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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>
Dastgeer, Ghulam,Khan, Muhammad Farooq,Nazir, Ghazanfar,Afzal, Amir Muhammad,Aftab, Sikandar,Naqvi, Bilal Abbas,Cha, Janghwan,Min, Kyung-Ah,Jamil, Yasir,Jung, Jongwan,Hong, Suklyun,Eom, Jonghwa American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.15
<P>Heterostructures comprising two-dimensional (2D) semiconductors fabricated by individual stacking exhibit interesting characteristics owing to their 2D nature and atomically sharp interface. As an emerging 2D material, black phosphorus (BP) nanosheets have drawn much attention because of their small band gap semiconductor characteristics along with high mobility. Stacking structures composed of p-type BP and n-type transition metal dichalcogenides can produce an atomically sharp interface with van der Waals interaction which leads to p-n diode functionality. In this study, for the first time, we fabricated a heterojunction p-n diode composed of BP and WS<SUB>2</SUB>. The rectification effects are examined for monolayer, bilayer, trilayer, and multilayer WS<SUB>2</SUB> flakes in our BP/WS<SUB>2</SUB> van der Waals heterojunction diodes and also verified by density function theory calculations. We report superior functionalities as compared to other van der Waals heterojunction, such as efficient gate-dependent static rectification of 2.6 × 10<SUP>4</SUP>, temperature dependence, thickness dependence of rectification, and ideality factor of the device. The temperature dependence of Zener breakdown voltage and avalanche breakdown voltage were analyzed in the same device. Additionally, superior optoelectronic characteristics such as photoresponsivity of 500 mA/W and external quantum efficiency of 103% are achieved in the BP/WS<SUB>2</SUB> van der Waals p-n diode, which is unprecedented for BP/transition metal dichalcogenides heterostructures. The BP/WS<SUB>2</SUB> van der Waals p-n diodes have a profound potential to fabricate rectifiers, solar cells, and photovoltaic diodes in 2D semiconductor electronics and optoelectronics.</P> [FIG OMISSION]</BR>
Shah Zada,Saleem Raza,Sikandar Khan,Arshad Iqbal,Zhang Kai,Aftab Ahmad,Midrar Ullah,Mohib Kakar,Pengcheng Fu,Haifeng Dong,Zhang Xueji 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.105 No.-
Heavy metals and other organic pollutants are the hazardous materials causing soil and water pollution,hence, bioremediation of these components is a matter of concern for environmental biotechnologists. Twenty one microalgal and cyanobacterial strains were evaluated for removal of copper from aqueoussolutions and soil containing 10 ppm copper. 5 out of 21 strains have shown comparatively higher toleranceto copper stress. The biosorption capabilities of all the five strains were assessed using techniqueslike ultraviolet (UV) spectrophotometers, scanning electron microscope (SEM), inductively coupledplasma mass spectrometry (ICP-MS), and confocal Microscopy. It was found that the five selected strainscould grow normally upon incubating with 20 ppm of Cu. Copper removal efficiencies of these microalgae(S. obliquus, A. braunii, C. fusca, L. JSC-1 and C. saccharophila in water were 99.9, 99.3, 97, 96.7, and 96%,while for soil was 73, 75, 71, 70, 68%, respectively. A minor leakage of nucleic acid and protein weredetected with time. Furthermore, no any visible morphological changes were observed after six daysof treatment, while minor changes were noticed after 12 days in water, and severe morphological deformationsoccurred after 24 days of bioremediation in soil. Our findings reveal that the selected microalgalstrains have high potential for Cu bioremediation at certain concentration for 12 days exposure fromwater and 24 from soil.
Shahbaz Ahmad,Aftab Ahmad,Sikandar Khan,Shujaat Ahmad,Idrees Khan,Shah Zada,Pengcheng Fu 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.72 No.-
Efficient reduction of GO was performed, using cellular extracts of three algal strains. The rGO werecharacterized by SEM, TEM, UV-Visible spectroscopy, XRD, FTIR, Raman spectroscopy, Zeta potential andredox potentials. The rGO were then used as decontaminating agents for heavy metals (Cu and Pb), inwaste water. GO reduced via JSC-1 have removed up to 93% Cu and 82% Pb (adsorption capacity of93 mg g 1 and 82 mg g 1, respectively), by 211-9a have removed 74% (74 mg g 1) Cu and 89% (89 mg g 1)Pb, while by 211-11n have adsorbed 91% (91 mg g 1) Cu and 95% Pb (95 mg g 1), within 30 min.
Nazir, Ghazanfar,Rehman, Malik Abdul,Khan, Muhammad Farooq,Dastgeer, Ghulam,Aftab, Sikandar,Afzal, Amir Muhammad,Seo, Yongho,Eom, Jonghwa American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.38
<P>As one of the newly discovered transition-metal dichalcogenides (TMDs), rhenium disulfide (ReS<SUB>2</SUB>) has been investigated mostly because of its unique characteristics such as the direct band gap nature even in bulk form, which is not prominent in other TMDs (e.g., MoS<SUB>2</SUB>, WSe<SUB>2</SUB>, etc.). However, this material possesses a low mobility and an on/off ratio, which restrict its usage in high-speed and fast switching applications. Low mobilities or on/off ratios can also be caused by substrate scattering as well as environmental effects. In this study, we used few-layer ReS<SUB>2</SUB> (FL-ReS<SUB>2</SUB>) as a channel material to investigate the substrate-dependent mobility, current on/off ratio, Schottky barrier height (SBH), and trap density of states of different dielectric substrates. The hexagonal boron nitride (h-BN)/FL-ReS<SUB>2</SUB>/h-BN structure was observed to exhibit a high mobility of 45 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>, current on/off ratio of about 10<SUP>7</SUP>, the lowest SBH of about 12 mV at a zero back-gate voltage (<I>V</I><SUB>bg</SUB>), and a low trap density of states of about 5 × 10<SUP>13</SUP> cm<SUP>-3</SUP>. These quantities are reasonably superior compared to the FL-ReS<SUB>2</SUB> devices on SiO<SUB>2</SUB> substrates. We also observed a nearly 5-fold improvement in the photoresponsivity and external quantum efficiency values for the FL-ReS<SUB>2</SUB> devices on h-BN substrates. We believe that the photonic characteristics of TMDs can be improved by using h-BN as the substrate and capping layer.</P> [FIG OMISSION]</BR>