Vladimir Mehandzhiev

Mr. Vladimir Mehandzhiev


Research Focus & Metrics

Academic Career Length

6Years (2021-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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19 February 2021 in Journal of Materials Science: Materials in Electronics
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Albena PaskalevaAlbena Paskaleva
Albena Paskaleva
BBBlagoy Spasov Blagoev
Blagoy Spasov Blagoev
PTPenka Terziyska
Penka Terziyska
VMVladimir Mehandzhiev
Vladimir Mehandzhiev
PTPetyr Tzvetkov
Petyr Tzvetkov
KGKostadinka Gesheva
Kostadinka Gesheva

24 May 2024 in Coatings
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PRPeter Metodiev Rafailov
Peter Metodiev Rafailov
VMVladimir Mehandzhiev
Vladimir Mehandzhiev
PSPeter Sveshtarov
Peter Sveshtarov
BBBlagoy Spasov Blagoev
Blagoy Spasov Blagoev
PTPenka Terziyska
Penka Terziyska
SLShiuan Lin
Shiuan Lin
The deposition of thin uniform dielectric layers on graphene is important for its successful integration into electronic devices. We report on the atomic layer deposition (ALD) of Al2O3 nanofilms onto graphene grown by chemical vapor deposition onto copper foil. A pretreatment with deionized water (DI H2O) for graphene functionalization was carried out, and, subsequently, trimethylaluminum and DI H2O were used as precursors for the Al2O3 deposition process. The proper temperature regime for this process was adjusted by means of the ALD temperature window for Al2O3 deposition onto a Si substrate. The obtained Al2O3/graphene heterostructures were characterized by Raman and X-ray photoelectron spectroscopy, ellipsometry and atomic force and scanning electron microscopy. Samples of these heterostructures were transferred onto glass substrates by standard methods, with the Al2O3 coating serving as a protective layer during the transfer. Raman monitoring at every stage of the sample preparation and after the transfer enabled us to characterize the influence of the Al2O3 coating on the graphene film.

4 October 2023 in Materials
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Armando GalluzziArmando Galluzzi
Armando Galluzzi
Krastyo BuchkovKrastyo Buchkov
Krastyo Buchkov
BBBlagoy Spasov Blagoev
Blagoy Spasov Blagoev
Albena PaskalevaAlbena Paskaleva
Albena Paskaleva
IAIvalina Avramova Avramova
Ivalina Avramova Avramova
Massimiliano PolichettiMassimiliano Polichetti
Massimiliano Polichetti
The magneto-optical (MO) Kerr effects for ZnO and ZnO:Ni-doped nanolaminate structures prepared using atomic layer deposition (ALD) have been investigated. The chemical composition and corresponding structural and morphological properties were studied using XRD and XPS and compared for both nanostructures. The 2D array gradient maps of microscale variations of the Kerr angle polarization rotation were acquired by means of MO Kerr microscopy. The obtained data revealed complex behavior and broad statistical dispersion and showed distinct qualitative and quantitative differences between the undoped ZnO and ZnO:Ni-doped nanolaminates. The detected magneto-optical response is extensively inhomogeneous in ZnO:Ni films, and a giant Kerr polarization rotation angle reaching up to ~2° was established. This marks the prospects for further development of magneto-optical effects in ALD ZnO modified by transition metal oxide nanostructures.

9 March 2022 in Molecules
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PRPeter Metodiev Rafailov
Peter Metodiev Rafailov
PSPeter K. Sveshtarov
Peter K. Sveshtarov
VMVladimir Mehandzhiev
Vladimir Mehandzhiev
IAIvalina Avramova Avramova
Ivalina Avramova Avramova
PTPenka Terziyska
Penka Terziyska
Imre Miklós SzilágyiImre Miklós Szilágyi
Imre Miklós Szilágyi
Graphene films were grown by chemical vapor deposition on Cu foil. The obtained samples were characterized by Raman spectroscopy, ellipsometry, X-ray photoelectron spectroscopy and electron back-scatter diffraction. We discuss the time-dependent changes in the samples, estimate the thickness of emerging Cu2O beneath the graphene and check the orientation-dependent affinity to oxidation of distinct Cu grains, which also governs the manner in which the initial strong Cu-graphene coupling and strain in the graphene lattice is released. Effects of electropolishing on the quality and the Raman response of the grown graphene layers are studied by microtexture polarization analysis. The obtained data are compared with the Raman signal of graphene after transfer on glass substrate revealing the complex interaction of graphene with the Cu substrate.

3 December 2023 in Materials
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BBBlagoy Spasov Blagoev
Blagoy Spasov Blagoev
BGBorislava Georgieva
Borislava Georgieva
KSKirilka Starbova
Kirilka Starbova
NSNikolay Starbov
Nikolay Starbov
IAIvalina Avramova Avramova
Ivalina Avramova Avramova
Albena PaskalevaAlbena Paskaleva
Albena Paskaleva
In this work, a novel approach is suggested to grow bilayer fibers by combining electrospinning and atomic layer deposition (ALD). Polyvinyl alcohol (PVA) fibers are obtained by electrospinning and subsequently covered with thin Al2O3 deposited at a low temperature by ALD. To burn the PVA core, the fibrous structures are subjected to high-temperature annealing. Differential scanning calorimetry (DSC) analysis of the PVA mat is performed to establish the proper annealing regime for burning off the PVA core and obtaining hollow fibers. The hollow fibers thus formed are covered with a ZnO layer deposited by ALD at a higher temperature within the ALD window of ZnO. This procedure allows us to prepare ZnO films with better crystallinity and stoichiometry. Different characterization methods—SEM, ellipsometry, XRD, and XPS—are performed at each step to investigate the processes in detail.

9 July 2025 in Materials
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Teodor Ivanov MilenovTeodor Ivanov Milenov
Teodor Ivanov Milenov
IAIvalina Avramova Avramova
Ivalina Avramova Avramova
VMVladimir Mehandzhiev
Vladimir Mehandzhiev
IZIvan Zahariev
Ivan Zahariev
GAGeorgi Avdeev
Georgi Avdeev
Valentin Nikolov PopovValentin Nikolov Popov
Valentin Nikolov Popov
This work presents a comparative analysis of the results of silicon carbide synthesis through the carbonization of Si (001) and Si (111) substrates in the temperature range 1130–1140 °C. The synthesis involved chemical vapor deposition utilizing thermally stimulated methane reduction in a hydrogen gas stream. The experiments employed an Oxford Nanofab Plasmalab System 100 apparatus on substrates from which the native oxide was removed according to established protocols. To minimize random experimental variations (e.g., deviations from set parameters), short synthesis durations of 3 and 5 min were analyzed. The resultant thin films underwent evaluations through several techniques, including X-ray photoelectron spectroscopy, X-ray diffractometry, optical emission spectroscopy with glow discharge, and transmission electron microscopy. A comparison and analysis were conducted between the results from both substrate orientations.