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Partially aliphatic homopolyimides and copolyimides were prepared from rel-(1′R,3S,5′S)-spiro[furan-3(2H),6′-[3]oxabicyclo[3.2.1]octane]-2,2′,4′,5(4H)-tetrone (DAn), 2,6-diaminoanthracene (AnDA), and 4,4′-oxydianiline (ODA) by varying the molar ratio of AnDA and ODA. We utilized these polyimide films as the resistive switching layer in transparent memory devices. While WORM memory behavior was obtained with the PI-A100-O0-based device (molar feed ratio of DAn : AnDA : ODA = 1 : 1 : 0), the PI-A70-O30-based device (molar feed ratio of DAn : AnDA : ODA = 1 : 0.7 : 0.3) exhibited bipolar resistive switching behavior with stable retention for 104s. This result implies that the memory properties can be controlled by changing the polyimide composition. The two devices prepared from PI-A100-O0 and PI-A70-O30 showed over 90% transmittance in the visible wavelength range from 400 to 800 nm. The behavior of the memory devices is considered to be governed by trap-controlled, space-charge limited conduction (SCLC) and local filament formation.

In this report, we employ an Al-doped ZnO (AZO) layer as a resistive switching layer for transparent resistive switching random access memory devices. An Indium-Tin-Oxide (ITO)/AZO/ITO/glass device exhibits a transmittance of ∼80% (including a glass substrate) in the visible wavelength region and demonstrates reliable bipolar resistive switching behavior over d.c. 300 sweeping cycles with a low operation voltage and a very low variation in the switching threshold voltage. These results indicate that the AZO film is a promising transparent resistive switching layer.

A high on/off ratio in oxide resistive devices is preferable for use in memory storage, especially when multibit operations are possible. Here, we demonstrate the effect of vacancy density on resistance by using three different Pt-copper oxide-W devices with different vacancy densities in the oxide layer. We show that a higher vacancy density in the oxide layer can enhance the on/off resistance ratio and demonstrate the advantage of this ratio in the realization of multi-bit operation. Finally, we successfully explain the impact of the vacancy density in the oxide layer using a simple model.

Abstract: We investigated the effect of the electrode on the resistive switching property of (Cu, Zn, Pt)-Cu2S-W structures to clarify the role of metallic ions and electrodes in forming conductive paths in solid-electrolytes and also to improve the switching property. Notably, Zn-Cu2S-W and Pt-Cu2S-W structures that lack of oxidizable metal electrodes exhibited bipolar switching characteristics, and practically preferable switching properties with appropriately higher a turn-ON voltage and resistance were achieved for Zn-Cu2S-W in comparison to Cu-Cu2S-W with too low turn-ON voltage. In contrast, the degrading evolution of switching was observed in Pt-Cu2S-W. A simplified but convincing model is also suggested and discussed to explain the observations.

Abstract: The structural, electrical, and optical properties of e-beam and sputter-deposited Indium-Tin-Oxide (ITO) films on sapphire and p-GaN wafers, as well as the post-deposition annealing effect for light-emitting-diode applications, were analyzed and compared. The specific contact resistance of the sputtered ITO film on a p-GaN wafer was found to be slightly higher than that of the e-beam deposited ITO films. However, in general, the electrical, structural and optical properties of the sputtered ITO films that were annealed at comparably lower temperature are better than those of the e-beam deposited ITO films, which is the consequence of a larger average grain size. The sputtered ITO film that was annealed at 500°C demonstrated a resistivity of as low as 3.6 × 10−4 Ω·cm, along with a high transmittance of ∼98% at 450 nm.

In this paper we present a study on the MOVPE growth and optical evaluation of strained InGaAs/GaAs quantum well (QW) structures with In contents of 17% and 22% on [111]A-oriented GaAs substrates. QW structures grown under different growth conditions were extensively analyzed by means of Photoluminescence (PL) spectroscopy. The dependence of the PL intensity and linewidth on the growth temperature and In content are investigated and compared to simultaneously grown [100]-oriented structures. It is shown that excellent QW interfaces with only ±(1–2) monolayer roughness were achieved for the [111]A-oriented structures with 17% In using a wide range of growth temperatures (550–670°C), whereas the interfacial properties of the [100] samples significantly degraded as the growth temperature was increased. For a [111]A QW structure with 22% In the PL characteristics are similar to those obtained for the 17% In sample; on the contrary, for the companion [100] sample a strong degradation of its optical properties is observed.

In this paper we present a study on the MOVPE growth and optical evaluation of strained InGaAs/GaAs quantum well (QW) structures with In contents of 17% and 22% on [1 1 1]A-oriented GaAs substrates. QW structures grown under different growth conditions were extensively analyzed by means of Photoluminescence (PL) spectroscopy. The dependence of the PL intensity and linewidth on the growth temperature and In content are investigated and compared to simultaneously grown [1 0 0]-oriented structures. It is shown that excellent QW interfaces with only ±(1-2) monolayer roughness were achieved for the [1 1 1]A-oriented structures with 17% In using a wide range of growth temperatures (550-670°C), whereas the interfacial properties of the [1 0 0] samples significantly degraded as the growth temperature was increased. For a [1 1 1]A QW structure with 22% In the PL characteristics are similar to those obtained for the 17% In sample; on the contrary, for the companion [1 0 0] sample a strong degradation of its optical properties is observed.

We review the recent advances in the fabrication and properties of GaAs/AlGaAs and InGaAs/GaAs quantum well (QW) structures grown on (111)A GaAs substrates by atmospheric pressure metalorganic vapor phase epitaxy (MOVPE). We show that a 25-period GaAs/AlGaAs multi-QW (MQW) structure was fabricated with good crystal quality, high photoluminescence (PL) emission intensity and monolayer (ML) interfacial roughness. A PL full width at half maximum (FWHM) of 10.5meV was achieved for a 25-period MQW with a well width of 44Å. This is the narrowest linewidth reported to date for any similar structures grown on (111)A or B substrates by any growth technique. We also report the properties of an InGaAs/GaAs single quantum well structure grown on (111)A GaAs. For this structure, the PL FWHM value was 9.1meV, corresponding to a 1ML interfacial roughness for a well width of 41Å. This is the first demonstration of an InGaAs/GaAs quantum well structure grown on (111)A or (111)B GaAs by MOVPE.

This paper reports a promising method to decrease the operating temperature during electrolysis of natural ilmenite to produce a porous and laminar flake-type intermetallic ferrotitanium (FexTi, x = 1, 2) with a thickness of less than 1 ?m by choosing a LiCl-Li2O electrolyte with a lower operating temperature (625 °C) under an inert atmosphere. Results indicate that the Li2O content in the electrolyte has a key effect on the phase transformation of natural ilmenite occurring in the electrochemical reduction process. Full conversion of natural ilmenite into ferrotitanium products can be achieved when the Li2O amount in the electrolyte and the cell voltage are approximately 1 wt.% and ?2.5 V, respectively. In addition, the electrochemical reduction mechanism of natural ilmenite is proposed and discussed based on our experimental results and thermodynamic analysis.