Comparison of diverse resistive switching characteristics and demonstration of transitions among them in Al-incorporated HfO2-based resistive switching memory for neuromorphic applications

Diverse resistive switching behaviors are observed in the Pt/HfAlOx/TiN memory device depending on the compliance current, the sweep voltage amplitude, and the bias polarity.

The Characteristics of Transparent Non-Volatile Memory Devices Employing Si-Rich SiOX as a Charge Trapping Layer and Indium-Tin-Zinc-Oxide

We fabricated the transparent non-volatile memory (NVM) of a bottom gate thin film transistor (TFT) for the integrated logic devices of display applications. The NVM TFT utilized indium–tin–zinc–oxide (ITZO) as an active channel layer and multi-oxide structure of SiO2 (blocking layer)/Si-rich SiOX (charge trapping layer)/SiOXNY (tunneling layer) as a gate insulator. The insulators were deposited using inductive coupled plasma chemical vapor deposition, and during the deposition, the trap states of the Si-rich SiOx charge trapping layer could be controlled to widen the memory window with the gas ratio (GR) of SiH4:N2O, which was confirmed by fourier transform infrared spectroscopy (FT-IR). We fabricated the metal–insulator–silicon (MIS) capacitors of the insulator structures on n-type Si substrate and demonstrated that the hysteresis capacitive curves of the MIS capacitors were a function of sweep voltage and trap density (or GR). At the GR6 (SiH4:N2O = 30:5), the MIS capacitor exhibited the widest memory window; the flat band voltage (ΔVFB) shifts of 4.45 V was obtained at the sweep voltage of ±11 V for 10 s, and it was expected to maintain ~71% of the initial value after 10 years. Using the Si-rich SiOX charge trapping layer deposited at the GR6 condition, we fabricated a bottom gate ITZO NVM TFT showing excellent drain current to gate voltage transfer characteristics. The field-effect mobility of 27.2 cm2/Vs, threshold voltage of 0.15 V, subthreshold swing of 0.17 V/dec, and on/off current ratio of 7.57 × 107 were obtained at the initial sweep of the devices. As an NVM, ΔVFB was shifted by 2.08 V in the programing mode with a positive gate voltage pulse of 11 V and 1 μs. The ΔVFB was returned to the pristine condition with a negative voltage pulse of −1 V and 1 μs under a 400–700 nm light illumination of ~10 mWcm−2 in erasing mode, when the light excites the electrons to escape from the charge trapping layer. Using this operation condition, ~90% (1.87 V) of initial ΔVFB (2.08 V) was expected to be retained over 10 years. The developed transparent NVM using Si-rich SiOx and ITZO can be a promising candidate for future display devices integrating logic devices on panels.

Electrical properties of Pt/SrBi2Ta2O9/Bi4Ti3O12/p-Si heterostructure prepared by sol-gel processing

Low-temperature processing as low as 550–700 °C of Pt/SrBi2Ta2O9 (SBT)/Bi4Ti3O12 (BIT)/p-Si heterostructure has been performed by a sol-gel method. The effects of annealing temperature on current density, C-V characteristics, and memory windows of Pt/SBT/BIT/p-Si heterostructure were investigated. The SBT/BIT multilayer films were polycrystalline with no pyrochlore phase and no preferred orientation. The leakage current density was under 3 × 10−7 A/cm2 at 5 V with asymmetry hysteresis loops for Pt/SBT/BIT/p-Si heterostructure. Although all C-V curves showed clockwise ferroelectric hysteresis loops and the memory window reached a maximum of 0.78 V at a sweep voltage of 5 V, the memory window changed asymmetrically with the variation of annealing temperature and sweep voltage. The maximum memory window of Pt/SBT/BIT/p-Si heterostructure prepared at lower temperatures was narrower at lower sweep voltage. The asymmetric behavior of the C-V characteristics was discussed in terms of electron injection from Si and the ferroelectric polarization effect.

A Study on Hysteresis Effect of Barium Strontium Titanate Thin Films for Alternative Gate Dielectric Application

Hysteresis effect of barium strontium titanate (BST) thin films for gate dielectric application has been studied. It is found that the “counterclockwise” hysteresis has strong sweep voltage and operating temperature dependence. It can be reduced or eliminated by proper thermal annealing or by using a barrier layer. A charge trapping and detrapping mechanism has been proposed.

Effect of Cerium Silicate Formation on the Structural and Electrical Properties of Pt/SrBi2Ta2O9/CeO2/Si Capacitors

We have fabricated metal/ferroelectric/insulator/semiconductor (MEFIS) capacitors of Pt/SrBi2Ta2O9(SBT)/CeO2/Si and Pt/SBT/Ce-Si-O/Si. The cerium silicate (Ce-Si-O) layer is formed by reaction between CeO2 thin film and SiO2/Si substrate at 1100 °C. The SBT film on the cerium silicate layer is smoother than the SBT/CeO2. The memory window of the SBT/Ce-Si-O increases to 1.4 V at a sweep voltage of ±5 V, whereas the memory window of the SBT/CeO2 is 0.8 V at the same sweep voltage.

La dissolution de l'anode de cuivre dans les solutions faiblement chlorurées

The dissolution of a copper anode has been studied in aqueous solution at pH 4 and in which the dissolved LiCl was varied between 0.005 M and 0.1 M. In the dissolution zone, the dissolution valence is unity between 0.03 M and 0.1 M and the step controlling the speed of dissolution is almost entirely attributable to the diffusion of CuCl2− ion in solution for the weakest voltage. The order of reaction with respect to the chloride ion (Cl−) is close to unity for voltage close to the reversible voltage (ECu/CuCl) of the reaction Cu + Cl− = CuCl + 1e, suggesting that diffusion of Cl− ions in solution tends also to become a controlling step when the voltage is close to ECu/CuCl.CuCl appears when the voltage reaches ECu/CuCl, that is when the linear sweep voltage curves show two peaks. These two peaks have the diffusion of ions in the solution as their limiting step. The height of these two peaks is explicable by the diffusion of Cl− ions in solution as the slowest step. On the other hand, the ratio between the peak of the second wave and that of the first is 2.14. This behaviour is in agreement with the fact that the valence of dissolution of copper increases from the first peak to the second. [Journal translation]