Browsing by Author "Petrova, Dimitrina"

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Atomic Layer-Deposited Al-Doped ZnO Thin Films for Display Applications
(2020-06-01)
Dimitrov, Dimitre
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Tsai, Che-Liang
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Petrov, Stefan
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Marinova, Vera
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Petrova, Dimitrina
The integration of high uniformity, conformal and compact transparent conductive layers into next generation indium tin oxide (ITO)-free optoelectronics, including wearable and bendable structures, is a huge challenge. In this study, we demonstrate the transparent and conductive functionality of aluminum-doped zinc oxide (AZO) thin films deposited on glass as well as on polyethylene terephthalate (PET) flexible substrates by using an atomic layer deposition (ALD) technique. AZO thin films possess high optical transmittance at visible and near-infrared spectral range and electrical properties competitive to commercial ITO layers. AZO layers deposited on flexible PET substrates demonstrate stable sheet resistance over 1000 bending cycles. Based on the performed optical and electrical characterizations, several applications of ALD AZO as transparent conductive layers are shown-AZO/glass-supported liquid crystal (LC) display and AZO/PET-based flexible polymer-dispersed liquid crystal (PDLC) devices.
FLEXIBLE AND STRETCHABLE OPTOELECTRONIC DEVICES USING GRAPHENE
(2019-01-01)
Chiou, Chung Chin
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Marinova, Vera
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Petrov, Stefan
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Fidanova, Cvetelina
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Angelova, Ina
In this paper we demonstrate flexible polymer dispersed liquid crystal (PDLC) devices using graphene as transparent conductive electrodes on polyethylene terephthalate (PET) substrate. Graphene was grown by Low Pressure Chemical Vapor Deposition (LPCVD) technique and characterized by Raman analysis, optical and electrical measurements. Several graphene-based PDLC devices have been fabricated and their electro-optical characteristics, response time and bending ability were measured and discussed. The results support the graphene promising features for integration in flexible optoelectronics.
Optical and holographic properties of Fe plus Mn co-doped Bi4Ge3O12 crystals
(2008-01-01)
Marinova, Vera
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Petrova, Dimitrina
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Lin, Shiuan Huei
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Hsu, Ken Yuh
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電子物理學系
The effect of iron and manganese co-doping on the light-induced, dark- and photoconductivity and holographic properties of Bi4Ge3O12 crystals in comparison with Fe- and Mn-single doping is studied. Fe+Mn co-doped crystals exhibited strong photochromic effect at room temperature, the photochromic effect being fully reversible by thermal annealing. The observed light-induced absorption changes and non-linear dependence of photoconductivity on light intensities indicate deep and shallow photoactive levels contribution to the charge transport mechanism of Fe+Mn co-doped BGO. Holographic gratings are successfully recorded at different wavelengths and a possibility to extend the photorefractive sensitivity into the red spectral range is demonstrated. It is found furthermore that Fe+Mn-doping combination leads to faster response time during holographic recording, especially after a preliminary exposure with ultraviolet light, in comparison with Fe- and Mn-single doping. (c) 2007 Elsevier B.V. All rights reserved.
Polymer Dispersed Liquid Crystals Devices on Rigid and Flexible Substrates Using Graphene Electrodes
(2019-01-01)
Angelova, Ina
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Chiou, Chong Chin
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Marinova, Vera
;
Lin, Shiuan Huei
;
Petrova, Dimitrina
Polymer Dispersed Liquid Crystal (PDLC) devices on rigid and flexible substrates using graphene as transparent conductive electrodes are fabricated and demonstrated. Graphene is growth by using low pressure Chemical Vapor Deposition (CVD) method on Cu foil and transferred on polyethylene terephthalate (PET) substrates. Electro-optical modulation characteristics of several PDLC devices are measured and discussed. It is found that the transmittance dependence on the driving voltage demonstrates high potential of graphene for next generation ITO-free optoelectronic and display technology.
Single and Multilayer Graphene Grown by CVD Technique: Characterization for Electro-optical Applications
(2019-01-01)
Fidanova, Tsvetelina
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Petrov, Stefan
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Napoleonov, Blagovest
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Marinova, Vera
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Petrova, Dimitrina
In this paper we demonstrate graphene growth by using Chemical Vapor Deposition (CVD) method. Single layer graphene was produced by a low pressure CVD method and multilayer graphtme by an atmospheric pressure CVD method. The graphene quality and number of layers were evaluated by Raman analysis and optical transmittance measurements.