5.2 Focused E-Beam Treatment: Fine Barcodes
and Quasi-superlattice
Focused E-beam irradiation has been used for precisely tailoring the optical and
structural properties of organic nanostructures at the nanoscale level [132, 133].
Recently, Hong et al. reported that individual light-emitting P3MT NWs can be
tailored successfully to contain multiple 1D serial sections, similar to a quasisuperlattice NW [62]. These sections can have different lengths and characteristics,
which can be modified precisely through treatment with a focused E-beam. The
spot size of the focused E-beam was adjusted between 50 and 100 nm, and the step
size of the focused E-beam irradiation was 2.4 nm, as shown in Fig. 23a.
Figure 23b, c shows the nanoscale optical properties of individual treated P3MT
NWs measured by CCD and LCM PL experiments. The PL color of the sections of
the pristine P3MT NW remained at the original green with relatively low brightness.
When designated positions of the single NW were irradiated with a focused E-beam
dose of 7.5 Â 10
16 electrons/cm
2
, the PL color changed from green to yellow, and the
emission intensity was clearly enhanced, as shown in the left image of Fig. 23b. The
LCM PL intensities of the treated sections (dose of 7.5 Â 10
16 electrons/cm
2
) were
approximately 12 times higher than those of the pristine P3MT NW. When the dose
was increased to 2.5 Â 10
17 electrons/cm
2
, the PL color of the treated P3MT NW
sections changed to bright red (middle image of Fig. 23b), and a significant increase
(~31 times) in the light-emission intensity was confirmed from the LCM PL images.
When the focused E-beam dose was increased to 2.5 Â 10
18 electrons/cm
2
, the PL
intensity of the treated sections decreased and bright yellow–green emission was
observed from the pristine sections of the same NW (right images of Fig. 23b, c). The
results indicate the existence of a critical E-beam dose (ED C ) for modification of the
optical properties of P3MT NWs and for E-beam energy transfer along the NWs. The
size of the sections in a P3MT NW treated with a focused E-beam can be controlled
on the basis of the designed patterns (including size and position). In the left and
middle images of Fig. 23b, the lengths of the treated sections on the NW were 1 and
2 μm, respectively. The lengths of the treated sections were also adjusted to 0.25, 0.5,
1, 2, 3, 4, 5, and 6 μm in the same NW.
The averaged LCM PL intensities of the NW sections, as obtained from the line
profile of the 3D LCM PL images, changed considerably with the E-beam dose, as
shown in Fig. 23d. The LCM PL intensity of the pristine P3MT NW was six photon
counts and those of the pristine sections in the treated P3MT NW were 7, 34 (Æ1),
265 (Æ5), and 326 (Æ14) photon counts for doses of 7.5 Â 10
16 , 2.5 Â 10
17 ,
2.5 Â 10
18 , and 1.0 Â 10
19 electrons/cm
2 , respectively. The LCM PL intensities
of the treated NW sections were 70 (Æ3), 185 (Æ6), 24 (Æ1), and 3 (Æ1), respectively, for these doses.
The LCM PL peak was gradually red-shifted from 520À530 nm for the pristine
NW to approximately 560 and 590À600 nm for the NW sections treated with doses
of 7.5 Â 10
16 and 2.5 Â 10
17 electrons/cm
2 , respectively, as shown in Fig. 23e.
The intensities of the LCM PL peaks of the treated sections with these doses were
Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting. . .
231
and Quasi-superlattice
Focused E-beam irradiation has been used for precisely tailoring the optical and
structural properties of organic nanostructures at the nanoscale level [132, 133].
Recently, Hong et al. reported that individual light-emitting P3MT NWs can be
tailored successfully to contain multiple 1D serial sections, similar to a quasisuperlattice NW [62]. These sections can have different lengths and characteristics,
which can be modified precisely through treatment with a focused E-beam. The
spot size of the focused E-beam was adjusted between 50 and 100 nm, and the step
size of the focused E-beam irradiation was 2.4 nm, as shown in Fig. 23a.
Figure 23b, c shows the nanoscale optical properties of individual treated P3MT
NWs measured by CCD and LCM PL experiments. The PL color of the sections of
the pristine P3MT NW remained at the original green with relatively low brightness.
When designated positions of the single NW were irradiated with a focused E-beam
dose of 7.5 Â 10
16 electrons/cm
2
, the PL color changed from green to yellow, and the
emission intensity was clearly enhanced, as shown in the left image of Fig. 23b. The
LCM PL intensities of the treated sections (dose of 7.5 Â 10
16 electrons/cm
2
) were
approximately 12 times higher than those of the pristine P3MT NW. When the dose
was increased to 2.5 Â 10
17 electrons/cm
2
, the PL color of the treated P3MT NW
sections changed to bright red (middle image of Fig. 23b), and a significant increase
(~31 times) in the light-emission intensity was confirmed from the LCM PL images.
When the focused E-beam dose was increased to 2.5 Â 10
18 electrons/cm
2
, the PL
intensity of the treated sections decreased and bright yellow–green emission was
observed from the pristine sections of the same NW (right images of Fig. 23b, c). The
results indicate the existence of a critical E-beam dose (ED C ) for modification of the
optical properties of P3MT NWs and for E-beam energy transfer along the NWs. The
size of the sections in a P3MT NW treated with a focused E-beam can be controlled
on the basis of the designed patterns (including size and position). In the left and
middle images of Fig. 23b, the lengths of the treated sections on the NW were 1 and
2 μm, respectively. The lengths of the treated sections were also adjusted to 0.25, 0.5,
1, 2, 3, 4, 5, and 6 μm in the same NW.
The averaged LCM PL intensities of the NW sections, as obtained from the line
profile of the 3D LCM PL images, changed considerably with the E-beam dose, as
shown in Fig. 23d. The LCM PL intensity of the pristine P3MT NW was six photon
counts and those of the pristine sections in the treated P3MT NW were 7, 34 (Æ1),
265 (Æ5), and 326 (Æ14) photon counts for doses of 7.5 Â 10
16 , 2.5 Â 10
17 ,
2.5 Â 10
18 , and 1.0 Â 10
19 electrons/cm
2 , respectively. The LCM PL intensities
of the treated NW sections were 70 (Æ3), 185 (Æ6), 24 (Æ1), and 3 (Æ1), respectively, for these doses.
The LCM PL peak was gradually red-shifted from 520À530 nm for the pristine
NW to approximately 560 and 590À600 nm for the NW sections treated with doses
of 7.5 Â 10
16 and 2.5 Â 10
17 electrons/cm
2 , respectively, as shown in Fig. 23e.
The intensities of the LCM PL peaks of the treated sections with these doses were
Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting. . .
231