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Pammi, S. V. N.,Hyun-June Jung,Soon-Gil Yoon IEEE 2011 IEEE TRANSACTIONS ON NANOTECHNOLOGY Vol.10 No.5
<P>Indium tin oxide (ITO) thin films were grown using nanocluster deposition (NCD) on glass substrates in low temperature range from 170 to 250°C. X-ray diffraction pattern revealed that ITO thin films deposited above 200°C were preferentially oriented along (1 1 1) direction. A dramatic change in electrical properties of ITO thin films deposited from 200 to 170°C was attributed to the change in microstructure and chemical bonding states. The ITO thin films deposited at 170°C exhibited semiconducting properties with high optical transmittance of 95% at 550-nm wavelength. Films of approximately 140 ± 5 nm thicknesses exhibited both the lowest resistivity of 7 × 10<SUP>-4</SUP> Ω·cm and the figure-of-merit value of 1.3 × 10<SUP>-2</SUP> Ω<SUP>-1</SUP>. The NCD technique is possible for deposition of ITO films crystallized at low temperatures below 200°C on glass or flexible polymer substrates.</P>
Antioxidant potential of medicinal plants
Pammi S. S. Sravanthi,Suresh Bastipati,Giri Archana 한국작물학회 2023 Journal of crop science and biotechnology Vol.26 No.1
Medicinal plants are used for health care either directly or indirectly as they are rich source of several ingredients. Ethnomedical traditions prove that they have a great therapeutic value and are important bioresources. Phytochemicals are naturally occurring compounds having immense antioxidant potential and are of great interest in securing health benefts of consumers. Each portion of the plant has its own medicinal properties possessing diferent types of secondary metabolites which plays important role in treatment of diferent types of diseases and for manufacturing of drugs. The phytopharmaceutical preparations should be safely assessed and well established before their usage. In spite of medicinal uses, phytochemicals have also been used in cosmetics, fragrance and as food supplements. Global research is recently focusing on search of new medicines or active compounds with proven signifcant scientifc output. This review focusses on the metabolic fngerprint and biological properties of various plants which play a major role in antioxidant activity along with their mechanisms of action
Pammi, S.V.N.,Chanda, A.,Seong, N.J.,Yoon, S.G. North Holland ; Elsevier Science Ltd 2010 Chemical physics letters Vol.490 No.4
High quality indium tin oxide (ITO) thin films were grown by nano-cluster deposition (NCD) technique at a low temperature. The lowest resistivity (∼2x10<SUP>-4</SUP>Omega;cm) and highest optical transparency (90%) were obtained for films deposited with optimum oxygen gas flow rate of 30sccm (standard ccmin<SUP>-1</SUP>. The absence of hydroxyl groups, organic contamination and carbon content in the films grown at a low temperature of 250<SUP>o</SUP> by NCD indicates the complete decomposition of metal-organic precursors.
Pammi, S. V.,Jella, V.,Choi, J. S.,Yoon, S. G. Royal Society of Chemistry 2017 Journal of Materials Chemistry C Vol.5 No.3
<P>We report the fabrication of Cu2-xSe NW-polyvinylidene fluoride (PVDF) composite flexible thin films using various approaches such as simple drop casting (DC), vacuum filtration (VF), and vacuum filtration followed by mechanical pressing (VFMP). The highest power factor of Cu2-xSe NW-PVDF composite films reached 105.32 mW m(-1) K-2 when mechanical pressing was performed following vacuum filtration at 303 K, and this was further enhanced to 253.49 mW m(-1) K-2 at 393 K. Cu2-xSe NW-PVDF composite films fabricated via vacuum filtration without mechanical pressing showed a reasonable power factor (<40 mu W m(-1) K-2 at room temperature), whereas films fabricated via the drop casting method showed a poor power factor (<10 mu W m(-1) K-2 at room temperature). VFMP-treated Cu2-xSe NW-PVDF thermoelectric films showed good mechanical durability until 1000 bending cycles without significant performance degradation. When all these results are considered, the fabricated composite films could be a feasible option for p-type thermoelectric materials in thermoelectric power generators.</P>
Strategic extended air stability of organolead halide perovskite nonvolatile memory devices
Yoo, Eunji,Pammi, S.V.N.,Kim, Kyu Young,Dang, Tran-Van,Eom, Ji-Ho,Choi, Young Jin,Yoon, Soon-Gil Elsevier 2019 Journal of alloys and compounds Vol.811 No.-
<P><B>Abstract</B></P> <P>In this study, we demonstrated long-term stability in the resistive switching (RS) properties of MAPbI<SUB>3</SUB> films, coated <I>via</I> a one-step chemical vapor deposition (CVD) method using no additives or polymers. The RS behavior of the CVD-fabricated memory devices compares favorably to that of spin-coated films; these devices exhibited reliably stable bipolar resistive switching properties for 30 days under ambient conditions, while spin-coated devices were stable for only 10 days. For further enhancement of air stability, a 20 nm-thick ZnO passivation layer was deposited on MAPbI<SUB>3</SUB> <I>via on-axis</I> and facing-target sputtered (FTS) techniques. The resistive random-access memory (ReRAM) devices with a ZnO passivation layer deposited <I>via</I> FTS technique exhibited extended air stability for 3 months under ambient conditions, whereas in the case of memory devices fabricated with an <I>on-axis</I> sputtered passivation layer, air stability was limited to 60 days. This extended air stability can be attributed to excellent step coverage and free of plasma damage during deposition. Memory devices fabricated <I>via</I> the CVD and FTS methods showed no significant variations at either set or reset levels of voltage and showed favorable levels in terms of both data retention and endurance performance with storage time.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Spin-coated memory devices are stable for only 10 days. </LI> <LI> CVD fabricated memory devices exhibited 30 days stability in air. </LI> <LI> Stable RS behaviour of FTS passivated devices with 3 months in air ambient. </LI> </UL> </P>