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Electron emission and ultraviolet electroluminescence from valence-band states and defect conduction bands of electroformed Al-Al <sub/>2</sub> O <sub/>3</sub> -Ag diodes
摘要： Electroforming of metal-insulator-metal (MIM) diodes is a soft dielectric breakdown which results in the formation of a conducting filament through the diode. It is a critical step in the development of conducting states between which switching can occur in resistive switching memories. Conduction, electron emission into vacuum (EM), and electroluminescence (EL) have been studied in two groups of electroformed Al-Al2O3-Ag diodes with amorphous anodic Al2O3 thicknesses between 20 nm and 49 nm. EM and EL appear simultaneously with the abrupt current increase that characterizes electroforming of Al-Al2O3-metal diodes. There is voltage-controlled differential negative resistance in the current-voltage (I-V) characteristics after electroforming. There is a temperature-independent voltage threshold for EM, VEM ? 4 V, where VS is the applied voltage, and there is an exponential increase of EM. There is a second exponential increase of EM in region III when VS exceeds a second temperature-independent voltage threshold, UEM. UEM is ～6.6 V for one group of Al-Al2O3-Ag diodes; it is ～7.9 V for the second group. EM is nearly constant in region II for 4 V ? VS ? UEM. Two band-pass filters have been used to characterize EL from electroformed Al-Al2O3-Ag diodes. The long-pass (LP) filter plus photomultiplier responds to photons with energies between ～1.8 eV and ～3.0 eV. The short-pass (SP) filter measures ultra-violet (UV) radiation between ～3.0 eV and ～4.2 eV. Corresponding to region I of EM, there are exponential increases of EL for VS greater than temperature-independent voltage thresholds: VLP ? 2.0 V and VSP ? 2.2 V. There is a second exponential increase of UV with the SP filter in region III for VS greater than a temperature-independent voltage threshold, USP. USP ? 7.9 V for one group of electroformed Al-Al2O3-Ag diodes and USP ? 8.8 V for the second group; USP > UEM. Both groups exhibit EM from valence band states of amorphous Al2O3. The difference in UEM and USP of the two groups of electroformed Al-Al2O3-Ag diodes is attributed to the presence or absence of a defect conduction band formed from the ground state of F0- or F+-centers, oxygen vacancies in amorphous Al2O3. The observation of exponentially increasing EM or EL in the low conductivity state of electroformed Al-Al2O3-metal diodes is not consistent with switching mechanisms of MIM diodes that involve rupture of the conducting filament since rupture that affects diode current, if it occurs, should also cut off EM and EL.
关键词： electroforming,electron emission,electroluminescence,defect conduction bands,resistive switching,Al-Al2O3-Ag diodes
更新于2025-09-23 15:22:29
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<i>Operando</i> diagnostic detection of interfacial oxygen ‘breathing’ of resistive random access memory by bulk-sensitive hard X-ray photoelectron spectroscopy
摘要： The HfO2-based resistive random access memory (RRAM) is one of the most promising candidates for non-volatile memory applications. The detection and examination of the dynamic behavior of oxygen ions/vacancies are crucial to deeply understand the microscopic physical nature of the resistive switching (RS) behavior. By using synchrotron radiation based, non-destructive and bulk-sensitive hard X-ray photoelectron spectroscopy (HAXPES), we demonstrate an operando diagnostic detection of the oxygen ‘breathing’ behavior at the oxide/metal interface, namely, oxygen migration between HfO2 and TiN during different RS periods. The results highlight the significance of oxide/metal interfaces in RRAM, even in filament-type devices.
关键词： resistive switching,HfO2,HAXPES,RRAM,interface
更新于2025-09-23 15:22:29
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New Uses of Micro and Nanomaterials || The Atomic Layer Deposition Technique for the Fabrication of Memristive Devices: Impact of the Precursor on Pre-deposited Stack Materials
摘要： Atomic layer deposition (ALD) is a standard technique employed to grow thin-film oxides for a variety of applications. We describe the technique and demonstrate its use for obtaining memristive devices. The metal/insulator/metal stack is fabricated by means of ALD-grown HfO2, deposited on top of a highly doped Si substrate with an SiO2 film and a Ti electrode. Enhanced device capabilities (forming free, self-limiting current, non-crossing hysteretic current-voltage features) are presented and discussed. Careful analysis of the stack structure by means of X-ray reflectometry, atomic force microscopy, and secondary ion mass spectroscopy revealed a modification of the device stack from the intended sequence, HfO2/Ti/SiO2/Si. Analytical studies unravel an oxidation of the Ti layer which is addressed for the use of the ozone precursor in the HfO2 ALD process. A new deposition process and the model deduced from impedance measurements support our hypothesis: the role played by ozone on the previously deposited Ti layer is found to determine the overall features of the device. Besides, these ALD-tailored multifunctional devices exhibit rectification capability and long enough retention time to deserve their use as memory cells in a crossbar architecture and multibit approach, envisaging other potential applications.
关键词： ReRAM,nonvolatile memory,complementary resistive switching cell,forming free memristive device,atomic layer deposition,redox-based resistive random access memory
更新于2025-09-23 15:21:21
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Effectively reducing the switching voltages based on CdS/ZnO heterostructure for resistive switching memory
摘要： Due to the two-terminal structure, non-destructive read and high integrable density, resistive switching random access memory (RRAM) has attracted much attention for its potential applications in semiconductor industry. Unfortunately, the unexpected failure behaviour is an obstacle for further applications. In our previous work, the CdS inter-layer was used to successfully suppress the failure behaviour in Cu2O based memory cell. However, the switching voltages are still too high and need to be signi?cantly reduced for further applications. In this work, the CdS/ZnO heterostructure is exploited to e?ectively reduce the switching voltages. Compared to the CdS/Cu2O based device, the switching voltages in Pt/CdS/ZnO/FTO cell are e?ectively reduced. The Pt/CdS/ZnO/FTO cell also exhibits remarkable resistive switching and stable data retention characteristics. This work proposes a feasible way to e?ectively optimize the RRAM devices for future applications.
关键词： CdS/ZnO,Switching voltages,Failure behaviours,Resistive switching
更新于2025-09-23 15:21:21
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Influence of blending ratio on resistive switching effect in donor-acceptor type composite of PCBM and PVK-based memory devices
摘要： The influence of blending ratio on resistive switching effect in donor-acceptor type composite of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly(N-vinylcarbazole) (PVK)-based memory devices are investigated. Current-voltage (I-V) curves for the ITO/PCBM + PVK/Al devices with 9 wt.% of PCBM showed a current bistability with a maximum OFF/ON resistance ratio of 9 × 104, which was 100 times larger than that of the device with 23 wt.% of PCBM and was 2000 times larger than that of the device with 41 wt.% of PCBM. Furthermore, the threshold voltage obviously decreased as the PCBM concentration increases. The retention time was above 105 s indicative of the memory stability of the as-fabricated devices. The I-V characteristics at OFF state dominantly comply with the rules of space-charge-limited-current behaviors, and I-V curve at ON state obey Ohmic laws. The proposed device suggests a promising approach for adjustale OFF/ON resistance ratio and threshold voltage in electronic memory devices.
关键词： Nonvolatile memory,Resistive switching,PVK,Organic memory,PCBM
更新于2025-09-23 15:21:21
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Ar-Plasma-Modulated Optical Reset in the SiO <sub/>2</sub> /Cu Conductive-Bridge Resistive Memory Stack
摘要： Our study using conductive atomic force microscope shows that the resistive switching voltage in the SiO2/Cu stack is reduced by 33% after Ar plasma treatment of the oxide. Besides, the negative photo-conductivity (NPC) effect, normally observed on many locations following electrical soft-breakdown, is suppressed. The NPC effect arises because the electrically-formed filamentary conductive path, comprising both Cu and oxygen vacancies, may be disrupted by the recombination of the vacancies with nearby light-excited interstitial oxygen ions. Increase of the O-H peak, as seen from FT-IR spectroscopy, indicates that surface defects generated by the Ar plasma may have adsorbed water molecules, which in turn act as counter anions (OH?) accelerating Cu-ion diffusion into the oxide, forming a more complete Cu filament that is non-responsive to light. The finding offers the possibility of both electrical and optical resistance control by a simple surface treatment step.
关键词： Ar plasma treatment,negative photo-conductivity,conductive atomic force microscope,resistive switching,SiO2/Cu stack
更新于2025-09-23 15:21:01
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Resistive switching and electric field control of ferromagnetism in SnO2 films deposited at room temperature
摘要： The SnO2 film deposited at room temperature (RT) on the substrate of Pt/Ti/SiO2/Si is nano-crystallized, which exhibits room temperature ferromagnetism (FM) due to the oxygen vacancies of SnO2 film. The bipolar and multilevel resistive switching (RS) can be observed in the Ta/SnO2/Pt devices, where SnO2 film was deposited at RT. The Ta/SnO2/Pt device has a large ON/OFF ratio (27000) and multilevel RS, which is of great significance for high-density data storage applications. The saturation magnetization of Ta/SnO2/Pt/Ti/SiO2/Si (Ta/SnO2/Pt device) is almost the same as SnO2/Pt/Ti/SiO2/Si, which implies that the influence of Ta top electrodes on the saturation magnetization of Ta/SnO2/Pt/Ti/SiO2/Si is much less. The Ta/SnO2/Pt device shows the non-volatile and reversible saturation magnetization modulation between low resistance state (LRS) and high resistance state (HRS), which results from the formation/rupture of oxygen vacancy filaments. The saturation magnetization at LRS is higher than that at HRS. In addition, the saturation magnetization also enhances with an increase the magnitude of positive DC sweeping voltage. Without DC loop current, the saturation magnetization of Ta/SnO2/Pt increases with an application of positive electric field and drops again with an application of certain negative electric field. The saturation magnetization of Ta/SnO2/Pt can be reversibly modulated in non-volatile by only electric voltage without DC loop current. Such modulation of Ms by only electric voltage without loop DC current is connected with the change in Vo+ density in a certain range of SnO2 films.
关键词： oxygen vacancies,electric field control,room temperature ferromagnetism,resistive switching,SnO2 film
更新于2025-09-23 15:21:01
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Flexible nonvolatile resistive switching memory devices based on Bi<sub>2</sub>Te<sub>3</sub> nanosheets films
摘要： Flexible nonvolatile resistive switching memory is a promising candidate for next generation storage technologies. Exploring new materials is of crucial importance to achieve further performances of flexible nonvolatile resistive switching memory. In this work, topological insulator bismuth telluride (Bi2Te3) nanosheets films were introduced into firstly, a typical sandwich construction of Ag/Bi2Te3/indium tin oxide/polyethylene terephthalate with good flexibility, which exhibits nonvolatile bipolar resistive switching characteristics of operation voltage, good mechanical flexibility, and good storage stability. Furthermore, trap-controlled space charge limited current, thermionic emission are the dominant conduction mechanisms in the carrier transport. This work will provide an opportunity for Bi2Te3 nanosheets to be used in flexible electronics application.
关键词： Resistive switching,Bismuth telluride,Flexible memory,Nonvolatile,Filtration
更新于2025-09-23 15:21:01
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Dielectric relaxation and resistive switching of Bi0.96Sr0.04Fe0.98Co0.02O3/CoFe2O4 thin films with different thicknesses of the Bi0.96Sr0.04Fe0.98Co0.02O3 layer
摘要： Bi0.96Sr0.04Fe0.98Co0.02O3/CoFe2O4(BSFCO/CFO) bilayered thin films with different thicknesses of the BSFCO layer are synthesized on FTO/glass substrates by chemical solution deposition method (CSD). The influence of BSFCO thickness on the microstructure, dielectric relaxation, ferroelectric properties and resistive switching (RS) of the thin films are researched. Strain exists in the prepared thin films and gives rise to structural distortion, which has an effect on charged defects and ferroelectric polarization. Dielectric relaxation that is closely related to the interfacial polarization at the BSFCO/CFO interface is observed, and the dielectric loss peaks along with decreasing intensity shift to high frequency with decreasing strain. The Maxwell-Wagner two-layer model is adopted to investigate the mechanism of dielectric relaxation, and the relaxation time τ is calculated and it shown to be directly proportional to the strain. It is found that the dielectric properties, including low dielectric loss, can be improved by controlling the BSFCO layer thickness. The ferroelectric properties improve with the decreasing strain, the 12-BSFCO/CFO thin film possesses a large Pr~102.9 μC/cm2 at 660 kV/cm. The observed resistive switching (RS) behavior is attributed to the interfacial conduction mechanism, it is found that strain-dependent the ferroelectric polarization switching modulates the width of depletion layer and the height of potential barrier at the interface, resulting in the different resistance states.
关键词： dielectric relaxation,bilayered thin film,BiFeO3,resistive switching,strain
更新于2025-09-23 15:21:01
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Impact of Laser Attacks on the Switching Behavior of RRAM Devices
摘要： The ubiquitous use of critical and private data in electronic format requires reliable and secure embedded systems for IoT devices. In this context, RRAMs (Resistive Random Access Memories) arises as a promising alternative to replace current memory technologies. However, their suitability for this kind of application, where the integrity of the data is crucial, is still under study. Among the different typology of attacks to recover information of secret data, laser attack is one of the most common due to its simplicity. Some preliminary works have already addressed the influence of laser tests on RRAM devices. Nevertheless, the results are not conclusive since different responses have been reported depending on the circuit under testing and the features of the test. In this paper, we have conducted laser tests on individual RRAM devices. For the set of experiments conducted, the devices did not show faulty behaviors. These results contribute to the characterization of RRAMs and, together with the rest of related works, are expected to pave the way for the development of suitable countermeasures against external attacks.
关键词： security,RRAM,resistive switching,laser attack
更新于2025-09-23 15:19:57