Electrical memory characteristics of a nondoped pi-conjugated polymer bearing carbazole moieties.
Poly[bis(9H-carbazole-9-ethyl)dipropargylmalonate] (PCzDPM) is a novel pi-conjugated polymer bearing carbazole moieties that has been synthesized by polymerization of bis(9H-carbazole-9-ethyl)dipropargylmalonate with the aid of molybdenum chloride solution as the catalyst. This polymer is thermally stable up to 255 degrees C under a nitrogen atmosphere and 230 degrees C in air ambient; its glass-transition temperature is 147 or 128 degrees C, depending on the polymer chain conformation (helical or planar structure). The charge-transport characteristics of PCzDPM in nanometer-scaled thin films were studied as a function of temperature and film thickness. PCzDPM films with a thickness of 15-30 nm were found to exhibit very stable dynamic random access memory (DRAM) characteristics without polarity. Furthermore, the polymer films retain DRAM characteristics up to 180 degrees C. The ON-state current is dominated by Ohmic conduction, and the OFF-state current appears to undergo a transition from Ohmic to space-charge-limited conduction with a shallow-trap distribution. The ON/OFF switching of the devices is mainly governed by filament formation. The filament formation mechanism for the switching process is supported by the metallic properties of the PCzDPM film, which result in the temperature dependence of the ON-state current. In addition, the structure of this pi-conjugated polymer was found to vary with its thermal history; this change in structure can affect filament formation in the polymer film.
Park
Samdae
S
Department of Chemistry, Center for Electro-Photo Behaviors in Advanced Molecular Systems, Division of Advanced Materials Science, National Research Lab for Polymer Physical Chemistry, Polymer Research Institute, and BK School of Molecular Science, Pohang University of Science & Technology, Pohang 790-784, Republic of Korea.
Lee
Taek Joon
TJ
Kim
Dong Min
DM
Kim
Jin Chul
JC
Kim
Kyungtae
K
Kwon
Wonsang
W
Ko
Yong-Gi
YG
Choi
Heungyeal
H
Chang
Taihyun
T
Ree
Moonhor
M