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  • Ovchinnikova, Olga S.  (7)
  • Physics  (7)
  • 1
    In: Applied Physics Letters, AIP Publishing, Vol. 123, No. 15 ( 2023-10-09)
    Abstract: Resistive switching in thin films has been widely studied in a broad range of materials. Yet, the mechanisms behind electroresistive switching have been persistently difficult to decipher and control, in part due to their non-equilibrium nature. Here, we demonstrate new experimental approaches that can probe resistive switching phenomena, utilizing amorphous TaOx as a model material system. Specifically, we applied scanning microwave impedance microscopy and cathodoluminescence (CL) microscopy as direct probes of conductance and electronic structure, respectively. These methods provide direct evidence of the electronic state of TaOx despite its amorphous nature. For example, CL identifies characteristic impurity levels in TaOx, in agreement with first principles calculations. We applied these methods to investigate He-ion-beam irradiation as a path to activate conductivity of materials and enable electroforming-free control over resistive switching. However, we find that even though He-ions begin to modify the nature of bonds even at the lowest doses, the films' conductive properties exhibit remarkable stability with large displacement damage and they are driven to metallic states only at the limit of structural decomposition. Finally, we show that electroforming in a nanoscale junction can be carried out with a dissipated power of & lt;20 nW, a much smaller value compared to earlier studies and one that minimizes irreversible structural modifications of the films. The multimodal approach described here provides a new framework toward the theory/experiment guided design and optimization of electroresistive materials.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    RVK:
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 2
    Online Resource
    Online Resource
    AIP Publishing ; 2018
    In:  Applied Physics Letters Vol. 112, No. 3 ( 2018-01-15)
    In: Applied Physics Letters, AIP Publishing, Vol. 112, No. 3 ( 2018-01-15)
    Abstract: The contrast formation mechanism in nanoscale Infrared (IR) Spectroscopy is analyzed. The temperature distribution and elastic displacement across the illuminated T-shape boundary between two materials with different IR-radiation absorption coefficients and thermo-physical and elastic properties located on a rigid substrate are calculated self-consistently for different frequencies f ∼ (1 kHz–1 MHz) of IR-radiation modulation (fully coupled problem). Analytical expressions for the temperature and displacement profiles across the “thermo-elastic step” are derived in the decoupling approximation for f = 0 (“static limit”), and conditions for approximation validity at low frequencies of IR-modulation are established. The step height was found to be thickness-independent for thick layers and proportional to the square of the thickness for very thin films. The theoretical results will be of potential interest for applications in the scanning thermo-ionic and thermal infrared microscopies for relatively long sample thermalization times and possibly for photothermal induced resonance microscopy using optomechanical probes.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    RVK:
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 3
    In: Macromolecules, American Chemical Society (ACS), Vol. 50, No. 21 ( 2017-11-14), p. 8670-8677
    Type of Medium: Online Resource
    ISSN: 0024-9297 , 1520-5835
    RVK:
    Language: English
    Publisher: American Chemical Society (ACS)
    Publication Date: 2017
    detail.hit.zdb_id: 1491942-4
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  • 4
    In: Advanced Materials, Wiley, Vol. 31, No. 49 ( 2019-12)
    Abstract: A new approach to generate a two‐photon up‐conversion photoluminescence (PL) by directly exciting the gap states with continuous‐wave (CW) infrared photoexcitation in solution‐processing quasi‐2D perovskite films [(PEA) 2 (MA) 4 Pb 5 Br 16 with n = 5] is reported. Specifically, a visible PL peaked at 520 nm is observed with the quadratic power dependence by exciting the gap states with CW 980 nm laser excitation, indicating a two‐photon up‐conversion PL occurring in quasi‐2D perovskite films. Decreasing the gap states by reducing the n value leads to a dramatic decrease in the two‐photon up‐conversion PL signal. This confirms that the gap states are indeed responsible for generating the two‐photon up‐conversion PL in quasi‐2D perovskites. Furthermore, mechanical scratching indicates that the different‐ n ‐value nanoplates are essentially uniformly formed in the quasi‐2D perovskite films toward generating multi‐photon up‐conversion light emission. More importantly, the two‐photon up‐conversion PL is found to be sensitive to an external magnetic field, indicating that the gap states are essentially formed as spatially extended states ready for multi‐photon excitation. Polarization‐dependent up‐conversion PL studies reveal that the gap states experience the orbit–orbit interaction through Coulomb polarization to form spatially extended states toward developing multi‐photon up‐conversion light emission in quasi‐2D perovskites.
    Type of Medium: Online Resource
    ISSN: 0935-9648 , 1521-4095
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 1474949-X
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  • 5
    In: Advanced Materials, Wiley, Vol. 31, No. 35 ( 2019-08)
    Abstract: Optoelectronic devices based on metal halide perovskites, including solar cells and light‐emitting diodes, have attracted tremendous research attention globally in the last decade. Due to their potential to achieve high carrier mobilities, organic–inorganic hybrid perovskite materials can enable high‐performance, solution‐processed field‐effect transistors (FETs) for next‐generation, low‐cost, flexible electronic circuits and displays. However, the performance of perovskite FETs is hampered predominantly by device instabilities, whose origin remains poorly understood. Here, perovskite single‐crystal FETs based on methylammonium lead bromide are studied and device instabilities due to electrochemical reactions at the interface between the perovskite and gold source–drain top contacts are investigated. Despite forming the contacts by a gentle, soft lamination method, evidence is found that even at such “ideal” interfaces, a defective, intermixed layer is formed at the interface upon biasing of the device. Using a bottom‐contact, bottom‐gate architecture, it is shown that it is possible to minimize such a reaction through a chemical modification of the electrodes, and this enables fabrication of perovskite single‐crystal FETs with high mobility of up to ≈15 cm 2 V −1 s −1 at 80 K. This work addresses one of the key challenges toward the realization of high‐performance solution‐processed perovskite FETs.
    Type of Medium: Online Resource
    ISSN: 0935-9648 , 1521-4095
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 1474949-X
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  • 6
    In: Applied Physics Letters, AIP Publishing, Vol. 116, No. 4 ( 2020-01-27)
    Abstract: Atomic and molecular resolved atomic force microscopy (AFM) images offer unique insights into materials' properties such as local ordering, molecular orientation, and topological defects, which can be used to pinpoint physical and chemical interactions occurring at the surface. Utilizing machine learning for extracting underlying physical parameters increases the throughput of AFM data processing and eliminates inconsistencies intrinsic to manual image analysis, thus enabling the creation of reliable frameworks for qualitative and quantitative evaluation of experimental data. Here, we present a robust and scalable approach to the segmentation of AFM images based on flexible pre-selected classification criteria. The usage of supervised learning and feature extraction allows us to retain the consideration of specific problem-dependent features (such as types of periodical structures observed in the images and the associated numerical parameters: spacing, orientation, etc.). We highlight the applicability of this approach for the segmentation of molecular resolved AFM images based on the crystal orientation of the observed domains, automated selection of boundaries, and collection of relevant statistics. Overall, we outline a general strategy for machine learning-enabled analysis of nanoscale systems exhibiting periodic order that could be applied to any analytical imaging technique.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    RVK:
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 7
    In: Applied Physics Letters, AIP Publishing, Vol. 113, No. 7 ( 2018-08-13)
    Abstract: The recent discovery of twin domains in MAPbI3 perovskites has initiated contentious discussion on the ferroic nature of hybrid perovskites. Ferroelectric polarization is thought to facilitate the dissociation of photoinduced electron-hole pairs, helping to explain the extraordinary photovoltaic performance exhibited by this class of materials. Alternate to ferroelectricity, which has yet to be unambiguously established despite considerable efforts to do so, ferroelasticity was also proposed in these materials. Meanwhile, given the coupling of ionic states and ferroelectricity and the interconnected nature of defect chemistry and ferroelasticity, the electrochemical reactivity can no longer be ignored. In this work, using band excitation piezoresponse force microscopy, we reveal the variation in elasticity between adjacent domains, indicating the ferroelasticity and the difference in the crystallographic states of the twin domain. Moreover, using band excitation contact Kelvin probe force microscopy, we dynamically map the evolution of the twinning structure under electric bias. These results help decipher the effect of the twin domains on ionic mobility and ion diffusion pathways. Combining these results, we reveal the interaction of twin domains and ionic activity in this material. Overall, this work provides insights into the twinning structure in MAPbI3 and its potential effects on the hybrid perovskite optoelectronics.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    RVK:
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
    Location Call Number Limitation Availability
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