Ion Beam Nanostructuration of Germanium for Renewable Energy Applications

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Short description of project idea : 
To implement ion implantation as a technological process to produce tailored porous semiconductor thin films, in particular of Germanium. The latter can be used for renewable energy applications like thermoelectric thin film devices and high performance lithium ion batteries or in sensing applications. The idea is to exploit a phenomenon of ion irradiation induced surface damage peculiar of Germanium and of few other reported semiconductors (GaSb, InSb). In fact, when heavy mass ions (mass similar or higher than Ge one) are irradiated at high fluence (> 5E14 ion/ cm2) on Ge surface, the latter transform in a nanometric porous surface, where pore diameter is on the order of 10 nm and their depth of 100 nm, varying with energy and fluence combinations. The appealing of the effect is that wide areas (wafers) of nanometric porous surfaces can be produced with a well-established semiconductor process (ion implantation) without any need of further steps like lithography, etching or similar. Furthermore, being the phenomenon only linked to the mass of the impinging ions, it is possible to design experiments bombarding with specific ions not only to induce porosity but also to produce a desired alloy (Ge-based).
Fondazione Bruno Kessler/ Center for Materials and Microsytems
Main areas of expertise: 
Inside CMM, the Micro-Nano characterization & fabrication Facility worksin two main areas: - microfabrication - materials characterization The Microfabrication Area runs two separate cleanrooms, the Detector Cleanroom dedicated to the development of radiation sensors and the MEMS cleanroom where micro devices and sensors for different applications are developed. The Detectors cleanroom is a complete CMOS like pilot line with lithographic capabilities down to a few hundred nanometers with a rather strict list of materials to be processed to avoid cross contamination. The MEMS cleanroom a much more flexible laboratory devoted to development of devices where the integration of different materials with silicon is needed. The Materials Characterization Area runs different laboratories for the physical/chemical analysis of materials, surfaces and interfaces. The techniques available include Secondary Ion Mass spectrometry (SIMS), Proton Transfer Mass Spectrometry (PTRMS), X-Ray Fluorescence (XRF), X-ray Diffraction (XRD), X-Ray Photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) and Electron Back Scatter Diffraction (EBSD), Scanning Probe Microscopy (SPM) with Atomic Force Microscopy (AFM), Scanning Spreading Resistance Microscopy (SSRM), Kelvin Probe Force Microscopy (FPFM), Scanning Capacitance Microscopy (SCM). Main experience of the MNF group on topics related to this project is on semiconductor physics, semiconductor doping, ion implantation and related processes (annealing, diffusion, etc.), semiconductor characterization.
Main objectives of the project and how will they be achieved: 
Main objectives
1. To understand the basic mechanism behind the phenomenon in order to exploit them to create porous surfaces/ thin films with the characteristics needed for specific technological applications. Furthermore, it should be investigated the possibility to produce similar structures on other semiconductor materials, specifically on Silicon. 2. To produce thin films (~100 nm thickness) either on insulator (thick SiO2 on Si wafers) or metallic substrates. In fact, most results reported in literature dealt with bulk substrates or very thick films (> 1 µm), whereas for most technological applications thin films are more appealing. To this aim, not only the optimization of the ion implantation process will be investigated but also complementary fabrication steps, like the deposition of thin films or the functionalization/ optimization of the produced nano-void structures. 3. To test the produced porous thin films on three main applications: thermoelectric thin films, lithium ion battery anodes, gas sensing or other detecting applications where high porosity together with conductive/ semiconductor nature can be of appealing.
Challenges that may determine the impact of the project: 
Optimization of Germanium nano-structures specifically tailored for requested applications
The phenomenon reported in literature has not been fully investigated so far neither in terms of fundamental mechanisms nor in view of technological applications. In particular, for technological applications some specific nano-void sizes and structures can be required. The investigation of the fundamental mechanisms should help understanding whether these requests are feasible or not and if the finally produced materials are actually optimal for the applications in exam.
Reduction of the production costs for Germanium nano-void network material.
The project aims to exploit well-established semiconductor fabrication processes (ion implantation, CVD, PVD) to induce precise nano-void network on areas as wide as typical Si wafers. From this point of view, the processes can look economically affordable and easily scalable to the industrial level. However, it is well known that Germanium is rather expensive, especially if compared to Silicon. Therefore, even if high performance applications can justify higher production costs, the project should also target two main research directions in order to reduce them: 1. To optimize the ion implantation based process to produce the nano-void network on Germanium thin films instead of bulk wafer. This would reduce the costs related to the substrate material. Furthermore, low cost Ge thin film deposition techniques (PVD/ evaporation) should be tested instead of CVD/ epitaxy. 2. To discover/ evaluate the possibility to induce the same effect of heavy ion induced nano-void network on Silicon. In particular, both theoretical work or basic experiments should be planned to investigate this possibility and evaluate the properties of the obtained porous material, if any.
Testing of the applications
The proposed applications for the nanostructured Germanium need to be addressed by expert groups of the respective sectors. Therefore, the choice of these partners is crucial in order to establish partnerships able not only to test the material properties but also to address the changes/ adjustments to maximize the results. The partner profile is of someone not only very skilled on some specific class of materials/ testing but also with a good vision of all the possibility of the application sector.
Partners that have already expressed interest in the project and expected role: 
Although we may have already contacted some possible partners dealing with ion beam science, at this stage we would prefer to wait to communicate them once a possible consortium has been actually established with really interested partners.
Profile of partners sought and expected role: 
Ion Beam Science Center/ Laboratory
The role of this partner should be of workhorse for all the experimental work, especially for the fundamental studies. The laboratory should be provided with several ion implantation tools able to cover a wide range of ion irradiation conditions in terms of ion species, energy, fluence and incidence angle, substrate temperature. Flexibility towards several substrates should be ensured in order to allow irradiation also of metallic substrates or other ‘not-standard’ materials. Possibly, some real time monitoring of the irradiation process or complimentary analytical techniques on site would allow a first check of the tested process.
Ion Beam Process Commercial/ Industrial provider
The partner can be a SME able to provide commercial services of ion implantation using industrial level equipment. Its role is double: to prepare samples on a wide scale and to prove the scalability of the proposed process. Relative flexibility in terms of ion species and conditions is also a request for this partner.
Characterization/ Electron Microscopy laboratory.
The partner must ensure a high-level characterization of the produced samples/ materials, specifically with electron microscopy. Both scanning electron microscope and transmission electron microscope should be present together with high-level technicians/ researchers able to provide ‘state-of-art’ characterizations.
Modelling/ Theoretical group working on ion beam/ solid interactions
The partner should be expert in modelling ion beam/ solid interactions, lattice defect generation and kinetics, solid state diffusion. Main roles would be to provide models to justify experimental results and propose experimental approaches/ solutions to target nano-void size and shape or to try to induce the same structures in new materials, e.g. Silicon.
Thermoelectric physics research group/ SME.
The partner should preferably be a SME (in alternative an academic research group) with a high-level experience on thermoelectric thin film research, in particular on semiconductors. The partner should provide the laboratory facilities to test the thermoelectric properties of the produced materials and give input for the research/ optimization directions.
Lithium Ion Battery research group/ SME.
The partner should preferably be a SME (in alternative an academic research group) with a high-level experience on lithium ion battery research, with particular reference to innovative anode materials. The partner should provide the laboratory facilities to test the properties of the produced materials as anode for batteries and give input for the research/ optimization directions.
Previous, relevant EU project experience: 
ANNA - European Integrated Activity of Excellence and Networking for Nano and Micro-Electronics Analysis
FP6 (Proposal/ contract No. 026134-I3)
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Name of the organisation: 
Short description of organisation: 
Fondazione Bruno Kessler is a research non-profit public interest entity. Being the result of a history that is more than half a century old, through 2 scientific hubs, 7 research centers, 410 researchers, 2 specialized libraries, 7 laboratories, FBK aims to results of excellence in science and technology with particular emphasis on interdisciplinary approaches and to the applicative dimension. The Centre for Materials and Microsystems (CMM) is an applied research centre that operates in the following areas of science and technology: materials and interfaces, devices and microsystems, integrated systems.

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