Supporting Information Flexible, Low-Power Thin-Film Transistors (TFTs) Made of Vapor-Phase Synthesized High-k, Ultrathin Polymer Gate Dielectrics Junhwan Choi, Munkyu Joo, Hyejeong Seong, Kwanyong Pak, Hongkeun Park, Chan Woo Park and Sung Gap Im,*. Chemical and Biomolecular Engineering and KI for NanoCentury at Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea. Wearable Device Research Section, Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon 34129, Republic of Korea. *Corresponding author: sgim@kaist.ac.kr S-1
The estimation of the deposition rate in icvd process To examine deposition rate, thicknesses with three different processing time scales were measured and line fit was attempted for each polymer. The deposition rates of pcea, pc3d1, pc1d1, and pc1d3 were 3.1, 2.2, 1.8, and 1.3 nm/min, respectively. The deposition rate was gradually decreased with increasing DEGDVE input flow rate ratio due to the nonhomopolymerizability of DEGDVE by radical polymerization. Figure S1. The estimation of deposition rate for each polymer. S-2
High-resolution XPS C1s and O1s spectra Figure S2 shows the high-resolution XPS C1s and O1s spectra of pcea and copolymers. In the C1s spectrum of pcea, four characteristic carbon peaks including C * =O (at 288.5 ev), C * N (at 286.7 ev), C * -O, C * -CN (overlapped at 286.1 ev), C * -C (at 284.8 ev) were detected. 1 The area of C * =O peak was identical to that of C * N in all spectra, because these two characteristic carbons are only present in CEA monomer, and decreased with respect to the DEGDVE flow rate. Since the higher amount of C * -O is present in DEGDVE monomer than C * -CN in CEA monomer, the increase of C * -O and C * -CN overlapped peak intensity and area was accompanied by the increase of DEGDVE monomer flow rate. In the same manner to C * =O and C * N in the C1s spectra, the peak area of O=C-O * and O * =C-O was identical in all O1s spectra. The C-O * -C peak was not detected in pcea homopolymer but appeared in all the copolymers and the peak intensity and area were increased by DEGDVE flow rate. 2 Figure S2. High-resolution XPS C1s and O1s spectra of pcea and copolymers and their peak interpretations. S-3
XPS depth profiles Figure S3 shows the XPS depth profiles of pcea and copolymers. The chemical compositions were successfully controlled and uniform throughout the films before the disturbance by the detection of Si atoms in the substrates. Figure S3. XPS depth profiles of the (a) pcea, (b) pc3d1, (c) pc1d1, and (d) pc1d3. S-4
The XRD spectra of the polymers Figure S4. The XRD spectra of pcea and copolymers. Al surface on glass substrate Figure S5. The AFM image of Al surface thermally deposited on glass substrate. S-5
Chemical stability test Figure S6. The AFM images of the pristine pcea and pc1d1 and those after soaked in the various organic solvents (scale bar: 1 µm). Table S1. The thickness changes of the pcea and pc1d1 after soaked in the organic solvents. The thicknesses of the samples used in the Figure S6 were measured. Thickness (nm) Pristine Acetone THF Toluene pcea 128.8 2.4 13.1 126.1 pc1d1 117.6 116.7 119.7 119.9 S-6
The performance recovery of C8-BTBT OTFTs released from the applied tensile strain Figure S7 shows the transfer characteristic and µ sat of pristine C8-BTBT OTFTs fabricated on PEN substrate and those when 2.1% of tensile strain was applied and after the devices were released from the strain. The initial µ sat of the devices (1.82 (±0.02) cm 2 /Vs) was decreased to 1.28 (±0.01) cm 2 /Vs when 2.1% of tensile strain was applied mainly due to the increasing intermolecular distance between the grains of polycrystalline organic semiconductor. 3-5 Therefore, the µ sat was reversibly recovered to 1.75 (±0.01) cm 2 /Vs when the devices were released from the applied tensile strain. Figure S7. The transfer curve (left) and µ sat (right) of pristine C8-BTBT OTFTs and those under 2.1% of applied strain and after released. S-7
The crystallinity of C8-BTBT Figure S8 shows the XRD theta-2theta scan spectrum and AFM image of C8-BTBT deposited on pc1d1 confirming the polycrystallinity of C8-BTBT. The XRD peak positions were consistent with previous reports. 6,7 Figure S8. The XRD spectra (left) and AFM image (right, scale bar: 1 µm) of C8-BTBT deposited on pc1d1. References (1) Sharp, J.; Bebensee, F.; Baricuatro, J.; Steinrück, H.-P.; Gottfried, J.; Campbell, C., Calcium Thin Film Growth on a Cyano-Substituted Poly (p-phenylene vinylene): Interface Structure and Energetics. J. Phys. Chem. C 2013, 117, 23781-23789. (2) Briggs, D.; Beamson, G., XPS Studies of the Oxygen 1s and 2s Levels in a Wide Range of Functional Polymers. Anal. Chem. 1993, 65, 1517-1523. (3) Jedaa, A.; Halik, M., Toward Strain Resistant Flexible Organic Thin Film Transistors. Appl. Phys. Lett. 2009, 95, 103309. (4) Nigam, A.; Schwabegger, G.; Ullah, M.; Ahmed, R.; Fishchuk, I. I.; Kadashchuk, A.; S-8
Simbrunner, C.; Sitter, H.; Premaratne, M.; Rao, V. R., Strain Induced Anisotropic Effect on Electron Mobility in C60 Based Organic Field Effect Transistors. Appl. Phys. Lett. 2012, 101, 083305. (5) Chen, F.-C.; Chen, T.-D.; Zeng, B.-R.; Chung, Y.-W., Influence of Mechanical Strain on the Electrical Properties of Flexible Organic Thin-Film Transistors. Semicond. Sci. Technol. 2011, 26, 034005. (6) Ebata, H.; Izawa, T.; Miyazaki, E.; Takimiya, K.; Ikeda, M.; Kuwabara, H.; Yui, T., Highly Soluble [1]Benzothieno[3,2-b]benzothiophene (BTBT) Derivatives for High- Performance, Solution-Processed Organic Field-effect Transistors. J. Am. Chem. Soc. 2007, 129, 15732-15733. (7) Izawa, T.; Miyazaki, E.; Takimiya, K., Molecular Ordering of High performance Soluble Molecular Semiconductors and Re evaluation of Their Field Effect Transistor Characteristics. Adv. Mater. 2008, 20, 3388-3392. S-9