sensitivity limit for Ge, in spite of the increase of bandgap by well-known quantum confinement effect in SiGe NCs.
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Cojocaru O, Lepadatu AM, Nemnes GA, Stoica T, Ciurea ML. Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals. Sci Rep 2021; 11:13582. [PMID: 34193909 PMCID: PMC8245600 DOI: 10.1038/s41598-021-92936-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 05/31/2021] [Indexed: 11/17/2022] Open
Abstract
We present a detailed study regarding the bandgap dependence on diameter and composition of spherical Ge-rich GexSi1−x nanocrystals (NCs). For this, we conducted a series of atomistic density functional theory (DFT) calculations on H-passivated NCs of Ge-rich GeSi random alloys, with Ge atomic concentration varied from 50 to 100% and diameters ranging from 1 to 4 nm. As a result of the dominant confinement effect in the DFT computations, a composition invariance of the line shape of the bandgap diameter dependence was found for the entire computation range, the curves being shifted for different Ge concentrations by ΔE(eV) = 0.651(1 − x). The shape of the dependence of NCs bandgap on the diameter is well described by a power function 4.58/d1.25 for 2–4 nm diameter range, while for smaller diameters, there is a tendency to limit the bandgap to a finite value. By H-passivation of the NC surface, the effect of surface states near the band edges is excluded aiming to accurately determine the NC bandgap. The number of H atoms necessary to fully passivate the spherical GexSi1−x NC surface reaches the total number atoms of the Ge + Si core for smallest NCs and still remains about 25% from total number of atoms for bigger NC diameters of 4 nm. The findings are in line with existing theoretical and experimental published data on pure Ge NCs and allow the evaluation of the GeSi NCs behavior required by desired optical sensor applications for which there is a lack of DFT simulation data in literature.
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Affiliation(s)
- Ovidiu Cojocaru
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania.,Faculty of Physics, University of Bucharest, 405 Atomistilor Street, 077125, Magurele, Romania
| | - Ana-Maria Lepadatu
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania
| | - George Alexandru Nemnes
- Faculty of Physics, University of Bucharest, 405 Atomistilor Street, 077125, Magurele, Romania
| | - Toma Stoica
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania.
| | - Magdalena Lidia Ciurea
- National Institute of Materials Physics, 405A Atomistilor Street, 077125, Magurele, Romania. .,Academy of Romanian Scientists, 54 Splaiul Independentei, 050094, Bucharest, Romania.
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Prepelita P, Garoi F, Craciun V. Structural and optical characteristics determined by the sputtering deposition conditions of oxide thin films. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2021; 12:354-365. [PMID: 33968560 PMCID: PMC8077636 DOI: 10.3762/bjnano.12.29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 04/03/2021] [Indexed: 05/16/2023]
Abstract
The influence of film thickness on the structural and optical properties of silicon dioxide (SiO2) and zinc oxide (ZnO) thin films deposited by radio frequency magnetron sputtering on quartz substrates was investigated. The deposition conditions were optimized to achieve stoichiometric thin films. The orientation of crystallites, structure, and composition were investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), while the surface topography of the samples was analyzed using scanning electron microscopy (SEM). The optical characteristics were measured for samples with the same composition but obtained with different deposition parameters, such as increasing thickness. The optical constants (i.e., the refractive index n, the extinction coefficient k, and the absorption coefficient α) of the SiO2 and ZnO oxide films were determined from the transmission spectra recorded in the range of 190-2500 nm by using the Swanepoel method, while the energy bandgap was calculated from the absorption spectra. The influence of thickness on the structural and optical properties of the oxide films was investigated. Good optical quality and performance were noticed, which makes these thin films worthy of integration into metamaterial structures.
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Affiliation(s)
- Petronela Prepelita
- National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-36, Magurele 077125, Ilfov, Romania
| | - Florin Garoi
- National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-36, Magurele 077125, Ilfov, Romania
| | - Valentin Craciun
- National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-36, Magurele 077125, Ilfov, Romania
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GeSi Nanocrystals Photo-Sensors for Optical Detection of Slippery Road Conditions Combining Two Classification Algorithms. SENSORS 2020; 20:s20216395. [PMID: 33182467 PMCID: PMC7665139 DOI: 10.3390/s20216395] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 10/29/2020] [Accepted: 11/05/2020] [Indexed: 02/06/2023]
Abstract
One of the key elements in assessing traffic safety on the roads is the detection of asphalt conditions. In this paper, we propose an optical sensor based on GeSi nanocrystals embedded in SiO2 matrix that discriminates between different slippery road conditions (wet and icy asphalt and asphalt covered with dirty ice) in respect to dry asphalt. The sensor is fabricated by magnetron sputtering deposition followed by rapid thermal annealing. The photodetector has spectral sensitivity in the 360–1350 nm range and the signal-noise ratio is 102–103. The working principle of sensor setup for detection of road conditions is based on the photoresponse (photocurrent) of the sensor under illumination with the light reflected from the asphalt having different reflection coefficients for dry, wet, icy and dirty ice coatings. For this, the asphalt is illuminated sequentially with 980 and 1064 nm laser diodes. A database of these photocurrents is obtained for the different road conditions. We show that the use of both k-nearest neighbor and artificial neural networks classification algorithms enables a more accurate recognition of the class corresponding to a specific road state than in the case of using only one algorithm. This is achieved by comparing the new output sensor data with previously classified data for each algorithm and then by performing an intersection of the algorithms’ results.
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