Highly (002)-oriented and columnar-grained ZnO thin films were prepared by radio frequency magnetron sputtering at room temperature. The Pt∕ZnO∕Pt devices exhibit reversible and steady bistable resistance switching behaviors with a narrow dispersion of the resistance states and switching voltage. Only a low forming electric field was required to induce the resistive switching characteristics. The resistance ratios of high resistance state to low resistance state were in the range of 3–4 orders of magnitude within 100cycles of test. It was also found that the conduction mechanisms dominating the low and high resistance states are Ohmic behavior and Poole-Frenkel emission, respectively.

Al 2 O 3 was deposited on In 0.15 Ga 0.85 As/ GaAs using atomic-layer deposition ͑ALD͒. Without any surface preparation or postthermal treatment, excellent electrical properties of Al 2 O 3 / InGaAs/ GaAs heterostructures were obtained, in terms of low electrical leakage current density ͑10 −8 to 10 −9 A/cm 2 ͒ and low interfacial density of states ͑D it ͒ in the range of 10 12 cm −2 eV −1. The interfacial reaction and structural properties studied by high-resolution x-ray photoelectron spectroscopy ͑HRXPS͒ and high-resolution transmission electron microscopy ͑HRTEM͒. The depth profile of HRXPS, using synchrotron radiation beam and low-energy Ar + sputtering, exhibited no residual arsenic oxides at interface. The removal of the arsenic oxides from Al 2 O 3 / InGaAs heterostructures during the ALD process ensures the Fermi-level unpinning, which was observed in the capacitance-voltage measurements. The HRTEM shows sharp transition from amorphous oxide to single crystalline semiconductor.

An interfacial self-cleaning phenomenon was found in the atomic layer deposition of HfO2 on In0.15Ga0.85As∕GaAs substrate using Hf(NCH3C2H5)4, i.e., TEMAH, and H2O as the precursors. The native oxides of InGaAs were all satisfactorily removed from the interface through ligand exchange (substitution) reactions with the TEMAH precursor. It relieves the Fermi-level pinning in the HfO2∕InGaAs heterostructure, as verified by the clear transition from accumulation to depletion in high-frequency capacitance-voltage relations and inversion in quasistatic measurement. A very low leakage current was also found from the metal-oxide-semiconductor capacitors of Au∕Ti∕HfO2∕InGaAs.

By changing the electrode combination of Pt and LaNiO3 (LNO), four capacitor types of Pt/PZT/Pt/Si, Pt/LNO/PZT/Pt/Si, Pt/LNO/PZT/LNO/Pt/Si, and Pt/PZT/LNO/Pt/Si, were prepared to investigate the fatigue and hysteresis characteristics of the sol-gel-derived Pb(Zr0.53Ti0.47)O3 (PZT) ferroelectric thin films. Among them, the (100)- and (001)-oriented PZT films were grown on the (100)-textured LNO electrode, but randomly oriented films were obtained on the Pt electrode. It was found that the use of LNO bottom electrode would improve the fatigue property quite significantly, but only the capacitor with LNO as both top and bottom electrodes is shown to be fatigue-free up to 1011 cycles, and the shapes of the hysteresis loop almost unchanged after the fatigue test.

Highly (100)-oriented LaNiO3(LNO) thin films were grown on Si, SiO2/Si, Pt/SiSiO2/Si, as well as glass substrates by rf magnetron sputtering deposition at substrate temperatures ranging from 150 to 500 °C. As-deposited LNO films are metallic; those prepared at substrate temperature ∼150–250 °C have a resistivity of 0.4–0.5 mΩ cm and can be used as the bottom electrode for the fabrication of integrated ferroelectric capacitors on Si. A subsequent deposition of sol-gel derived Pb(Zr0.53Ti0.47)O3 (PZT) thin film on the LNO-coated substrate was also found to have a significant (100)- and (001)-oriented texture. The ferroelectric capacitor fabricated from these films displays a good P–E hysteresis characteristic.

Crystals of FeSe0.88 and FeSeMn0.1 have been grown from KCl solutions. Crystals measuring 2−3 mm across and 0.1−0.3 mm thick grow with a hexagonal plate like habit. Powder X-ray diffraction (XRD) measurements show strong peaks corresponding to the tetragonal α-FeSe phase and weak hexagonal β-FeSe peaks in both cases. The plate side of the crystal is identified to be the (101) face of the tetragonal α-FeSe. Energy dispersive X-ray spectroscopic (EDS) measurements show that Mn substitutes for Fe. Both types of crystals show a superconducting transition at 8 K in the DC magnetization measurements and a broad resistive transition with zero resistance at 7.5 K with an onset at 11 K. Specific heat measurements also confirm bulk superconductivity in the crystals. Crystals could also be grown using KBr as a solvent.

The densification behavior, microstructure, and electrical properties of ZnO-V2O5 ceramics were studied with V2O5 as the only additive ranging from 0.01 to 1.0 mol %. The addition of V2O5 to zinc oxide shows a tendency to enhance the densification rate and promote grain growth. However, a microstructure that consisted of anomalously grown grains was found for the specimens containing V2O5≥0.05 mol % when sintered at 1100 °C for 2 h. The x-ray diffraction and SEM-EDS microanalysis revealed that the sintered specimens had a two-phase microstructure, i.e., a vanadium-rich intergranular phase formed between ZnO grains. The formation of the grain boundary barrier layer was confirmed by the non-ohmic I-V behavior and the quick drop of apparent dielectric constant with increasing frequency of the ceramics. A nonlinearity coefficient of 2.4–2.8 was obtained at a current density of 10 mA/cm2 for a series ZnO-V2O5 ceramics, and a Schottky barrier height of 0.44–0.47 eV (at 25 °C) was determined from the I-V and C-V experimental data, based on the thermionic emission theory, and the model of back-to-back double Schottky barriers.

Articles you may be interested inDielectric properties of (110) oriented Pb Zr O 3 and La-modified Pb Zr O 3 thin films grown by sol-gel process on Pt ( 111 ) ∕ Ti ∕ Si O 2 ∕ Si substrate J. Appl. Phys. 100, 044102 (2006); 10.1063/1.2234819 Competition between ferroelectric and semiconductor properties in Pb ( Zr 0.65 Ti 0.35 ) O 3 thin films deposited by sol-gel J. Appl. Phys. 93, 4776 (2003); 10.1063/1.1562009Dielectric and ferroelectric properties of highly oriented ( Pb,Nb )( Zr,Sn,Ti ) O 3 thin films grown by a sol-gel process Appl.Antiferroelectric PbZrO 3 ͑PZ͒ films have been fabricated on LaNiO 3 /Pt/Ti/SiO 2 /Si substrates using a sol-gel process. The films with perovskite structure showed highly ͗001͘ preferred orientation. An antiferroelectric phase was identified by the presence of 1/4͕110͖ superlattice spots in a ͓001͔ selected area electron diffraction pattern. The field-induced antiferroelectric to ferroelectric phase switching was demonstrated at room temperature with full saturation and a maximum polarization of 40 C/cm 2 . Dielectric properties were investigated as a function of both temperature and frequency. The presence of a conductive buffer layer of LaNiO 3 on Pt/Ti/SiO 2 /Si substrate enabled the growth of high quality and highly oriented PZ antiferroelectric thin films that showed near zero remanent polarization and squared hysteresis loops.