Periodic Reporting for period 1 - RADICAL (Fundamental Breakthrough in Detection of Atmospheric Free Radicals)
Berichtszeitraum: 2020-11-01 bis 2021-10-31
Atmospheric radicals, particularly hydroxyl (•OH) and nitrate (•NO3) radicals, are the drivers of chemical processes that determine atmospheric composition and thus influence local and global air quality and climate. Current techniques for measuring radicals are based on spectroscopic methods, which are technically complex, cumbersome and expensive. As a result, the measurement of atmospheric radicals is far-from-routine and only a few research groups worldwide can perform them in a very limited number of geographic locations.
There is therefore a clear need to develop new radical detection techniques which are much easier to implement and deploy than existing methods. The central aim of RADICAL is to develop and deliver the science and technology to electrically detect and quantify, for the first time, short lived •OH and •NO3 radicals in the atmosphere via new, low-cost and easily accessible Si junctionless nanowire transistor (Si JNT) devices. These devices will lead to improved monitoring and control of air quality and better predictions of climate change.
Three breakthrough science and technology targets have been identified: 1) fabrication and functionalisation of arrays of Si JNTs for the selective and highly sensitive electrical detection of •OH and •NO3 radicals, 2) electrical detection of atmospheric •OH and •NO3 radicals under a range of laboratory conditions and 3) evaluation and validation of the radical sensors under realistic conditions in an atmospheric simulation chamber and via deployment in the ambient atmosphere.
Expertise in electronics, computer modelling, materials and surface science, nanofabrication, radical chemistry and atmospheric science is integrated on a pan-European level to achieve the overall aim of the project. The knowledge developed in RADICAL has the potential to bring about a dramatic breakthrough in air quality and climate monitoring, leading to health benefits for European citizens.
There is therefore a clear need to develop new radical detection techniques which are much easier to implement and deploy than existing methods. The central aim of RADICAL is to develop and deliver the science and technology to electrically detect and quantify, for the first time, short lived •OH and •NO3 radicals in the atmosphere via new, low-cost and easily accessible Si junctionless nanowire transistor (Si JNT) devices. These devices will lead to improved monitoring and control of air quality and better predictions of climate change.
Three breakthrough science and technology targets have been identified: 1) fabrication and functionalisation of arrays of Si JNTs for the selective and highly sensitive electrical detection of •OH and •NO3 radicals, 2) electrical detection of atmospheric •OH and •NO3 radicals under a range of laboratory conditions and 3) evaluation and validation of the radical sensors under realistic conditions in an atmospheric simulation chamber and via deployment in the ambient atmosphere.
Expertise in electronics, computer modelling, materials and surface science, nanofabrication, radical chemistry and atmospheric science is integrated on a pan-European level to achieve the overall aim of the project. The knowledge developed in RADICAL has the potential to bring about a dramatic breakthrough in air quality and climate monitoring, leading to health benefits for European citizens.
Progress towards Objective 1.1 - 'Creation of TCAD-based models of optimal Si JNT devices.'
Smartcom have successfully modelled Si JNT devices using two commercial simulators: COMSOL and Sentaurus. The models were calibrated based on experimental data from Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and University College Cork (UCC) and will be further optimised using electrical data from prototype JNT devices fabricated in HZDR. Smartcom have also developed a suitable compact model in Matlab to predict current-voltage behaviour in Si JNTs. The compact model results match TCAD simulations, allowing its use in the initial simulation of JNT device behaviour. The accuracy of the compact model will be further optimised by Smartcom based on the electrical data obtained from prototype JNT devices produced in RADICAL.
Progress towards Objective 1.2 - 'Fabrication of radical detection devices based on optimal design.'
The top-down fabrication of Si nanowires on silicon-on-insulator (SOI) substrates has been achieved by HZDR. Nickel (20 nm) and gold (140 nm) have been used as source and drain contact metals to form Si JNT devices.
Progress towards Objective 1.3 - 'Detailed electrical and structural characterisation of the Si JNT devices.'
The electrical characteristics of individual and multi-arrays of JNT devices without any oxide shell have been examined. The transfer characteristics of the devices were obtained using back-gate voltages (VBG) ranging between -30 V to 30 V and a drain-to-source voltage (VDS) of 0.25 or 0.5 V.
Progress towards Objective 2.1 - 'Determine model organic compounds for the detection of oxidising radicals.'
Methods have been optimised for functionalising glass slides and SiO2 nanoparticles using organosilane precursors. The methods developed will also be employed to functionalise Si nanowires.
Ozonoloysis experiments have been undertaken on functionalised glass slides and SiO2 nanoparticles, using a continuous flow of air (2 slm) containing 97 ppm of ozone for 5 hours.
Progress towards Objective 2.2 - 'Functionalise model Si substrates and Si JNTs with organic molecules for detecting •OH and •NO3 radicals.'
Density functional theory studies have successfully probed the morphology of the surface of alpha-quartz, as a model for the oxide layer and its structure in Si JNTs, when subjected to certain functionalisation schemes.
Interactions of selected sensing molecules with •OH and •NO3 radicals and ozone were investigated by calculating the total energy of the most stable geometries
Progress towards Objective 3.1 - 'Perform a comprehensive series of tests on sensor selectivity and sensitivity in order to optimise their capability in detecting radicals.'
An atmospheric chamber, made of Teflon FEP foil with a dimension of 6.5 m3, was prepared for sensor testing, e.g. leak test, ozone generation etc.
A small (100 cm3) gas-tight probe station has been built for electrical and sensor characteristics testing of JNT devices.
A detector mounting platform was designed and built to accommodate JNT sensor chips.
Progress towards Objective 5.1 - 'Support the widest dissemination of the project’s results and to lay the foundations for new interdisciplinary and transdisciplinary research directions.'
A Dissemination, Exploitation and Communication (DEC) Plan has been developed which focuses on reaching research and industry peers through the widest dissemination of RADICAL results, and includes a calendar of key conferences, events and online campaigns to support this dissemination. In addition, a RADICAL website, two social media channels, and related videos and graphics have been developed to give the project clear brand recognition and presence within the sensor and air quality monitoring communities. These channels are actively maintained and updated by UCC Academy in accordance with the DEC Plan.
Smartcom have successfully modelled Si JNT devices using two commercial simulators: COMSOL and Sentaurus. The models were calibrated based on experimental data from Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and University College Cork (UCC) and will be further optimised using electrical data from prototype JNT devices fabricated in HZDR. Smartcom have also developed a suitable compact model in Matlab to predict current-voltage behaviour in Si JNTs. The compact model results match TCAD simulations, allowing its use in the initial simulation of JNT device behaviour. The accuracy of the compact model will be further optimised by Smartcom based on the electrical data obtained from prototype JNT devices produced in RADICAL.
Progress towards Objective 1.2 - 'Fabrication of radical detection devices based on optimal design.'
The top-down fabrication of Si nanowires on silicon-on-insulator (SOI) substrates has been achieved by HZDR. Nickel (20 nm) and gold (140 nm) have been used as source and drain contact metals to form Si JNT devices.
Progress towards Objective 1.3 - 'Detailed electrical and structural characterisation of the Si JNT devices.'
The electrical characteristics of individual and multi-arrays of JNT devices without any oxide shell have been examined. The transfer characteristics of the devices were obtained using back-gate voltages (VBG) ranging between -30 V to 30 V and a drain-to-source voltage (VDS) of 0.25 or 0.5 V.
Progress towards Objective 2.1 - 'Determine model organic compounds for the detection of oxidising radicals.'
Methods have been optimised for functionalising glass slides and SiO2 nanoparticles using organosilane precursors. The methods developed will also be employed to functionalise Si nanowires.
Ozonoloysis experiments have been undertaken on functionalised glass slides and SiO2 nanoparticles, using a continuous flow of air (2 slm) containing 97 ppm of ozone for 5 hours.
Progress towards Objective 2.2 - 'Functionalise model Si substrates and Si JNTs with organic molecules for detecting •OH and •NO3 radicals.'
Density functional theory studies have successfully probed the morphology of the surface of alpha-quartz, as a model for the oxide layer and its structure in Si JNTs, when subjected to certain functionalisation schemes.
Interactions of selected sensing molecules with •OH and •NO3 radicals and ozone were investigated by calculating the total energy of the most stable geometries
Progress towards Objective 3.1 - 'Perform a comprehensive series of tests on sensor selectivity and sensitivity in order to optimise their capability in detecting radicals.'
An atmospheric chamber, made of Teflon FEP foil with a dimension of 6.5 m3, was prepared for sensor testing, e.g. leak test, ozone generation etc.
A small (100 cm3) gas-tight probe station has been built for electrical and sensor characteristics testing of JNT devices.
A detector mounting platform was designed and built to accommodate JNT sensor chips.
Progress towards Objective 5.1 - 'Support the widest dissemination of the project’s results and to lay the foundations for new interdisciplinary and transdisciplinary research directions.'
A Dissemination, Exploitation and Communication (DEC) Plan has been developed which focuses on reaching research and industry peers through the widest dissemination of RADICAL results, and includes a calendar of key conferences, events and online campaigns to support this dissemination. In addition, a RADICAL website, two social media channels, and related videos and graphics have been developed to give the project clear brand recognition and presence within the sensor and air quality monitoring communities. These channels are actively maintained and updated by UCC Academy in accordance with the DEC Plan.
Over the past 12 months RADICAL researchers have taken the first steps towards to fabricating the Si JNTs that will form the platform of the atmospheric radical sensor. The electrical properties of these sensors have been successfully modelled and within the next 12 months, the first experiments on the sensitivity and selectivity of the RADICAL sensors will be undertaken. There are also opportunities to advance the technology to detect other atmospheric pollutants of interest.
The key Intellectual property identified from the project so far includes (i) the Si nanowire functionalisation processes and (ii) the overall sensor platform, which includes the creation of Si JNT devices and the subsequent surface functionalisation of the JNT channels. Over the next 12 months RADICAL members will focus on attending key networking events and conferences to create a road map for commercial exploitation.
A key focus in the first year of the RADICAL project has been the induction and training of RADICAL early-career researchers (PhD students and postdoctoral researchers). In addition to the mentorship provided by individual supervisors and institutions, RADICAL has also provided a series of four training workshops focused on science communication skills, and a training session on Open Science and FAIR data. These sessions not only support the communication and dissemination of RADICAL results, but they also empower young researchers with a range of cross-disciplinary skills essential for leadership in any research or industry field.
The key Intellectual property identified from the project so far includes (i) the Si nanowire functionalisation processes and (ii) the overall sensor platform, which includes the creation of Si JNT devices and the subsequent surface functionalisation of the JNT channels. Over the next 12 months RADICAL members will focus on attending key networking events and conferences to create a road map for commercial exploitation.
A key focus in the first year of the RADICAL project has been the induction and training of RADICAL early-career researchers (PhD students and postdoctoral researchers). In addition to the mentorship provided by individual supervisors and institutions, RADICAL has also provided a series of four training workshops focused on science communication skills, and a training session on Open Science and FAIR data. These sessions not only support the communication and dissemination of RADICAL results, but they also empower young researchers with a range of cross-disciplinary skills essential for leadership in any research or industry field.