Limits...
Evidence of Filamentary Switching in Oxide-based Memory Devices via Weak Programming and Retention Failure Analysis.

Younis A, Chu D, Li S - Sci Rep (2015)

Bottom Line: Furthermore, the metal oxide-based (CeO2:Gd) memory device was found to possess electrical and neuromorphic multifunctionalities.In addition, a short-term to long-term memory transition analogous to the forgetting process in the human brain, which is regarded as a key biological synaptic function for information processing and data storage, was realized.Based on a careful examination of the device's retention behaviour at elevated temperatures, the filamentary nature of switching in such devices can be understood from a new perspective.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, University of New South Wales, Sydney, 2052, NSW, Australia.

ABSTRACT
Further progress in high-performance microelectronic devices relies on the development of novel materials and device architectures. However, the components and designs that are currently in use have reached their physical limits. Intensive research efforts, ranging from device fabrication to performance evaluation, are required to surmount these limitations. In this paper, we demonstrate that the superior bipolar resistive switching characteristics of a CeO2:Gd-based memory device can be manipulated by means of UV radiation, serving as a new degree of freedom. Furthermore, the metal oxide-based (CeO2:Gd) memory device was found to possess electrical and neuromorphic multifunctionalities. To investigate the underlying switching mechanism of the device, its plasticity behaviour was studied by imposing weak programming conditions. In addition, a short-term to long-term memory transition analogous to the forgetting process in the human brain, which is regarded as a key biological synaptic function for information processing and data storage, was realized. Based on a careful examination of the device's retention behaviour at elevated temperatures, the filamentary nature of switching in such devices can be understood from a new perspective.

No MeSH data available.


Related in: MedlinePlus

The generation and annihilation of conducting filaments under various conditions.(a) The formation of a single filament, in the absence of UV exposure, under an applied positive potential. (b) UV exposure causes an increase in the OB concentration on or near the GDC film surface. (c) The formation of multiple conducting filaments under the combination of UV irradiation and a positive potential, increasing the current level of the low-resistance state (d) The annihilation/rupture of conducting filaments as a consequence of an applied negative potential.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4555098&req=5

f6: The generation and annihilation of conducting filaments under various conditions.(a) The formation of a single filament, in the absence of UV exposure, under an applied positive potential. (b) UV exposure causes an increase in the OB concentration on or near the GDC film surface. (c) The formation of multiple conducting filaments under the combination of UV irradiation and a positive potential, increasing the current level of the low-resistance state (d) The annihilation/rupture of conducting filaments as a consequence of an applied negative potential.

Mentions: GDC nanocrystals are generally considered to have many surface defects, such as oxygen vacancies that can interact with oxygen molecules in the atmosphere. These interactions can generate various intermediates, such as superoxide (O2−), peroxide (O22−) and O− species, before reducing these intermediates to lattice oxygen (O2−)34. It is believed that UV radiation can preferentially facilitate the formation of superoxides (chemically adsorbed oxygen) through the reaction of oxygen molecules with electrons trapped on the surface35. To verify this hypothesis, XPS studies were conducted using the same GDC sample without and with UV radiation exposure, as presented in Figures S5 and S3, respectively. UV exposure was found to facilitate the formation of chemisorbed oxygen (OB). Under the application of a suitable potential, OB can be attracted towards the top electrode through Columbic interactions. This results in the evolution of a conducting filament and enhances device conductance. With a further increase in the applied potential, the increased OB migration towards the anode generates more oxygen vacancies at a proportional concentration. As a result of this migration, conducting filaments consisting of oxygen vacancies grow between two electrodes. In the case of device operation without UV exposure, the relatively low OB concentration is likely to result in a small or weakly conducting filament between the two electrodes. By contrast, under UV exposure, the higher OB concentration, likely facilitates the formation of one strong filament or multiple filaments between the cathode and the anode. As a consequence, an elevated current level was observed for the device in the LRS [Fig. 1(a)], along with much more rapid response times for programming and erasing [Fig. 2(a)]. The proposed mechanism of filament formation and annihilation in the absence or presence of UV irradiation is schematically illustrated in Fig. 6.


Evidence of Filamentary Switching in Oxide-based Memory Devices via Weak Programming and Retention Failure Analysis.

Younis A, Chu D, Li S - Sci Rep (2015)

The generation and annihilation of conducting filaments under various conditions.(a) The formation of a single filament, in the absence of UV exposure, under an applied positive potential. (b) UV exposure causes an increase in the OB concentration on or near the GDC film surface. (c) The formation of multiple conducting filaments under the combination of UV irradiation and a positive potential, increasing the current level of the low-resistance state (d) The annihilation/rupture of conducting filaments as a consequence of an applied negative potential.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4555098&req=5

f6: The generation and annihilation of conducting filaments under various conditions.(a) The formation of a single filament, in the absence of UV exposure, under an applied positive potential. (b) UV exposure causes an increase in the OB concentration on or near the GDC film surface. (c) The formation of multiple conducting filaments under the combination of UV irradiation and a positive potential, increasing the current level of the low-resistance state (d) The annihilation/rupture of conducting filaments as a consequence of an applied negative potential.
Mentions: GDC nanocrystals are generally considered to have many surface defects, such as oxygen vacancies that can interact with oxygen molecules in the atmosphere. These interactions can generate various intermediates, such as superoxide (O2−), peroxide (O22−) and O− species, before reducing these intermediates to lattice oxygen (O2−)34. It is believed that UV radiation can preferentially facilitate the formation of superoxides (chemically adsorbed oxygen) through the reaction of oxygen molecules with electrons trapped on the surface35. To verify this hypothesis, XPS studies were conducted using the same GDC sample without and with UV radiation exposure, as presented in Figures S5 and S3, respectively. UV exposure was found to facilitate the formation of chemisorbed oxygen (OB). Under the application of a suitable potential, OB can be attracted towards the top electrode through Columbic interactions. This results in the evolution of a conducting filament and enhances device conductance. With a further increase in the applied potential, the increased OB migration towards the anode generates more oxygen vacancies at a proportional concentration. As a result of this migration, conducting filaments consisting of oxygen vacancies grow between two electrodes. In the case of device operation without UV exposure, the relatively low OB concentration is likely to result in a small or weakly conducting filament between the two electrodes. By contrast, under UV exposure, the higher OB concentration, likely facilitates the formation of one strong filament or multiple filaments between the cathode and the anode. As a consequence, an elevated current level was observed for the device in the LRS [Fig. 1(a)], along with much more rapid response times for programming and erasing [Fig. 2(a)]. The proposed mechanism of filament formation and annihilation in the absence or presence of UV irradiation is schematically illustrated in Fig. 6.

Bottom Line: Furthermore, the metal oxide-based (CeO2:Gd) memory device was found to possess electrical and neuromorphic multifunctionalities.In addition, a short-term to long-term memory transition analogous to the forgetting process in the human brain, which is regarded as a key biological synaptic function for information processing and data storage, was realized.Based on a careful examination of the device's retention behaviour at elevated temperatures, the filamentary nature of switching in such devices can be understood from a new perspective.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, University of New South Wales, Sydney, 2052, NSW, Australia.

ABSTRACT
Further progress in high-performance microelectronic devices relies on the development of novel materials and device architectures. However, the components and designs that are currently in use have reached their physical limits. Intensive research efforts, ranging from device fabrication to performance evaluation, are required to surmount these limitations. In this paper, we demonstrate that the superior bipolar resistive switching characteristics of a CeO2:Gd-based memory device can be manipulated by means of UV radiation, serving as a new degree of freedom. Furthermore, the metal oxide-based (CeO2:Gd) memory device was found to possess electrical and neuromorphic multifunctionalities. To investigate the underlying switching mechanism of the device, its plasticity behaviour was studied by imposing weak programming conditions. In addition, a short-term to long-term memory transition analogous to the forgetting process in the human brain, which is regarded as a key biological synaptic function for information processing and data storage, was realized. Based on a careful examination of the device's retention behaviour at elevated temperatures, the filamentary nature of switching in such devices can be understood from a new perspective.

No MeSH data available.


Related in: MedlinePlus