27-05-2014, 12:01 PM
TRANSEPARENT RESISTIVE RANDOM ACCESS MEMORY
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Introduction
scientists at the Korean Advanced Institute of Science and Technology, have created the world's first transparent computer chip.
The chip, known as (TRRAM) or transparent resistive random access memory, is similar to existing chips known as (CMOS) or metal-oxide semiconductor memory, which we use in new electronics.
The difference is that TRRAM is completely clear and transparent. What is the benefit of having transparency?
"It is a new milestone of transparent electronic systems," says Jung Won Seo. "By integrating TRRAM with other transparent electronic components, we can create a total see-through embedded electronic systems."
The technology could enable the windows or mirrors in your home to be used as computer monitors and television screens.
Summary
This report covers the fabrication of a fully transparent resistive random access memory (TRRAM) device based on an ITO (indium tin oxide)/ZnO/ITO capacitor structure and its resistive switching characteristics. The fabricated TRRAM has a transmittance of 81% (including the substrate) in the visible region and an excellent switching behaviour under 3 V. The retention measurement suggests that the memory property of the TRRAM device could be maintained for more than 10 years. We believe that the TRRAM device presented in this work could be a milestone of future see-through electronic devices.
TRANSPARENT resistive switching random access memory (TRRAM) device is potentially useful in the futuristic transparent electronics. It is meant to be integrated with other transparent electronic devices to produce the so called see-through system-on-glass [1], which belongs to the domain of macro electronics. ZnO, with high transmittance in the visible region and tunable conductivity by doping, has been demonstrated to be a good candidate for constructing the TRRAM device due to its abundance in nature, highly evolved growth technologies, and compatibility with complementary metal–oxide–semiconductor technology. On the other hand, Ga-doped ZnO is a promising alternative of indium tin oxide (ITO) with lower cost, resource availability, and nontoxicity. Thus, it is possible to construct an In-free TTRAM device based purely on ZnO, in contrast to previous studies of using ITO electrodes. Thus, this letter introduces the fabrication of TRRAM device
by utilizing ZnO with different Ga doping concentration to construct the metal–insulator–metal (MIM) thin-film structure. The resistivity of our GZO electrode is about 3 × 10−4 Ω ・ cm [4]. The resistive switching characteristic was investigated, and the conduction mechanism was discussed in detail.
EXPERIMENTAL DETAIL
All the functional films were fabricated by a homemade metal organic chemical vapor deposition (MOCVD) system without breaking the vacuum. With all layers fabricated by the same MOCVD system, the process is much simplified. Trimethylgallium (TMGa), dimethylzinc (DMZn), and oxygen were used as reaction sources, and nitrogen was employed as the carrier gas for the metal organics. A 200-nm bottom electrode (BE) of GZO was deposited on the glass slide substrate at 300 ◦C with a chamber pressure of 25 torr. Then, multiple insulative
films of Ga2O3 (50 nm)-ZnO (120 nm)-Ga2O3 (50 nm) were subsequently deposited on the BE film at 400 ◦C with a chamber pressure of 40 torr. Finally, a 200-nm top electrode (TE) array of GZO was deposited with a shadow mask on the insulating layers. The crystal structure of ZnO and GZO was examined by X-ray diffraction (XRD), and the I–V characteristic was also measured.
CONCLUSION
In conclusion, a transparent indium-free RRAM device based on GZO-Ga2O3-ZnO-Ga2O3-GZO structure has been fabricated by MOCVD. This TRRAM device has shown bipolar switching behavior with good cycle endurance and retention time. Local filamentary conduction probably dominates the resistive switching behavior. The electrochemical migration of oxygen vacancies and oxygen ions in ZnO film mainly of oxygen vacancies and oxygen ions in ZnO film mainly accounts for the formation and rupture of filament, which leads to switching between HRS and LRS.