Papers by Mostafa Moonir Shawrav
The Marie Curie Alumni Association is a strong supporter of open science and for the empowerment ... more The Marie Curie Alumni Association is a strong supporter of open science and for the empowerment of researchers, for example as described in our February 2020 statement 'Researchers call on EU institutions to ensure free circulation of scientific knowledge', our December 2019 statement 'Researchers support sharing of peer-reviewed research without embargoes and restrictions', our September 2018 'Joint Statement on Open Access for Researchers via Plan S' and our May 2019 input to the 'Stakeholder consultation on the future of scholarly publishing and scholarly communication'. <strong>Our previous efforts and positions align well with today's announcement from cOAlition S on a new 'Rights Retention Strategy', which we therefore warmly welcome. </strong> Researchers should never be forced by a publisher to hand over the rights to their work, and we reiterate our previous call upon those publishers that still force barriers on the ...
This Declaration on Sustainable Researcher Careers provides recommendations, drawn up based on a ... more This Declaration on Sustainable Researcher Careers provides recommendations, drawn up based on a symposium organised by major researcher communities, in an effort to empower researchers and secure a globally competitive European Research Area (ERA) and Higher Education sector. The Marie Curie Alumni Association (MCAA), and the European Council of Doctoral Candidates and Junior Researchers (Eurodoc) jointly urge the following critical points to be considered by all stakeholders of European research, especially by research funders and universities: 1. Provide sustainable career prospects for researchers 2. Deploy career management services at organisations employing researchers 3. Put more emphasis on transferable skills training and recognition 4. Provide a wide variety of networking options and services in and outside of academia Failure to address these recommendations is expected to negatively impact on the 1.88 million researchers (in and outside of academia) currently working in the 28 European Union member states in terms of their job security, employability, and mental health, and we therefore urge stakeholders to act promptly.
Beilstein Journal of Nanotechnology, 2017
This work presents a highly effective approach for the chemical purification of directly written ... more This work presents a highly effective approach for the chemical purification of directly written 2D and 3D gold nanostructures suitable for plasmonics, biomolecule immobilisation, and nanoelectronics. Gold nano- and microstructures can be fabricated by one-step direct-write lithography process using focused electron beam induced deposition (FEBID). Typically, as-deposited gold nanostructures suffer from a low Au content and unacceptably high carbon contamination. We show that the undesirable carbon contamination can be diminished using a two-step process – a combination of optimized deposition followed by appropriate postdeposition cleaning. Starting from the common metal-organic precursor Me2-Au-tfac, it is demonstrated that the Au content in pristine FEBID nanostructures can be increased from 30 atom % to as much as 72 atom %, depending on the sustained electron beam dose. As a second step, oxygen-plasma treatment is established to further enhance the Au content in the structures,...
Scientific Reports, 2016
This work introduces an additive direct-write nanofabrication technique for producing extremely c... more This work introduces an additive direct-write nanofabrication technique for producing extremely conductive gold nanostructures from a commercial metalorganic precursor. Gold content of 91 atomic % (at. %) was achieved by using water as an oxidative enhancer during direct-write deposition. A model was developed based on the deposition rate and the chemical composition, and it explains the surface processes that lead to the increases in gold purity and deposition yield. Co-injection of an oxidative enhancer enabled Focused Electron Beam Induced Deposition (FEBID)-a maskless, resistless deposition method for three dimensional (3D) nanostructures-to directly yield pure gold in a single process step, without post-deposition purification. Gold nanowires displayed resistivity down to 8.8 μΩ cm. This is the highest conductivity achieved so far from FEBID and it opens the possibility of applications in nanoelectronics, such as directwrite contacts to nanomaterials. The increased gold deposition yield and the ultralow carbon level will facilitate future applications such as the fabrication of 3D nanostructures in nanoplasmonics and biomolecule immobilization. Gold nanostructures are a promising candidate for applications in plasmonics, biosensors, and electrical contacts owing to their excellent dielectric function, biocompatibility, and electrical properties 1-3. However, most applications require either highly pure or highly conductive gold. To fabricate such nanostructures, there are several nanofabrication techniques, such as conventional photolithography and electron beam lithography, that are used in conjunction with metal layer deposition. Nevertheless, these methods fabricate nanostructures only on planar, smooth surfaces and require a complex multi-step process sequence to pattern material. They are further limited by the obligatory use of photoresist. To overcome these fabrication limitations, an additive direct-write lithography that can generate nanostructures without the need for resist or a photomask would be beneficial. Focused Ion Beam-Induced Deposition (FIBID) has become popular as direct-write nanolithography 4. However, Ga + implantation during deposition and atomic mixing are major downsides of the FIBID process 5. Focused Electron Beam-Induced Deposition (FEBID) is another such direct-write nanofabrication technique, in which an electron beam of a scanning electron microscope is used to locally dissociate precursor molecules, and thereby deposit the desired material on the nanometre scale 6,7. This technique has already shown its potential for different applications. For example, various materials, including iron 8-10 , cobalt 11,12 , tungsten 13 , and platinum 14,15 have already been deposited for applications such as nanomagnet logic 16 , magnetic force microscopy 17-19 , hall sensors 11,20 , patterning stencil masks 21 , separating nanoparticles 22,23 , and plasmonics 24,25. FEBID has also been used to deposit gold nanostructures for metal-oxide semiconductor capacitors 26 and nanoantennas for surface-enhanced Raman spectroscopy 27,28. However, FEBID gold nanostructures are generally fabricated using organometallic precursors such as AuMe 2 (acac) or AuMe 2 (tfac), which contain a large amount of carbon. Therefore, these structures suffer from a carbon contamination problem. Generally, commercially available precursor produces gold nanostructures with a metal purity around 25 at. % 27,29. Such low metal content is the real challenge for a wider application of FEBID gold structures. Previously, carbon-free precursors have been used, which show high metal content 30,31. However, these precursors became unpopular owing to their thermal instability, resulting in premature decomposition. Different post-deposition purification techniques 32-34 , such as annealing 35,36 , substrate heating 37,38 , laser-assisted
Chlorine based focused electron beam induced etching: A novel way to pattern germanium
Materials Science in Semiconductor Processing, 2016
Abstract Focused electron beam induced etching (FEBIE) with chlorine as etching agent has been us... more Abstract Focused electron beam induced etching (FEBIE) with chlorine as etching agent has been used to geometrically shape and to electrically modify semiconductor nanodevices. Selected sections of monocrystalline nanowires were modified directly without the requirement for a photomask or a resist layer. FEBIE as a subtractive nanofabrication technology allows to locally etch active semiconductor devices made of Si or Ge. In this work, chlorine is used as the etchant gas to thin germanium channel structures fabricated by standard photolithography. For effective material removal a sufficiently high electron influence is essential to avoid the pitfalls of this method. Topography and conductivity of FEBIE-modified structures prior and after the etching process was studied by AFM and by electrical I–V characteristics. The presented work demonstrates the potential of Cl-based FEBIE for device prototyping and electrical trimming of future Ge-based nanodevices.
Electron beam deposited noble metals for nanoelectronics applications
In-situ controlled Focused Electron Beam Induced Etching of Semiconductor Nanowires
3-dimensional Processing and Imaging of Gold and Platinum Nanostructures with a SEM
2D and 3D Noble Metal Nanostructures – FEBID Processing and Applications
Hybrids (Spin) Electronic
Applied Physics A, 2014
During the last decades, focused electron beam induced deposition (FEBID) has become a successful... more During the last decades, focused electron beam induced deposition (FEBID) has become a successful approach for direct-write fabrication of nanodevices. Such a deposition technique relies on the precursor supply to the sample surface which is typically accomplished by a gas injection system using a tube-shaped injector nozzle. This precursor injection strategy implies a position-dependent concentration gradient on the surface, which affects the geometry and chemistry of the final nanodeposit. Although simulations already proposed the local distribution of nozzle-borne gas molecules impinging on the surface, this isolated step in the FEBID process has never been experimentally measured yet. This work experimentally investigates the local distribution of impinging gas molecules on the sample plane, isolating the direct impingement component from surface diffusion or precursor depletion by deposition. The experimental setup used in this work maps and quantifies the local impinging rate of argon gas over the sample plane. This setup simulates the identical conditions for a precursor molecule during FEBID. Argon gas was locally collected with a sniffer tube, which is directly connected to a residual gas analyzer for quantification. The measured distribution of impinging gas molecules showed a strong position dependence. Indeed, a 300-lm shift of the deposition area to a position further away from the impingement center spot resulted in a 50 % decrease in the precursor impinging rate on the surface area. With the same parameters, the precursor distribution was also simulated by a Monte Carlo software by Friedli and Utke and showed a good correlation between the empirical and the simulated precursor distribution. The results hereby presented underline the importance of controlling the local precursor flux conditions in order to obtain reproducible and comparable deposition results in FEBID.
Among various multi-metal combinations, Au-Fe nanoalloys are envisaged as prospective materials f... more Among various multi-metal combinations, Au-Fe nanoalloys are envisaged as prospective materials for data storage applications. Here we report on the first successful achievement of Au-Fe nanoalloys using focused electron beam-induced deposition (FEBID), exploiting the possibility of directly writing nanostructures at nanometer resolution. Gaseous organometallic precursors are injected simultaneously into the deposition chamber to co-deposit Fe and Au within the same nanostructure. Fabricated nanostructures show a spatially uniform elemental ratio of iron to gold that can be tailored by experimental conditions.
Focused electron beam-induced CVD of iron: A practical guide for direct writing
ABSTRACT Magnetic materials synthesized on the nanometer-scale level are essential for several ap... more ABSTRACT Magnetic materials synthesized on the nanometer-scale level are essential for several applications, such as spintronics and magnetologic. As a successful nanofabrication approach, focused electron beam-induced deposition (FEBID) stands out as a direct-write technique. FEBID uses an electron beam to locally induce a CVD process, avoiding the use of masks and resists. In this work, Fe–based nanostructures are synthesized on Si(100) by FEBID, starting from iron pentacarbonyl. A systematic variation of FEBID parameters is performed, to study their influence on the geometry and composition of the deposit. Based on the results, specific deposition conditions are suggested for magneto-logic applications and fabrication of large structures.
ACS applied materials & interfaces, Jan 21, 2015
Three-dimensional gold (Au) nanostructures offer promise in nanoplasmonics, biomedical applicatio... more Three-dimensional gold (Au) nanostructures offer promise in nanoplasmonics, biomedical applications, electrochemical sensing and as contacts for carbon-based electronics. Direct-write techniques such as focused-electron-beam-induced deposition (FEBID) can provide such precisely patterned nanostructures. Unfortunately, FEBID Au traditionally suffers from a high nonmetallic content and cannot meet the purity requirements for these applications. Here we report exceptionally pure pristine FEBID Au nanostructures comprising submicrometer-large monocrystalline Au sections. On the basis of high-resolution transmission electron microscopy results and Monte Carlo simulations of electron trajectories in the deposited nanostructures, we propose a curing mechanism that elucidates the observed phenomena. The in situ focused-electron-beam-induced curing mechanism was supported by postdeposition ex situ curing and, in combination with oxygen plasma cleaning, is utilized as a straightforward purifi...
Mask-free prototyping of metal-oxide-semiconductor devices utilizing focused electron beam induced deposition
physica status solidi (a), 2013
ABSTRACT Focused electron beam induced deposition (FEBID) is a novel direct-writing technique to ... more ABSTRACT Focused electron beam induced deposition (FEBID) is a novel direct-writing technique to produce noble metal nanostructures. In this work, FEBID has been employed for the first time to fabricate metal-oxide-semiconductor capacitors (MOSCAPs). Experimental parameters such as precursor temperature, substrate temperature and the (de)focus of the electron beam have been optimized to deposit electrode structures of a relatively large area within a short timeframe. Using FEBID, gold electrodes have been deposited on top of an atomic layer deposited (ALD) dielectric aluminum oxide layer. Chemical composition of the produced structures has been studied using energy dispersive X-ray spectroscopy (EDX). Current–voltage (I–V) measurements have confirmed the conductivity of FEBID gold nanowires (NWs). Measured capacitance–voltage (C–V) characteristics of FEBID-fabricated MOSCAP prototypes resemble the typical C–V characteristics of conventionally fabricated MOSCAPs, thus confirming the functionality of our FEBID devices.Illustration of a MOS capacitor fabricated by FEBID.
physica status solidi (a), 2013
ACS Applied Materials & Interfaces, 2014
Nanomagnet logic (NML) is a relatively new computation technology that uses arrays of shape-contr... more Nanomagnet logic (NML) is a relatively new computation technology that uses arrays of shape-controlled nanomagnets to enable digital processing. Currently, conventional resist-based lithographic processes limit the design of NML circuitry to planar nanostructures with homogeneous thicknesses. Here, we demonstrate the focused electron beam induced deposition of Fe-based nanomaterial for magnetic inplane nanowires and out-of-plane nanopillars. Three-dimensional (3D) NML was achieved based on the magnetic coupling between nanowires and nanopillars in a 3D array. Additionally, the same Fe-based nanomaterial was used to produce tilt-corrected high-aspect-ratio probes for the accurate magnetic force microscopy (MFM) analysis of the fabricated 3D NML gate arrays. The interpretation of the MFM measurements was supported by magnetic simulations using the Object Oriented MicroMagnetic Framework. Introducing vertical out-of-plane nanopillars not only increases the packing density of 3D NML but also introduces an extra magnetic degree of freedom, offering a new approach to input/output and processing functionalities in nanomagnetic computing.
arXiv: Optics, 2020
The determination of the chemical content is crucial for the quality control in high-precision de... more The determination of the chemical content is crucial for the quality control in high-precision device fabrication and advanced process development. For reliable chemical composition characterization, certain interaction volume of the target material is necessary for conventional techniques such as energy-dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS). This remains however a challenge for nanostructures. We hereby propose an alternative technique for measuring chemical composition of nanostructures with limited volume. By measuring the differences in the optical absorption of the nanostructure due to the differences in the chemical composition with the resonance frequency detuning of a nanomechanical resonator as well as the assistance of the analytical optical modelling, we demonstrate the possibility of characterizing the carbon content in the direct-write focused electron beam induced deposition (FEBID) gold nanostructures.
Nanomaterials
Biomimetic structures such as structural colors demand a fabrication technology of complex three-... more Biomimetic structures such as structural colors demand a fabrication technology of complex three-dimensional nanostructures on large areas. Nanoimprint lithography (NIL) is capable of large area replication of three-dimensional structures, but the master stamp fabrication is often a bottleneck. We have demonstrated different approaches allowing for the generation of sophisticated undercut T-shaped masters for NIL replication. With a layer-stack of phase transition material (PTM) on poly-Si, we have demonstrated the successful fabrication of a single layer undercut T-shaped structure. With a multilayer-stack of silicon oxide on silicon, we have shown the successful fabrication of a multilayer undercut T-shaped structures. For patterning optical lithography, electron beam lithography and nanoimprint lithography have been compared and have yielded structures from 10 µm down to 300 nm. The multilayer undercut T-shaped structures closely resemble the geometry of the surface of a Morpho b...
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Papers by Mostafa Moonir Shawrav