Metal-oxide-metal nanowires for sensors development
Project Director: Dr. Elena MATEI
Contract no.: PN-III-P4-ID-PCE-2020-2291
Project Director: Dr. Matei Elena
Project Type: National
Project Program: PCE
Funded by: Romanian Ministry of Education and Research, CNCS - UEFISCDI
Contractor: National Institute of Materials Physics
Project Status: In progress
Start Date: January 4th, 2021
End Date: December 31st, 2023
In this project we aim to obtaining multisegment nanowires with an architecture consisting of metal I-(metal II oxide)-metal I (MOM), starting from nanowires of type metal I-metal II-metal I, by combining electrodeposition in a template with a selective oxidation process using electrochemical, thermal or plasma techniques. Finally, we will aim to modulate the electrical properties of MOM nanowires by the preparation process parameters and identify the possible applications. The transport characteristics of the devices based on MOM nanowires will be influenced by the electrodeposition process’ parameters but also by the oxidation process parameters. Moreover, by conveniently tailoring the processes the amount of point defects will be controlled, this being an essential parameter in the transport properties. Another one is the quality of the contact. It is expected that by using nanowires of this structure type to enhance the functionality and performance of the devices.
- Dr. Elena Matei
- Dr. Ionut Enculescu
- Dr. Monica Enculescu
- Dr. Andreea Costas
- Drd. Melania Loredana Onea
- Dr. Mihaela Beregoi
- Dr. Mihaela Bunea
Stage 1 (2021): Deposition of uni-segment nanowires and testing of oxidation processes
Summary of the stage: In this stage of the project, one of the objectives was to obtain single-segment metallic nanowires, which will later be used in the production of metal- metallic oxide -metal (MOM) nanowires The metallic segment will be either positioned at the extremities of the segmented nanowires or to obtain the central oxidic component. For this, Ni, Cu, Co, Sn, Au, Pt metallic nanowires were prepared using a polymer template and electrodeposition. This approach allows obtaining of nanostructures with well-controlled characteristics. Very important is the possibility to control the structure/structural orientation of the nanowires only through the electrodeposition potential. For the oxidation tests of the metal nanowires, three methods were employed, namely: thermal treatment, plasma exposure and electrochemical oxidation, the purpose being to determine the parameters of obtaining the oxidic material. The parameters used in the oxidation tests were chosen considering the reduced dimensions of the starting material. The samples subjected to the oxidation processes were characterized from the morphological, structural, compositional and optical properties point of view. Thus, the characterization data showed metallic nanowires covered with an oxide layer with a weakly crystallized structure and a band gap close in value to the results reported in the literature. The morphology of oxidized nanowires is strongly influenced by the method used, an interesting result being obtained after thermal treatment of Co nanowires, resulting in secondary cobalt oxide nanowires that decorate the surface of the initial nanowire. It is interesting to note that these secondary nanowires probably have diameters of only a few nanometers, the equivalent of several tens of atoms, being probably some of the thinnest structures synthesized.
Stage 2 (2022): Deposition of multi-segment metallic nanowires and testing of selective oxidation processes
In this stage, multi-segment nanowires of the Au(Pt)-M (Ni, Cu, Co, Sn)-Au(Pt) type were prepared by electrodeposition using the template method. The nanowires were deposited sequentially from two different baths, one containing Au (Pt) to obtain the edge segments and another one containing metal ions for the central one. Multi-segmented metallic nanowires were prepared replicating the shape of the cylindrical pores, the desired lengths of the segments, having smooth surfaces and a good Au(Pt)-M interface. The next step was the testing of the selective oxidation processes of the metallic multi-segment nanowires considering the results of the previous step. Thus, for oxidation were tested thermal treatment and plasma with discharge in humidified air. Besides the final goal, for the choice of the parameters of the two techniques, it was considered that the integrity of the nanowires to not be affected. All types of multi-segment nanowires were characterized from the point of view of physico-chemical properties. A particularly strong influence of the thermal process on the central segment of the nanowires was observed, obtaining almost complete oxidation. The morphology of the oxidized nanowires is strongly influenced by the method used. The most interesting result obtained was after the thermal treatment of Au(Pt)-Co-Au(Pt) nanowires, of course, when the CoOx segment present the specific morphology with secondary nanowires decorating the surface.
Multi-segment nanowires with an oxide central segment and noble metal segments can be the basis for the development of sensor platforms with superior performances due to their characteristics.
- M.L. Onea, E. Matei, M. Enculescu, V. Kuncser, I. Enculescu, Ni Nanowires Propertie.s for Functional Magnetic Materials Applications , CREMS 2021, 21-22 October 2021, National Institute of Materials Physics, Magurele, Romania, hybrid format, oral presentation.
- I. Boukhoubza; E. Matei; A. Jorio; M. Enculescu; I. Enculescu, Electrochemical Deposition of ZnO Nanowires on CVD-Graphene/Copper Substrates, Nanomaterials 2022, 12, 2858, https://doi.org/10.3390/nano12162858.
- M.L. Onea, E. Matei, M. Enculescu, M. Beregoi, I. Enculescu, The influence of process parameters on structural and morphological properties of different metallic nanowires”, prezentare orala la conferinta 12th APMAS 2022 – International Advances in Applied Physics & Materials Science Congress & Exhibition, 13-19 oct. 2022, Oludeniz, Turcia.
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