Final Report Summary - NANOS4 (Nano-structured solid-state gas sensors with superior performances)
In the frame of ' Nano-structured solid-state gas sensors with superior performances' (NANOS4), solid state metal oxide (MOx) sensors selective and stable have been prepared by considering top-down and self-assembled bottom-up approaches:
1. Single crystal and stable nanobelts of In2O3, SnO2 and ZnO have deposited by vapour phase transport process via catalysed epitaxial crystal growth over pre-seeded substrates (self-assembled bottom-up). Innovative methods for selective patterning and removal of nanowires allowing direct integration into devices have been developed. The devices have been transferred over micromachined hotplates heater substrates based on silicon-on-insulator (SOI). Beside, to overcome the contacting difficulties, the feasibility of producing optical based sensors has been demonstrated.
2. MOX thin films have been prepared patterned by optical and FIB nanolithography to produce devices as nanowires and nanodots (top-down).
3. nanocrystals and nanopowders have been prepared as colloids and by hot injection techniques
4. Other bottom up techniques have been explored as electron beam evaporation and hydrothermal and electrochemical synthesis
Materials development has been supported by a wide range of morphological and physico-chemical characterisation techniques like HRTEM and Raman. Beside theoretical aspects of gas-surface interactions and electrical models have been developed. The newly developed technologies have been benchmarked towards more state-of-the art technologies and established commercial products. A few among state-of-the-art benchmarking materials have been optimised and kept inside the final arrays.
Gas sensor arrays were embedded into tiny micro reactor systems and operated by micro-pumps in an active sampling mode. A portable micro-reactor sensor array has been developed, which proves to be a promising device and is expected to qualify for commercial applications after further development. Photoactivation has been investigated with the aim of reducing sensor operation temperatures and improving selectivity by inducing adsorption / desorption of target gas species at well defined surface state energy. A field emission lamp based on micro machined silicon tip array covered by nano-reticule carbon and different phosphorous materials has been designed and implemented.
As for sensor performance degradation possible candidates for MOx-surface poisoning - which can be present in the operation ambient - were chosen to be investigated. No appreciable degradation of sensor performances in a concentration range compatible with applications was detected.
A sensor database has been established consisting of information about main response gases and gases with lower sensitivity of each characterised sensor (benchmarking and newly developed sensors). A graphical user interface provided by a chemometric technique - (PCA) principal component analysis -, based on the measured results in the database, proposals of sets of sensing layers and sensor operation conditions most suitable for the specific target application envisaged.
The industrial partners involved in the project have assembled during the first year a comprehensive definition requirement document covering the different target applications and the specifications of the gas sensors. Nine applications have been defined: fire detection (AOA), aircraft early fire detection (EADS), cabin air monitoring (EADS), upper-air soundings of ozone (VAI), industrial safety measurements of ozone (VAI), oxygen measurements in semiconductor and gas production (VAI), industrial safety measurements of carbon monoxide (VAI), combustion (UB) and environmental monitoring of bad odours and nuisance (SACMI).
Sensors underwent mechanical and environmental stability tests with the aim to determine stability versus vibrations, acid environment, accidental falls and other possibilities that may occur in sensors system applications. Sensors endowed with a cap passed mechanical and environmental tests. A test protocol for functional testing and validation of devices has been prepared. Five prototypes of a multipurpose sensor system has been designed and built for in field tests, a completely autonomous instrument equipped with a measurement chamber (sensor chamber), a proper front end electronics, a pneumatic circuit (valves, pump, flowmeter) and a bundled software. Beside a multi-sensor detector system has been built especially for fire applications. Field test campaigns have been carried out in chosen sites, for example the mock-up of an Airbus A340 cargo bay, and best promising sensor arrays including N4 sensors were identified.
Some applications, like fire detection, comprise a commercial sensor, i.e. a straylight sensor. A list of the application segments covered by business opportunity survey has been prepared by the industrial partners enclosing an indication of the total market potential. Application segments inside and outside the consortium have been identified.
A production business plan was prepared for three selected production processes: thin films, nanowires and nanopowders. The intellectual property rights (IPRs) support team carried out an inquiry into the scientific and patent literature in order to compare the technical results of the project with the state of the art of technology. Other dissemination measures put in action are: internet through a web homepage http://www.nanos4.org presentation at scientific conferences, workshops, publications in magazines and specialised journals.
Coordination has successfully ensured a timely delivery of results, components and subassemblies to assure a smooth workflow in and between the different work packages.
1. Single crystal and stable nanobelts of In2O3, SnO2 and ZnO have deposited by vapour phase transport process via catalysed epitaxial crystal growth over pre-seeded substrates (self-assembled bottom-up). Innovative methods for selective patterning and removal of nanowires allowing direct integration into devices have been developed. The devices have been transferred over micromachined hotplates heater substrates based on silicon-on-insulator (SOI). Beside, to overcome the contacting difficulties, the feasibility of producing optical based sensors has been demonstrated.
2. MOX thin films have been prepared patterned by optical and FIB nanolithography to produce devices as nanowires and nanodots (top-down).
3. nanocrystals and nanopowders have been prepared as colloids and by hot injection techniques
4. Other bottom up techniques have been explored as electron beam evaporation and hydrothermal and electrochemical synthesis
Materials development has been supported by a wide range of morphological and physico-chemical characterisation techniques like HRTEM and Raman. Beside theoretical aspects of gas-surface interactions and electrical models have been developed. The newly developed technologies have been benchmarked towards more state-of-the art technologies and established commercial products. A few among state-of-the-art benchmarking materials have been optimised and kept inside the final arrays.
Gas sensor arrays were embedded into tiny micro reactor systems and operated by micro-pumps in an active sampling mode. A portable micro-reactor sensor array has been developed, which proves to be a promising device and is expected to qualify for commercial applications after further development. Photoactivation has been investigated with the aim of reducing sensor operation temperatures and improving selectivity by inducing adsorption / desorption of target gas species at well defined surface state energy. A field emission lamp based on micro machined silicon tip array covered by nano-reticule carbon and different phosphorous materials has been designed and implemented.
As for sensor performance degradation possible candidates for MOx-surface poisoning - which can be present in the operation ambient - were chosen to be investigated. No appreciable degradation of sensor performances in a concentration range compatible with applications was detected.
A sensor database has been established consisting of information about main response gases and gases with lower sensitivity of each characterised sensor (benchmarking and newly developed sensors). A graphical user interface provided by a chemometric technique - (PCA) principal component analysis -, based on the measured results in the database, proposals of sets of sensing layers and sensor operation conditions most suitable for the specific target application envisaged.
The industrial partners involved in the project have assembled during the first year a comprehensive definition requirement document covering the different target applications and the specifications of the gas sensors. Nine applications have been defined: fire detection (AOA), aircraft early fire detection (EADS), cabin air monitoring (EADS), upper-air soundings of ozone (VAI), industrial safety measurements of ozone (VAI), oxygen measurements in semiconductor and gas production (VAI), industrial safety measurements of carbon monoxide (VAI), combustion (UB) and environmental monitoring of bad odours and nuisance (SACMI).
Sensors underwent mechanical and environmental stability tests with the aim to determine stability versus vibrations, acid environment, accidental falls and other possibilities that may occur in sensors system applications. Sensors endowed with a cap passed mechanical and environmental tests. A test protocol for functional testing and validation of devices has been prepared. Five prototypes of a multipurpose sensor system has been designed and built for in field tests, a completely autonomous instrument equipped with a measurement chamber (sensor chamber), a proper front end electronics, a pneumatic circuit (valves, pump, flowmeter) and a bundled software. Beside a multi-sensor detector system has been built especially for fire applications. Field test campaigns have been carried out in chosen sites, for example the mock-up of an Airbus A340 cargo bay, and best promising sensor arrays including N4 sensors were identified.
Some applications, like fire detection, comprise a commercial sensor, i.e. a straylight sensor. A list of the application segments covered by business opportunity survey has been prepared by the industrial partners enclosing an indication of the total market potential. Application segments inside and outside the consortium have been identified.
A production business plan was prepared for three selected production processes: thin films, nanowires and nanopowders. The intellectual property rights (IPRs) support team carried out an inquiry into the scientific and patent literature in order to compare the technical results of the project with the state of the art of technology. Other dissemination measures put in action are: internet through a web homepage http://www.nanos4.org presentation at scientific conferences, workshops, publications in magazines and specialised journals.
Coordination has successfully ensured a timely delivery of results, components and subassemblies to assure a smooth workflow in and between the different work packages.
