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Suche nach „[Benstetter] [Günther]“ hat 151 Publikationen gefunden
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    NachhaltigElektrotechnik und MedientechnikIQMA

    Zeitschriftenartikel

    Christoph Metzke, Werner Frammelsberger, Jonas Weber, F. Kühnel, K. Zhu, M. Lanza, Günther Benstetter

    On the Limits of Scanning Thermal Microscopy of Ultrathin Films

    Materials, vol. 13, no. 3

    2020

    DOI: 10.3390/ma13030518

    Abstract anzeigen

    Heat transfer processes in micro- and nanoscale devices have become more and more important during the last decades. Scanning thermal microscopy (SThM) is an atomic force microscopy (AFM) based method for analyzing local thermal conductivities of layers with thicknesses in the range of several nm to µm. In this work, we investigate ultrathin films of hexagonal boron nitride (h-BN), copper iodide in zincblende structure (γ-CuI) and some test sample structures fabricated of silicon (Si) and silicon dioxide (SiO2) using SThM. Specifically, we analyze and discuss the influence of the sample topography, the touching angle between probe tip and sample, and the probe tip temperature on the acquired results. In essence, our findings indicate that SThM measurements include artefacts that are not associated with the thermal properties of the film under investigation. We discuss possible ways of influence, as well as the magnitudes involved. Furthermore, we suggest necessary measuring conditions that make qualitative SThM measurements of ultrathin films of h-BN with thicknesses at or below 23 nm possible.

    NachhaltigElektrotechnik und MedientechnikIQMA

    Zeitschriftenartikel

    W. Ni, L. Liu, Y. Zhang, C. Niu, H. Fan, G. Song, D. Liu, Günther Benstetter, G. Lei

    Effect of intermittent He/D ion irradiations on W nano-fuzz growth over W targets

    Vacuum, vol. 173, no. March

    2020

    DOI: 10.1016/j.vacuum.2019.109146

    Abstract anzeigen

    The intermittent He/D ion irradiations of polycrystalline W have been performed at the ion energy of 50 eV by changing the time of the single irradiations and the irradiation temperature. All irradiated W specimens have been observed by scanning electron microscopy, and the effect of intermittent He/D ion irradiations on the W fuzz growth has been analyzed. The W fuzz growth over W targets does not show the clear dependence on the intermittent He/D ion irradiations, where the He/D ion fluence of the single irradiations typically varies from 5.0 × 1024 to 2.5 × 1025/m2. However, a slight change in the W surface temperature during the single He ion irradiations significantly affects the W fuzz growth rate. Analysis indicates that W fuzz growth is significantly affected by the total He ion fluence varying from 5.0 × 1024 to 5.0 × 1025/m2 and the irradiation temperature varying from 1100 to 1450 K. This current study will play a crucial role in understanding the W fuzz growth under the periodic He/D ion irradiations of W divertor in fusion reactors, such as ELMs.

    NachhaltigElektrotechnik und MedientechnikIQMA

    Vortrag

    Christoph Metzke, Günther Benstetter, Werner Frammelsberger, Jonas Weber, F. Kühnel

    Temperature dependent investigation of hexagonal boron nitride films using scanning thermal microscopy

    Poster presentation

    6th Nano Today Conference 2019, Lisbon, Portugal

    2019

    NachhaltigElektrotechnik und MedientechnikIQMA

    Zeitschriftenartikel

    Z. Bi, D. Liu, Y. Zhang, L. Liu, Y. Xia, Y. Hong, H. Fan, Günther Benstetter, G. Lei, L. Yan

    The evolution of He nanobubbles in tungsten under fusion-relevant He ion irradiation conditions

    Nuclear Fusion, vol. 59, no. 8

    2019

    DOI: 10.1088/1741-4326/ab2472

    Abstract anzeigen

    He-induced W nanofuzz growth over the W divertor target is one of the main limiting factors affecting the current design and development of fusion reactors. In this paper, based on He reaction rate model in W, we simulate the growth and evolution of He nanobubbles during W nanofuzz formation under fusion-relevant He+ irradiation conditions. Our modeling unveils the existence of He nanobubble-enriched W surface layer (<10 nm), formed due to the He diffusion in W crystal into defect sites. At an elevated temperature, the growth of He bubbles in the W surface layer prevents He atoms diffusing into the deep layer (>10 nm). The formation of W nanofuzz at the surface is attributed to surface bursting of high-density He bubbles with their radius of ~4 nm, and an increase in the surface area of irradiated W. Our findings have been well confirmed by the experimental measurements.

    NachhaltigElektrotechnik und MedientechnikIQMA

    Zeitschriftenartikel

    W. Ni, L. Liu, Y. Zhang, H. Fan, G. Song, D. Liu, Günther Benstetter, G. Lei

    Mass loss of pure W, W-Re alloys, and oxide dispersed W under ITER-relevant He ion irradiations

    Journal of Nuclear Materials, vol. 527

    2019

    DOI: 10.1016/j.jnucmat.2019.151800

    Abstract anzeigen

    In this study, polycrystalline W, W-Re alloys, and La2O3 and Y2O3 dispersion-strengthened W have been irradiated by our large-power materials irradiation experimental system (LP-MIES) at the irradiation temperature of 1360–1460 K. Our measurements show that the W nano-fuzz layer which is < 5.2 μm thick has been formed over all the specimens exposed to the low-energy (50 or 100 eV) and high-flux (1.37 × 1022–1.62 × 1022 ions/m2⋅s) He+ irradiations. The mass loss of the fuzz layer almost linearly increases with the He+ fluence, which does not show any dependence on the thickness of fuzz layer varying from 1.1 to 5.2 μm La2O3 and Y2O3 dispersions into W significantly suppress the growth of W fuzz, indicating that He diffusion and the evolution of He nano-bubbles in the near-surface can be significantly influenced due to the dispersion. After He+ (100 eV) irradiation at He+ fluence of 5.83 × 1026/m2, the mass loss of 0.1 vol% - 1.0 vol% La2O3-dispersed W is about 20% lower than the one of the pure W, and the La2O3 dispersed W exhibits the best erosion resistance among various W material grades. Our analysis indicates that both the surface sputtering of W fuzz by energetic ions and surface bursting of He nano-bubbles can be responsible for the mass loss of W under ITER-relevant He+ irradiations.

    NachhaltigElektrotechnik und MedientechnikIQMA

    Zeitschriftenartikel

    C. Wen, X. Jing, F. Hitzel, C. Pan, Günther Benstetter, M. Lanza

    In Situ Observation of Current Generation in ZnO Nanowire Based Nanogenerators Using a CAFM Integrated into an SEM

    ACS Applied Materials & Interfaces, vol. 11, no. 17, pp. 15183-15188

    2019

    DOI: 10.1021/acsami.9b00447

    Abstract anzeigen

    In this work, we monitor in situ the movement of ZnO piezoelectric nanowires by using a conductive atomic force microscope integrated into a scanning electron microscope. This setup allows seeing the bending of the nanowires and simultaneously measuring the currents generated. We conclude that the currents generated not only come from piezoelectric effect, but also from contact potential and triboelectric effect. These contributions have been ignored in all previous reports in this field, meaning that the power conversion efficiency of these devices may have been systematically overestimated. Our study helps to clarify the working mechanism of piezoelectric nanogenerators based on ZnO nanowires.

    NachhaltigElektrotechnik und MedientechnikIQMAMaschinenbau und Mechatronik

    Zeitschriftenartikel

    L. Jiang, Jonas Weber, F. Puglisi, P. Pavan, L. Larcher, Werner Frammelsberger, Günther Benstetter, M. Lanza

    Understanding Current Instabilities in Conductive Atomic Force Microscopy

    Materials, vol. 12, no. 3

    2019

    DOI: 10.3390/ma12030459

    Abstract anzeigen

    Conductive atomic force microscopy (CAFM) is one of the most powerful techniques in studying the electrical properties of various materials at the nanoscale. However, understanding current fluctuations within one study (due to degradation of the probe tips) and from one study to another (due to the use of probe tips with different characteristics), are still two major problems that may drive CAFM researchers to extract wrong conclusions. In this manuscript, these two issues are statistically analyzed by collecting experimental CAFM data and processing them using two different computational models. Our study indicates that: (i) before their complete degradation, CAFM tips show a stable state with degraded conductance, which is difficult to detect and it requires CAFM tip conductivity characterization before and after the CAFM experiments; and (ii) CAFM tips with low spring constants may unavoidably lead to the presence of a ~1.2 nm thick water film at the tip/sample junction, even if the maximum contact force allowed by the setup is applied. These two phenomena can easily drive CAFM users to overestimate the properties of the samples under test (e.g., oxide thickness). Our study can help researchers to better understand the current shifts that were observed during their CAFM experiments, as well as which probe tip to use and how it degrades. Ultimately, this work may contribute to enhancing the reliability of CAFM investigations.

    NachhaltigElektrotechnik und MedientechnikIQMA

    Zeitschriftenartikel

    L. Liu, S. Li, D. Liu, Günther Benstetter, O. Man, J. Michalicka, Y. Zhang, Y. Hong, H. Fan, W. Ni, Q. Yang, Y. Wu, Z. Bi

    The effect of O2 impurity on surface morphology of polycrystalline W during low-energy and high-flux He+ irradiation

    Fusion Engineering and Design, vol. 139, pp. 96-103

    2019

    DOI: 10.1016/j.fusengdes.2019.01.003

    Abstract anzeigen

    The interaction between the impurities (such as carbon, nitrogen, oxygen) and the plasma-facing materials (PFMs) can profoundly influence the performance and service of the PFMs. In this paper, we investigated the influence of oxygen (O2) impurity in the helium radio frequency (RF) plasma on the surface morphology of polycrystalline tungsten (W) irradiated at the surface temperature of 1450 ± 50 K and the ion energy of 100 eV. The pressure ratio of O2 to He (R) in RF source varied from 4.0 × 10−6 to 9.0 × 10-2. The total irradiation flux and fluence were ˜1.2 × 1022 ions·m-2·s-1 and ˜1.0 × 1026 ions·m-2, respectively. After He+ irradiation, the specimen surface morphology was observed by scanning electron microscopy. It was found that with increasing R from 4.0 × 10−6 to 9.0 × 10-2 the thickness of nano-fuzz layer at the W surface was thinner and thinner, accompanied by the formation of rod-like structures. The erosion yield increased from 5.2 × 10-4 to 2.3 × 10-2 W/ion when R varied from 4.0 × 10-6 to 9.0 × 10-2. The X-ray diffraction analysis shows that tungsten oxides were formed at the near surface of specimens when R exceeded 1.8 × 10-2. The erosion yield measurements revealed that in addition to surface physical sputtering process, the chemical erosion process could occur due to the interaction between oxygen-containing species and W at the surface. The results indicated that the presence of O2 impurity in He plasma can obviously affect the surface microstructure of W. The study suggested that O2 impurity can effectively reduce the growth of nano-fuzz structures.

    NachhaltigElektrotechnik und MedientechnikIQMA

    Vortrag

    D. Liu, H. Fan, L. Liu, Y. You, Günther Benstetter, F. Zhang

    Surface diffusion and growth of W self-interstitials during low-energy and large-flux H/He ion irridiations of polycrystalline W

    International Conference on Plasma Surface Interactions in Controlled Fusion Devices, Princeton University, NJ, USA

    2018

    NachhaltigElektrotechnik und MedientechnikIQMA

    Vortrag

    W. Lehermeier, Christoph Metzke, Günther Benstetter, Werner Frammelsberger

    Evaluation of Topography effects of SThM Measurements on Thin thermoelectric Films

    Poster

    4th Ed. Smart Materials and Surfaces - SMS Conference 2018, Venedig, Italien

    2018

    NachhaltigElektrotechnik und MedientechnikIQMA

    Vortrag

    Günther Benstetter, Christoph Metzke, W. Lehermeier

    Advances in Electrical and Thermal Characterization of Surfaces and Thin Films

    Invited Talk

    4th Ed. Smart Materials and Surfaces - SMS Conference 2018, Venedig, Italien

    2018

    NachhaltigElektrotechnik und MedientechnikIQMA

    Vortrag

    Tobias Berthold, Günther Benstetter, Werner Frammelsberger, Manuel Bogner, R. Rodríguez, M. Nafría

    Protective nanometer films for reliable Cu-Cu connections

    Invited Talk

    IEEE International Reliability Physics Symposium (IRPS), San Francisco, CA, USA

    2018

    NachhaltigElektrotechnik und MedientechnikIQMA

    Zeitschriftenartikel

    S. Chen, L. Jiang, M. Buckwell, X. Jing, Y. Ji, E. Grustan-Gutierrez, Günther Benstetter, F. Hui, Y. Shi, M. Rommel, A. Paskaleva, W. Ng, A. Mehonic, A. Kenyon, M. Lanza

    On the Limits of Scalpel AFM for the 3D Electrical Characterization of Nanomaterials

    Advanced Functional Materials, vol. 28, no. 52

    2018

    DOI: 10.1002/adfm.201802266

    Abstract anzeigen

    Conductive atomic force microscopy (CAFM) has been widely used for electrical characterization of thin dielectrics by applying a gentle contact force that ensures a good electrical contact without inducing additional high‐pressure related phenomena (e.g., flexoelectricity, local heat, scratching). Recently, the CAFM has been used to obtain 3D electrical images of thin dielectrics by etching their surface. However, the effect of the high contact forces/pressures applied during the etching on the electrical properties of the materials has never been considered. By collecting cross‐sectional transmission electron microscopy images at the etched regions, it is shown here that the etching process can modify the morphology of Al2O3 thin films (producing phase change, generation of defects, and metal penetration). It is also observed that this technique severely modifies the electrical properties of pSi and TiO2 wafers during the etching, and several behaviors ignored in previous studies, including i) observation of high currents in the absence of bias, ii) instabilities of etching rate, and iii) degradation of CAFM tips, are reported. Overall, this work should contribute to understand better the limitations of this technique and disseminate it among those applications in which it can be really useful.

    Elektrotechnik und MedientechnikIQMA

    Vortrag

    Manuel Bogner, C. Yang, Günther Benstetter, Y. Fu, M. Grundmann

    Nanoscale thermal properties of next generation transparent/flexible thermoelectric copper iodide films

    Posterpräsentation

    5. Tag der Forschung, Deggendorf

    2018

    NachhaltigElektrotechnik und MedientechnikIQMA

    Zeitschriftenartikel

    L. Liu, S. Li, D. Liu, Günther Benstetter, Y. Zhang, Y. Hong, H. Fan, W. Ni, Q. Yang, Y. Wu, Z. Bi

    Surface damages of polycrystalline W and La2O3-doped W induced by high-flux He plasma irradiation

    Journal of Nuclear Materials, vol. 501, no. April, pp. 275-281

    2018

    Abstract anzeigen

    In this study, polycrystalline tungsten (W) and three oxide dispersed strengthened W with 0.1 vol %, 1.0 vol % and 5.0 vol % lanthanum trioxide (La2O3) were irradiated with low-energy (200 eV) and high-flux (5.8 × 1021 or 1.4 × 1022 ions/m2⋅s) He+ ions at elevated temperature. After He+ irradiation at a fluence of 3.0 × 1025/m2, their surface damages were observed by scanning electron microscopy, energy dispersive spectroscopy, scanning electron microscopy-electron backscatter diffraction, and conductive atomic force microscopy. Micron-sized holes were formed on the surface of W alloys after He+ irradiation at 1100 K. Analysis shows that the La2O3 grains doped in W were sputtered preferentially by the high-flux He+ ions when compared with the W grains. For irradiation at 1550 K, W nano-fuzz was formed at the surfaces of both polycrystalline W and La2O3-doped W. The thickness of the fuzz layers formed at the surface of La2O3-doped W is 40% lower than the one of polycrystalline W. The presence of La2O3 could suppress the diffusion and coalescence of He atoms inside W, which plays an important role in the growth of nanostructures fuzz.

    NachhaltigElektrotechnik und MedientechnikIQMAMaschinenbau und Mechatronik

    Beitrag (Sammelband oder Tagungsband)

    Günther Benstetter, Alexander Hofer, D. Liu, Werner Frammelsberger, M. Lanza

    Chapter 3: Fundamentals of CAFM Operation Modes

    Conductive Atomic Force Microscopy: Applications in Nanomaterials, Weinheim

    2017

    ISBN: 978-3-527-34091-0

    Elektrotechnik und MedientechnikIQMA

    Vortrag

    Manuel Bogner, C. Yang, Günther Benstetter, Y. Fu, M. Grundmann

    Nanoscale thermal properties of next generation transparent/flexible thermoelectric copper iodide films

    Posterpräsentation

    5th Nano Today Conference, Hawaii, USA

    2017

    NachhaltigElektrotechnik und MedientechnikIQMAMaschinenbau und Mechatronik

    Beitrag (Sammelband oder Tagungsband)

    Tobias Berthold, Günther Benstetter, Werner Frammelsberger, Manuel Bogner, R. Rodríguez, M. Nafría

    Protective nanometer films for reliable Cu-Cu connections

    Best Paper Award

    Proceedings of the 28h European Symposium on Reliability of Electron Devices, Failure Physics and Analysis (ESREF) [25-28 September, 2017; Bordeaux, Frankreich]

    2017

    NachhaltigElektrotechnik und MedientechnikIQMA

    Zeitschriftenartikel

    C. Yang, D. Souchay, M. Kneiß, Manuel Bogner, H. Wei, M. Lorenz, O. Oeckler, Günther Benstetter, Y. Fu, M. Grundmann

    Transparent flexible thermoelectric material based on non-toxic earth-abundant p-type copper iodide thin film

    nature COMMUNICATIONS, no. July

    2017

    DOI: 10.1038/ncomms1607

    Abstract anzeigen

    Thermoelectric devices that are flexible and optically transparent hold unique promise for future electronics. However, development of invisible thermoelectric elements is hindered by the lack of p-type transparent thermoelectric materials. Here we present the superior room-temperature thermoelectric performance of p-type transparent copper iodide (CuI) thin films. Large Seebeck coefficients and power factors of the obtained CuI thin films are analysed based on a single-band model. The low-thermal conductivity of the CuI films is attributed to a combined effect of the heavy element iodine and strong phonon scattering. Accordingly, we achieve a large thermoelectric figure of merit of ZT=0.21 at 300 K for the CuI films, which is three orders of magnitude higher compared with state-of-the-art p-type transparent materials. A transparent and flexible CuI-based thermoelectric element is demonstrated. Our findings open a path for multifunctional technologies combing transparent electronics, flexible electronics and thermoelectricity.

    NachhaltigElektrotechnik und MedientechnikIQMAMaschinenbau und Mechatronik

    Zeitschriftenartikel

    Tobias Berthold, Günther Benstetter, Werner Frammelsberger, R. Rodríguez, M. Nafría

    Numerical Study of Hydrodynamic Forces for AFM Operations in Liquid Scanning (Article ID 6286595, 12 pages)

    Scanning, no. Article ID 6286595, pp. 1-12

    2017

    DOI: 10.1155/2017/6286595

    Abstract anzeigen

    For advanced atomic force microscopy (AFM) investigation of chemical surface modifications or very soft organic sample surfaces, the AFM probe tip needs to be operated in a liquid environment because any attractive or repulsive forces influenced by the measurement environment could obscure molecular forces. Due to fluid properties, the mechanical behavior of the AFM cantilever is influenced by the hydrodynamic drag force due to viscous friction with the liquid. This study provides a numerical model based on computational fluid dynamics (CFD) and investigates the hydrodynamic drag forces for different cantilever geometries and varying fluid conditions for Peakforce Tapping (PFT) in liquids. The developed model was verified by comparing the predicted values with published results of other researchers and the findings confirmed that drag force dependence on tip speed is essentially linear in nature. We observed that triangular cantilever geometry provides significant lower drag forces than rectangular geometry and that short cantilever offers reduced flow resistance. The influence of different liquids such as ultrapure water or an ethanol-water mixture as well as a temperature induced variation of the drag force could be demonstrated. The acting forces are lowest in ultrapure water, whereas with increasing ethanol concentrations the drag forces increase.