Development and morphology characterization of Nanocrystalline Thin Film coatings for fibre optics obtained by Magnetron Sputtering

Project leaders

Mauro Zarrelli, Lidia Ghimpu

Agreement

MOLDOVA - ASM-not in force - Academy of Sciences of Moldova

Call

CNR/ASM 2015-2016

Department

Chemical sciences and materials technology

Thematic area

Chemical sciences and materials technology

Status of the project

New

Research proposal

Research Proposal: introduction
As a major semiconductor, zinc oxide and tin dioxide such as doped and un-doped thin films have a wide range of application such as solar cells, electric, piezoelectric or luminescent devices and also as gas sensors and chemical sensors. Zinc oxide inevitably occupied a place among other metal oxides for many applications, due to its unique combination of interesting properties such as non-toxicity, good electrical, optical and piezoelectric behavioral stability in a hydrogen plasma atmosphere and low price. As the material gas sensor, ZnO can be used to measure the reducing gases (CO and H2), O2, O3 and humidity. Recently, gas sensors based on nanocrystalline ZnO has attracted interest due to their good detection of toxic gases, alcohols and food freshness, especially fish freshness, or gas detection thin films integrated on one chip to make an"electronic nose". These thin films have been prepared by various spraying techniques, metalorganic chemical vapor deposition and pyrolysis. It is well known that the detection mechanism of semiconductor oxide gas sensor is based on the surface reaction and a high surface-volume ratio. Crystallite size and the porosity of the detection material nanowires are the most important factors for high sensitivity and short response sensors. Semiconductor gas sensors based on metal oxides have attracted the attention of ecologists and other researchers. Hydrocarbon gases, including liquid petroleum gas (LPG) find useful applications as a clean source of energy for both the domestic and industrial areas. However, the explosive nature of liquid petroleum gas sensor makes requirement of reliable and effective gas sensorsindispensable. Tin dioxide (SnO2) in thin layer form of a is most promising for gas sensing applications due to advantages such as high sensitivity, low cost, fast response and recovery rate. SnO2 exhibits sensitivity to various gases, and therefore catalysts are introduced to make the sensor selective. In addition to improving the selectivity, catalysts also modulate the electron transport properties of the sensing SnO2 layer and give improved response characteristics are obtained.
In this project, we focus on the crystalline structure, morphology, optical and eventually gas detections properties of nanofibrous and nanoporous ZnO and SnO2 thin films prepared by magnetron sputtering on optical fiber. One of the earliest applications of nanotechnology that has been realized is the development of improved chemical and biological sensors. Aim of the present proposal is to develop and characterised from the morphological point of view, nanocristalline thin films developed by magneton sputtering technique to an enhancement effect of the optical near field induced by semiconductive structures.

The current level of knowledge on the subject proposed
Metal oxide semiconductor as material for detection of gases is intensively studied for longer period of time because this material has a future of stability, good sensitivity with environment and simplicity in production. More researches were made for understanding and improvement of properties, particularly detection of flammable and toxic elements, but only few wares are available for production of sensors for liquefied petroleum gas detection. Sensors for gas based on semiconductors with controlled electric conductivity for gas exposure had draw attention because of their small dimension, which eases miniaturization of electronic circuits and simplifies method of detection. Were developed new materials for gas detection in which metal oxides have chemical and physical stability and are studied in present. More metal oxides nowadays are in vogue for detection of gases which suffers changes in area on what it is exposed. ZnO and SnO2, CuO and Fe2O3 were studied as detectors for water, oxygen, hydrogen and GPL vapors. From these materials, zinc oxide is a promising material to fit these requirements. ZnO has a variety of morphology and can be used on a large scale of applicability in devices, as is detection sensor for liquefied petroleum gas from fiber optic. Thus for same need can be used tin dioxide, which is a wide band gap material, doping with different metals SnO2 becomes more sensitive and poses higher response. With all above, there are very few scientific reports available for SnO2:F developing as: sensors for gases on thin layer basis. More techniques of deposition were used for increasing films of SnO2 with and without doping, including spreading, electron beam evaporation, spray pyrolysis and sol-gel. Among these techniques, magnetron deposition is one of the most promising, due to simplicity of the device, cost-efficiency, uniformity of the thin layers and is the most adequate for large scale production. Another important cause is using of the technique for obtaining thin layers of oxide metals on the optical fiber for gas sensors production. The principle of operation of the refractometric sensor is based on the fact that the changes in the optical and geometric properties of the layer modify the power level reflected by the fiber/layer interface. Today wide band gap semiconductor materials are of particular interest for use in various industries. When the existing technologies for producing these materials are compatible with Si-based technologies, then important perspectives for the integration of optoelectronic and microelectronic devices appears. Among wide band gap materials, ZnO and SnO2 are most relevant because of the their advantages compared to other alloys such as: ZnNb2O6, and the existence of massive crystals affordable in trade and high exciton energy of 60 meV compared to other materials makes it possible to operate the devices at different temperatures and different environments.

Research goals

The main objective of the proposed collaboration between the Laboratory of Nanotechnologies (ASM) and the IPCB is to develop and characterized the morphological features of inorganic coatings to be employed as potential functional substrate of optical fiber gas sensor by refractometry.
Modernization will touch the technological basis for obtaining nanometric layers by using the method of magnetron deposition for obtaining ZnO and SnO2 layers with directed roughness and programmed electrophysical parameters.
In IIEN laboratory of nanotechnologies has been created a modern technological infrastructure for production of semiconductor material, including nanostructured layers made of wide band gap materials. In last years, IPCB-CNR group has been involved in research activities focused on the development of novel opto-chemical nano-sensors employing near field effects to enhance the overall performance of the final device.

The main stages of the project will be:
A. Obtaining reproducible thin films of ZnO and SnO2 nanostructured materials with morphology and opto-electrical properties well-defined and their realization on thin optical fiber.
B. Establishing the structure, superstructure and physicochemical properties (mass and surface) of inorganic components.
C. Study of the morfological (SEM, TEM, AFM) strucure of nanocristalline thin films of ZnO and SnO2.
D. Potential application of manufactured thin filmed fiber optics as gas sensor

Last update: 13/05/2024