Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

Magnetic oxides show a variety of extrinsic magnetotransport phenomena: grain-boundary, tunnelling and domain-wall magnetoresistance. In view of these phenomena the role of some magnetic oxides is outstanding: these are believed to be half-metallic having only one spin-subband at the Fermi level. These fully spin-polarized oxides have great potential for applications in spin-electronic devices and have, accordingly, attracted intense research activity in recent years. This review is focused on extrinsic magnetotransport effects in ferromagnetic oxides. It consists of two parts; the second part is devoted to an overview of experimental data and theoretical models for extrinsic magnetotransport phenomena. Here a critical discussion of domain-wall scattering is given. Results on surface and interfacial magnetism in oxides are presented. Spin-polarized tunnelling in ferromagnetic junctions is reviewed and grain-boundary magnetoresistance is interpreted within a model of spin-polarized tunnelling through natural oxide barriers. The situation in ferromagnetic oxides is compared with data and models for conventional ferromagnets. The first part of the review summarizes basic material properties, especially data on the spin polarization and evidence for half-metallicity. Furthermore, intrinsic conduction mechanisms are discussed. An outlook on the further development of oxide spin-electronics concludes this review.

Extrinsic magnetotransport phenomena in ferromagnetic oxides

We have investigated the high-performance oxide thin-film transistor (TFT) with an amorphous indium gallium zinc oxide (a-IGZO) channel and ZrO2 gate dielectrics. The a-IGZO TFT is fully fabricated at room temperature without any thermal treatments. ZrO2 is one of the most promising high-k materials. The a-IGZO TFT (channel W/L = 240/30 ?m) with ZrO2 shows high performance such as high on current of 2.11 mA and high field effect mobility of 28 cm2/(V·s) at the gate voltage 10 V. The threshold voltage and the subthreshold swing are 3.2 V and 0.56 V/decade, respectively. Note that the high-performance a-IGZO TFT is higher than ever shown in previous researches.

High-Performance a-IGZO TFT With $\hbox{ZrO}_{2}$ Gate Dielectric Fabricated at Room Temperature

https://ir.nctu.edu.tw/bitstream/11536/21381/1/000316677900001.pdf

Growth, dielectric properties, and memory device applications of ZrO2 thin films

The objective of this study was to evaluate the effect of fiber treatment on both morphological and single fiber tensile strength of empty fruit bunch (EFB). EFB fiber was treated with boiling water, 2% sodium hydroxide (NaOH) and combination both NaOH and boiling water. Fiber morphology was characterized by scanning electron microscopy (SEM). Thermogravimetric analysis (TGA) was further used to measure the amount and rate of change in the weight (weight loss) of treated fiber as a function of temperature. Based on the results of this work it seems that alkali treatment improved most of the fiber properties. NaOH treatment was found to alter the characteristic of the fiber surface topography as seen by the SEM. The thermal stability of NaOH treated and water boiling treated EFB fiber was found to be significantly higher than untreated fiber. The best results were obtained for alkali treated fiber where the tensile strength and Young’s modulus increased compared to untreated fibers. The overall results showed that alkali treatment on EFB fiber enhanced the tensile strength and thermal stability of the fiber samples.

/pdf/effects-of-fiber-treatment-on-morphology-tensile-and-efmabpigy0.pdf

Effects of fiber treatment on morphology, tensile and thermogravimetric analysis of oil palm empty fruit bunches fibers

Ultrathin ZrO2 gate dielectrics have been deposited on strain-compensated Si0.69Ge0.3C0.01 layers by rf magnetron sputtering. High-resolution transmission electron microscopy along with energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy show the formation of a polycrystalline ZrO2 and an amorphous Zr–germano–silicate interfacial layer between the deposited oxide and SiGeC films. A dielectric constant of 17.5 for ZrO2 and 7.0 for an interfacial-silicate layer have been calculated from the high-frequency capacitance–voltage measurements. These dielectrics show an equivalent oxide thickness as low as 1.9 nm for ZrO2 and 2.0 nm for the interfacial silicate layer. An extremely low leakage current density of ∼9×10−8 A/cm2 at a gate voltage of −1.0 V, breakdown field of 7 MV/cm and moderate interface state density of 6×1011 cm−2 eV−1 have been obtained for the fabricated capacitors.

Electrical and interfacial characteristics of ultrathin ZrO2 gate dielectrics on strain compensated SiGeC/Si heterostructure

A direct method of evaluating the scaling exponent H of a self‐affine fractal surface from a single topographic image recorded by using scanning probe microscopy is presented. This method uses the fact that for these surfaces the root‐mean‐square roughness increases with length as LH. The method is applied to study the fractal nature of silver films of different thicknesses and it is observed that the variation in the scaling exponent H is in correlation with the surface roughness and the observed growth mode.

Evaluation of the scaling exponent of self‐affine fractal surface from a single scanning probe microscope image

An experimental set-up involving a combination of reverse electrochemical etching and the floating-layer technique of tip preparation is presented. In the model only dc bias is used, avoiding the shortcomings of ac bias. The collection of two tips in a single etching process and mechanical auto-breaking of the circuit are emphasized. This cost and time effective, easy in-laboratory approach yields two sharp tips without paying attention to switching off the circuit. The nature of the tip shape arising from the floating-layer technique has been explained in terms of the electrical field distribution between the electrodes. The addition of some new information together with a few established facts will enrich and enlighten the art of tip preparation.

https://iopscience.iop.org/article/10.1088/0957-0233/11/10/302/pdf

A reverse electrochemical floating-layer technique of SPM tip preparation

Dehydration and phase transformation in sepiolite

Scanning tunnelling microscopic (STM) and spectroscopic (STS) investigations have been carried out on the grain boundaries (GBs) of sintered pellets of giant magnetoresistive perovskite manganites (LCMO), (LYMCO) and (LPMCO). Based on spectroscopic data obtained and estimation of band gap, it has been concluded that these materials possess some sort of semiconducting intergranular layer (IGL) whose thicknesses are in the range of a few nm to about 100 nm and the band gap is in the range of 0.3-0.45 eV. IGLs are usually more resistive than the grains. For semiconducting samples like LCMO and LYCMO (room temperature band gap = 0.23 and 0.27 eV respectively), IGLs bend the energy band near GBs. This bending has been estimated to be about 40-50 meV with the depletion depth of few tens of nm extending on both sides of the IGL. The decrease in conductivity near the GB is due to the disorder induced carrier scattering and the bending of the band. LPCMO is almost conducting at room temperature. The GBs in this material sometimes exhibit conducting behaviour which may be due to the accumulation of some conducting material or the trapping centres in the IGL. Scanning electron microscopic and electrical measurements also justify the STM/STS results.

https://iopscience.iop.org/article/10.1088/0953-8984/10/48/003/pdf

Scanning tunnelling microscopic and spectroscopic investigation of the microstructural and electronic properties of the grain boundaries of giant magnetoresistive manganites

B. K. Mathur

Papers

Electrical and interfacial characteristics of ultrathin ZrO2 gate dielectrics on strain compensated SiGeC/Si heterostructure

Evaluation of the scaling exponent of self‐affine fractal surface from a single scanning probe microscope image

A reverse electrochemical floating-layer technique of SPM tip preparation

Dehydration and phase transformation in sepiolite

Scanning tunnelling microscopic and spectroscopic investigation of the microstructural and electronic properties of the grain boundaries of giant magnetoresistive manganites