Dr. Andreea Costas - project leader

Prof. Dr. Stefan Antohe - mentor

Nowadays, optoelectronic devices have become very important from scientific, computing, communication and socio-economic point of view. Especially, photodetectors and light emitting diodes (LEDs) have been successfully used in flame detection, advanced communications, ozone sensing, missile warning systems, sensors, optical fibers, traffic lights, etc. Given the demand for continuous miniaturization and reduced energy consumption, development of nanoscale optoelectronic devices with semiconductor nanowires as key elements have attracted the attention of researchers. Core-shell heterojunction nanowires are emerging as a new powerful class of smart materials with controlled interfaces and enhanced multi-functionalities that could led to the development of the next generation high performance optoelectronic devices. In this context, the scope of the project is to prepare vertically aligned core-shell nanowire arrays based on TiO2 and CuO by using a two-step process, combining a hydrothermal method or thermal oxidation with radio-frequency magnetron sputtering. Moreover, their optoelectronic properties will be investigated in detail in order to assess their integration as single nanowires into optoelectronic devices like photodetectors or light emitting diodes by employing lithographic techniques. The development of high performance and energy efficient optoelectronic devices based on single core-shell TiO2-CuO heterojunction nanowires can expand the area of applications of optoelectronic devices to advanced military defense warning systems, UV communications, wearable intelligent electronics, environmental monitoring, medicine etc., due to the their multi-functionalities arising from the synergistic effect of the radial heterojunction formed between the two semiconductors in the TiO2-CuO core-shell nanowires.

The main objective of the project is focused on the preparation of core-shell nanowire arrays based on TiO2 and CuO by using a two-step process, combining wet (hydrothermal) or dry (thermal oxidation) methods with radio-frequency magnetron sputtering. Their optoelectronic properties were investigated in detail in order to assess their integration as key elements into optoelectronic devices like photodetectors or light emitting diodes.

In the first stage of the project, TiO2 nanowire arrays were prepared using a hydrothermal route. In the second stage of the project, TiO2-CuO core-shell nanowires were obtained by radio-frequency magnetron sputtering. Their structural, morphological, compositional and optical properties were thoroughly evaluated. Single TiO2 and TiO2-CuO core-shell nanowires were contacted by employing electron beam lithography (EBL) in order to assess their optoelectronic properties.  The optoelectronic measurements put in evidence a typical photodetector behavior confirming the potential integration of  TiO2-CuO core-shell nanowires in optoelectronic devices.

Articles published:

1. Andreea Costas, Camelia Florica, Nicoleta Preda, Andrei Kuncser, Ionut Enculescu, Photodetecting properties of single CuO–ZnO core–shell nanowires with p–n radial heterojunction. Sci. Rep. 10, 18690 (2020).
2. Nicoleta Preda, Andreea Costas, Mihaela Beregoi, Nicoleta Apostol, Andrei Kuncser, Carmen Curutiu, Florin Iordache. Ionut Enculescu, Functionalization of eggshell membranes with CuO–ZnO based p–n junctions for visible light induced antibacterial activity against Escherichia coli, Sci. Rep. 10, 20960 (2020).
3. Nicoleta Preda, Andreea Costas, Matteo Lilli, Francesca Sbardella, Christina Scheffler, Jacopo Tirillo, Fabrizio Sarasini, Functionalization of basalt fibers with ZnO nanostructures by electroless deposition for improving the interfacial adhesion of basalt fibers/epoxy resin composites. Composites Part A 149, 106488 (2021).
4. Andreea Costas, Camelia Florica, Nicoleta Preda, Cristina Besleaga, Andrei Kuncser, Ionut Enculescu, Self-connected CuO-ZnO radial core-shell heterojunction nanowire arrays grown on interdigitated electrodes for visible-light photodetectors, Sci. Rep. 12, 6834 (2022).

Articles in preparation:

1. Andreea Costas, Nicoleta Preda, Andrei Kuncser, Sorina Iftimie, Stefan Antohe, Ionut Enculescu, TiO₂-CuO radial core-shell heterojunction nanowires for visible-light photodetectors.

Book published:

1. “Metal oxide nanowires as building blocks for optoelectronic devices”, Andreea Costas, Nicoleta Preda, Camelia Florica, Ionut Enculescu, Nanowires - Recent Progress, Intech Open, 2020, DOI: 10.5772/intechopen.94011, ISBN 978-1-83962-392-9.

Patent request at OSIM:

1. “Procedeu de obtinere a unor matrici de nanofire de tip miez-coaja pe baza de oxid de cupru si dioxid de titan”, Andreea Costas, Nicoleta Preda, Camelia Florica, Irina Zgura, Monica Enculescu, Ionut Enculescu, A/00627/2020.

Scientific papers presented at international conferences:

1. “Tailoring core-shell nanowires based on metal oxide materials for optoelectronic applications”, Andreea Costas, Nicoleta Preda, Camelia Florica, Stefan Antohe, Ionut Enculescu, Symposium R: Nanomaterials- electronics & -photonics, poster presentation at the 2021 Fall Meeting Conference of the European Materials Research Society (E-MRS).
2. “ TiO₂ nanowire arrays: Synthesis and characterization”, Andreea Costas, Nicoleta Preda, Ionut Enculescu, E-poster presentation at the International Conference on Smart Material Engineering 2021.
3. “Core-shell nanowires based on TiO₂ and CuO with enhanced optoelectronic properties”, Andreea Costas, Nicoleta Preda, Monica Enculescu, Andrei Kuncser, Ionut Enculescu, Symposium C: Semiconductor nanostructures towards opto-electronic and photonic device applications, oral presentation at the 2022 Spring Meeting Conference of the European Materials Research Society (E-MRS).
4. “Metal oxide core-shell nanowires decorated with silver nanoparticles prepared by a straightforward dry approach”, Andreea Costas, Nicoleta Preda, Andrei Kuncser, Nicoleta Apostol, Carmen Curutiu, Ionut Enculescu, Symposium C: Semiconductor nanostructures towards opto-electronic and photonic device applications, poster presentation at the 2022 Spring Meeting Conference of the European Materials Research Society (E-MRS).
5. “Semiconductor core-shell nanowires: synthesis, characterization and photodetecting applications”, Andreea Costas, Nicoleta Preda, Monica Enculescu, Andrei Kuncser, Ionut Enculescu, poster presentation at the 2022 12^th International Advances in Applied Physics & Materials Science Congress & Exhibition (APMAS).

andreea.costas@infim.ro