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Carbon-based Nanomaterials and Nanostructures for Advanced Sensing Applications

Final Report Summary - CARBONNASA (Carbon-based Nanomaterials and Nanostructures for Advanced Sensing Applications)

The four-year exchange project involves knowledge transfer and networking between Aston University, UK (Aston), the University of Aveiro, Portugal (UAvr), Alfred University, USA (Alfred), Norfolk State University, USA (NSU), National Institute for Materials Science, Japan (NIMS), Chinese Academy of Science, China (CAS), and Changshu Institute of Technology, China (CIT). The project aims to establish long-term stable research cooperation among the partners in the UK, Portugal, USA, Japan and China, each with complimentary expertise and knowledge. The project objectives and challenges present a balanced mix between industrial application focused knowledge transfer and development and more far-looking studies for potentially ground-breaking applications of using carbon-based nanomaterials and nanostructures for advanced sensing applications (CarbonNASA), including high-temperature strain sensors, Raman laser systems, and fiber Bragg grating sensors for lithium batteries.

The four-year IRSES project deals with staff and researcher exchange among the consortium partners by exploring the carbon-based nanomaterials and nanostructures for advanced sensing applications. Major efforts have been dedicated to the growth of high quality diamond thin films using the microwave plasma enhanced chemical vapor deposition method. Impacts of microwave power, reactive gas concentration and nitrogen/ oxygen additives have been investigated and optimized to find the high growth rate of diamond films without deteriorating the film quality [1-3]. Femtosecond lasers have been applied to a diamond surface to fabricate laser–induced microfluidic channels on single crystalline diamonds [4]. It is possible to fabricate the self-embedded electronic / photonics devices based on a diamond crystal itself, subject to fine-tuning of the laser focusing and micro-plasma energy control.

The consortium has been working on the application of nanomaterials for lithium batteries. Significant progress has been made towards the performance of the lithium battery. It has been proven that developed nanomaterials and nanostructures can significantly increase the behavior and storage properties of lithium batteries, for example, the electrospun TiO2 with a variety of morphologies [5], the Co3O4 nanostructures as anode materials [6], the porous tin film synthesized by electrodeposition [7], and the nanodiamond converted graphene for supercapacitors [8]. In terms of electronic ceramics for strain sensors application, it was found that Mn-doped CaCu3-xMnxTi4O12 (0≤x≤1) ceramics has shown negative temperature coefficient thermistor behavior [9], and Yb-doped Ca0.9-xYbxLa0.1MnO3 Ceramics has shown strong Thermoelectric Properties [10].

By controlling the process of carbonization, polyacrylonitrile derived carbon nano-fibers have been synthesized successfully, which have been fully characterized by the impedance spectroscopy [11]. The as-formed carbon fibers, if surface functionalized, could be used as the facilitator for bone-cell growth and antimicrobial resistance research. A proposal based on rare-earth doped nanodiamonds for intercellular temperature sensing has received additional financial support. It was found that rare-earth doped CuAlO2 fibers show a strong luminescence which offers a great potential for optoelectronics and emerging applications [12].

In order to perform pressure sensing at high temperatures, a self-integrated metal-piezoelectric-insulator-semiconductor (MPIS) field-effect transistor (FET) device concept was proposed. The reasons to select diamond were: (i) diamond is the best semiconductor for high-temperature applications as it has a wide bandgap (5. 5 eV), a high breakdown electric field, a high carrier mobility, and the highest thermal conductivity, and (ii) diamond is the ideal MEMS material due to its outstanding properties such as the highest Young’s modulus, the highest hardness, a hydrophobic surface, low mass density, and high corrosion resistance upon caustic chemicals. On the other hand, high-Curie temperature ferroelectrics are required as the gate insulator on semiconductor. BixTiyOz (BTO) has a high Curie temperature above 500 oC and also shows high ferroelectric polarization. To fabricate the ultimate MPIS-FET, the interface properties between the gate oxide and the semiconductor should be understood and controlled. Due to the low bandgap of BTO, wide bandgap oxide such as Al2O3 is firstly selected as the gate oxide on diamond to reduce the leakage current of the MIPS-FET. The Al2O3 layer can also act as a buffer layer for BTO growth on diamond. We developed for the first time the impedance spectroscopy for the characterization the interface of the MOS structure based on p-type diamond. An Al2O3 layer was used as the gate oxide on diamond with a p-type channel due to surface hydrogenation. The advantage of the impedance spectroscopy (IS) over the normal capacitance-voltage technique is that the series resistance effect in the device and measurement system can be avoided, so that the origin of the frequency dispersion effect can be distinguished. Based on the IS data analysis with a combination of the C-V technique, the interface states of the MOS structure can also be understood. Therefore, a precise gate capacitance can be obtained in principle. By using the IS technique, we obtained a dielectric value close to 9, which was larger than that obtained by C-V method [13-14].

Color centers in diamond are prominent candidates to generate and manipulate quantum states of light, even at room temperature. However, the efficiency of photon collection in bulk diamond is greatly reduced by the refraction at diamond/air interface. To address this issue, arrays of diamond nanostructures of different diameters and top end shapes have been fabricated with HSQ, PMMA and Cr as the etching masks, for large scale fabrication of nitrogen vacancy (NV) embedded diamond single photon source with enhanced collection efficiency. With mixture of O2 and CHF3 gas plasma, diamond pillars with diameter down to 45 nm have been achieved. The top end shape evolution has also been traced with a simple model. The size dependent single photon collection efficiency of NV centers buried in the diamond pillars was investigated. It was found that the best enhancement factor was larger than 10 folds while no obvious relation between the enhancement effect and the diameter has been observed [15].

The IRSES project deals with staff and researcher exchange with training and knowledge transfer activities embedded. Four specialised workshops were organized alongside the project. The 1st Project workshop on diamond growth and characterization associated with this project was successfully held in October 2013 at the Changshu Institute of Technology (China). The workshop attracted 30 local postgraduates and research staff to participate the discussion. The second Project workshop on diamond electronics took place in Aston University, Birmingham, in January 2015. The third workshop on nanofabrication was held at Chinese Academy of Science, Beijing, in September 2015. The fourth workshop on electrospinning technology was held in conjunction with participation of 40th International Conference and Expo on Advanced Ceramics and Composites at USA in January 2016. Research staff and students from the consortium partners and the hosting institution have attended the workshops actively.

The consortium has received further funding to support a Marie Curie International Incoming Fellow from Japan and has successfully applied for a H2020 Individual Fellowship to support an early career researcher. A Memorandum of Understanding between Aston University and University of Chinese Academy of Science has been signed for further sustainable collaboration in both teaching and research. A joint project between Aston University and Chinese Academy of Science on nanodiamond/graphene composites has been submitted for funding under the Newton Advanced Fellowship Programme. An ECR consolidator grant and a Newton MRC UK-China Joint Project application on Nanodiamonds for Antimicrobial Resistance Research have been submitted for funding.

The potential impact and use.
The project pursues the development of a new platform for the next generation of carbon-based nanomaterials and nanostructures - physical devices operating on principles of nanosize scale. Therefore, in addition to impact on materials science, the additional impact will be made on science including nanotechnology, optical fiber, photonics, laser science, and theory of Raman scattering. Further progress of the concept and applications of fibre Bragg grating, diamond Raman lasers, high temperature strain sensors - recently emerged interdisciplinary areas - will potentially have a significant impact on a broad range of other research fields. The project is of broad interest to the academic communities ranging from fundamental materials science and semiconductor devices through to optical fibers and sensing, but also will have a strong impact on the photonic industry. We will seek to establish further collaborative links in Europe to further the impact of the research. We believe that new classes of strain sensors and Raman laser and high performance lithium battery that we are designing and demonstrating in this project will also be of relevance and interest to other emerging applications including medicine, bio-photonics, metrology, and secure communications. The project promotes research and training excellence, exploits new emerging opportunities and provides the co-evolution of education, research, and applications and, therefore, contributes to the transition of Europe to a knowledge-based society, driving the transformation of industry towards higher added value and sustainable development as outlined in FP7 strategic objectives.

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