7.4 Strategy C: Local Deprotection of PS 690 -b-PtBA 1210 Films
135
Fig. 7.8 a Schematic of the diameter of the D halo and D center b Plot of the diameter changes of
unmodified area and the halo. c Scaling analysis of D halo versus t −1 d Scaling analysis of D center
versus t
into the polymer film. For low ink coverages surface diffusion can be assumed to
largely govern the flux of the trifluoroacetic acid. Although the diffusion constant
of organic acids is small, typically D ≈ 10
−5 cm
2 s
−1 , its effects are dramatic at
the microscale. Simulations by Delamarche et al. [15] show that traveling distance
of molecules on a surface by diffusion is about 100 μm within ~15 ms. From the
above analysis, pronounced diffusion must have occurred, when D halo > D center . In
this case, the resolution of the pattern will be limited. In contrast, if D halo = D center ,
negligible diffusion has occurred during local hydrolysis and the pattern of the stamp
is faithfully transferred (see also below).
7.4.2 Analysis by AFM
Using AFM, possible changes of the morphology of PS 690 -b-PtBA 1210 films as a
result of the local hydrolysis were studied systematically. Here only the effect of
ink loading on the local hydrolysis was investigated in detail. Figure 7.9 shows
135
Fig. 7.8 a Schematic of the diameter of the D halo and D center b Plot of the diameter changes of
unmodified area and the halo. c Scaling analysis of D halo versus t −1 d Scaling analysis of D center
versus t
into the polymer film. For low ink coverages surface diffusion can be assumed to
largely govern the flux of the trifluoroacetic acid. Although the diffusion constant
of organic acids is small, typically D ≈ 10
−5 cm
2 s
−1 , its effects are dramatic at
the microscale. Simulations by Delamarche et al. [15] show that traveling distance
of molecules on a surface by diffusion is about 100 μm within ~15 ms. From the
above analysis, pronounced diffusion must have occurred, when D halo > D center . In
this case, the resolution of the pattern will be limited. In contrast, if D halo = D center ,
negligible diffusion has occurred during local hydrolysis and the pattern of the stamp
is faithfully transferred (see also below).
7.4.2 Analysis by AFM
Using AFM, possible changes of the morphology of PS 690 -b-PtBA 1210 films as a
result of the local hydrolysis were studied systematically. Here only the effect of
ink loading on the local hydrolysis was investigated in detail. Figure 7.9 shows