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Our study shows that metastable quintet state of spin crossover complex [Fe(dpp)2(NCS)2] · py (dpp=dipyrido[3,2-a:2′,3′-c] phenazine, py=pyridine) at low temperatures may be realized by a rapid cooling. The relaxation from quintet state to singlet spin at low temperatures depends on the both of time and previous history of the sample. The U-shaped dents of the magnetic effective moment depending on the temperature after initial rapid zero-field cooling indicate an obvious affection of magnetic field to the realization of singlet state in the transition range. The observations for this sample are indeed consistent with the fact that cooperative effects play a very important role in the spin transition. © 1999 American Institute of Physics.

Gradual switching between multiple resistance levels is desirable for analog in-memory computing using resistive random-access memory (RRAM). However, the filamentary switching of HfOx-based conventional RRAM often yields only two stable memory states instead of gradual switching between multiple resistance states. Here, we demonstrate that a thermal barrier of Ge2Sb2Te5 (GST) between HfOx and the bottom electrode (TiN) enables wider and weaker filaments, by promoting heat spreading laterally inside the HfOx. Scanning thermal microscopy suggests that HfOx + GST devices have a wider heating region than control devices with only HfOx, indicating the formation of a wider filament. Such wider filaments can have multiple stable conduction paths, resulting in a memory device with more gradual and linear switching. The thermally enhanced HfOx + GST devices also have higher on/off ratio (>103) than control devices (<102) and a median set voltage lower by approximately 1 V (∼35%), with a corresponding reduction of the switching power. Our HfOx + GST RRAM shows 2× gradual switching range using fast (∼ns) identical pulse trains with amplitude less than 2 V. [ABSTRACT FROM AUTHOR]

Magnetization switching induced by spin–orbit torque is of fundamental interest for developing spintronic devices with low-power consumption and nonvolatility. Here, we report on the spin–orbit torque induced magnetization switching behavior of (001) oriented tetragonal Heusler alloy D022-Mn3Ga films with an intrinsic ferrimagnetic spin structure grown on the GaAs(001) substrate by molecular-beam epitaxy. The out-of-plane hysteresis loop and anomalous Hall effect demonstrated a large perpendicular magnetic anisotropy and low saturation magnetization of D022-Mn3Ga thin films. The spin–orbit torque induced magnetization switching has been realized in D022-Mn3Ga/Pt heterostructure based Hall devices under an in-plane external field. It is found that the critical switching current density Jc is much smaller than that of the L10-MnGa/heavy metal system. Besides, both a dampinglike effective field HDL and a fieldlike effective field HFL are quantified by performing harmonic Hall voltage measurements. All these results indicate that ferrimagnetic D022-Mn3Ga can be a promising candidate material for realizing high-density and energy-efficient spintronic devices. [ABSTRACT FROM AUTHOR]

High-performance Y2O3/In2O3-based transparent thin-film transistors were processed featuring low thermal budget. The device shows a field-effect mobility of 43.5 cm2 V-1 s-1, a subthreshold swing of 0.28 V/decade, and an on/off current ratio of 108. These results are attributed to the high dielectric constant of Y2O3 and unique electronic structure of In2O3. Furthermore, the cubic phases of crystalline Y2O3 and In2O3 films have the identical crystal structure with a small lattice mismatch, which provides a well-defined dielectric/semiconductor interface for the optimal performance. [ABSTRACT FROM AUTHOR]

We report magnetoresistance (MR) measurements for structures with micrometer-thick regioregular, polythiophene (rr-P3HT) polymer layers between two ferromagnetic contacts. Hole spin transport through the polymer layer leads to a relative MR value in 300 mT fields of 0.3% at 300 K and increasing to 18% at 25 K. The inferred intrinsic spin lifetime and diffusion length are about 7 ms and 0.4 μm, respectively. The spin transport coherence length is enhanced by the electric field, leading to an enhancement in MR with increasing applied voltage. [ABSTRACT FROM AUTHOR]

Reflection high energy electron diffraction, atomic force microscopy, and theoretical studies based on classical nucleation theory have been used to interpret the morphology, orientation relationship, and stability of Cu2O nanoclusters on SrTiO3 (100) (STO). We propose that the competing interfacial and elastic energies facilitate an in-plane rotation of the Cu2O clusters by 45° with respect to the STO substrate and stabilize Cu2O clusters on STO(100) with an orientation relationship of (001)Cu2O//(001)SrTiO3 and <100>Cu2O//<110>SrTiO3. Our preliminary theoretical analysis also suggests that this particular orientation results in smaller critical nucleus sizes and lower nucleation barriers and also indicates a chemical potential (growth rate) dependence of the orientation relationship. [ABSTRACT FROM AUTHOR]

Epitaxial LaAlO3 films have been grown on Si (001) by molecular beam epitaxy with an ultrathin SrTiO3 seed layer. High resolution x-ray diffraction and transmission electron microscopy show the high quality epitaxial structure of LaAlO3 films, and the epitaxial relationship of LaAlO3 with Si is LaAlO3(001)∥Si(001) and LaAlO3[100]∥Si[110]. The band gap of epitaxial LaAlO3 films was measured to be 6.5±0.1 eV from O 1s loss spectra. Band offsets between crystalline LaAlO3 films and Si were determined to be partitioned equally with 2.86±0.05 eV for valence-band offset and 2.52±0.1 eV for conduction-band offset by using x-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWNTs) have been grown via chemical vapor deposition on high-κ dielectric SrTiO[sub 3]/Si substrates, and high-performance semiconducting SWNT field-effect transistors have been fabricated using the thin SrTiO[sub 3] as gate dielectric and Si as gate electrode. The transconductance per channel width is 8900 μS/μm. The high transconductance cannot be explained by the increased gate capacitance; it is proposed that the increased electric field at the nanotube–electrode interface due to the high-κ SrTiO[sub 3] decreases or eliminates the nanotube-electrode Schottky barrier. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report effusive evaporation of Ga[sub 2]O[sub 3] thin films on GaAs(001) substrates in a production-type molecular-beam epitaxy system. A polycrystalline Ga[sub 2]O[sub 3] charge heated in a high-temperature effusion cell is used as the evaporation source. The Ga[sub 2]O[sub 3]-GaAs structures are characterized by atomic force microscopy (AFM), Rutherford backscattering spectroscopy (RBS), ellipsometry, and transmission electron microscopy (TEM). The Ga[sub 2]O[sub 3] films are amorphous and stoichiometric by transmission electron diffraction and RBS, respectively. Under optimal growth conditions, the Ga[sub 2]O[sub 3] film surface has a typical roughness of 2-3 Å as revealed by AFM, while the Ga[sub 2]O[sub 3]-GaAs interface is atomically abrupt as confirmed by the cross-sectional TEM. Such amorphous and stoichiometric Ga[sub 2]O[sub 3] oxide paves the way for GaAs gate dielectrics applications. [ABSTRACT FROM AUTHOR]