ABSTRACT
In this study, we propose the use of an ionic liquid crystal (ILC) as a new resistive switching layer in nonvolatile resistive random-access memory (ReRAM) devices. The high-quality vacuum-deposited ILC films of 1-hexadecyl-3-methylimidazolium hexafluorophosphate ([C16mim][PF6]) enabled to demonstrate the first operation of ReRAM devices with a low set voltage of â¼1 V and stable switching behavior for up to â¼44 cycles. The key to the successful operation is that the ILC layer is in the liquid crystal phase (smectic A), where the electric double layers formed at the electrode-ILC interfaces play a significant role. The results of basic electrical properties and I-V curve fittings suggested the following operation principle: the formation and rupture of charge-composed filaments within the ILC film, where the current conduction is primarily governed by the trap charge limited current (TCLC) mechanism. These achievements will pave the way for advanced studies of ILC-based electronic devices.
ABSTRACT
Understanding the formation process of organic-inorganic halide perovskite (OIHP) thin films is important for the fabrication of high-quality thin films, which, in turn, are crucial for achieving high-performance devices. To address this challenge, we developed an in situ system of infrared multiple-angle incidence-resolved spectroscopy (IR-MAIRS) combined with a vacuum deposition system. "Orientation-free" isotropic spectra constructed from IR-MAIRS spectra enable us to perform quantitative analysis of the formation process of C(NH2)3SnI3 (GASnI3) thin films from unreacted C(NH2)3I (guanidine hydroiodide (GAI))/SnI2 bilayer structures predeposited in a vacuum. The analysis of the dependence of the GASnI3 formation rate on the reaction temperature using the Avrami model has revealed that a diffusion-controlled reaction process of GAI and SnI2 governs the formation kinetics. The present study points to the usefulness of in situ IR-MAIRS analysis in understanding the growth mechanisms of vacuum-deposited OIHP thin films and hence the potential to accelerate the development of vacuum processes for the fabrication of high-quality OIHP thin films.
ABSTRACT
Terbium monoxide, TbO, with an unusual valence state of Tb2+ ([Xe]4f85d1) has been known to exist as a gas phase. In this study, we report a solid phase rock-salt structured TbO in the form of an epitaxial thin film. This TbO is a narrow gap ferromagnetic semiconductor with a bandgap of â¼0.1 eV and high Curie temperature of 231 K, and exhibited negative magnetoresistance of -14% at 9 T and 2 K. Its magnetization steeply increased with the appearance of a wasp-waisted hysteresis curve significantly below the Curie temperature at about 20 K. These results suggested that both 4f and 5d magnetic sublattices were formed at a single magnetic Tb2+ site in TbO.
ABSTRACT
We report a superconducting transition in a LaO epitaxial thin film with the superconducting transition onset temperature ( Tc) at around 5 K. This Tc is higher than those of other lanthanum monochalcogenides and opposite to their chemical trend: Tc = 0.84, 1.02, and 1.48 K for LaX (X = S, Se, Te), respectively. The carrier control resulted in a dome-shaped Tc as a function of electron carrier density. In addition, the Tc was significantly sensitive to epitaxial strain in spite of the highly symmetric crystal structure. This rock-salt superconducting LaO could be a building block to design novel superlattice superconductors.
ABSTRACT
C-rare earth structure lutetium sesquioxide Lu2O3 has been recognized as a high-k widegap insulator with closed shell Lu3+ ions. In this study, rock-salt structure lutetium monoxide LuO with unusual valence of Lu2+ (4f145d1), previously known as the gaseous phase, was synthesized as an epitaxial thin film by the pulsed laser deposition method. In contrast with transparent and highly insulating Lu2O3, LuO possessed a dark-brown color and high electrical conductivity concomitant with strong spin-orbit coupling as a manifestation of Lu 5d electron carriers.
