Chi-Fong Ai

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.

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.

Oxygen plasma immersion ion implantation treatment to enhance data retention of tungsten nanocrystal nonvolatile memory

Data retention characteristics of tungsten nanocrystal (W-NC) memory devices using an oxygen plasma immersion ion implantation (PIII) treatment are investigated. With an increase of oxygen PIII bias voltage and treatment time, the capacitance–voltage hysteresis memory window is increased but the data retention characteristics become degraded. High-resolution transmission electron microscopy images show that this poor data retention is a result of plasma damage on the tunneling oxide layer, which can be prevented by lowering the bias voltage to 7 kV. In addition, by using the elevated temperature retention measurement technique, the effective charge trapping level of the WO3 film surrounding the W-NCs can be extracted. This measurement reveals that a higher oxygen PIII bias voltage and treatment time induces more shallow traps within the WO3 film, degrading the retention behavior of the W-NC memory.

Super Critical Fluid Technique to Enhance Current Output on Amorphous Silicon-Based Photovoltaic

A low temperature, non-destructive treatment technique with supercritical carbon dioxide mixing water was demonstrated on thin film type photovoltaic devices to enhance current output. Assembled P-I-N amorphous Si-based devices were treated in a high pressure reaction chamber. Generation of light current under indoor illumination was improved by about 80% after treatment. To clarify the origin of improvement, the drive-level capacity profiling method with capacitance–voltage (C–V) measurement was used, as it shows the relationship between defect density and location. Such measurements reveal that the amount of interface defects was significantly reduced after treatment. A dynamic reaction model was also proposed to explain the defect passivation reaction. This technique can be effectively applied to amorphous silicon solar cell devices to enhance performance.