Conference Paper
Switching properties of PST ferroelectric films for memory applications using conductive oxide LSCO electrodes
Fecha
2009Autor
de Jesus Martinez-Gomez, A.
Manolache, S.O.
Gonzalez-Alvarez, V.
Young, R.A.
Denes, F.S.
Institución
Resumen
The surface functionalization process was accomplished in a consecutive 3 step process including: (1) Argon- and oxygen-plasma enhanced generation of free radical sites on cellophane surfaces; (2) "In situ" gas phase derivatization in the absence of plasma using hydrazine, ethylene diamine, or propylene diamine; (3) Second "in situ", gas phase derivatization in the absence of plasma using oxallyl chloride or "ex situ" derivatization in the presence of glutaraldehyde. The presence of free radical sites on the plasma exposed cellophane surfaces was demonstrated using "in situ" sulfur dioxide and nitric oxide labeling techniques. It was shown that the free radical sites readily react under "in situ" conditions with the stable chain-precursor components and generate the desired spacer-chain molecules. ESCA, ATR-FTIR analysis and dying techniques were used to monitor the cellophane surface changes. A factorial design was used for selecting the optimal plasma parameters. Functionalized cellophane substrates were used for immobilization of ?-chymotrypsin in the presence of spacer-chain molecules. The activity of the immobilized ?-chymotrypsin was found to be lower in comparison to the activity of the free enzyme and the presence of virgin cellophane in the free enzyme solution also reduced significantly the activity of the enzyme. It is suggested that the swollen state of the cellophane plays a significant role in the decrease of the immobilized enzyme activity. " Springer Science+Business Media B.V. 2009.",,,,,,"10.1007/s10570-009-9274-4",,,"http://hdl.handle.net/20.500.12104/44862","http://www.scopus.com/inward/record.url?eid=2-s2.0-67349251175&partnerID=40&md5=fe56c0386924e370284f13fccf19ab8b",,,,,,"3",,"Cellulose",,"501 517",,"16",,"Scopus WOS",,,,,,"?-Chymotrypsin immobilization; Cellophane; Plasma functionalization; Primary amine and carboxylic functionalities; Spacer-chain molecules",,,,,,"Surface functionalization via in situ interaction of plasma-generated free radicals with stable precursor-molecules on cellulose",,"Article"
"46666","123456789/35008",,"Martínez, E., Centro de Ciencias de la Materia Condensada, UNAM, Apdo. Postal 2681, C.P. 22800, Ensenada, B.C, Mexico; Blanco, O., Centro de Investigación en Materiales, CUCEI- U.de G, Guadalajara, Mexico; Siqueiros, J.M., Centro de Ciencias de la Materia Condensada, UNAM, Apdo. Postal 2681, C.P. 22800, Ensenada, B.C, Mexico",,"Martinez, E. Blanco, O. Siqueiros, J.M.",,"2005",,"We have investigated the switching properties of ferroelectric lead strontium titanate (PbxSr1-x)TiO3 (PST) capacitors using epitaxial and polycrystalline La0.5Sr 0.5CoO3 (LSCO) electrodes to evaluate its potential for non-volatile memory applications (PRAM'S). The electrical performance of the PST based capacitors grown on epitaxial and polycrystalline LSCO substrates were evaluated through Polarization-Voltage (P-V) and Fatigue measurements. The ?001? preferentially oriented PST ferroelectric capacitor did not show a decrease in polarization up to 108 switching cycles at an applied voltage of 4 volts and a frequency of 100 kHz. Polycrystalline PST films, on the other hand were severely fatigued. It is proposed that the good performance of the PST capacitors can be attributed to the high degree of orientation of the PST films in the ?001? direction induced by the epitaxial LSCO film. However, after 1010 switching cycles in the fatigue tests, the decay of the non-volatile polarization of these films was about 18% of its initial value. We use a simple model to describe two major microscopic scenarios for the suppression of polarization at the electrodes interfaces. This model is supported by Auger Electron Spectroscopy to determine the bulk and interfacial characteristics. The depth distribution of the elements of the PST film is nearly uniform throughout the volume of the film; however the relative concentrations of Pb and O were abnormally distributed on the surface. It is concluded that, in spite of the good performance due to the favorable conditions for the growth of the PST films provided by the textured LSCO, higher quality interfaces and better control of composition is necessary to improve on fatigue. " 2005 Materials Research Society.