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  • 1
    Online Resource
    Online Resource
    Convolutional kernel with PrCaMnOx-based resistive random-access memory for neuromorphic image processing
    AIP Publishing ; 2023
    In:  AIP Advances Vol. 13, No. 1 ( 2023-01-01)
    Details
    In: AIP Advances, AIP Publishing, Vol. 13, No. 1 ( 2023-01-01)
    Abstract: This paper investigated the conductance-state stability of TiN/PrCaMnOx (PCMO)-based resistive random-access memory (RRAM), which serves as a kernel weight element in convolutional neural networks (CNNs), to realize accurate feature extraction from images. On application of the initial forming process that actively drives more oxygen ions to form an interfacial layer between TiN and PCMO to RRAM devices with a high voltage of ±4 V, resistive switching behavior with a noticeable memory window was observed. However, the achieved conductance states continued to decrease during repeated cycling. The oxidation at the interface tended to occur thermodynamically, implying an increase in interfacial layer thickness. Considering the hardware implementation of the kernel weight matrix, with specifically assigned conductance values of the RRAM, state instability in the RRAM renders image edge detection difficult, eventually degrading the overall recognition accuracy of the CNN. Thus, we introduced an asymmetric programming voltage method, wherein a higher set voltage of −3 V than a reset voltage of +2.5 V can shift more oxygen ions back into PCMO. Consequently, when the RRAM devices programmed to different states were maintained without degradation in the 1 K cross-point array, eight clearly distinct weighted sum currents were demonstrated in the 3 × 1 subarray. Based on the measurement results, we performed feature extraction in CNN algorithms through MATLAB simulation, demonstrating input image edge detection with a high accuracy of 92%.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    URL: Article
    DOI: 10.1063/5.0133846
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 2583909-3
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  • 2
    Online Resource
    Online Resource
    Understanding synaptic characteristics of nonvolatile analog redox transistor based on mobile ion-modulated-electrolyte thickness model for neuromorphic applications
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 121, No. 7 ( 2022-08-15)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 121, No. 7 ( 2022-08-15)
    Abstract: Linear and symmetric updates of the channel current of the redox transistor are involved in bulk mobile ion motion. In this study, we introduce the concept of a variable effective electrolyte thickness (teff) precisely tuned by gate voltage-driven ions into the drain current equation of a conventional transistor. In order to understand the switching characteristics of a nonvolatile analog redox transistor that serves as an artificial synapse for neuromorphic systems, we developed a physics-based model in MATLAB. The simulated synaptic update curves obtained using identical gate pulses were in good agreement with the fabricated Cu-ion-actuated CuOx/HfOx/WOx redox transistor. We then analyzed the impact of geometrical and material-related parameters on the synaptic behavior, taking into account the ion speed and the degree of allowable electric field through the electrolyte. In addition, we performed Monte Carlo simulation to create a non-uniformly changed teff circumstance. With this, we reproduced the fluctuated update of the channel current every gate pulse, which is occasionally observed experimentally when mobile ions are easily moved randomly. Our simulation results revealed that the redox transistor immune to the unevenly changed teff can be achieved by lowering the ion velocity.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0099827
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 3
    Online Resource
    Online Resource
    Analog synaptic behavior of mobile ion source-limited electrochemical RAM using CuOx oxide electrode for deep learning accelerator
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 120, No. 12 ( 2022-03-21)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 120, No. 12 ( 2022-03-21)
    Abstract: We demonstrate the synaptic characteristics of analogously modulated channel currents in Cu-ion-actuated electrochemical RAM (ECRAM) based on an HfOx electrolyte and a WOx channel. Uncontrolled synaptic response is found as a function of the gate pulse when a Cu-rich gate electrode delivers mobile ions, presumably due to many ions injected from the infinite ion reservoir. As a result, we propose a CuOx oxide electrode to limit ion sources, which is indirectly validated by a physical examination of the degree of chemical bonding between Cu and oxygen, thereby boosting gate controllability over the channel. In addition, the HfOx electrolyte needs to be designed to facilitate the adequate migration of Cu ions, considering thickness and film quality. Using material stack engineering, the channel current of optimized CuOx/HfOx/WOx ECRAM can be steadily tuned via repeated identical gate pulses. The channel current and its change are proportional to the device area and the amount of migrated ions relevant to the gate pulse conditions, respectively. The homogeneous flow of ions across the entire area can, thus, be used to explain the obtained analog switching. The gate-controllable synaptic behavior of the ECRAM accelerates deep neural network training based on backpropagation algorithms. An improved pattern recognition accuracy of ∼88% for handwritten digits is achieved by linearly tuned multiple current states with more than 100 pulses and asymmetric gate voltage conditions in a three-layer neural network validated in simulation.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0086164
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 4
    Online Resource
    Online Resource
    Reduction of dislocations in GaN films on AlN/sapphire templates using CrN nanoislands
    AIP Publishing ; 2008
    In:  Applied Physics Letters Vol. 92, No. 9 ( 2008-03-03)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 92, No. 9 ( 2008-03-03)
    Abstract: We report significant reduction of threading dislocations in GaN films grown by hydride vapor phase epitaxy on AlN/sapphire templates by employing CrN nanoislands on the AlN. High quality GaN films with very small twist mosaic as well as small tilt mosaic have been grown on the AlN/sapphire templates, which had small tilt but very large twist mosaic. The CrN nanoislands were formed by nitridation of a thin Cr film deposited by sputtering on the AlN/sapphire template, where the AlN/sapphire template was prepared by metal organic vapor phase epitaxy. The full width at half maximum values of x-ray rocking curves from the GaN film with the CrN were 114, 209, and 243arcsec for (0002), (10−12), and (11−20) reflections, respectively, while those of the GaN film without the CrN were 129, 1130, and 1364arcsec, respectively. Evaluation of total dislocation density of the GaN films by plan view transmission electron microscopy revealed that the dislocation density was reduced to 2.7×108 from 6.4×109cm−2 by employing the CrN nanoislands. The CrN nanoislands play a key role in reducing the threading dislocations by masking the propagation of dislocations as well as by bending the dislocations.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.2890488
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2008
    detail.hit.zdb_id: 211245-0
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  • 5
    Online Resource
    Online Resource
    Effect of fluorine incorporation on silicon dioxide prepared by high density plasma chemical vapor deposition with SiH4∕O2∕NF3 chemistry
    AIP Publishing ; 2004
    In:  Journal of Applied Physics Vol. 96, No. 3 ( 2004-08-01), p. 1435-1442
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 96, No. 3 ( 2004-08-01), p. 1435-1442
    Abstract: The effect of fluorine incorporation on properties of silicon dioxide thin films has been studied as a function of NF3∕O2 gas flow ratio. Fluorine was incorporated into silicon dioxide films during high density plasma chemical vapor deposition with the SiH4∕O2∕NF3∕He gas mixture used to improve the gap-filling ability for shallow trench isolation of devices. Refractive index measured by ellipsometry decreased with increasing NF3∕O2 flow ratios for both as-deposited and annealed films. X-ray reflectivity measurements showed that both fluorine incorporation and thermal annealing reduced the film density. The analysis of infrared absorption spectra showed the relaxation of the Si-O-Si bond with increasing NF3∕O2 flow ratios and thermal annealing. The secondary ion mass spectroscopy and x-ray photoelectron spectroscopy studies confirmed the behavior of fluorine diffusion and the binding energy for each species in the films, respectively. These results showed that through fluorine incorporation and thermal annealing, the network structures of silicon dioxide could be modified from low order rings to high order rings accompanied by the enlargement of nanovoids.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1767979
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2004
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 6
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    Online Resource
    Corrected Article: “Ultraprecise microreproduction of a three-dimensional artistic sculpture by multipath scanning method in two-photon photopolymerization” [Appl. Phys. Lett 90, 013113 (2007)]
    AIP Publishing ; 2007
    In:  Applied Physics Letters Vol. 90, No. 7 ( 2007-02-12)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 90, No. 7 ( 2007-02-12)
    Abstract: Ultraprecise fabrication of three-dimensional (3D) microstructures comes up to be one of the most important issues in two-photon induced photopolymerization. To date, it has been difficult to fabricate 3D microstructures without any deformation due to the surface tension between a rinsing material and solidified microstructures during the developing process: In general, the surface tension significantly affects the precision of the resulting 3D microstructures. To overcome this problem, the authors propose a simple and effective laser scanning method to reinforce the strength of 3D microstructures without loss of precision. Overall, a complex 3D artistic sculpture such as “The Thinker” was reproduced in the controlled ultraprecise form, which shows that the proposed method enables the fabrication of 3D patterns with dramatically improved precision and stability.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.2692435
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2007
    detail.hit.zdb_id: 211245-0
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  • 7
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    Online Resource
    Measurement of the electron energy distribution function in CO2 inductively coupled plasma
    AIP Publishing ; 2019
    In:  Physics of Plasmas Vol. 26, No. 12 ( 2019-12-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 26, No. 12 ( 2019-12-01)
    Abstract: CO2 inductively coupled plasmas (ICPs) were generated using a radio frequency power of 13.56 MHz at 100 mTorr. Electron energy distribution functions (EEDFs) were measured using a single Langmuir probe, and various plasma parameters such as the electron density and electron temperature were obtained from the measured EEDFs. EEDFs with multislope structures are obtained. However, changes in the gas composition in the ICP were observed via optical emission spectroscopy. The electron density barely increases when a sudden change in the gas composition occurs. The E to H mode transition occurs at a stationary gas composition as the absorbed power increases. The EEDFs of CO2 plasma, CO plasma, and O2 plasma were calculated using BOLSIG+, which is a two term Boltzmann solver [G. Hagelaar and L. Pitchford, Plasma Sources Sci. Technol. 14(4), 722 (2005)]. The measured EEDF is closest to the EEDF of the CO plasma.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.5125423
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 1472746-8
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  • 8
    Online Resource
    Online Resource
    Effect of RF bias power on discharge mode transition and its hysteresis in inductively coupled plasmas
    AIP Publishing ; 2022
    In:  Physics of Plasmas Vol. 29, No. 1 ( 2022-01-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 29, No. 1 ( 2022-01-01)
    Abstract: Hysteresis, one of the interesting characteristics of inductively coupled plasmas, takes place due to the nonlinearities of absorbed power or dissipated power [M. M. Turner et al., Plasma Sources Sci. Technol. 8, 313 (1999)]. In this work, the bias power effect on discharge mode transition and its hysteresis is investigated by measuring the antenna coil currents, time-average substrate voltages, electron densities, and electron energy probability functions (EEPFs). The behavior of hysteresis is comparatively analyzed by introducing a global model that considers the evolution of EEPFs and excitation state species (multi-step ionization). In the absence of bias power, a typical hysteresis appears at a gas pressure of 300 mTorr. The measured EEPF evolves from a Druyvesteyn distribution in the E mode to a Maxwellian distribution in the H mode with growing the antenna power from 25 W to 60 W. Interestingly, when a bias power of 30 W is applied to the substrate, the hysteresis vanishes, and the shape of the EEPF is maintained in each mode. The possible factors are considered the diminished changes in total energy loss (reduced nonlinearity of dissipated power) and in power transfer efficiency between E mode and H mode during the mode transition.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/5.0064438
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 1472746-8
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  • 9
    Online Resource
    Online Resource
    Highly efficient tris(8-hydroxyquinoline) aluminum-based organic light-emitting diodes utilized by balanced energy transfer with cosensitizing fluorescent dyes
    AIP Publishing ; 2009
    In:  Applied Physics Letters Vol. 95, No. 14 ( 2009-10-05)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 95, No. 14 ( 2009-10-05)
    Abstract: We report on the development of highly efficient organic light-emitting diodes (OLEDs) utilized by balancing the energy transfer between multiple dopants, that is, multiple emissions from the multiple dopants were realized by balanced distributed energy transfer. From the cosensitizing fluorescent OLEDs, the peak external quantum efficiency (EQE) of 4.8% at 130 cd/m2 is demonstrated, which realized theoretical limits of ∼5.0% and means that nearly 100% of the singlet excitons are radiative. Also, the optimized device accompanying thickness-modulated electron transport layer for the enhanced light outcoupling demonstrated the highly improved peak EQE and current efficiency of 6.7%, and 23.4 cd/A.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.3243689
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2009
    detail.hit.zdb_id: 211245-0
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  • 10
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    Online Resource
    Hysteresis and current reduction during E–H mode transition in an inductively coupled plasma
    AIP Publishing ; 2020
    In:  Physics of Plasmas Vol. 27, No. 3 ( 2020-03-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 27, No. 3 ( 2020-03-01)
    Abstract: A hysteresis loop has been observed during the E–H mode transition in an inductively coupled plasma at high pressures. The cause of the hysteresis has been reported as a nonlinearity of the transferred and dissipated powers due to capacitive coupling, multi-step ionization, the change in the electron energy probability function (EEPF), and so on [M. M. Turner and M. A. Lieberman, Plasma Sources Sci. Technol. 8(2), 313–324 (1999) and H. C. Lee and C. W. Chung, Sci. Rep. 5, 15254 (2015)]. However, when a coil current reduction is considered, the previous interpretation of hysteresis cannot explain the observations in the intermediate pressure region, where the coil current reduction occurs, but hysteresis is not observed. In this work, the E–H mode transition and its hysteresis are discussed in three pressure regions, the low, intermediate, and high pressure regions, whether or not the coil current and the hysteresis are observed. The power transfer efficiency, transferred power, EEPF, and total energy loss are obtained at 10, 100, and 300 mTorr. Hysteresis is only observed at 300 mTorr, and the coil current reduces at 100 and 300 mTorr during the E–H mode transition. The mechanism of hysteresis is explained in a power balance diagram that includes the transferred power and the dissipated power by considering the power transfer efficiency in the E and H modes. In addition, the conditions of hysteresis and coil current reduction are revealed and classified in this work.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.5133449
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
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