showed a dielectric constant e = 6.9 ± 0.3 across
a 102- to 105-Hz frequency range, with a low leakage current corresponding to r > 1014 ohm cm
(Fig. 4B, inset). These e values agree with predictions from the Bruggeman effective medium
theory for a film composed of nanoscale Al2O3
grains (6) and are slightly lower than e for dense
Al2O3 films deposited through atomic layer deposition (ALD; e = 7.7 ± 0.4) (24). The refractive
index (n) of patterned Al2O3 films, measured with
ellipsometry at 632.8 nm, was 1.40 and can be
compared with n = 1.5 to 1.6 for ALD-grown
dense Al2O3 films. Higher n values were observed
for ZrO2, ZnO, and CeO2 NC layers (n = 1.62, 1.67,
and 1.82, respectively) patterned by using PAG
ligands (fig. S19) (6). Very similar refractive indices were measured for NC films prepared without photoactive ligands.
The performance of solution-processed semi-
conductor devices has advanced in recent years,
but methods for the integration of these devices
into complex circuits have yet to be established.
To assess the quality of semiconductor layers pat-
terned by means of DOLFIN, we made prototype
FETs (6). Their transfer and output character-
istics are shown in Fig. 4, C to F, and figs. S20 and
S21. Both PAG- and T T T-based photosensitive lig-
ands demonstrated good FET performance. For
example, a 30-nm-thick film of CdSe NCs photo-
patterned with (Ph2I)2CdCl4 ligands showed elec-
tron mobility ( me) of 20 cm2/V s (fig. S20), which
is similar to the values reported for CdSe NCs
with structurally related but not photosensitive
ligands (16). CdSe NCs with compositionally
matched Cd2Se32− semiconductor solders (25), pat-
terned by using (p-CH3S-C6H4)(C6H5)2S+OTf− PAG
(6), enabled FETs with me > 100 cm2/V s (Fig. 4,
C and D). Transparent IGZO films, patterned by
using the same PAG, demonstrated robust FETs
with me = 4 to 10 cm2/V s, current modulation
>104, and negligible hysteresis (Fig. 4, E and F,
and fig. S21). These numbers are on par with
state-of-the-art solution-processed FETs (1, 8, 20).
The above examples show that PAG- and TTT-
based surface ligands enable direct optical pat-
terning of numerous inorganic materials with
resolution comparable with that of traditional
photolithography, without compromising the
electronic and optical characteristics of patterned
materials. We view this approach as an important
step toward a broad technological adaption of
solution-processed metals, dielectrics, and semi-
conductors. The compatibility with a broad range
of substrates—including silicon, glass, and polymers—
provides an avenue for the development of var-
ious hybrid devices.
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We thank N. Ludwig for help with image analysis; A. Filatov for
x-ray diffraction analysis; M. Hudson for providing selenocadmate
ligands; and B. Tian, J. Park, V. Srivastava, and T. Shpigel for reading
the manuscript. The work was supported by the U.S. Department
of Defense Air Force Office of Scientific Research under grant
FA9550-14-1-0367, NSF under award CHE-1611331, NSF Materials
Research Science and Engineering Center Program under award
DMR-1420709, and the II-VI Foundation. Use of the Center for
Nanoscale Materials was supported by the U.S. Department of
Energy, Office of Science, Office of Basic Energy Sciences, under
contract DE-AC02-06CH11357. Data supporting the findings of this
study are available within the article and the supplementary
materials and from the corresponding authors upon reasonable
request. The quantum dot samples can be provided by the authors
under a materials transfer agreement with the university. Y. W., H. Z.,
and D.V. T. are inventors on patent application U.S. 62/486,566
submitted by the University of Chicago that covers nanocrystal
patterning chemistry and methods.
Materials and Methods
Figs. S1 to S21
Tables S1 to S4
23 March 2017; accepted 27 June 2017
-20 0 20
µsat = 73 cm2/Vs
µlin = 109 cm2/Vs
0 10 20 30
-20 0 20
µsat = 4.1 cm2/Vs
µlin = 4.5 cm2/Vs
VDS = 3 V
VDS = 30 V
0 10 20 30
400 500 600 700
Patterned RGB film
ZnSe/ZnS QDs solution
InP/ZnS QDs solution
InP/ZnS QDs solution
102 103 104 105
-40 -20 0 20 40
Fig. 4. Properties of directly optically patterned semiconductor and dielectric materials.
(A) Photoluminescence spectrum of pixels composed of red-, green-, and blue-emitting QDs
patterned by using NH4CS2N3 ligands. The emission spectra of corresponding QD solutions
are shown as dashed lines. The excitation wavelength was 360 nm. (B) Dielectric constant of
Al2O3 layer patterned by using NH4CS2N3 ligands. The measurements were carried out for an
Al/Al2O3/Al flat capacitor with a 125-nm-thick Al2O3 layer and an area of 0.64 mm2. (Inset)
A current-voltage relation (I-V) characteristic used to measure resistivity of the Al2O3 layer.
(C and D) Transfer and output characteristics of an FET with a channel made of compositionally
matched CdSe/Cd2Se32− ligands and CdCl2 treatment (6). (E and F) Transfer and output
characteristics of a FET with an IGZO channel. The channel length was 30 mm, and the channel
width was 180 mm.