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Nanostructures of semiconductor oxides CuO, MoO3 and ZnO for gas detection

Author: Crețu Vasilii
Degree:doctor of Physics
Speciality: 01.04.10 - Semiconductors physics and engineering
Scientific adviser: Oleg Lupan
doctor habilitat, associate professor (docent)
Institution: Technical University of Moldova


The thesis was presented on the 12 April, 2017
Approved by NCAA on the 31 May, 2017


Adobe PDF document1.89 Mb / in romanian


CZU 621.3.049.77

Adobe PDF document 9.40 Mb / in romanian
196 pages


CuO, MoO3, ZnO, nanostructures, technologies, nanosensors, gas sensors


Thesis structure: Thesis was perfected at the Technical University of Moldova, it is written in Romanian language and consists of introduction, four chapters, general conclusions and recommendations, bibliography of 241 titles, 142 pages of basic text, 64 figures, 8 tables. The obtained results were published in 35 scientific works, including two invention patents, 12 articles in scientific journals ISI and SCOPUS, 17 reports presented and published at the National and International Conferences, 4 publications of sole authorship, including 2 articles in National journals, category C.

Field of study: nanotechnology and physics of functional nanosystems.

Purpose of work: is to develop cost-effective nanotechnologies for growth and identification methods for controlled modification of nanostructured materials based on CuO, Cu2O, MoO3 and ZnO with physico-chemical properties suitable for gas sensors (H2 gas and ethanol vapors). Advanced chemical analysis and physical characterization of their properties. Identify physico-chemical sensing mechanisms and their analysis for the developed sensors and nanodevices.

Objectives: Development of cost-effective technological routes for the pure and doped nanostructured films and nanostructures of CuO, MoO3 and ZnO, as well as their investigation as materials for gas sensors. Providing contributions to applied physics of these semiconducting oxides by expanding the database on their physical-chemical characterization using advanced methods of scientific accuracy, as well as identification of sensor applications. Analysis of the physical-chemical mechanisms for the developed sensor and nanodevices were made.

Novelty and scientific originality: α-MoO3 crystal nanostructures were grown via a novel method of synthesis and investigated in detail as gas sensor materials. There were obtained and investigated as the materials for the gas sensors: the nanostructured films of zinc-doped copper oxide with nano-heterojunctions, as well as networks of copper oxide nanowires. They were grown and investigated as multifunctional nanosensors based on a single nanowire oxide (Cu and Zn). It was developed a technological process for integration of ZnO 3D networks functionalized on surface with noble metals and studied sensory structures under their selectivity. Based on research using techniques SEM, EDX, XRD, RAMAN, TEM, HRTEM, XPS, SIMS was determined the quality and characteristics of semiconductor oxide crystals that meet to rEcuirements for development of gas sensors by the "bottom-up" nanotechnologies. The gas sensing mechanisms have been identified and proposed as physical-chemical models.

Solved scientific problem: consist in development of cost-effective technologies to growth nanomaterials CuO, α-MoO3, ZnO with properties important for nanosensorial devices with selective and highly sensitive detection of ethanol vapor and H2 gas.

Theoretic significance and applicative value of work: a new technological route for synthesis of α-MoO3 nanostructures and further integration in sensor structures which can be implemented at the specialized companies; ethanol vapour sensing mechanism for α-MoO3 belt; a cost-effective technological flow for fabrication of CuO/Cu2O and CuO:Zn/Cu2O:Zn nano-heterojunctions demonstrating new perspectives for fabrication ethanol vapor and H2 gas sensors; integration of a single CuO nanowire or α-MoO3 in nanodevice for ultra-fast detection of low ethanol vapors concentrations; gas sensing mechanism for detection of hydrogen gas and ethanol vapors by CuO:Zn/Cu2O:Znand CuO/Cu2O nano-heterojunction was developed; method for integration of three-dimensional ZnO networks functionalized with different noble metals for elaboration of sensors with high selectivity to different gases.