Yu-Ren Ye

Hybrid aluminum and indium conducting filaments for nonpolar resistive switching of Al/AlOx/indium tin oxide flexible device

The nonpolar resistive switching characteristics of an Al/AlOx/indium tin oxide (ITO) device on a plastic flexible substrate are investigated. By analyzing the electron diffraction spectroscopy results and thermal coefficient of resistivity, it is discovered that the formation of aluminum and indium conducting filaments in AlOx film strongly depends on the polarity of the applied voltage. The metal ions arising from the Al and ITO electrodes respectively govern the resistive switching in corresponding operation polarity. After 104 times of mechanical bending, the device can perform satisfactorily in terms of resistance distribution, read sequence of high and low resistive states, and thermal retention properties.

High-Performance Multilevel Resistive Switching Gadolinium Oxide Memristors With Hydrogen Plasma Immersion Ion Implantation Treatment

Multilevel resistive switching (RS) of gadolinium oxide (Gd_xO_y) memristors treated by hydrogen plasma immersion ion implantation (PIII) was investigated. Hydrogen ions were implanted at the Pt/Gd_xO_y interface to modify the oxygen-vacancy distribution, which was examined by the X-ray photoelectron spectroscopy. After the hydrogen PIII treatment, a forming process is needed to operate the Gd_xO_y memristors and the RS mechanism is changed from Schottky emission to space-charge-limited conduction. Superior multilevel RS properties such as data retention for more than 10⁴ s at 85°C, and sequentially cycling test for more than 10³ times with a resistance ratio of approximately one order of magnitude between each state are realized, making the future high-density flash memory possible.

Characteristics of gadolinium oxide resistive switching memory with Pt–Al alloy top electrode and post-metallization annealing

The characteristics of gadolinium oxide (GdxOy) resistive switching memories (RRAMs) with a Pt–Al alloy (5.88 at% Al) top electrode (TE) and the effect of post-metallization annealing (PMA) were investigated. Resistance of high resistance state increased with increasing PMA temperature, achieving a resistance ratio of more than 104 owing to the increased Schottky barrier height between the TE and GdxOy film. The change in set and reset voltages corresponded to the concentration of oxygen vacancies at the TE/GdxOy interface, which was examined by x-ray photoelectron spectroscopy. At the PMA temperatures for higher than 350 °C, the GdxOy RRAMs with Pt–Al alloy TEs presented superior retention behaviour for more than 104 s at a testing temperature of 130 °C. Al diffusion into the GdxOy film to form AlxOy at the TE/GdxOy interface is responsible for the retention enhancement because it prevented the oxygen ions from out-diffusion through the Pt grain boundaries.

Low-Power and High-Reliability Gadolinium Oxide Resistive Switching Memory with Remote Ammonia Plasma Treatment

The effects of remote NH3 plasma treatment on a Pt/GdxOy/W resistive random access memory (RRAM) metal–insulator–metal (MIM) structure were investigated. We found that a decrease in the electron barrier height caused by nitrogen incorporation at the Pt–GdxOy interface can help reduce the operational set and reset voltages. Nitrogen atoms from the NH3 plasma prevent oxygen atoms in the film from diffusing through Pt grain boundaries into the atmosphere, resulting in superior retention properties (>104 s). The stability of the endurance behavior of GdxOy RRAMs was significantly improved owing to the passivation of defects in GdxOy films by nitrogen and hydrogen atoms from the remote NH3 plasma, markedly reducing plasma damage.

Tunable bandgap energy of fluorinated nanocrystals for flash memory applications produced by low-damage plasma treatment

A plasma system with a complementary filter to shield samples from damage during tetrafluoromethane (CF(4)) plasma treatment was proposed in order to incorporate fluorine atoms into gadolinium oxide nanocrystals (Gd(2)O(3)-NCs) for flash memory applications. X-ray photoelectron spectroscopy confirmed that fluorine atoms were successfully introduced into the Gd(2)O(3)-NCs despite the use of a filter in the plasma-enhanced chemical vapour deposition system to shield against several potentially damaging species. The number of incorporated fluorine atoms can be controlled by varying the treatment time. The optimized memory window of the resulting flash memory devices was twice that of devices treated by a filterless system because more fluorine atoms were incorporated into the Gd(2)O(3)-NCs film with very little damage. This enlarged the bandgap energy from 5.48 to 6.83 eV, as observed by ultraviolet absorption measurements. This bandgap expansion can provide a large built-in electric field that allows more charges to be stored in the Gd(2)O(3)-NCs. The maximum improvement in the retention characteristic was >60%. Because plasma damage during treatment is minimal, maximum fluorination can be achieved. The concept of simply adding a filter to a plasma system to prevent plasma damage exhibits great promise for functionalization or modification of nanomaterials for advanced nanoelectronics while introducing minimal defects.

Performance improvement of gadolinium oxide resistive random access memory treated by hydrogen plasma immersion ion implantation

Characteristics improvement of gadolinium oxide (GdxOy) resistive random access memories (RRAMs) treated by hydrogen plasma immersion ion implantation (PIII) was investigated. With the hydrogen PIII treatment, the GdxOy RRAMs exhibited low set/reset voltages and a high resistance ratio, which were attributed to the enhanced movement of oxygen ions within the GdxOy films and the increased Schottky barrier height at Pt/GdxOy interface, respectively. The resistive switching mechanism of GdxOy RRAMs was dominated by Schottky emission, as proved by the area dependence of the resistance in the low resistance state. After the hydrogen PIII treatment, a retention time of more than 104 s was achieved at an elevated measurement temperature. In addition, a stable cycling endurance with the resistance ratio of more than three orders of magnitude of the GdxOy RRAMs can be obtained.

Yield improvement of gadolinium oxide resistive switching memory with oxygen post-metallization annealing

Different post-metallization annealing gas ambient has been performed in the gadolinium oxide resistive switching memories to enhance the fabrication yield. The superior memory properties such as the low set and reset voltages (-1.4 V and 2.1 V) and high resistance ratio (~104) are successfully achieved. With no degradation of the memory characteristics, the fabrication yield of the oxygen post-metallization annealed gadolinium oxide resistive switching memories can be increased to over 60% due to the sufficient mobile oxygen ions supplied in the gadolinium oxide layers.

Retention behavior of graphene oxide resistive switching memory on flexible substrate

This work presents a flexible carbon based memory with the Al/graphene oxide (GO)/ITO structure fabricated at room temperature. The Al/GO/ITO devices show the unipolar resistive switching behavior with the resistance ratio to over 30, and sustain over 250 cycling without any resistance window closure. However, the retention fails due to the resistance increase of low resistance state (LRS). The mechanisms of switching and retention failure are studied.

Robust nitrogen plasma immersion ion implantation treatment on gadolinium oxide resistive switching random access memory

In this paper, we demonstrate gadolinium oxide RRAM with nitrogen plasma immersion ion implantation (PIII) treatment technique at first time. For nitrogen plasma treatment, the nitrogen ions were incorporated with gadolinium oxide. We controlled the implantation voltage that the nitrogen ions exist near the surface of gadolinium oxide and it was forming a GdxOyNz layer. This can reduce the leakage current to reach a low current and power consumption operation. In addition, the retention and endurance characteristics were also improved.