Process Optimization of Ni Nanocrystals Formation Using O2 Plasma Oxidation to Fabricate Low-molecular Organic Nonvolati
- PDF / 543,592 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 102 Downloads / 202 Views
1071-F05-21
Process Optimization of Ni Nanocrystals Formation Using O2 Plasma Oxidation to Fabricate Low-molecular Organic Nonvolatile Memory Woo Sik Nam, Gon-Sub Lee, Sung Ho Seo, and Jea Gun Park Electronic engineering, National Program Center for Terabit-level Nonvolatile Memory Development, HIT 101 Handangdong Seongdonggu Hanyang University, Seoul, Korea, Seoul, Korea, Republic of ABSTRACT We fabricated organic nonvolatile memory with a device structure of Al/Alq3 (aluminum tris (8-hydroxyquinoline))/Ni nanocrystals surrounded by NiO/Alq3/Al. We obtained the best bistable switching characteristics at a 30-nm Alq3 thickness, 0.1-Å/sec evaporation rate, and 10-nm Ni nanocrystal layer thickness. The electrical behavior of the bistable switching devices was obtained by sweeping the voltage from 0 to 10 V. Our devices showed excellent bistable memory characteristics, such as a Vth of 2 V, Vp of 3 V, Ve of 5 V, and Ion/Ioff ratio of greater than 104. We found that a region of negative differential resistance exists between Vp and Ve. INTRODUCTION Various kinds of organic nonvolatile memory have been reported. They can be generally classified as organic nonvolatile memory embedded with metal nanocrystals in a conductive organic layer (low-molecular organic, polymer etc.) [1-6], with a single charge-complex layer [58], and with a single conductive organic layer, etc. [5-6, 9-10]. We previously researched lowmolecular organic nonvolatile memory with metal nanocrystals embedded in the low-molecular organic layer. This memory achieved a Ion/Ioff ratio of more than 101. However, the nanocrystals in these devices had irregular shapes and non-uniform distribution because the nanocrystal layer contained large-grained Al and was deposited at very low evaporation rates. Accordingly, the devices showed very bad reproducible I-V characteristics. To overcome this weakness, we formed a Ni nanocrystal layer having regular shaped and uniformly distributed grains using insitu O2 plasma oxidation. We found that the Ni nanocrystals surrounded by NiO reveal the I-V and memory characteristics of organic nonvolatile memory during fabrication. As a result, we determined the optimal conditions for forming Ni nanocrystals to obtain good bistable memory characteristics in organic nonvolatile memory embedded with Ni nanocrystals. EXPERIMENTAL DETAILS First, Si/SiO2 substrates were coated with Al by thermal evaporation to be the bottom electrode, which was patterned by a shadow mask technique. The bottom organic layer and the metal layer in the middle were sequentially deposited on the bottom electrode. Ni was evaporated, followed by O2 plasma oxidation for 300 sec at 200 W in a 10-4-Pa vacuum. Next, the top organic layer and the top electrode were deposited. All the fabrication processes for the organic nonvolatile memories were done in an in-situ multi-chamber apparatus by simply changing and aligning the masks. In a repeat of the process, we confirmed that the amount of
oxidation and Ni nanocrystals formed was in accordance with the various
Data Loading...
