Browsing by Author "Wang, Ming-Hui"

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Analyzing Electric Field Effect by Applying an Ultra-Short Time Pulse Condition in Hafnium Oxide-Based RRAM
(2018-08-01)
Wu, Cheng-Hsien
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Lin, Shih-Kai
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Pan, Chih-Hung
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Chen, Po-Hsun
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Lin, Wen-Yan
In this letter, we determine the importance of the electrical field distribution and strength during the switching process by demonstrating different trends in the degree of reset and the reset pulse time. In general, a longer reset pulse time results in a higher reset energy; a higher reset energy leads to a higher degree of reset, which we obtainedby applying different width square waves. But quite notably, the opposite result was obtained using triangle waves, where a higher degree of reset occurred with a shorter rising time and lower reset energy. We believe that this is due to the electric field effect: if the voltage rises faster than the filament oxidation, the device can produce a larger effective electric field and a higher resistance in the reset process. To further investigate the mechanism, the procedure of the reset process was analyzed in detail, and COMSOL simulation is also carried out for confirmation.
Conduction Mechanism and Improved Endurance in HfO2-Based RRAM with Nitridation Treatment
(2017-10-26)
Yuan, Fang-Yuan
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Deng, Ning
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Shih, Chih-Cheng
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Tseng, Yi-Ting
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Chang, Ting-Chang
A nitridation treatment technology with a urea/ammonia complex nitrogen source improved resistive switching property in HfO2-based resistive random access memory (RRAM). The nitridation treatment produced a high performance and reliable device which results in superior endurance (more than 10(9) cycles) and a self-compliance effect. Thus, the current conduction mechanism changed due to defect passivation by nitrogen atoms in the HfO2 thin film. At a high resistance state (HRS), it transferred to Schottky emission from Poole-Frenkel in HfO2-based RRAM. At low resistance state (LRS), the current conduction mechanism was space charge limited current (SCLC) after the nitridation treatment, which suggests that the nitrogen atoms form Hf-N-Ox vacancy clusters (V-o(+)) which limit electron movement through the switching layer.
Enhanced electrical behavior from the galvanic effect in Ag-Cu alloy electrode conductive bridging resistive switching memory
(2018-07-30)
Tseng, Yi-Ting
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Chen, I-Chieh
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Chang, Ting-Chang
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Huang, J. C.
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Shih, Chih-Cheng
In this study, an Ag-Cu alloy was chosen as the electrode in conductive bridging random access memory (CBRAM), with results indicating a significant decrease in forming voltage. In addition, resistive switching characteristics as well as a retention test indicated better stability and a resistive switching window of at least an order, The switching time of the Ag-Cu alloy CBRAM is shorter than that of both Ag and Cu electrode CBRAMs under fast current-voltage (fast I-V). The experimental result indicated that the mechanism was dominated by the galvanic effect. Active atoms (Ag) captured electrons of inactive atoms (Cu) and generated metallic ions (Cu ions) in the alloy electrode, Cu ions drifted into the insulator and generated a conductive path when applying voltage bias, The use of this alloy as an electrode in CBRAM can significantly decrease forming voltage and enhance CBRAM characteristics. Published by AIP Publishing.
Enhancement of Surface Chemical and Physical Properties of Germanium-Sulfur Thin Film Using a Water-Supplemented Carbon Dioxide Supercritical Fluid Treatment Technique
(2018-11-09)
Yang, Chih-Cheng
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Chen, Po-Hsun
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Shih, Chih-Cheng
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Wang, Ming-Hui
;
Tsai, Tsung-Ming
In this study, an oxidation treatment technique suitable for the material and electronic device applications proceeding at low temperature (only 80 degrees C) and high pressure (3000 psi) utilizing a carbon dioxide (CO2) supercritical fluid (SCF), also known as scCO(2), which is supplemented with water molecules, is reported. To demonstrate the possible effects on material and devices for the proposed SCF treatment, an amorphous germanium-sulfur (GeS) thin film and a GeS-based resistance random access memory (RRAM) device are prepared. After the SCF treatment, electrical measurements confirm that the GeS-based RRAM device exhibits a lower forming voltage, more stable resistance switching characteristics, and higher concentration distributions of high and low resistance states when compared to the device without SCF treatment. As for the material effects, both chemical and physical properties are examined based on material analyses results. It is concluded that the original amorphous GeS thin film transforms to a polycrystallized GeO film, confirmed by a reaction model for the SCF treatment illustrating possible oxidation and crystallization effects induced by this SCF treatment. This water-enhanced scCO(2) SCF treatment technique, thus, shows its capability as a feasible synthetic method for material modification as well as suitability for device level applications.
Improving Performance by Doping Gadolinium Into the Indium-Tin-Oxide Electrode in HfO2-Based Resistive Random Access Memory
(2016-05)
Chen, Po-Hsun
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Chang, Kuan-Chang
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Pan, Chih-Hung
This letter investigates the characteristics of doping gadolinium (Gd) in an indium-tin-oxide (ITO) electrode in HfO2-based resistive random access memory (RRAM). Identical bottom electrodes and insulators were made but then capped by either pure ITO or a Gd: ITO top electrode. Doping Gd in the ITO electrode produces lower operation currents in both high-resistance state (HRS) and low-resistance state (LRS) as well as enlarging the memory window. This excellent performance suggests a remarkable potential to improve RRAM applications. Schottky emission mechanism dominates both HRS and LRS according to current fitting results, and is confirmed by temperature effect experiments. The resistive switching behavior of the Gd:ITO device is explained by our model and is also confirmed by material analysis and electrical measurements. Furthermore, reliability tests verify the Gd: ITO device\'s capability to perform data storage as a nonvolatile memory.
Performance improvement after nitridation treatment in HfO2-based resistance random-access memory
(2018-08-01)
Wang, Ming-Hui
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Chang, Ting-Chang
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Shih, Chih-Cheng
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Tseng, Yi-Ting
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Tsai, Tsung-Ming
Nitrogen atoms were introduced into a Pt/HfO2/TiN resistance random-access memory (RRAM) device to improve the resistive switching characteristics induced by a high-pressure nitridation treatment. Compared with a similar untreated HfO2 device, it exhibited superior performance, including a lower forming voltage, a higher on/off ratio, and high-endurance cycle operations. Current-voltage curve-fitting results confirmed the difference of the carrier transport mechanisms after the nitridation treatment. Finally, a reaction model was proposed to explain the improvement of RRAM switching due to the introduction of nitrogen atoms. (C) 2018 The Japan Society of Applied Physics