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RISS 인기검색어
- 검색키워드
- 저자 : Shania REHMAN (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Phase transformation induced resistive switching behavior in Al/Cu<sub>2</sub>Se/Pt
Rehman, Shania,Kim, Kihwan,Hur, Ji-Hyun,Kim, Deok-kee IOP 2017 Journal of Physics. D, Applied Physics Vol.50 No.13
<P>The phase transformation induced resistive switching behavior of an Al/Cu<SUB>2</SUB>Se/Pt device was studied. While the device did not demonstrate any resistive switching behavior at room temperature, it exhibited resistive switching behavior at 125 °C, near the transition temperature of copper(I) selenide (Cu<SUB>2</SUB>Se) (137 °C), where Cu<SUB>2</SUB>Se is known to transform from the monoclinic to superionic phase. The increase in ionic conductivity and structural variations (from ordered to disordered structure) associated with phase transformation were observed to be responsible for the origin of the switching behavior and increase in the on/off resistance ratio near the transition temperature. Thermodynamic calculations showed that a reduction in Gibb’s free energy of nucleation and an increase in the migration speed of the Cu ion associated with the ionic conductivity and order to disorder the transition of the Cu<SUB>2</SUB>Se at the transition temperature were the important factors responsible for the reduction in the SET voltages at 155 °C.</P>
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Rehman, Shania,Hur, Ji-Hyun,Kim, Deok-kee American Chemical Society 2018 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.122 No.20
<P>The control of resistive switching, in low-cost solution-processed Cu<I><SUB>x</SUB></I>O thin films, was demonstrated on the basis of intentional manipulation of intrinsic point defects. Cu interstitials offered a unique way to create metallic Cu filament even in the absence of electrochemically active Cu top electrode. The concentration of these Cu interstitials was controlled by annealing the CuO films at low temperature (300 °C) in Ar environment with different oxygen contents. By varying the oxygen content, profound effect was observed on the resistivity of Cu<I><SUB>x</SUB></I>O thin films, which in turn controlled the memory windows in different devices. Annealing at 0% O<SUB>2</SUB> atmosphere created abundant cationic defects, which resulted in poor switching behavior. With the addition of 20% oxygen and increased annealing time, transition of CuO to Cu<SUB>2</SUB>O, determined by X-ray diffraction and Raman spectroscopy, resulted in deterministic increase in on/off ratio by 3 orders of magnitude and improved endurance. On increasing the oxygen content above 20%, switching behavior was degraded. Increasing the oxygen content reduces the cationic defects, which cause hindrance in the formation of filament responsible for switching behavior. Grain boundaries seem to play a vital role in controlling the variation in SET and RESET voltages. We found that precise control on the switching properties can be attained by modulating the Cu interstitials in these Cu<I><SUB>x</SUB></I>O devices.</P> [FIG OMISSION]</BR>
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Thickness-dependent resistive switching in black phosphorus CBRAM
Rehman, Shania,Khan, Muhammad Farooq,Aftab, Sikandar,Kim, Honggyun,Eom, Jonghwa,Kim, Deok-kee The Royal Society of Chemistry 2019 Journal of materials chemistry. C, Materials for o Vol.7 No.3
<P>The main challenge encountered by most 2D materials for their use in non-volatile memory technology is their low <I>R</I>on/off ratio. Recently, black phosphorus (BP), an emerging 2D layered material has replaced transition metal dichalcogenides (TMDS) due to its unique electronic properties. In this paper, we have investigated the resistive switching behavior of BP Conductive Bridge Random Access Memory (CBRAM), in which resistive switching is driven by the formation of a metallic (Cu) filament and the active layer is solely composed of BP thin films. The on/off ratio is controlled by using different thicknesses of BP. It is notably found that the <I>R</I>on/off ratio has a strong dependence on the thickness of BP. Thicker BP devices showed stable bipolar switching with a low operating voltage of 0.6 eV ± 0.1 V and an <I>R</I>on/off of 10<SUP>4</SUP>. The main hindrance to commercial applications of BP devices is that the BP films are susceptible to degradation on exposure to ambient conditions. To make these BP devices environmentally stable, we have utilized the strategy of growing native oxide on thicker BP devices as a protective layer by utilizing deep ultra violet light and elucidated an improved <I>R</I>on/off up to 10<SUP>5</SUP>. To the best of our knowledge, here, we report for the first time the resistive switching characteristics of BP CBRAM.</P>
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