High-Performance
Nonvolatile Organic Transistor Memory
Devices Using the Electrets of Semiconducting Blends
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Abstract
Organic nonvolatile transistor memory
devices of the <i>n</i>-type semiconductor <i>N</i>,<i>N</i>′-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic
diimide (BPE-PTCDI) were prepared using various electrets (i.e., three-armed
star-shaped poly[4-(diphenylamino)benzyl methacrylate] (N(PTPMA)<sub>3</sub>) and its blends with 6,6-phenyl-C<sub>61</sub>-butyric acid
methyl ester (PCBM), 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pen)
or ferrocene). In the device using the PCBM:N(PTPMA)<sub>3</sub> blend
electret,
it changed its memory feature from a write-once-read-many (WORM) type
to a flash type as the PCBM content increased and could be operated
repeatedly based on a tunneling process. The large shifts on the reversible
transfer curves and the hysteresis after implementing a gate bias
indicated the considerable charge storage in the electret layer. On
the other hand, the memory characteristics showed a flash type and
a WORM characteristic, respectively, using the donor/donor electrets
TIPS-pen:N(PTPMA)<sub>3</sub> and ferrocene:N(PTPMA)<sub>3</sub>.
The variation on the memory characteristics was attributed to the
difference of energy barrier at the interface when different types
of electret materials were employed. All the studied memory devices
exhibited a long retention over 10<sup>4</sup> s with a highly stable
read-out current. In addition, the afore-discussed memory devices
by inserting another electret layer of poly(methacrylic acid) (PMAA)
between the BPE-PTCDI layer and the semiconducting blend layer enhanced
the write-read-erase-read (WRER) operation cycle as high as 200 times.
This study suggested that the energy level and charge transfer in
the blend electret had a significant effect on tuning the characteristics
of nonvolatile transistor memory devices