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Forming-free bipolar resistive switching in nonstoichiometric ceria films.

Ismail M, Huang CY, Panda D, Hung CJ, Tsai TL, Jieng JH, Lin CA, Chand U, Rana AM, Ahmed E, Talib I, Nadeem MY, Tseng TY - Nanoscale Res Lett (2014)

Bottom Line: X-ray photoelectron spectroscopy study confirmed the presence of oxygen vacancies in both of the said regions.In the low-resistance ON state, the electrical conduction was found to be of ohmic nature, while the high-resistance OFF state was governed by trap-controlled space charge-limited mechanism.The stable resistive switching behavior and long retention times with an acceptable resistance ratio enable the device for its application in future nonvolatile resistive random access memory (RRAM).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electronics Engineering and Institute of Electronics, National Chiao Tung University, Hsinchu 30010, Taiwan. tseng@cc.nctu.edu.tw.

ABSTRACT
The mechanism of forming-free bipolar resistive switching in a Zr/CeOx/Pt device was investigated. High-resolution transmission electron microscopy and energy-dispersive spectroscopy analysis indicated the formation of a ZrOy layer at the Zr/CeOx interface. X-ray diffraction studies of CeOx films revealed that they consist of nano-polycrystals embedded in a disordered lattice. The observed resistive switching was suggested to be linked with the formation and rupture of conductive filaments constituted by oxygen vacancies in the CeOx film and in the nonstoichiometric ZrOy interfacial layer. X-ray photoelectron spectroscopy study confirmed the presence of oxygen vacancies in both of the said regions. In the low-resistance ON state, the electrical conduction was found to be of ohmic nature, while the high-resistance OFF state was governed by trap-controlled space charge-limited mechanism. The stable resistive switching behavior and long retention times with an acceptable resistance ratio enable the device for its application in future nonvolatile resistive random access memory (RRAM).

No MeSH data available.


Related in: MedlinePlus

XPS binding energy profiles. (a) Depth profiles of Zr, Ce, O, Pt, and W for the W/Zr/CeOx/Pt structure, (b) Ce 3d, (c) Zr 3d, and (d) O 1 s in the Zr/CeOx/Pt device.
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Figure 2: XPS binding energy profiles. (a) Depth profiles of Zr, Ce, O, Pt, and W for the W/Zr/CeOx/Pt structure, (b) Ce 3d, (c) Zr 3d, and (d) O 1 s in the Zr/CeOx/Pt device.

Mentions: The ZrOy layer is also observed from XPS signals at the interface of Zr and CeO2 layers. XPS analysis was carried out to examine the surface chemical composition and the valence/oxidation states of Ce and Zr species involved in the device by inspecting the spectral line shape and signal intensities associated with the core-level electrons. Figure 2a shows the depth profile of chemical composition in the Zr/CeOx/Pt device. The interdiffusion of O, Ce, and Zr atoms are evident from the spectra. This is an indication of the formation of an interfacial ZrOy layer between the CeOx and Zr top electrode. The formation of the ZrOy layer is further confirmed from the shifting of Zr 3d peaks from a higher binding energy position to lower ones (Figure 2c). The CeOx 3d spectrum shown in Figure 2b consists of two sets of spin-orbit multiplets. These multiplets are the characteristics of 3d3/2 and 3d5/2 (represented as u and v, respectively) [15]. The spin-orbit splitting is about 18.4 eV. The highest peaks at around 880.2 and 898.7 eV, recognized as v0 and u0 respectively, correspond to Ce3+ with the highest satellites as v′ (885.1 eV) and u′ (903.3 eV). Low-intensity peaks, i.e., v (882.5 eV) and u (900.9 eV) along with satellite features represented as v″ (889.4 eV), v‴ (897.5 eV), u″ (905.4 eV), and u‴ (914.6 eV), are observed, corresponding to the Ce4+ state.


Forming-free bipolar resistive switching in nonstoichiometric ceria films.

Ismail M, Huang CY, Panda D, Hung CJ, Tsai TL, Jieng JH, Lin CA, Chand U, Rana AM, Ahmed E, Talib I, Nadeem MY, Tseng TY - Nanoscale Res Lett (2014)

XPS binding energy profiles. (a) Depth profiles of Zr, Ce, O, Pt, and W for the W/Zr/CeOx/Pt structure, (b) Ce 3d, (c) Zr 3d, and (d) O 1 s in the Zr/CeOx/Pt device.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 2: XPS binding energy profiles. (a) Depth profiles of Zr, Ce, O, Pt, and W for the W/Zr/CeOx/Pt structure, (b) Ce 3d, (c) Zr 3d, and (d) O 1 s in the Zr/CeOx/Pt device.
Mentions: The ZrOy layer is also observed from XPS signals at the interface of Zr and CeO2 layers. XPS analysis was carried out to examine the surface chemical composition and the valence/oxidation states of Ce and Zr species involved in the device by inspecting the spectral line shape and signal intensities associated with the core-level electrons. Figure 2a shows the depth profile of chemical composition in the Zr/CeOx/Pt device. The interdiffusion of O, Ce, and Zr atoms are evident from the spectra. This is an indication of the formation of an interfacial ZrOy layer between the CeOx and Zr top electrode. The formation of the ZrOy layer is further confirmed from the shifting of Zr 3d peaks from a higher binding energy position to lower ones (Figure 2c). The CeOx 3d spectrum shown in Figure 2b consists of two sets of spin-orbit multiplets. These multiplets are the characteristics of 3d3/2 and 3d5/2 (represented as u and v, respectively) [15]. The spin-orbit splitting is about 18.4 eV. The highest peaks at around 880.2 and 898.7 eV, recognized as v0 and u0 respectively, correspond to Ce3+ with the highest satellites as v′ (885.1 eV) and u′ (903.3 eV). Low-intensity peaks, i.e., v (882.5 eV) and u (900.9 eV) along with satellite features represented as v″ (889.4 eV), v‴ (897.5 eV), u″ (905.4 eV), and u‴ (914.6 eV), are observed, corresponding to the Ce4+ state.

Bottom Line: X-ray photoelectron spectroscopy study confirmed the presence of oxygen vacancies in both of the said regions.In the low-resistance ON state, the electrical conduction was found to be of ohmic nature, while the high-resistance OFF state was governed by trap-controlled space charge-limited mechanism.The stable resistive switching behavior and long retention times with an acceptable resistance ratio enable the device for its application in future nonvolatile resistive random access memory (RRAM).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electronics Engineering and Institute of Electronics, National Chiao Tung University, Hsinchu 30010, Taiwan. tseng@cc.nctu.edu.tw.

ABSTRACT
The mechanism of forming-free bipolar resistive switching in a Zr/CeOx/Pt device was investigated. High-resolution transmission electron microscopy and energy-dispersive spectroscopy analysis indicated the formation of a ZrOy layer at the Zr/CeOx interface. X-ray diffraction studies of CeOx films revealed that they consist of nano-polycrystals embedded in a disordered lattice. The observed resistive switching was suggested to be linked with the formation and rupture of conductive filaments constituted by oxygen vacancies in the CeOx film and in the nonstoichiometric ZrOy interfacial layer. X-ray photoelectron spectroscopy study confirmed the presence of oxygen vacancies in both of the said regions. In the low-resistance ON state, the electrical conduction was found to be of ohmic nature, while the high-resistance OFF state was governed by trap-controlled space charge-limited mechanism. The stable resistive switching behavior and long retention times with an acceptable resistance ratio enable the device for its application in future nonvolatile resistive random access memory (RRAM).

No MeSH data available.


Related in: MedlinePlus