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Physical and chemical mechanisms in oxide-based resistance random access memory.

Chang KC, Chang TC, Tsai TM, Zhang R, Hung YC, Syu YE, Chang YF, Chen MC, Chu TJ, Chen HL, Pan CH, Shih CC, Zheng JC, Sze SM - Nanoscale Res Lett (2015)

Bottom Line: Furthermore, the activation energy of chemical reactions can be extracted by changing temperature during the reset process, from which the oxygen ion reaction process can be found in the RRAM device.The outstanding device characteristics are attributed to the oxidation and reduction of graphene oxide flakes formed during the sputter process.Besides, we have also adopted a new concept of supercritical CO2 fluid treatment to efficiently reduce the operation current of RRAM devices for portable electronic applications.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung, Taiwan.

ABSTRACT
In this review, we provide an overview of our work in resistive switching mechanisms on oxide-based resistance random access memory (RRAM) devices. Based on the investigation of physical and chemical mechanisms, we focus on its materials, device structures, and treatment methods so as to provide an in-depth perspective of state-of-the-art oxide-based RRAM. The critical voltage and constant reaction energy properties were found, which can be used to prospectively modulate voltage and operation time to control RRAM device working performance and forecast material composition. The quantized switching phenomena in RRAM devices were demonstrated at ultra-cryogenic temperature (4K), which is attributed to the atomic-level reaction in metallic filament. In the aspect of chemical mechanisms, we use the Coulomb Faraday theorem to investigate the chemical reaction equations of RRAM for the first time. We can clearly observe that the first-order reaction series is the basis for chemical reaction during reset process in the study. Furthermore, the activation energy of chemical reactions can be extracted by changing temperature during the reset process, from which the oxygen ion reaction process can be found in the RRAM device. As for its materials, silicon oxide is compatible to semiconductor fabrication lines. It is especially promising for the silicon oxide-doped metal technology to be introduced into the industry. Based on that, double-ended graphene oxide-doped silicon oxide based via-structure RRAM with filament self-aligning formation, and self-current limiting operation ability is demonstrated. The outstanding device characteristics are attributed to the oxidation and reduction of graphene oxide flakes formed during the sputter process. Besides, we have also adopted a new concept of supercritical CO2 fluid treatment to efficiently reduce the operation current of RRAM devices for portable electronic applications.

No MeSH data available.


Relationship of device resistance versus reset voltage at 77 K. The reset voltages are operated within a fixed voltage range (0.5 V to 0.7 V) with 0.01 V interval for 1,000 s at 77 K to assure the reaction is accomplished completely.
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Fig7: Relationship of device resistance versus reset voltage at 77 K. The reset voltages are operated within a fixed voltage range (0.5 V to 0.7 V) with 0.01 V interval for 1,000 s at 77 K to assure the reaction is accomplished completely.

Mentions: In view of the analytic results for multi-HRS during reset procedure, the carrier transport mechanism is understood to be converted from Ohmic conduction to Schottky emission. This suggests that the conductive filament in initial LRS was oxidized through layer by layer by oxygen ions returned from the TiN electrode, and the filament was gradually disconnected from the TiN electrode to form a weak Schottky barrier during reset procedure. In the study, the experiment was designed to prove the oxidation procedure in conductive filament, which was observed by quantized resistance states with various reset voltage as shown in Figure 7. Each reset voltage was applied on device for a long time (1,000 s) to ensure complete oxidation of the conductive filament. Besides, the temperature of measurement environment was cooled down to 77 K to lessen thermodynamic effect during the reset procedure of RRAM. Figure 7 shows the correlation of the equilibrium resistance states with various reset voltage operation. The voltage bias was applied on the RRAM with suitable reaction time to initiate the oxidation of filament. The resistance states of RRAM start to change as the applied voltage exceed the first critical reaction voltage (VC1). The resistance states of RRAM were maintained at the first level of resistive states (HRS1) and the second level of high resistive states (HRS2) while the applied voltage was switched from VC1 to the second critical reaction voltage (VC2); and it was quite the same for the resistance change process when VC2 switched to the third critical reaction voltage (VC3). The resistance states of RRAM were transferred into higher resistance step by step as the reset voltage was raised gradually. The quantized reaction procedures for the RRAM transferred from the LRS to the HRS are illustrated in the upper site insets schematically. Moreover, the thickness of reaction layer will grow gradually, and the conductive filament becomes further away from the TiN electrode layer by layer. A higher reset voltage is necessary to supply enough electric field for the chemical reaction. Therefore, the resistance states would be kept until the reset voltage reaches the critical reaction electric field to initiate the next layer reaction of conductive filament. In this experiment, we demonstrated that the reset procedure of RRAM device is a layer-by-layer oxidation process. Therefore, atomic-level quantized oxidation must exist between the different reaction layers during reset procedure. This phenomenon can be observed obviously through the quantized current variation in ultra-cryogenic temperature (4 K) environment, which is shown in Figure 4.Figure 7


Physical and chemical mechanisms in oxide-based resistance random access memory.

Chang KC, Chang TC, Tsai TM, Zhang R, Hung YC, Syu YE, Chang YF, Chen MC, Chu TJ, Chen HL, Pan CH, Shih CC, Zheng JC, Sze SM - Nanoscale Res Lett (2015)

Relationship of device resistance versus reset voltage at 77 K. The reset voltages are operated within a fixed voltage range (0.5 V to 0.7 V) with 0.01 V interval for 1,000 s at 77 K to assure the reaction is accomplished completely.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4388104&req=5

Fig7: Relationship of device resistance versus reset voltage at 77 K. The reset voltages are operated within a fixed voltage range (0.5 V to 0.7 V) with 0.01 V interval for 1,000 s at 77 K to assure the reaction is accomplished completely.
Mentions: In view of the analytic results for multi-HRS during reset procedure, the carrier transport mechanism is understood to be converted from Ohmic conduction to Schottky emission. This suggests that the conductive filament in initial LRS was oxidized through layer by layer by oxygen ions returned from the TiN electrode, and the filament was gradually disconnected from the TiN electrode to form a weak Schottky barrier during reset procedure. In the study, the experiment was designed to prove the oxidation procedure in conductive filament, which was observed by quantized resistance states with various reset voltage as shown in Figure 7. Each reset voltage was applied on device for a long time (1,000 s) to ensure complete oxidation of the conductive filament. Besides, the temperature of measurement environment was cooled down to 77 K to lessen thermodynamic effect during the reset procedure of RRAM. Figure 7 shows the correlation of the equilibrium resistance states with various reset voltage operation. The voltage bias was applied on the RRAM with suitable reaction time to initiate the oxidation of filament. The resistance states of RRAM start to change as the applied voltage exceed the first critical reaction voltage (VC1). The resistance states of RRAM were maintained at the first level of resistive states (HRS1) and the second level of high resistive states (HRS2) while the applied voltage was switched from VC1 to the second critical reaction voltage (VC2); and it was quite the same for the resistance change process when VC2 switched to the third critical reaction voltage (VC3). The resistance states of RRAM were transferred into higher resistance step by step as the reset voltage was raised gradually. The quantized reaction procedures for the RRAM transferred from the LRS to the HRS are illustrated in the upper site insets schematically. Moreover, the thickness of reaction layer will grow gradually, and the conductive filament becomes further away from the TiN electrode layer by layer. A higher reset voltage is necessary to supply enough electric field for the chemical reaction. Therefore, the resistance states would be kept until the reset voltage reaches the critical reaction electric field to initiate the next layer reaction of conductive filament. In this experiment, we demonstrated that the reset procedure of RRAM device is a layer-by-layer oxidation process. Therefore, atomic-level quantized oxidation must exist between the different reaction layers during reset procedure. This phenomenon can be observed obviously through the quantized current variation in ultra-cryogenic temperature (4 K) environment, which is shown in Figure 4.Figure 7

Bottom Line: Furthermore, the activation energy of chemical reactions can be extracted by changing temperature during the reset process, from which the oxygen ion reaction process can be found in the RRAM device.The outstanding device characteristics are attributed to the oxidation and reduction of graphene oxide flakes formed during the sputter process.Besides, we have also adopted a new concept of supercritical CO2 fluid treatment to efficiently reduce the operation current of RRAM devices for portable electronic applications.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung, Taiwan.

ABSTRACT
In this review, we provide an overview of our work in resistive switching mechanisms on oxide-based resistance random access memory (RRAM) devices. Based on the investigation of physical and chemical mechanisms, we focus on its materials, device structures, and treatment methods so as to provide an in-depth perspective of state-of-the-art oxide-based RRAM. The critical voltage and constant reaction energy properties were found, which can be used to prospectively modulate voltage and operation time to control RRAM device working performance and forecast material composition. The quantized switching phenomena in RRAM devices were demonstrated at ultra-cryogenic temperature (4K), which is attributed to the atomic-level reaction in metallic filament. In the aspect of chemical mechanisms, we use the Coulomb Faraday theorem to investigate the chemical reaction equations of RRAM for the first time. We can clearly observe that the first-order reaction series is the basis for chemical reaction during reset process in the study. Furthermore, the activation energy of chemical reactions can be extracted by changing temperature during the reset process, from which the oxygen ion reaction process can be found in the RRAM device. As for its materials, silicon oxide is compatible to semiconductor fabrication lines. It is especially promising for the silicon oxide-doped metal technology to be introduced into the industry. Based on that, double-ended graphene oxide-doped silicon oxide based via-structure RRAM with filament self-aligning formation, and self-current limiting operation ability is demonstrated. The outstanding device characteristics are attributed to the oxidation and reduction of graphene oxide flakes formed during the sputter process. Besides, we have also adopted a new concept of supercritical CO2 fluid treatment to efficiently reduce the operation current of RRAM devices for portable electronic applications.

No MeSH data available.