In order to further testify the existence of the
carbon layer selleck chemicals and find its chemical bonding type, FTIR was used to analyze the sputtered carbon thin film. C-H stretch peak can be observed at the wave number of 2,800 to 3,000 cm-1, as shown in the FTIR spectra of Figure 3b. To clarify the current transportation mechanism, the current vs. voltage (I-V) is presented in Figure 4. The LRS shows symmetric I-V curve at positive and negative electrical field. The electron transport exhibits Poole-Frenkel and Hopping conduction at middle and high voltage. However, the I-V curve is asymmetric in HRS, but the current transportation mechanism is Schottky emission and Hopping at middle and high voltage. The resistive switching mechanism of LRS and HRS is given in detail as follows. Figure 4 I-V curve fitting of Pt/a-C:H/TiN memory device with various carrier transport mechanisms. On the basis of the electrical and material analyses, we proposed a reaction model to explain the transfer of carrier conduction mechanism of the amorphous carbon RRAM as shown in Figure 5. The conductive
filament will be formed after the forming process, which is attributed to the connection between Staurosporine sp2 carbon fractions in the amorphous carbon layer [46]. Due to the current compliance, there is remaining amorphous carbon between conductive sp2 regions, as shown in left insert of Figure 5. Because the current pass through the boundaries of sp2 regions, the current fitting is dominated by Poole-Frenkel conduction in LRS. As higher voltage was applied, the significant barrier lowering caused the conduction dominated by hopping conduction through
conjugation double bonds of sp2 carbon filament. When the bottom TiN electrode is applied with a negative bias to perform a reset process, hydrogen atoms were pulled from the Pt electrode and absorbed by double bonds of sp2 carbon, namely hydrogenation process. The hydrogenation reaction will transfer the conductive sp2 carbon filament into insulated sp3 carbon filament. As shown in the right insert of Figure 5, the region of filament near Pt electrode forms insulated sp3 carbon dominated, which mafosfamide leads to the current conduction exhibit Schottky conduction in HRS. The Hopping conduction is attributed to significant barrier lowering as the higher voltage was applied. Contrariwise, the hydrogen atoms were repelled to Pt electrode to form sp2 carbon filament during set process, called as dehydration process. Based on the hydrogen redox model, a repeatable switching behavior can be obtained in C-RRAM device. Figure 5 Hydrogen redox model of Pt/a-C:H/TiN memory device in LRS and HRS states. Conclusion In conclusion, the amorphous carbon RRAM has been fabricated to investigate the resistive switching characteristics. The device has good resistive switching properties due to hydrogenation and dehydrogenation of H atoms in carbon RRAM.
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