| 1. |
- Slav, A., et al.
(author)
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Influence of preparation conditions on structure and photosensing properties of GeSi/TiO2 multilayers
- 2017
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In: 2017 International Semiconductor Conference (CAS). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509039852 ; , s. 63-66
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Conference paper (peer-reviewed)abstract
- The photosensing properties related to the structure of GeSi/TiO2 multilayers prepared under different conditions are studied. TiO2 cap/(GeSi/TiO2)2 multilayers (ML) were deposited by magnetron sputtering (MS) and annealed by rapid thermal annealing. Trilayers of TiO2 cap/GeSi/TiO2 (TL) were also deposited using reactive high power impulse MS (HiPIMS) for TiO2 layers and dc MS for the GeSi layer. For TL samples a two-step annealing was employed, one before and the second after depositing TiO2 cap. Structure and morphology characterization (X-ray diffraction, scanning and transmission electron microscopy) was carried out and photocurrent measurements (voltage dependences, spectral curves) were performed. The annealed ML samples are formed of GeSi NCs with 5-10 nm sizes, while in the annealed TL samples, the GeSi NCs are larger (20-30 nm). These morphologies determine the multilayers photosensing properties in VIS-NIR of ML structures and in UV in TL ones, respectively.
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| 2. |
- Sultan, M. T., et al.
(author)
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Efficacy of annealing and fabrication parameters on photo-response of SiGe in TiO2 matrix
- 2019
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In: Nanotechnology. - : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 30:36
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Journal article (peer-reviewed)abstract
- SiGe nanoparticles dispersed in a dielectric matrix exhibit properties different from those of bulk and have shown great potential in devices for application in advanced optoelectronics. Annealing is a common fabrication step used to increase crystallinity and to form nanoparticles in such a system. A frequent downside of such annealing treatment is the formation of insulating SiO2 layer at the matrix/SiGe interface, degrading the optical properties of the structure. An annealing process that could bypass this downside would therefore be of great interest. In this work, a short-time furnace annealing of a SiGe/TiO2 system is applied to obtain SiGe nanoparticles without formation of the undesired SiO2 layer between the dielectric matrix (TiO2) and SiGe. The structures were prepared by depositing alternate layers of TiO2 and SiGe films, using direct-current magnetron sputtering technique. A wide range spectral response with a response-threshold up to similar to 1300 nm was obtained, accompanied with an increase in photo-response of more than two-orders of magnitude. Scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopy and grazing incidence x-ray diffraction were used to analyze the morphological changes in respective structures. Photoconductive properties were studied by measuring photocurrent spectra using applied dc-voltages at various temperatures.
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| 3. |
- Sultan, M. T., et al.
(author)
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Enhanced photoconductivity of embedded SiGe nanoparticles by hydrogenation
- 2019
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In: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 479, s. 403-409
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Journal article (peer-reviewed)abstract
- We investigate the effect of room-temperature hydrogen-plasma treatment on the photoconductivity of SiGe nanoparticles sandwiched within SiO 2 layers. An increase in photocurrent intensity of more than an order magnitude is observed after the hydrogen plasma treatment. The enhancement is attributed to neutralization of dangling bonds at the nanoparticles and to passivation of nonradiative defects in the oxide matrix and at SiGe/matrix interfaces. We find that increasing the partial pressure of hydrogen to pressures where H 3 + and H 2 + were the dominant ions results in increased photocurrent.
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| 4. |
- Sultan, M. T., et al.
(author)
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Obtaining SiGe nanocrystallites between crystalline TiO2 layers by HiPIMS without annealing
- 2020
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In: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 511
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Journal article (peer-reviewed)abstract
- Formation of SiGe nanocrystals in an oxide matrix via deposition and subsequent annealing is a widely applied approach as it gives good control over optical properties by varying the Ge atomic fraction, the size, shape and crystallinity of the nanocrystals. A common drawback of annealing is a strain relaxation in the structure creating dislocations, point defects, dangling bonds, Ge clustering and altered interface morphology. All these phenomena are well-known to degrade the optoelectronic and electrical properties of the structure. As a proof of concept, in this study we have utilized a modern technique of high impulse power magnetron sputtering (HiPIMS) to obtain a crystalline TiO2/SiGe/TiO2 structure without any pre-/post-annealing. It is furthermore demonstrated how a control of the nano-crystallite size is obtained by altering the HiPIMS discharge power alone. Grazing incidence X-ray diffraction analysis was carried out for the structural characterization, while photocurrent measurements were utilized to access the role of TiO2 structural morphology over interface integrity in determining spectral feature and sensitivity. An increase of 1 - 2 orders magnitude in spectral intensity was achieved for as-grown structures fabricated via HiPIMS in comparison to annealed structure, sputtered with conventional direct current magnetron sputtering.
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| 5. |
- Sultan, M. T., et al.
(author)
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Photoluminescence study of Si1-xGex nanoparticles in various oxide matrices
- 2021
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In: 2021 International Semiconductor Conference (Cas). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 21-24
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Conference paper (peer-reviewed)abstract
- We investigate the photoluminescence properties of structures comprising of Si1-xGex nanoparticles (NPs) within SiO2, GeO2, TiO2 and Ta2O5 oxide matrices. Of the investigated structures, it was observed that the structures with GeO2 and TiO2 matrices provide increased spectral response (at similar to 907 and 844 nm respectively) and increased PL intensity. The improved PL characteristic have been attributed to increased diffusion barrier against oxygen which otherwise would result in formation of unwanted oxide at the film-oxide interface, thereby deteriorating the optical properties.
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| 6. |
- Sultan, M. T., et al.
(author)
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The Effect of H2/Ar Plasma Treatment over Photoconductivity of Sige Nanoparticles Sandwiched between Silicon Oxide Matrix
- 2018
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In: Proceedings of the International Semiconductor Conference, CAS. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538644829 ; , s. 257-260
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Conference paper (peer-reviewed)abstract
- The effect of room temperature hydrogen plasma treatment on the photoconductive properties of the SiO2 matrix containing SiGe nanoparticles is investigated. A considerable increase in photocurrent intensity is observed after plasma treatment. The increase is partly attributed to neutralization of dangling bonds around the nanoparticles and partly to passivation of non-radiative centers and defects in the matrix and at the nanoparticles-matrix interfaces.
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