Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals

Cojocaru, Ovidiu; Lepadatu, Ana-Maria; Nemneş, George Alexandru; Stoïca, T.; Ciurea, Magdalena Lidia

doi:10.1038/s41598-021-92936-z

Cited by 11 publications

(14 citation statements)

References 48 publications

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“…Thus, SWIR spectral sensitivity (cut-off wavelength) was pushed up to 1700 nm for cooled structures (100 K), and up to 1400 nm at room temperature [25], in comparison with Ge NCs embedded in TiO 2 for which a cut-off of 1250 nm was obtained [23]. Density functional theory (DFT) computations of the energy gap of alloy GeSi NCs with high Ge content for finding bandgap diameter dependence for different Ge contents and bigger diameters in agreement to the experimental data can be used for the design and characterization of GeSi NCs-based optical sensors [32]. Based on all these results, recently, we developed an optical sensor system with a photoactive layer of GeSi NCs in the SiO 2 matrix that discriminates between different slippery road conditions, to be mounted on a platform for warning drivers in due time and at sufficient distance [33].…”

Section: Introductionmentioning

confidence: 78%

Nanocrystallized Ge-Rich SiGe-HfO2 Highly Photosensitive in Short-Wave Infrared

et al. 2021

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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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Section: Introductionmentioning

confidence: 78%

Nanocrystallized Ge-Rich SiGe-HfO2 Highly Photosensitive in Short-Wave Infrared

et al. 2021

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“…Hydrogen passivation (saturate the surface bonds in the c-direction with −H groups) was applied to stabilize the structures, which has proven to show minimal effects on the calculated band structures and bandgap energies. 83,84 First, the charge density difference and Bader charge analysis revealed that an increased charge accumulation around the interfacial S atoms can be obtained for the heterojunction ZnS-Au 2 S structure as compared to that for the pure ZnS and Au 2 S configurations (Figure 5a−c). 85 Quantitatively, the charge donation of Au increased from −0.13e to −0.19e, and the S atom accepted a total of around 0.54e from both Au and Zn atoms, doubled the charge accumulation on S atoms compared to the Au 2 S (0.26e) system (Table S8).…”

Section: Charge Carrier Dynamics Of Hncsmentioning

confidence: 99%

Type-I CdS/ZnS Core/Shell Quantum Dot-Gold Heterostructural Nanocrystals for Enhanced Photocatalytic Hydrogen Generation

Jin,

Sun,

Shi

et al. 2023

J. Am. Chem. Soc.

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Developing Type-I core/shell quantum dots is of great importance toward fabricating stable and sustainable photocatalysts. However, the application of Type-I systems has been limited due to the strongly confined photogenerated charges by the energy barrier originating from the wide-bandgap shell material. In this project, we found that through the decoration of Au satellite-type domains on the surface of Type-I CdS/ZnS core/shell quantum dots, such an energy barrier can be effectively overcome and an over 400-fold enhancement of photocatalytic H2 evolution rate was achieved compared to bare CdS/ZnS quantum dots. Transient absorption spectroscopic studies indicated that the charges can be effectively extracted and subsequently transferred to surrounding molecular substrates in a subpicosecond time scale in such hybrid nanocrystals. Based on density functional theory calculations, the ultrafast charge separation rates were ascribed to the formation of intermediate Au2S layer at the semiconductor–metal interface, which can successfully offset the energy confinement introduced by the ZnS shell. Our findings not only provide insightful understandings on charge carrier dynamics in semiconductor–metal heterostructural materials but also pave the way for the future design of quantum dot-based hybrid photocatalytic systems.

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“…Additionally, DFT calculations for mainly determining the bandgap energy were performed, that are useful for design and characterization of Ge and SiGe NCsbased photosensitive structures [87].…”

Section: Vis-nir-swir Photosensingmentioning

confidence: 99%

FROM Si NANOWIRES TO Ge NANOCRYSTALS FOR VIS-NIR-SWIR SENSORS AND NON-VOLATILE MEMORIES: A REVIEW

Lepadatu¹,

Stavarache²,

Palade³

et al. 2022

AnnalsARSciPhysChem

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"Nanocrystalline Si and Ge are ofhigh interestfor integrated Si photonics related to light emission, opticul sensors, photodetectors, solar energy harvesting and conversion devices, and also forfloating gate non-volatile memories (NVMs). In this review, we have focused on nanocrystalline porous Si (nc-PS) with extension to Si nanodots, and Ge nanocrystals (NCs)Zquantum dots (QDs)/nanoparticles (NPs) embedded in oxides (SiCh, TiCE, HfCh, AI2O3). The great asset ofnc-PS is its intense photoluminescence in VIS at room temperature (RT), while Ge NCs/NPs embedded in oxides show high photosensitivity in VISNIR-SWIR in the spectral photocurrent up to 1325 nm at RT. Ge NCs/NPs/QDsfloating gate NVMs present high memory performance, the retention characteristics corresponding to the state of the art for NCs floating gate NVMs. We prove the relevance of controlling the preparation parametersfor obtainingfilms with targetedphotoluminescence, photosensitivity and charge storage properties for applications, e.g. VIS-NIR-SWIR optical sensors and photodetectors, and electronic and photoelectric NVMs. We evidence the correlation of preparation conditions, morphology, composition and crystalline structure with optical, electrical, photoelectrical and charge storage properties and also evidence the contribution ofquantum confinement effect, localized States and trapping centers."

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Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals

Cited by 11 publications

References 48 publications

Nanocrystallized Ge-Rich SiGe-HfO2 Highly Photosensitive in Short-Wave Infrared

Nanocrystallized Ge-Rich SiGe-HfO2 Highly Photosensitive in Short-Wave Infrared

Type-I CdS/ZnS Core/Shell Quantum Dot-Gold Heterostructural Nanocrystals for Enhanced Photocatalytic Hydrogen Generation

FROM Si NANOWIRES TO Ge NANOCRYSTALS FOR VIS-NIR-SWIR SENSORS AND NON-VOLATILE MEMORIES: A REVIEW

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