Varasteanu Varasteanu

Mr. Varasteanu Varasteanu

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Research Focus & Metrics

Academic Career Length

8Years (2019-Present)

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

Representative Publications

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21 September 2021 in Nanomaterials
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Journal Article
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VVVarasteanu Varasteanu
Varasteanu Varasteanu
ARAntonio Radoi
Antonio Radoi
OTOana Andreea Brincoveanu - Tutunaru
Oana Andreea Brincoveanu - Tutunaru
Anton FICAIAnton FICAI
Anton FICAI
Razvan PascuRazvan Pascu
Razvan Pascu
IMIuliana Mihalache
Iuliana Mihalache
In this work, we report the development of self-powered photodetectors that integrate silicon nanoholes (SiNHs) and four different types of metal nanowires (AgNWs, AuNWs, NiNWs, PtNWs) applied on the SiNHs’ surface using the solution processing method. The effectiveness of the proposed architectures is evidenced through extensive experimental and simulation analysis. The AgNWs/SiNHs device showed the highest photo-to-dark current ratio of 2.1 × 10−4, responsivity of 30 mA/W and detectivity of 2 × 1011 Jones along with the lowest noise equivalent power (NEP) parameter of 2.4 × 10−12 WHz−1/2 in the blue light region. Compared to the bare SiNHs device, the AuNWs/SiNHs device had significantly enhanced responsivity up to 15 mA/W, especially in the red and near-infrared spectral region. Intensity-modulated photovoltage spectroscopy (IMVS) measurements revealed that the AgNWs/SiNHs device generated the longest charge carrier lifetime at 470 nm, whereas the AuNWs/SiNHs showed the slowest recombination rate at 627 nm. Furthermore, numerical simulation confirmed the local field enhancement effects at the MeNWs and SiNHs interface. The study demonstrates a cost-efficient and scalable strategy to combine the superior light harvesting properties of SiNHs with the plasmonic absorption of metallic nanowires (MeNWs) towards enhanced sensitivity and spectral-selective photodetection induced by the local surface plasmon resonance effects.

6 September 2019 in Journal of Applied Crystallography
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Cosmin RomanitanCosmin Romanitan
Cosmin Romanitan
MKMihaela Kusko
Mihaela Kusko
MPMarian Catalin Popescu
Marian Catalin Popescu
VVVarasteanu Varasteanu
Varasteanu Varasteanu
ARAntonio Radoi
Antonio Radoi
Cristina PachiuCristina Pachiu
Cristina Pachiu


11 May 2021 in Applied Sciences
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VVVarasteanu Varasteanu
Varasteanu Varasteanu
MKMihaela Kusko
Mihaela Kusko
Modifying the structure of surface plasmon resonance based sensors by adding 2D materials has been proven to considerably enhance the sensor’s sensitivity in comparison to a traditional three layer configuration. Moreover, a thin semiconductor film placed on top of the metallic layer and stacked together with 2D materials enhances even more sensitivity, but at the cost of worsening the plasmonic couplic strength at resonance (minimum level of reflectivity) and broadening the response. With each supplementary layer added, the complexity of optimizing the performance increases due to the extended parameter space of the sensor. This study focused on overcoming these difficulties in the design process of sensors by employing a multi-objective genetic algorithm (NSGA II) alongside a transfer matrix method (TMM) and, at the same time, optimizing the sensitivity to full width at half maximum (FWHM), and the reflectivity level at a resonance for a four layer sensor structure. Firstly, the thin semiconductor’s refractive index was optimized to obtain the maximum achievable sensitivity with a narrow FWHM and a reflectivity level at a resonance of almost zero. Secondly, it was shown that refractive indices of barium titanate (BaTiO3) and silicon (Si) are the closest to the optimal indices for the silver—graphene/WS2 and MoS2 modified structures, respectively. Sensitivities up to 302 deg/RIU were achieved by Ag–BaTIO3–graphene/WS2 configurations with an FWHM smaller than 8 deg and a reflectivity level less than 0.5% at resonance.

1 December 2021 in Biophysical Chemistry
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Journal Article
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ECElena Constantin
Elena Constantin
VVVarasteanu Varasteanu
Varasteanu Varasteanu
IMIuliana Mihalache
Iuliana Mihalache
GCGabriel Craciun
Gabriel Craciun
Raul - Augustin MitranRaul - Augustin Mitran
Raul - Augustin Mitran
MSMonica Simion
Monica Simion