Rainer Adelung

Christian-Albrechts-Universität zu Kiel, Kiel, Schleswig-Holstein, Germany

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Publications (118)516.51 Total impact

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    ABSTRACT: Research on semiconducting oxide nanocrystals will likely remain one of the leading topics in condensed matter physics and advanced functional materials. Looking beyond this field, chemically heterogeneous nanocrystals systems based on mixed phases have been assembled as reported here for shell-core Ga2O3/GaN:Ox@SnO2 nanocables, i. e. long and single crystalline SnO2 belts/wires as core surrounded with a shell composed of GaN:Ox and Ga2O3 nanoparticles. Subsequently, nano- and micro-sensors from an individual shell-core Ga2O3/GaN:Ox@SnO2 nanocable on the chip have been realized via localized maskless growth of metal using dual-beam FIB-SEM instrument. In contrast to pure SnO2 nanowire-based sensor, here fabricated nano- and micro-devices on individual hybrid nano- or micro-cables on chip are quite stable, highly sensitive (the current ratio IUVON/IOFF > 104), higher and faster switching in UV photodetection, as well as air/vacuum and temperature sensing capabilities. The SnO2 nano- and microbelts/wires networks were synthesized by the flame transport synthesis and a shell layer composed of Ga2O3/GaN:Ox nanoparticle was deposited on them by magnetron sputtering. The scanning electron microscopy and transmission electron microscopy results revealed that the Ga2O3/GaN:Ox nanocrystallite shells are uniformly deposited on SnO2 networks. The detailed TEM structural studies on the as-grown and annealed structures confirmed that the nanocable is made from mixed phases by an excellent agreement with the standard data for rutile SnO2, amorphous GaN:Ox and monoclinic β-Ga2O3. Herein, we resolve two essential problems regarding the nano-construction of an efficient nanosensor. First, the simplest process fabrication of the highly protected shell-core nanocables with improved electrical properties is achieved by cost-effective synthesis in a controlled manner. Second, construction of a non-planar 3D nanoscale double-heterojunctions with a large surface area is realized via an efficient technique. It allows surface protection of nanosensors during its fabrication and operation in different ambient conditions. The developed nanomaterial sparks interest for further studies on different hybrid semiconducting oxides as promising candidates for fabricating multifunctional nano- and micro-sensors and photodetectors.
    Sensors and Actuators B Chemical 06/2015; Online Accepted Article. DOI:10.1016/j.snb.2015.06.112 · 3.84 Impact Factor
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    ABSTRACT: Growth of freestanding nano- and microstructures with complex morphologies is a highly desired aspect for real applications of nanoscale materials in various technologies. Zinc oxide tetrapods (ZnO-T) which exhibit three-dimensional (3D) shapes, are of major importance from technological applications point of view, thus efficient techniques for growth of different variety of tetrapod-based networks is demanded. Here, we demonstrate the versatile and single step synthesis of ZnO-T with different arm morphologies by simple flame transport synthesis (FTS) approach forming a network. The morphological evolutions and the structural intactness of these tetrapods have been investigated in detail by scanning electron microscopy, X-ray diffraction, and micro-Raman measurements. For a deeper understanding about the crystallinity, detailed high- resolution transmission electron microscopy studies on a typical ZnO tetrapod structure are presented. The involved growth mechanism for ZnO tetrapods with various arm morphologies is discussed under the influence of variations in experimental conditions. These ZnO-T have been utilized for photocatalytic degradation and nanosensing applications. The photocatalytic activities of these ZnO-T with different arm morphologies forming networks have been investigated through the photocatalytic decolorization of a methylene blue solution under ultra-violet (UV) light illumination at ambient temperature. The results show that these ZnO-T exhibit strong photocatalytic activities against MB and its complete degradation can be achieved in very short time. In another application, a prototype of nano-electronic sensing device has been built from these ZnO-T's interconnected networks and accordingly utilized for UV detection and H2 gas sensing. The fabricated device structures showed excellent sensing behaviours for promising practical applications. The involved sensing mechanisms with respect to UV photons and H2 gas have been discussed in detail. We consider that such multifunctional nanodevices based on ZnO tetrapods interconnected network will be of interest for various advanced applications.
    ACS Applied Materials & Interfaces 06/2015; Just Accepted. DOI:10.1021/acsami.5b02816 · 5.90 Impact Factor
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    ABSTRACT: Stretchable ceramic networks built from quasi-one-dimensional (Q1D) structures are important candidates for various applications of nanostructures in real-world technologies. Here, a flame transport synthesis approach is developed enables versatile synthesis of interconnected SnO2 nanowire networks. These SnO2 structures exhibit interesting defects that are very relevant for oxide material-engineering community. Devices based on Q1D SnO2 structure networks show enormous potential for gas/UV sensing
    06/2015; DOI:10.1002/aelm.201500081
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    physica status solidi (RRL) - Rapid Research Letters 03/2015; 9(3):Cover Story. DOI:10.1002/pssr.201570615 · 2.34 Impact Factor
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    ABSTRACT: In this paper, we show that long-duration-photoconductivity decay (LDPCD) and persistent photoconductivity (PPC) in porous InP structures fabricated by anodic etching of bulk substrates can be controlled through the modification of the sample morphology. Particularly, the PPC inherent at low temperatures to porous InP layers with the thickness of skeleton walls comparable with pore diameters is quenched in structures consisting of ultrathin walls produced at high anodization voltages. The relaxation of photoconductivity in bulk InP substrates, porous layers, and utrathin membranes is investigated as a function of temperature and excitation power density. The obtained results suggest that PPC in porous InP layers is due to porosity induced potential barriers which hinder the recombination of photoexcited carriers, while the photoconductivity relaxation processes in ultrathin membranes are governed by surface states.
    Semiconductor Science and Technology 03/2015; 30(3). DOI:10.1088/0268-1242/30/3/035014 · 2.21 Impact Factor
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    ABSTRACT: Titania (TiO2) exists in several phases possessing differ-ent physical properties. In view of this fact, we report on three types of hydrogen sensors based on individual TiO2 nanotubes (NTs) with three different structures con-sisting of amorphous, anatase or anatase/rutile mixed phases. Different phases of the NTs were produced by controlling the temperature of post-anodization thermal treatment. Integration of individual TiO2 nanotubes on the chip was performed by employing metal deposition function in the focused ion beam (FIB/SEM) instrument. Gas response was studied for devices made from an as-grown individual nanotube with an amorphous structure, as well as from thermally annealed individual nanotubes exhibiting anatase crystalline phase or anatase/rutile mixed heterogeneous structure. Based on electrical measurements using two Pt metal contacts deposited on a single TiO2 nanotube, we show that an individual NT with a mixed anatase/rutile crystal structure (annealed at 650°C) has the highest gas response to hydrogen at room temperature. The obtained results demonstrate that the structural properties of the TiO2 NTs make them a viable new gas sensing nanomaterial at room temperature.
    physica status solidi (RRL) - Rapid Research Letters 02/2015; 9(3):171–174. DOI:10.1002/pssr.201409562 · 2.34 Impact Factor
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    ABSTRACT: Three dimensional (3D) elastic hybrid networks built from interconnected nano- and microstructure building units, in the form of semiconducting-carbonaceous materials, are potential candidates for advanced technological applications. However, fabrication of these 3D hybrid networks by simple and versatile methods is a challenging task due to the involvement of complex and multiple synthesis processes. In this paper, we demonstrate the growth of Aerographite-GaN 3D hybrid networks using ultralight and extremely porous carbon based Aerographite materials as templates by a single step hydride vapor phase epitaxy process. The GaN nano- and microstructures grow on the surface of Aerographite tubes and follow the network architecture of the Aerographite template without agglomeration. The synthesized 3D networks are integrated with the properties from both, i.e., nanoscale GaN structures and Aerographite in the form of flexible and semiconducting composites which could be exploited as next generation materials for electronic, photonic and sensors applications.
    Scientific Reports 02/2015; 5:8839. DOI:10.1038/srep08839 · 5.58 Impact Factor
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    ABSTRACT: We show that long-duration-photoconductivity decay (LDPCD) and persistent photoconductivity (PPC) in porous InP structures produced by anodization of InP substrates can be controlled through the control of their morphology. Particularly, the PPC inherent at low temperatures to porous InP layers with the thickness of skeleton walls comparable with pore diameters is quenched in structures consisting of ultrathin walls produced at high anodization voltages.
    8th International Conference on Microelectronics and Computer Science, Chisinau; 10/2014
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    ABSTRACT: ZnO particles of different size and structures were used as fillers to modify the silicone rubber, in order to reveal the effect of the filler shape in the polymer composites. Tetrapodal shaped microparticles, short microfibers/whiskers, and nanosized spherical particles from ZnO have been used as fillers to fabricate the different ZnO-Silicone composites. The detailed microstructures of the fillers as well as synthesized composites using scanning electron microscopy have been presented here. The tensile elastic modulus and water contact angle, which are important parameters for bio-mimetic applications, of fabricated composites with different fillers have been measured and compared. Among all three types of fillers, tetrapodal shaped ZnO microparticles showed the best performance in terms of increase in hydrophobicity of material cross-section as well as the stiffness of the composites. It has been demonstrated that the tetrapodal shaped microparticles gain their advantage due to the special shape, which avoids agglomeration problems as in the case for nanoparticles, and the difficulty of achieving truly random distribution for whisker fillers.
    PLoS ONE 09/2014; 9:e106991. DOI:10.1371/journal.pone.0106991 · 3.53 Impact Factor
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    ABSTRACT: The different mechanisms contributing to adhesion between two polymer surfaces are summarized and described in individual examples, which represent either seminal works in the field of adhesion science or novel approaches to achieve polymer-polymer adhesion. A further objective of this article is the development of new methodologies to achieve strong adhesion between low surface energy polymers.
    Macromolecular Rapid Communications 09/2014; 35(18). DOI:10.1002/marc.201400200 · 4.61 Impact Factor
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    ABSTRACT: Specific applications of particles and particle agglomerates with semiconductor surfaces are provided. The particles and particle agglomerates display a high affinity for viral particles, and may be used therapeutically and/or prophylactically to treat or prevent viral infections. The particles and particle agglomerates may also be used to remove viral particles from a surface or fluid, e.g., as an absorbent in a filter, applied to surfaces to render them virostatic, and as tool to handle viral particles, e.g., for research, diagnostic, or decontamination purposes.
    Ref. No: US20140056947A1, Year: 08/2014
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    ABSTRACT: The characterization of the wetting on superhydrophobic surfaces is rather complex. Usual contact angle experiments are difficult to perform and the lateral movement of droplets as well as the pinning at point defects on the surface can disturb the measurements. Even if precise contact angle measurements can be performed the information gain is limited if the surface is heterogeneously wetted. This results in the possibility of two surfaces with different roughness, different surface energy and thus different underlying wetting mechanisms exhibiting the same contact angle. We introduce the utilization of dynamic wetting experiments as an additional surface probe which allows a better characterization of superhydrophobic surfaces. A theoretical model is presented which describes the spreading of water jets on a superhydrophobic surface and allows the determination of the wetted fraction of a heterogeneously wetted superhydrophobic surface. The determined values for the wetted fraction identify a common problem when building artificial super hydrophobic surfaces and can fundamentally improve their understanding.
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    ABSTRACT: We present a fully integrated microelectromechanical magnetic field sensor based on the Delta E effect. The vacuum encapsulated sensor extends our previous approach [B. Gojdka et al., Appl. Phys. Lett. 99, 223502 (2011); Nature 480, 155 (2011)] and now involves an intermediate piezoelectric AlN layer between a SiO2 cantilever and a magnetostrictive FeCoBSi top layer. The AlN layer serves two functions: It drives the resonator, and it is used for electrical read out. The limit of detection was strongly enhanced to 12 nT/root Hz p at 10 Hz. (C) 2014 AIP Publishing LLC.
    Applied Physics Letters 08/2014; 105(5):052414. DOI:10.1063/1.4891540 · 3.52 Impact Factor
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    ABSTRACT: We demonstrate a new technique that requires a relatively low temperature of 670-800 degrees C to synthesize in 10-20 min high crystalline quality MoO3 nano- and microbelts and ribbons. The developed technological process allows rapid synthesis of large amounts of MoO3 nano- and microsheets, belts, and ribbons, and it can be easily scaled up for various applications. Scanning electron microscopy (SEM) studies revealed that the MoO3 nano- and microbelts and ribbons are synthesized uniformly, and the thickness is observed to vary from 20 to 1000 nm. The detailed structural and vibrational studies on grown structures confirmed an excellent agreement with the standard data for orthorhombic alpha-MoO3. Also, such freestanding nano- and microstructures can be transferred to different substrates and dispersed individually. Using focused ion beam SEM, MoO3- based 2D nano- and microsensors have been integrated on a chip and investigated in detail. The nanosensor structures based on MoO3 nano- and microribbons are quite stable and moderately reversible with respect to rises and drops in ethanol vapors. It was found that MoO3 nano- and microribbons of various sizes exhibit different sensitivity and selectivity with respect to ethanol, methanol, and hydrogen gases. The developed technique has great potential for further studies of different metal oxides, nano- and microsensor fabrication, and especially for multifunctional applications.
    The Journal of Physical Chemistry C 06/2014; 118(27):15068–15078. DOI:10.1021/jp5038415 · 4.84 Impact Factor
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    ABSTRACT: In this work we present the fabrication of metal and metal oxide nanowires directly on chip by a new top-down technique based on thin film fracture (TFF) approach. Developed procedure works on the simple principle of constructive-destruction and cracks/fractures formation on photoresist film between two pre-patterned gold contacts on silicon chip. The metal and metal oxide nanowires were grown directly on the pre-patterned chip. A detailed overview about the formation of different types of fractures has been depicted. Nanowire fabrication by TFF approach involves only two steps, i.e., fracturing a lithographically patterned photoresist followed by physical vapor deposition process. With this approach, nanowires from desired inorganic materials (metals, metal-oxides or mixed oxides etc.) can be easily synthesized in a controlled manner. Nanowires from Au, Cu, Ti and ZnO with different thicknesses have been prepared on Si substrates and characterized. The morphological evolutions of the fabricated nanowires have been investigated by atomic force microscopy. Since these nanowires are directly integrated on the chips between two gold electrical contacts, electrical characteristics of device structures have been performed and discussed. A photodetector was designed based on such a simple technique by nanobridging individual ZnO nanowire into electrically accessible device structures. Obtained results are very important for further development of nanoelectronics based on ZnO nanowires-bridged devices integrated on chip in a controlled manner and cost-effective procedure due to its unique potential for integrating with silicon based technology.
    Journal of Nanoelectronics and Optoelectronics 05/2014; 9:239-246. DOI:10.1166/jno.2014.1576 · 0.37 Impact Factor
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    ABSTRACT: Direct growth of quasi-one-dimensional nano- and microstructures in desired places of complex shaped substrates using simple growth methods is highly demanded aspect for various applications. In this work we have demonstrated direct integration of ZnO nano- and microneedles into Si trenches by a novel flame transport synthesis approach in a single fabrication step. Growth of partially and fully covered or filled trenches in Si substrate with ZnO nano- and microneedles has been investigated and is discussed here. Detailed microstructural studies revealed the evolution of the ZnO nano- and microneedles as well as their firm adhesion to the wall in the Si trenches. Micro-photoluminescence measurements at different locations along the length of needles confirmed the good crystalline quality and also the presence of whispering gallery mode resonances on the top of needles due to their hexagonal shape. Faceted ZnO nano- and microstructures are also very important candidates with regard to photocatalytic activity. First photocatalytic measurements from the grown ZnO nano- and microneedles have shown strong degradation of methylene blue which demonstrate that these structures can be of significant interest for photocatalysis and self-cleaning chromatography columns.
    ACS Applied Materials & Interfaces 04/2014; 6(10). DOI:10.1021/am5010877 · 5.90 Impact Factor
  • Ion Tiginyanu, Rainer Adelung
    Journal of Nanoelectronics and Optoelectronics 04/2014; 9(2). DOI:10.1166/jno.2014.1588 · 0.37 Impact Factor

Publication Stats

1k Citations
516.51 Total Impact Points

Institutions

  • 1998–2015
    • Christian-Albrechts-Universität zu Kiel
      • • Institute for Materials Science
      • • Institute of Experimental and Applied Physics (IEAP)
      • • Chair of Multicomponent Materials
      • • Faculty of Engineering
      • • Institut für Theoretische Physik und Astrophysik
      Kiel, Schleswig-Holstein, Germany
  • 2014
    • Friedrich Schiller University Jena
      Jena, Thuringia, Germany
  • 2010
    • University Medical Center Schleswig-Holstein
      Kiel, Schleswig-Holstein, Germany
  • 2002–2004
    • Case Western Reserve University
      • Department of Materials Science and Engineering
      Cleveland, Ohio, United States
    • University of Hamburg
      • Institute of Applied Physics
      Hamburg, Hamburg, Germany