Materials Characterization and Device Performance of a CMR-Ferroelectric Heterostructure

Abstract:The films of colossal magnetoresistive La0.67Ca0.33MnO3 (LCMO) and ferroelectric SbSI were grown by pulsed laser deposition method for fabricating their heterostructures. By varying the processing conditions during film growth and controlling subsequently the annealing conditions, the resistivity transport properties of the LCMO films could be greatly modified. Preliminary tests on the ferroelectric field effect transistor (FeFET) based on LCMO-SbSI heterostructure showed that the device behaves like a nonvolatile memory element. The FeFET showed a maximum channel modulation of ∼10% at room temperature, and the switching voltage was less than 2 V.</jats:p

Infrared Spectroscopy of Epitaxial Antimony Sulpho Iodide Thin Films

AbstractThin films of antimony sulpho iodide (SbSI) were grown on platinized silicon substrates by the pulsed laser deposition method. As grown films were amorphous and annealing at 250 °C for 5 minutes introduced crystallinity in the films. Infrared reflectance measurements were done in the frequency range ∼ 500 – 5000 cm−1 (wavelength ∼ 2–20 μm). The reflectance measurements were taken at temperatures above and below the ferroelectric transition of SbSI ∼ 20° C. The index of refraction for a (121) oriented film was determined to be 2.83 ± 0.35 at a temperature of 25.6 °C, and 2.80 ± 0.35 at a temperature of 9.6 °C. For a (002) oriented film, the index was 3.82 ± 0.48 at a temperature of 26.5 °C, and 3.76 ± 0.48 at a temperature of 8.0 °C. Pyro-optic coefficients of 1.5 × 10−3 °C−1 for the (121) oriented film, and 3.2 × 10−3 °C−1 for the (002) oriented film were obtained. These results are consistent with measurements done in the visible region, and demonstrate the potential of SbSI as an infrared detector material.</jats:p

Synthesis of Porphyrins Bearing Hydrocarbon Tethers and Facile Covalent Attachment to Si(100)

The use of redox-active molecules as the active storage elements in memory chips requires the ability to attach the molecules to an electroactive surface in a reliable and robust manner. To explore the use of porphyrins tethered to silicon via carbosilane linkages, 17 porphyrins have been synthesized. Fourteen porphyrins bear a tether at a single meso site, and three porphyrins bear functional groups at two β sites for possible two-point attachment. Two high-temperature processing methods (400 °C under inert atmosphere) have been developed for rapid (minutes), facile covalent attachment to Si platforms. The high-temperature processing conditions afford attachment either by direct deposition of a dilute solution (1 μM−1 mM) of the porphyrin sample onto the Si substrate or sublimation of a neat sample onto the Si substrate. The availability of this diverse collection of porphyrins enables an in-depth examination of the effects of the tether (length, composition, terminal functional group, number of tethers) and steric bulk of nonlinking substituents on the information-storage properties of the porphyrin monolayers obtained upon attachment to silicon. Attachment proceeds readily with a wide variety of hydrocarbon tethers, including 2-(trimethylsilyl)ethynyl, vinyl, allyl, or 3-butenyl directly appended to the porphyrin and iodo, bromomethyl, 2-(trimethylsilyl)ethynyl, ethynyl, vinyl, or allyl appended to the 4-position of a meso-phenyl ring. No attachment occurs with substituents such as phenyl, p-tolyl, mesityl, or ethyl. Collectively, the studies show that the high-temperature attachment procedure (1) has broad scope encompassing diverse functional groups, (2) tolerates a variety of arene substituents, and (3) does not afford indiscriminate attachment. The high-temperature processing conditions are ideally suited for use in fabrication of hybrid molecular/semiconductor circuitry

Magnetic properties of La0.65Ca0.30Pb0.05Mn0.9B0.1O3 (B = Co, Ni, Cu and Zn)

WOS: 000345749500123The La0.65Ca0.30Pb0.05Mn0.9B0.1O3 (A = Co, Ni, Cu and Zn) manganites have been prepared via sol-gel method and sintered at 1100 degrees C for 24 h. The aim of the study was to investigate B-site cation doping effects on the magnetic properties. XRD analysis reveals that all samples have rhombohedral structure belonging to the R (3) over barc space group. The Curie temperature decreases as a result of Mn replacement with Co, Ni, Cu and Zn, respectively. The maximum magnetic entropy changes of the samples doped with Co, Ni, Cu and Zn for a field change of 1 T were found to be 2.10, 1.71, 3.20 and 1.42 J/kg K respectively. For La0.65Ca0.30Pb0.05MnO3, this is 2.60 J/kg K. The maximum magnetic entropy change increases as a result of Cu doping. Additionally, the metal-insulator transition temperature decreases due to the B-site doping. (C) 2014 Elsevier B.V. All rights reserved