@article{MTMT:34536907, title = {Noise tailoring, noise annealing, and external perturbation injection strategies in memristive Hopfield neural networks}, url = {https://m2.mtmt.hu/api/publication/34536907}, author = {Fehérvári, János Gergő and Balogh, Zoltán and Török, Tímea Nóra and Halbritter, András Ernő}, doi = {10.1063/5.0173662}, journal-iso = {APL mach. learn.}, journal = {APL machine learning.}, volume = {2}, unique-id = {34536907}, abstract = {The commercial introduction of a novel electronic device is often preceded by a lengthy material optimization phase devoted to the suppression of device noise as much as possible. The emergence of novel computing architectures, however, triggers a paradigm shift in noise engineering, demonstrating that non-suppressed but properly tailored noise can be harvested as a computational resource in probabilistic computing schemes. Such a strategy was recently realized on the hardware level in memristive Hopfield neural networks, delivering fast and highly energy efficient optimization performance. Inspired by these achievements, we perform a thorough analysis of simulated memristive Hopfield neural networks relying on realistic noise characteristics acquired on various memristive devices. These characteristics highlight the possibility of orders of magnitude variations in the noise level depending on the material choice as well as on the resistance state (and the corresponding active region volume) of the devices. Our simulations separate the effects of various device non-idealities on the operation of the Hopfield neural network by investigating the role of the programming accuracy as well as the noise-type and noise amplitude of the ON and OFF states. Relying on these results, we propose optimized noise tailoring and noise annealing strategies, comparing the impact of internal noise to the effect of external perturbation injection schemes.}, year = {2024}, eissn = {2770-9019}, orcid-numbers = {Balogh, Zoltán/0000-0002-9580-361X; Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:34554374, title = {Voltage-time dilemma and stochastic threshold-voltage variation in pure-silver atomic switches}, url = {https://m2.mtmt.hu/api/publication/34554374}, author = {Nyáry, Anna and Balogh, Zoltán and Vigh, Máté and Sánta, Botond and Pósa, László and Halbritter, András Ernő}, doi = {10.1103/PhysRevApplied.21.014027}, journal-iso = {PHYS REV APPL}, journal = {PHYSICAL REVIEW APPLIED}, volume = {21}, unique-id = {34554374}, issn = {2331-7019}, abstract = {The formation and dissolution of silver nanowires plays a fundamental role in a broad range of resistive-switching devices, which fundamentally rely on the electrochemical-metallization phenomenon. It has been shown that resistive switching may also appear in pure metallic nanowires lacking any silver-ion-hosting embedding environment but this pure atomic switching mechanism differs fundamentally from the conventional electrochemical-metallization-based resistive switching. To facilitate the quantitative description of the former phenomenon, we investigate a broad range of Ag atomic junctions, with a special focus on the frequency dependence and the fundamentally stochastic cycle-to-cycle variation of the switching-threshold voltage. These devices are established in an ultrahigh-purity environment in which electrochemical metallization can be excluded. The measured characteristics are successfully described by a vibrational-pumping model, yielding consistent predictions for the weak frequency dependence and the large variance of the switching-threshold voltage. We also demonstrate that electrochemical-metallization-based resistive switching and pure atomic switching may appear in the same device structure and therefore the proper understanding of the pure atomic switching mechanism has a very relevant importance in silver-based electrochemical-metallization cells. © 2024 American Physical Society.}, keywords = {SILVER; NANOWIRES; Atoms; metal ions; stochastic systems; Threshold voltage; Switching mechanism; silver nanowires; resistive switching; metallisation; stochastics; Electrochemicals; Frequencies dependence; Atomic switches; Switching threshold voltage; Threshold voltage variation}, year = {2024}, eissn = {2331-7019}, orcid-numbers = {Vigh, Máté/0000-0001-5668-7735; Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:34040360, title = {Configuration-Specific Insight into Single-Molecule Conductance and Noise Data Revealed by the Principal Component Projection Method}, url = {https://m2.mtmt.hu/api/publication/34040360}, author = {Balogh, Zoltán and Mezei, Gréta and Tenk, N. and Magyarkuti, András and Halbritter, András Ernő}, doi = {10.1021/acs.jpclett.3c00677}, journal-iso = {J PHYS CHEM LETT}, journal = {JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, volume = {14}, unique-id = {34040360}, issn = {1948-7185}, abstract = {We explore the merits of neural network boosted, principal-component-projection-based,unsupervised data classification in single-molecule break junctionmeasurements, demonstrating that this method identifies highly relevanttrace classes according to the well-defined and well-visualized internalcorrelations of the data set. To this end, we investigate single-moleculestructures exhibiting double molecular configurations, exploring therole of the leading principal components in the identification ofalternative junction evolution trajectories. We show how the properprincipal component projections can be applied to separately analyzethe high- or low-conductance molecular configurations, which we exploitin 1/f-type noise measurements on bipyridine molecules. This approachuntangles the unclear noise evolution of the entire data set, identifyingthe coupling of the aromatic ring to the electrodes through the pi orbitals in two distinct conductance regions, and its subsequent uncouplingas these configurations are stretched.}, keywords = {Chemistry, Physical; JUNCTIONS; SHOT-NOISE; THERMOPOWER; Materials Science, Multidisciplinary; Nanoscience & Nanotechnology}, year = {2023}, pages = {5109-5118}, orcid-numbers = {Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:33548398, title = {Analysis of malaria infection byproducts with Mueller matrix transmission ellipsometry}, url = {https://m2.mtmt.hu/api/publication/33548398}, author = {Basa, Péter and Fodor, B. and Nagy, Zs. and Oyunbolor, B. and Hajtman, A. and Bordács, Sándor and Kézsmárki, István and Halbritter, András Ernő and Orbánová, Agnesa}, doi = {10.1016/j.tsf.2022.139637}, journal-iso = {THIN SOLID FILMS}, journal = {THIN SOLID FILMS}, volume = {766}, unique-id = {33548398}, issn = {0040-6090}, abstract = {In this work, hemozoin, a microcrystalline byproduct of the malaria parasites was studied by transmission Mueller matrix ellipsometry. Measurement data was collected for different magnetic field orientations and as a function of the density of the hemozoin suspension. Our ellipsometric study demonstrates the magnetic alignment of the hemozoin crystals via the corresponding large linear birefringence and dichroism signals. These results reveal optical anisotropies of this material, which could be utilized for future optimization of detection schemes or optical instruments for diagnostic use.}, keywords = {IRON; Environment; Materials Science, Multidisciplinary; Physics, Applied; Materials Science, Coatings & Films}, year = {2023}, eissn = {1879-2731}, orcid-numbers = {Basa, Péter/0000-0003-1317-1709; Bordács, Sándor/0000-0003-0420-5997; Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:33831558, title = {Picosecond Time-Scale Resistive Switching Monitored in Real-Time}, url = {https://m2.mtmt.hu/api/publication/33831558}, author = {Csontos, Miklós and Horst, Y. and Olalla, N.J. and Koch, U. and Shorubalko, I. and Halbritter, András Ernő and Leuthold, J.}, doi = {10.1002/aelm.202201104}, journal-iso = {ADV ELECTRON MATER}, journal = {ADVANCED ELECTRONIC MATERIALS}, volume = {9}, unique-id = {33831558}, issn = {2199-160X}, year = {2023}, eissn = {2199-160X}, orcid-numbers = {Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:33879666, title = {Interplay of Thermal and Electronic Effects in the Mott Transition of Nanosized VO2 Phase Change Memory Devices}, url = {https://m2.mtmt.hu/api/publication/33879666}, author = {Pósa, László and Hornung, Péter and Török, Tímea Nóra and Schmid, Sebastian Werner and Arjmandabasi, Sadaf and Molnár, György and Baji, Zsófia and Dražić, Goran and Halbritter, András Ernő and Volk, János}, doi = {10.1021/acsanm.3c00150}, journal-iso = {ACS APPL NANO MATER}, journal = {ACS APPLIED NANO MATERIALS}, volume = {6}, unique-id = {33879666}, abstract = {Volatile memory devices relying on the Mott-type insulator-to-metaltransition of vanadium oxide (VO2) are widely utilizedin the field of neuromorphic computing. Such devices, however, arerealized in a nanoscale geometry, where the switching relies on theself-heating of an ultrasmall spot as well as the presence of extremelyhigh electric fields in the active region. In this paper, we investigatethe interplay of such nanoscale thermal and nonlinear electronic phenomenaby investigating the temperature and voltage dependent conductionproperties of our custom-designed VO2 devices, where aV-shaped electrode focuses the switching to an ultrasmall single-spotactive region. This simplified spatial structure of the active volumefacilitates the device modeling and the identification of physicalmechanisms behind the phase transition. We find that purely thermalor electronic effects fail to describe the device operation, however,according to our finite element simulations, a combined electronicand thermal model provides a precise description of the device characteristics.These results facilitate the understanding as well as the thermaland electronic design of novel VO2-based neuronal devices.}, year = {2023}, eissn = {2574-0970}, pages = {9137-9147}, orcid-numbers = {Molnár, György/0000-0002-4792-5516; Baji, Zsófia/0000-0001-5051-3128; Halbritter, András Ernő/0000-0003-4837-9745; Volk, János/0000-0003-3633-6190} } @article{MTMT:34431981, title = {Quantum Transport Properties of Nanosized Ta2O5 Resistive Switches: Variable Transmission Atomic Synapses for Neuromorphic Electronics}, url = {https://m2.mtmt.hu/api/publication/34431981}, author = {Török, Tímea Nóra and Makk, Péter and Balogh, Zoltán and Csontos, Miklós and Halbritter, András Ernő}, doi = {10.1021/acsanm.3c04769}, journal-iso = {ACS APPL NANO MATER}, journal = {ACS APPLIED NANO MATERIALS}, volume = {6}, unique-id = {34431981}, year = {2023}, eissn = {2574-0970}, pages = {21340-21349}, orcid-numbers = {Török, Tímea Nóra/0000-0001-5238-5895; Balogh, Zoltán/0000-0002-9580-361X; Csontos, Miklós/0000-0002-2766-6860; Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:32821968, title = {Tunable, Nucleation-Driven Stochasticity in Nanoscale Silicon Oxide Resistive Switching Memory Devices}, url = {https://m2.mtmt.hu/api/publication/32821968}, author = {Török, Tímea Nóra and Fehérvári, János Gergő and Mészáros, Gábor and Pósa, László and Halbritter, András Ernő}, doi = {10.1021/acsanm.2c00722}, journal-iso = {ACS APPL NANO MATER}, journal = {ACS APPLIED NANO MATERIALS}, volume = {5}, unique-id = {32821968}, abstract = {Resistive switching memory devices hold extensive possibilities for realizing artificial neural networks along with nonconventional computing paradigms. Studying and understanding phenomena arising at single resistive switching elements is necessary for utilizing their particular traits for computation. Tuning the variability of the set time the timespan before the onset of the transition from a high-resistance OFF state to a low-resistance ON state is key for making use of the inherently stochastic nature of the resistance switching effect. Here, we study the set time statistics in nanometer-sized graphene-SiOx-graphene resistive switching memory devices. For dedicated OFF state configurations, we demonstrate a universal variance of the logarithmic set time values, which is characteristic to a nucleation-driven crystallization process. Furthermore, we observe clear correlation between the OFF state resistance and the set time, and hence we explore the tunability of the set time statistics via changing the reset amplitude parameter in sequential pulsed measurements. The latter phenomenon could prove useful for controlling stochasticity in memristor-based probabilistic computing applications via the control of the active volume's nanostructure. © 2022 The Authors. Published by American Chemical Society.}, keywords = {NUCLEATION; Phase change memory; Silicon oxide; memristor; Resistive switching memory; graphene nanogap}, year = {2022}, eissn = {2574-0970}, pages = {6691-6698}, orcid-numbers = {Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:32183347, title = {1/f noise spectroscopy and noise tailoring of nanoelectronic devices}, url = {https://m2.mtmt.hu/api/publication/32183347}, author = {Balogh, Zoltán and Mezei, Gréta and Pósa, László and Sánta, Botond and Magyarkuti, András and Halbritter, András Ernő}, doi = {10.1088/2399-1984/ac14c8}, journal-iso = {NANO FUTURES}, journal = {NANO FUTURES}, volume = {5}, unique-id = {32183347}, year = {2021}, eissn = {2399-1984}, orcid-numbers = {Halbritter, András Ernő/0000-0003-4837-9745} } @misc{MTMT:32800966, title = {Noise Tailoring in Memristive Filaments}, url = {https://m2.mtmt.hu/api/publication/32800966}, author = {Botond, Sánta and Zoltán, Balogh and Pósa, László and Tímea, Nóra Török and Dániel, Molnár and Miklós, Csontos and Halbritter, András Ernő}, unique-id = {32800966}, abstract = {We present the possibilities of noise tailoring in filamentary resistive switching memory devices. The resistance and frequency scaling of the low-frequency 1/f-type noise properties are studied in representative mainstream material systems. It is shown that the overall noise floor is tailorable by the proper material choice, as demonstrated by the order-of-magnitude smaller noise levels in Ta2O5 and Nb2O5 transition-metal oxide memristors compared to Ag-based devices. Furthermore, the variation of the resistance states allows orders-of-magnitude tuning of the relative noise level in all of these material systems. This behavior is analyzed in the framework of a point-contact noise model highlighting the possibility for the disorder-induced suppression of the noise contribution arising from remote fluctuators. These findings promote the design of multipurpose resistive switching units, which can simultaneously serve as analog-tunable memory elements and tunable noise sources in probabilistic computing machines.}, year = {2021}, orcid-numbers = {Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:31868928, title = {Structural Memory Effects in Gold–4,4′-Bipyridine–Gold Single-Molecule Nanowires}, url = {https://m2.mtmt.hu/api/publication/31868928}, author = {Magyarkuti, András and Balogh, Zoltán and Mezei, Gréta and Halbritter, András Ernő}, doi = {10.1021/acs.jpclett.0c03765}, journal-iso = {J PHYS CHEM LETT}, journal = {JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, volume = {12}, unique-id = {31868928}, issn = {1948-7185}, year = {2021}, pages = {1759-1764}, orcid-numbers = {Magyarkuti, András/0000-0002-7041-3404; Balogh, Zoltán/0000-0002-9580-361X; Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:32040083, title = {Noise diagnostics of graphene interconnects for atomic-scale electronics}, url = {https://m2.mtmt.hu/api/publication/32040083}, author = {Pósa, László and Balogh, Zoltán and Krisztián, Dávid and Balázs, Péter and Sánta, Botond and Furrer, Roman and Csontos, Miklós and Halbritter, András Ernő}, doi = {10.1038/s41699-021-00237-w}, journal-iso = {NPJ 2D MATER APPL}, journal = {NPJ 2D MATERIALS AND APPLICATIONS}, volume = {5}, unique-id = {32040083}, abstract = {Graphene nanogaps are considered as essential building blocks of two-dimensional electronic circuits, as they offer the possibility to interconnect a broad range of atomic-scale objects. Here we provide an insight into the microscopic processes taking place during the formation of graphene nanogaps through the detailed analysis of their low-frequency noise properties. Following the evolution of the noise level, we identify the fundamentally different regimes throughout the nanogap formation. By modeling the resistance and bias dependence of the noise, we resolve the major noise-generating processes: atomic-scale junction-width fluctuations in the nanojunction regime and sub-atomic gap-size fluctuations in the nanogap regime. As a milestone toward graphene-based atomic electronics, our results facilitate the automation of an optimized electrical breakdown protocol for high-yield graphene nanogap fabrication.}, year = {2021}, eissn = {2397-7132}, orcid-numbers = {Furrer, Roman/0000-0002-3748-5027; Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:31867344, title = {Noise Tailoring in Memristive Filaments}, url = {https://m2.mtmt.hu/api/publication/31867344}, author = {Sánta, Botond and Balogh, Zoltán and Pósa, László and Krisztián, Dávid and Török, Tímea Nóra and Molnár, Dániel and Sinkó, Csaba and Hauert, Roland and Csontos, Miklós and Halbritter, András Ernő}, doi = {10.1021/acsami.0c21156}, journal-iso = {ACS APPL MATER INTER}, journal = {ACS APPLIED MATERIALS & INTERFACES}, volume = {13}, unique-id = {31867344}, issn = {1944-8244}, year = {2021}, eissn = {1944-8252}, pages = {7453-7460}, orcid-numbers = {Balogh, Zoltán/0000-0002-9580-361X; Pósa, László/0000-0001-7303-4031; Török, Tímea Nóra/0000-0001-5238-5895; Csontos, Miklós/0000-0002-2766-6860; Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:31265427, title = {Unsupervised feature recognition in single-molecule break junction data}, url = {https://m2.mtmt.hu/api/publication/31265427}, author = {Magyarkuti, András and Balogh, Nóra and Balogh, Zoltán and Venkataraman, Latha and Halbritter, András Ernő}, doi = {10.1039/D0NR00467G}, journal-iso = {NANOSCALE}, journal = {NANOSCALE}, volume = {12}, unique-id = {31265427}, issn = {2040-3364}, year = {2020}, eissn = {2040-3372}, pages = {8355-8363}, orcid-numbers = {Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:31694496, title = {Voltage-Controlled Binary Conductance Switching in Gold-4,4 '-Bipyridine-Gold Single-Molecule Nanowires}, url = {https://m2.mtmt.hu/api/publication/31694496}, author = {Mezei, Gréta and Balogh, Zoltán and Magyarkuti, András and Halbritter, András Ernő}, doi = {10.1021/acs.jpclett.0c02185}, journal-iso = {J PHYS CHEM LETT}, journal = {JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, volume = {11}, unique-id = {31694496}, issn = {1948-7185}, abstract = {We investigate gold-4,4'-bipyridine-gold single-molecule junctions with the mechanically controllable break junction technique at cryogenic temperature (T = 4.2 K). We observe bistable probabilistic conductance switching between the two molecular binding configurations, influenced both by the mechanical actuation and by the applied voltage. We demonstrate that the relative dominance of the two conductance states is tunable by the electrode displacement, whereas the voltage manipulation induces an exponential speedup of both switching times. The detailed investigation of the voltage-tunable switching rates provides an insight into the possible switching mechanisms.}, year = {2020}, pages = {8053-8059}, orcid-numbers = {Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:31592175, title = {A non-oxidizing fabrication method for lithographic break junctions of sensitive metals}, url = {https://m2.mtmt.hu/api/publication/31592175}, author = {Nyáry, Anna and Gubicza, Ágnes and Overbeck, Jan and Pósa, László and Makk, Péter and Calame, Michel and Halbritter, András Ernő and Csontos, Miklós}, doi = {10.1039/D0NA00498G}, journal-iso = {NANOSCALE ADV}, journal = {NANOSCALE ADVANCES}, volume = {2}, unique-id = {31592175}, issn = {2516-0230}, year = {2020}, eissn = {2516-0230}, pages = {3829-3833}, orcid-numbers = {Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:31043925, title = {Nanosecond resistive switching in Ag/AgI/PtIr nanojunctions}, url = {https://m2.mtmt.hu/api/publication/31043925}, author = {Sánta, Botond and Molnár, Dániel and Haiber, P and Gubicza, A and Szilágyi, Edit and Zolnai, Zsolt and Halbritter, András Ernő and Csontos, Miklós}, doi = {10.3762/bjnano.11.9}, journal-iso = {BEILSTEIN J NANOTECH}, journal = {BEILSTEIN JOURNAL OF NANOTECHNOLOGY}, volume = {11}, unique-id = {31043925}, issn = {2190-4286}, abstract = {Nanometer-scale resistive switching devices operated in the metallic conductance regime offer ultimately scalable and widely reconfigurable hardware elements for novel in-memory and neuromorphic computing architectures. Moreover, they exhibit high operation speed at low power arising from the ease of the electric-field-driven redistribution of only a small amount of highly mobile ionic species upon resistive switching. We investigate the memristive behavior of a so-far less explored representative of this class, the Ag/AgI material system in a point contact arrangement established by the conducting PtIr tip of a scanning probe microscope. We demonstrate stable resistive switching duty cycles and investigate the dynamical aspects of non-volatile operation in detail. The high-speed switching capabilities are explored by a custom-designed microwave setup that enables time-resolved studies of subsequent set and reset transitions upon biasing the Ag/AgI/PtIr nanojunctions with sub-nanosecond voltage pulses. Our results demonstrate the potential of Ag-based filamentary memristive nanodevices to serve as the hardware elements in high-speed neuromorphic circuits.}, year = {2020}, eissn = {2190-4286}, pages = {92-100}, orcid-numbers = {Zolnai, Zsolt/0000-0003-3457-7679; Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:31126336, title = {Breaking the Quantum PIN Code of Atomic Synapses}, url = {https://m2.mtmt.hu/api/publication/31126336}, author = {Török, Tímea Nóra and Csontos, Miklós and Makk, Péter and Halbritter, András Ernő}, doi = {10.1021/acs.nanolett.9b04617}, journal-iso = {NANO LETT}, journal = {NANO LETTERS}, volume = {20}, unique-id = {31126336}, issn = {1530-6984}, year = {2020}, eissn = {1530-6992}, pages = {1192-1200}, orcid-numbers = {Halbritter, András Ernő/0000-0003-4837-9745} } @misc{MTMT:32800980, title = {Universal 1/f type current noise of Ag filaments in redox-based memristive nanojunctions}, url = {https://m2.mtmt.hu/api/publication/32800980}, author = {B., Sánta and Z., Balogh and A., Gubicza and Pósa, László and D., Krisztián and G., Mihály and M., Csontos and Halbritter, András Ernő}, unique-id = {32800980}, abstract = {The microscopic origins and technological impact of 1/f type current fluctuations in Ag based, filamentary type resistive switching devices have been investigated upon downscaling toward the ultimate single atomic limit. The analysis of the low-frequency current noise spectra revealed that the main electronic noise contribution arises from the resistance fluctuations due to internal dynamical defects of Ag nanofilaments. The resulting 0.01–1% current noise ratio, i.e. the total noise level with respect to the mean value of the current, is found to be universal: its magnitude only depends on the total resistance of the device, irrespective of the materials aspects of the surrounding solid electrolyte and of the specific filament formation procedure. Moreover, the resistance dependence of the current noise ratio also displays the diffusive to ballistic crossover, confirming that stable resistive switching operation utilizing Ag nanofilaments is not compromised even in truly atomic scale junctions by technologically impeding noise levels.}, year = {2019}, orcid-numbers = {Halbritter, András Ernő/0000-0003-4837-9745} } @article{MTMT:30538957, title = {Universal 1/f type current noise of Ag filaments in redox-based memristive nanojunctions}, url = {https://m2.mtmt.hu/api/publication/30538957}, author = {Sánta, Botond and Balogh, Zoltán and Gubicza, Ágnes and Pósa, László and Krisztián, Dávid and Mihály, György and Csontos, Miklós and Halbritter, András Ernő}, doi = {10.1039/c8nr09985e}, journal-iso = {NANOSCALE}, journal = {NANOSCALE}, volume = {11}, unique-id = {30538957}, issn = {2040-3364}, year = {2019}, eissn = {2040-3372}, pages = {4719-4725}, orcid-numbers = {Mihály, György/0000-0001-8986-3299; Halbritter, András Ernő/0000-0003-4837-9745} }