Proceedings of MatricesFor IITTEP – ICoMaNSEd 2015
ISBN: 978-602-74204-0-3
Physics Page 252
competitive in size of photoresponsive and its useful life. But organic material has the advantage of lucrative applications are relatively faster response, variations in the nature
easily managed through changes in the composition and molecular structure concerned, and the modification of the properties of materials and fabrication of the device could also
relatively simple.
DR-1 molecules is known as chromospheres having second order nonlinear optical microscopic properties first hiperpolarisabilitas,
� is high = 125 x 10
-30
esu Prasad et al., 1991, relating to noncentrosimetric structure do not have a center of
symmetry. But though the molecule noncentrosimetric, second order nonlinear optical properties of the crystals depend on the arrangement of the dipoles of molecules. If the dipole-
dipole of molecules arrangement in parallel polar orientation perpendicular to the substrate, then the amount of dipole moment to be great and the film to have second order nonlinear
optical properties SHG, but if the anti-parallel arrangement, then the second order nonlinear optical properties will be lost and appearing only third harmonic generation THG Wenas,
2009.
This research is aimed to study surfactant effect of Indium Tin Oxide ITO substrate and the effect of external electric field applied during the deposition procces on properties of the
resulted film. Further, the optical property of the film is also investigated to study the effect of the applied electric field.
2. Materials and Methods
DR-1 molecule has a composition that consists of three main groups as shown in Figure 1 below. The DR-1 4-[N-ethyl-N-2-hydroxyethyl] amino-
4’-nitroazobenzene powder used in
this research was obtained commercially from Aldrich. The molecule has a formula weight of 314.3, a melting point of 153
C with the onset temperature of thermal decomposition at 219 C as determined by TGA measurement Taunaumang, et al, 2001.
Donor D Bridge B Acceptor A
Figure 1. Molecular structure of Disperse Red-1
Samples in the form of thin films were deposited on an ITO substrates by using Vacuum Evaporator from Ulvac Sinku Kiko VPC-410. The ITO substrate was placed at about 10 cm
above the crucible with a stainless mesh electrode positioned in between. The films were prepared for various external electric field strengths of zero field, 1.9 MVm, and 3.3 MVm.
The duration of the deposition process of the film was about 1 hour. No further treatment was performed on the deposited films.
Optical properties of Disperse Red-1 molecule in the form of solution in NMP solvent and film were extracted from UV-Visible measurement by using UV-Vis Spectrometer Lamda
Series-35 Perkin Elmer. The UV-Vis measurement was carried out in the wavelength range of 200-800 nm, in both the transmission and reflection modes. The frequency shift of SPR dip
was measured by using ATR Attenuation Total Reflection, which was operated with He-Ne
Proceedings of MatricesFor IITTEP – ICoMaNSEd 2015
ISBN: 978-602-74204-0-3
Physics Page 253
laser =632,8 nm, with the angle of incidence scanned over the range from 30 to 90
. The thickness of the film was determined by using a reflectometer NanoCalc-2000 VIS.
3. Results and Discussion
The resulted films generally exhibit smooth surface and homogeneous thickness. The measured thicknesses of the thin films vary from 100 to 150 nm for different films.
Figure 2. UV-Vis absorption: a DR1 film Physical Vapor Deposition PVD method; b DR1 solution NMP solvent
UV-Vis spectrum of DR-1 solution NMP solvent and DR-1 films deposited by PVD over the ITO substrate is shown in Figure 2. UV-Vis spectrum DR1 solution shows high
absorption band seamlessly in the visible region at a wavelength of 500 nm associated with an electronic transition energy E
e
2.48 eV. In the figure it is seen that the film DR-1 PVD deposition results have absorption bands at wavelengths of 405 nm E
e
= 3.06 eV. This absorption band associated with electronic transitions π-π
of DR1 molecule is from the group of donor to acceptor groups through conjugated group azobenzen. The abrupt change was the
result of the orientation of molecules deposited upright vertical surface of the ITO substrate and the aggregation of molecules in the film because of the strong interaction of each dipole
of molecules arranged antiparallel in the film.
The UV-Vis spectrum of DR-1 film measured in the transmission mode at zero field, 1.9 MVm, and 3.3 MVm on the ITO substrate is shows in Figure 3. In the UV-VIS spectrum
mode of transmission, absorption is associated with excitation, especially along the molecular chain. At zero field and a small external electric field, the DR-1 molecules which sleep more
contribute absorbance. For the greater the electric field, the number of DR-1 molecules who sleep less because it has become oriented perpendicular vertical substrate so that the
contribution of the absorbance decreases.
In the Figure 3 is shown that the greater the electric field is applied, the absorption peak decreases and shifts to blue shift frequency, meaning that aggregation of molecules deposited
occur perpendicular to the ITO substrate surface Marino, et al., 2008. This phenomenon as an indication that the higher an electric field is given, the more molecules become upright
vertical, composed extend straight chain. resembling with the contribution of aggregate or not aggregate the sleep decreases.
Proceedings of MatricesFor IITTEP – ICoMaNSEd 2015
ISBN: 978-602-74204-0-3
Physics Page 254
Figure 3. UV-Vis spectrum of DR-1 film measured in the transmission mode at zero field, 1.9 MVm, and 3.3 MVm.
Figure 4. UV-Visible absorption spectra of the DR1 film measured in the reflection mode at zero field, 1.9 MVm, and 3.3 MVm.
Figure 4, shows the UV-Vis spectrum of DR-1 films on ITO substrates for reflection mode with a variation of the electric field. Compared to transmission mode Figure 3, it appears
that the UV-Vis spectrum of DR-1 films of reflection mode for the entire curve, there was a big reversal absorbance against the influence of external electric field. Increased electric field
resulting in increased absorption peak, this is due to the contribution of the transition associated with the length conjugation along the chain of conjugation and short conjugation
benzene, which in the transmission mode does not appear, but in reflection mode appears. The emergence shoulder around 700 nm which is when the transmission mode but
does not appear in the reflection mode it appears related to the contribution of the length conjugation along the chain of conjugation.
We turn next to the Surface Plasmon Resonance SPR spectra of the thin films deposited on the ITO substrate at zero field, 1.9 MVm and 3.3 MVm as depicted in Figure 5. This figure shows that The
Proceedings of MatricesFor IITTEP – ICoMaNSEd 2015
ISBN: 978-602-74204-0-3
Physics Page 255
SPR dip occurred at increasing incident angle for films deposited in stronger electric field corresponding to higher refractive index of the film as shown in Table 1. This result is consistent with
the theoretical prediction.
64 66
68 70
72 0,76
0,78 0,80
0,82 0,84
0,86 0,88
0,90
R e
fl e
ct e
d I
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ty a
.u .
Angle of incidence degree E= zero field
E= 1.9 MVm E= 3.3 MVm
Figure 5. SPR result from films as deposited for various external electric poling fields T
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Refractive Index n Thickness of Films nm
1.512 126.2
1.9 3.3
1.568 1.598
126.3 126.3
4. Conclusion
