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Jang et al. Nano Convergence (2018) 5:20 https://doi.org/10.1186/s40580-018-0152-3

LETTERS Open Access

Hybrid dielectrics composed of ­Al2O3 and phosphonic acid self‑assembled monolayers for performance improvement in low voltage organic feld efect transistors Sukjae Jang, Dabin Son, Sunbin Hwang, Minji Kang, Seoung‑Ki Lee, Dae‑Young Jeon, Sukang Bae, Sang Hyun Lee, Dong Su Lee and Tae‑Wook Kim*

Abstract Low voltage operational organic transistors (< 4 V) based on pentacene were successfully fabricated with hybrid dielectric flms composed of aluminum using atomic layer deposition and various phosphonic acid-based self-assembled monolayers as the gate dielectrics. High capacitances up to 279 nF/cm2, low leakage current densities 8 2 of ­10− A/cm at 6 V, and high breakdown felds up to 7.5 MV/cm were obtained. The transistors with the octade‑ cylphosphonic acid hybrid dielectric exhibited an improved saturation mobility of 0.58 cm2/Vs, a subthreshold slope of 151 mV/decade, a threshold voltage of 1.84 V and an on–of current ratio of ­106. The low surface energies of the self-assembled monolayers having non-polar− terminal groups, such as methyl and pentafuorophenoxy, improved the carrier conduction of the transistors due to the pentacene growth with an edge-on orientation for low voltage opera‑ tion. The pentafuorophenoxy end-group showed an accumulation of holes at the semiconductor-dielectric interface.

Keywords: Hybrid dielectrics, ALD ­Al2O3, PA-SAM, Phosphonic acid, contact angle, Organic transistor

Organic feld-efect transistors (OFETs) have great poten- than those of low-k gate dielectrics [7]. High-k dielectric tial for a wide variety of applications, such as fexible dis- flms, such as , were typically deposited using plays, electronic paper, radiofrequency identifcation tags atomic layer deposition (ALD) based on the sequen- and sensors, due to their low cost, low temperature fab- tial use of a self-limited surface reaction [8, 9]. Te ALD rication, process compatibility, light weight and technique has various advantages, such as precise thick- mechanical fexibility compared with conventional inor- ness control, high quality flms based on layer-by-layer ganic materials [1–4]. Te relative high operating volt- growth, a lower growth temperature (< 350 °C) than that ages of OFETs have hindered their development in the of classical chemical vapor deposition methods, a high commercial market. To implement low voltage operating uniformity, an excellent conformality over high aspect OFETs, signifcant eforts have been devoted to increas- ratio structures, and dense and pinhole free flms [8, 10]. ing the capacitive density of gate dielectrics by decreas- Among the various high-k dielectrics, aluminum oxide ing the thickness of the gate dielectrics or increasing the ­(Al2O3) is considered as a potential gate dielectric flm of dielectric constant (k) of the dielectric flms [5, 6]. feld efect transistors due to its thermodynamic stabil- High-k dielectric flms can induce greater surface ity on Si up to high temperatures, mechanical robustness charge densities at the semiconductor-dielectric interface and highly insulating properties that are due to its high band gap (8.7 eV) and medium-k value (8–9) [7]. Another strategy for low voltage OFETs is improving *Correspondence: [email protected] Functional Composite Materials Research Center, Institute of Advanced the charge transport in organic semiconductors. Charge Composite Materials, Korea Institute of Science and Technology, transport occurs in the few monolayers near the inter- Wanju‑gun, Jeollabuk‑do 55324, Republic of Korea face between the organic semiconductor/dielectric and

© The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat​iveco​mmons​.org/licen​ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Jang et al. Nano Convergence (2018) 5:20 Page 2 of 8

is limited by the thermally activated hopping process Terefore, hybrid dielectrics composed of PA-SAMs between the in the disordered regions [11, on a high-k dielectric are excellent candidates for OFET 12]. To improve the device performance, the disordered applications [15]. Tey are suitable for gate dielectrics in region of the semiconductor should be suppressed, OFETs due to their low voltage operation, low gate leak- and additional interface treatments are required for age currents and interface modifcation by the functional optimal charge transport. For example, the molecular end-groups of SAMs. In this letter, we introduce various parameters of organic semiconductors were modifed hybrid dielectrics comprised of PA-SAMs on ALD Al­ 2O3 by controlling their regioregularity, molecular weight, and further investigate the relationship between various side chain length, doping level and end-group. Inter- functional end-groups of PA-SAMs and the device per- face engineering has been introduced to improve the formances of OFETs. molecular ordering, orientation, assembly, packing and Figure 1 illustrates the schematic structure of an flm morphology of organic semiconductors [13]. Self- OFET with a hybrid dielectric consisting of ALD Al­ 2O3 assembled monolayers (SAMs) are good candidates for and PA-SAMs and molecular structures of various PA- efective surface treatment due to their high-packing SAMs with diferent functional end-groups. We pre- density, being only a few nm thick and allowing inter- pared seven kinds of PA-SAMs to investigate the efects face control with end-functional groups [14]. Among of the alkyl chain length and functional end-groups on various SAMs with diferent binding groups, such as the OFET performance. Hexylphosphonic acid (HPA), carboxyl groups, thiols and silanes, phosphonic acid dodecylphosphonic acid (DDPA), octadecylphosphonic self-assembled monolayers (PA-SAMs) have attracted acid (ODPA), phosphonohexadecanoic acid (PHDA), attention due to readily assembling on activated metal 12-mercaptododecylphosphonic acid (MDPA), 12-pen- oxides because their reaction is not limited by the con- tafuorophenoxydodecylphosphonic acid (PFPA), tents of surface hydroxyl groups and supplies their 11-hydroxyundecylphosphonic acid (HUPA), penta- own hydroxyl moieties [15]. Tey also have the advan- cene (99.9% purity) and isopropanol (99.8% purity) tages of stability and prevention of homocondensation were purchased commercially from Sigma-Aldrich, between phosphonic acid molecules compared with Korea and used as received. HPA (C6), DDPA (C12) other binding groups, resulting in the highly ordered, and ODPA (C18) are methyl-terminated PA-SAMs with dense and robust monolayers of phosphonic acid mol- increasing alkyl chain lengths ranging from C6 to C18. ecules on metal oxide surfaces. PHDA, MDPA, PFPA and HUPA have diferent end

Fig. 1 a Schematic structure of an OFET with a hybrid dielectric. b Molecular structures of the various PA-SAMs used in this study. [1: Hexylphosphonic acid (HPA) (C6), 2: dodecylphosphonic acid (DDPA) (C12), 3: octadecylphosphonic acid (ODPA) (C18), 4: 16-phosphonohexadecanoic acid (PHDA), 5: 12-mercaptododecylphosphonic acid (MDPA), 6: 12-pentafuorophenoxydodecylphosphonic acid (PFPA), 7: 11-hydroxyundecylphosphonic acid (HUPA)] Jang et al. Nano Convergence (2018) 5:20 Page 3 of 8

functionalized terminals with the carboxyl group, thiol, Phosphonic acid were prepared by dissolving (2,3,4,5,6-pentafuorophenoxy) group and hydroxyl 3 mM of each phosphonic acid in 1 ml of isopropanol. group, respectively (Fig. 1b). Te ­Al2O3 thin flms were exposed to UV-Ozone for Heavily n-doped bare Si (100) substrates were diced, 30 min to generate enough density of the hydroxyl groups cleaned using ultra-sonication in acetone and isopro- on the surface for the SAM treatment. Te prepared PA- panol for 10 min, and then dried with gas. An SAM solutions after fltration with a 0.45 µm PTFE mem- n+-doped bare Si wafer acted as the back-gate electrode brane were immediately spin-coated on the UV-Ozone in the OFETs. Te cleaned substrates were annealed in treated ­Al2O3 thin flms at a spin rate of 3000 rpm for a convection oven for 1 h to remove residual solvent. 20 s and annealed at 140 °C for 10 min in a nitrogen-flled ­Al2O3 dielectric flms were deposited on the cleaned glovebox. Te annealed substrates were rinsed using substrates by 200 ALD cycles (Lucida D100 ALD, NCD) ultra-sonication in isopropanol for 10 min to remove any at a process temperature of 200 °C. Trimethylaluminum remaining phosphonic acids except for the self-assem- (TMA, Al(CH3)3) and water were used as the Al and bled monolayer on the surface. O precursors, respectively. Te growth rate per cycle Figure 2a displays images of water droplets on the (GPC) was calculated to be ~ 0.12 nm/cycle. hybrid dielectrics that were modifed with various PA- SAM molecules and the measured water contact angles.

Fig. 2 a Water droplets on hybrid dielectrics and measured contact angles, b capacitive densities–frequency (Ci–F) and c leakage current densities– voltage (J–V) of hybrid dielectrics with various PA-SAMs Jang et al. Nano Convergence (2018) 5:20 Page 4 of 8

Te contact angle of the reference Al­ 2O3 surface was k measured to be less than 10°, implying a hydrophilic Ci = ε0 ti (1) property. After the formation of PA-SAM molecules on the ­Al2O3 dielectric, the water contact angles were dra- matically changed depending on the kind of molecules where ε0 is the permittivity of free space and ti is the that were formed. Alkyl- SAMs and PFPA thickness of the insulator. Te thickness of ­Al2O3 pro- exhibited a low energy surface with a high contact angle duced by 200 ALD cycles was measured to be ~ 23 nm, (> 100°) due to their methyl and fuorinated functional and the calculated k of the reference ­Al2O3 was ~ 7.2, groups, respectively [15]. Te contact angle diferences which is lower than the ideal value of bulk ­Al2O3 (k ~ 8–9) between the PA-SAMs were explained by the polarity of [18] but higher than the typical value of sputtering-grown the end-functional groups of the SAM molecules. Non- ­Al2O3 (k ~ 7) [19]. Te discrepancy of the ideal and meas- polar end-groups, such as methyl and 2,3,4,5,6-pentafuo- ured value of the k of Al­ 2O3 might originate from the rophenoxy of alkyl-phosphate SAMs and PFPA, enabled amorphous phase, the existence of native ­SiO2, the series highly hydrophobic surfaces based on the their remark- capacitance, the depletion of the ­n+ Si bottom electrode ably low surface energies compared to other SAMs. How- or an interface charge. ever, MDPA, HUPA and PHDA exhibited relatively lower Ci is formed by the two-series capacitive densities and water contact angles due to their increased polarity of is described as follows: the end-groups, such as the thiol, hydroxyl and carboxyl 1 1 1 groups. Alkyl-phosphate SAMs (HPA, DDPA and ODPA) = + Ci Ci,Al O Ci,PA−SAM (2) have slightly increased contact angles as the alkyl chain 2 3 length is increased. Tese phenomena were attributed Ci,Al O to the fact that increasing an alkyl chain length increases where 2 3 and Ci,PA-SAM are the capacitive densities of the Van der Waals interaction between the alkyl chains, the ­Al2O3 dielectric and the PA-SAM, respectively. From leading to a more crystalline, all-trans conformation of Eqs. (1) and (2), the Ci,PA-SAM and k of each PA-SAM, the chains and a highly packed hydrophobic monolayer respectively, were extracted and summarized with related with lower surface energies [16, 17]. parameters in 1. To investigate the electrical properties of hybrid Te overall capacitive densities of the hybrid dielectrics 2 dielectrics with diverse PA-SAMs, metal–insulator- (Ci) were decreased from 279 nF/cm for the reference 2 semiconductor (MIS) capacitors and OFETs were both ­Al2O3 to 222–245 nF/cm for each PA-SAM treatment. prepared on the same substrates. Pentacene flms (50 nm Tese results provide evidence of the molecular layer thick) were evaporated onto a hybrid dielectric using formation on the ­Al2O3 surface, which contributed to a shadow mask with a deposition rate of 0.2–0.3 Å/s at reducing their capacitive densities. Te Ci of the hybrid ­10−7 Torr. (50 nm thick) source/drain electrodes dielectrics are sufcient for an operating voltage of less (250 μm × 200 μm) for the OFET and top contact elec- than 5 V but can be optimized by further reducing the trodes (square, 200 μm × 200 μm) for the MIS capacitors thickness of the ­Al2O3 for lower voltage operation of the were concurrently deposited using thermal evaporation OFETs. at ­10−6 Torr. Te electrical characteristics of the hybrid Figure 2c shows the leakage current densities as a func- dielectric were measured using a probe station, a semi- tion of the applied voltage to the MIS capacitor. Te conductor parameter analyzer (4145B, HP) and a semi- breakdown electric felds were extracted and ranged from conductor characterization system (4200-SCS, Keithley) 7.5 to 8 MV/cm based on the PA-SAM type, which was in a nitrogen-flled glove box system. Additional fle 1: better than the Al­ 2O3 deposited by RF-magnetron sput- Figure S1a displays the optical microscopic image of the tering system (3–5 MV/cm) [19] but smaller than that OFET and MIS capacitor used for the characterization of of thermally grown SiO­ 2 (14 MV/cm) [20]. Te leakage the hybrid dielectric. current densities of 10­ −8 A/cm2 were maintained at 6 V Te capacitance measurements and breakdown meas- without the appearance of tunneling currents. Te high 2 urements were evaluated via MIS capacitors. Figure 2b capacitive densities (Ci > 220 nF/cm ) and low leakage −8 2 displays the measured capacitive densities (Ci) of hybrid current densities ­(10 A/cm at 6 V) of the hybrid die- dielectrics as a function of frequencies from 300 Hz to lectrics (ti < 25 nm), which originated from the high-k and 1 MHz. We took the Ci values at 10 kHz for the conveni- dense inorganic thin flm of ­Al2O3, were adequate for low ent characterization. Ci of the reference Al­ 2O3 without voltage operation of the OFETs. a PA-SAM was measured to be ~ 279 nF/cm2. Te die- For the sake of the relationship between the hybrid lectric constant k can be calculated from the following dielectric with various PA-SAMs and the electrical per- equation: formance of the OFETs, the OFETs (Channel width Jang et al. Nano Convergence (2018) 5:20 Page 5 of 8

Table 1 Thin flm parameters of the hybrid dielectrics with PA-SAMs

a b 2 c Dielectric Molecular length­ (nm) ti (nm) Contact angle (º) Ci at 10 kHz (nF/cm ) Estimated k

Al2O3 – 23 < 10 279 7.2 HPA 1 0.91 102 246 2.2 DDPA 1.74 1.59 105.5 230 2.6 ODPA 2.49 2.27 109.8 222 2.8 PHDA 2.25 2.05 25.9 223 2.6 MDPA 1.9 1.74 65.1 240 3.4 PFPA 2.24 2.04 102 234 3.3 HUPA 1.72 1.57 28.5 239 3.0

2 Molecular length (nm), thickness of insulator (ti) (nm), contact angle (°), capacitive density (Ci) at 10 kHz (nF/cm ) and Estimated dielectric constant k a The molecular lengths of the PA-SAMs were estimated by assuming the conditions, such as the ideal bonding length and fat molecules according to the alkyl chain axis. The molecular lengths were defned as the distance between the atom at the phosphonic acid and the opposite end atom along the alkyl chain axis b ti was the thickness of each ­Al2O3 and PA-SAM layer (not hybrid dielectric). The ti of the reference Al­ 2O3 was a measured value. The ti of the PA-SAMs were calculated by assuming the calculated molecular lengths, the tilted bonding angle to the substrate (24°) and full coverage with a high density on the substrate c k was the calculated dielectric constant of each ­Al2O3 and PA-SAM layer (not hybrid dielectric) using Eqs. (1) and (2)

where (I ) is the drain current in the saturation W = 200 μm and channel length L = 15 μm) were fab- DS sat ricated in a bottom gate, top contact architecture on regime, μsat is the feld efect mobility in the saturation ­Al2O3/PA-SAM hybrid dielectrics. Figure 3 shows the regime, VT is the threshold voltage, VDS is the source- transfer characteristics and the square root of I­DS of the drain voltage and VGS is the gate-drain voltage. We could OFETs with various PA-SAMs as a function of VGS at estimate the threshold voltage as the x intercept of the linear ft for the square root of I -V and the satura- VDS = − 4 V in the saturation regime. Te drain current DS GS of the OFET in the saturation regime is described as tion feld efect mobility of OFETs using Eq. (3). Te follows: subthreshold slope (SS) was calculated using the inverse slope of log (IDS)-VGS in the subthreshold region of the W 2 (IDS) = µsat Ci (VGS − V ) sat L Th (3) one-decade current increase.

Fig. 3 Transfer characteristics (solid line) and the square root of IDS (dashed line) as a function of VGS of the OFETs with hybrid dielectrics with various PA-SAMs a reference Al­ 2O3, b HPA, c DDPA, d ODPA, e PHDA, f MDPA, g PFPA and h HUPA Jang et al. Nano Convergence (2018) 5:20 Page 6 of 8

For comparison, reference transistors with an ­Al2O3 [15]. Te formation of hydrophobic self-assembled mon- dielectric (ti = 23 nm, without PA-SAM) were prepared olayers (SAMs) on inorganic dielectric surfaces induces (Fig. 3a). Te reference transistor showed stable p-type the edge-on orientation of the organic semiconductor transfer characteristics and negligible hysteresis with an on hydrophobic SAMs during the organic semiconduc- operating voltage below − 4 V. Te reference transistor tor growth [14]. In the horizontal OFET confguration, exhibited substandard performances, such as the feld the in-plane π–π stacking of the edge-on orientation is efect mobility in the saturation regime (μsat), the sub- highly suitable for high in-plane charge transport from threshold slope (SS), the threshold voltage (VT) and the the source to the drain, resulting in the improvement of on–of current ratio (/Iof), which were approximately the mobility of the OFET. Furthermore, the low surface 2 5 0.05 cm /Vs, 345 mV/decade, − 2.18 V and ~ 10 , respec- energy of the hydrophobic surface promotes a greater tively. Te output characteristics of the OFETs as a func- difusion of organic semiconductor molecules dur- tion of VGS are shown in Additional fle 1: Figure S2. Te ing the thin flm growth and enables a larger grain size device characteristics of the OFETs with hybrid dielec- of the organic semiconductor [21, 22]. Te large grains trics of the PA-SAM type are summarized in Table 2. of pentacene suppress the disordered regions, limiting Te OFETs with a hybrid dielectric commonly exhib- their charge transport by the thermally activated hopping ited transfer characteristics with negligible hysteresis process and resulting in an improvement of the mobility. 2 with an operating voltage below − 4 V in the accumula- PFPA also showed a high mobility of 0.27 cm /Vs, which tion mode; the transfer characteristics were analogous was comparable to the alkyl- of the SAMs to the reference transistor. Te gate leakage currents due to their high hydrophobic surface, as well as the low- (IGS) of the hybrid dielectrics were negligible compared est VT of − 0.58 V. Tis threshold voltage shift of PFPA with the drain currents during the operation (less than compared with the reference transistor originated from 4 V) as discussed above (Fig. 2c and Additional fle 1: the charge carrier accumulation of holes at the semicon- Figure S1). Te OFETs with the alkyl-phosphate SAMs ductor-dielectric interface by the electronegative fuorine and PFPA exhibited noticeable improvements in the atoms of the 2,3,4,5,6-pentafuorophenoxy end-func- device performances, including one order of magnitude tional group [23–25]. PHDA exhibited the lowest VT of of the saturation feld-efect mobility (μsat) and the lower − 2.35 V. Te relative hydrophilic PA-SAMs with a high threshold voltage (VT), as well as one order of magni- surface energy tended to induce a growth of the penta- tude of the on–of current ratio (Ion/Iof) compared with cene semiconductor with a face-on orientation due to the the reference transistor. Te most important parameter stronger substrate–flm interactions and represented the of the OFET charge transport is the carrier mobility. Te lower mobilities of the OFETs [22]. hybrid dielectric with ODPA showed the highest satu- Figure 4 shows the saturation mobilities and sub- ration mobility of 0.58 cm2/Vs, the lowest subthreshold threshold slopes of the OFETs as a function of the slope of 151 mV/decade, a threshold voltage of − 1.84 V water contact angle. Tis fgure again presents how the and an on–of current ratio of ­106. Te all methyl-ter- dependence of the device performances signifcantly minated alkyl-phosphate SAMs have common higher depends on the type of PA-SAMs. Te non-polar end- performances among the PA-SAMs because of their functional groups of PA-SAMs with a lower the surface hydrophobic surface based on their low surface energy energy, resulted in pentacene with the edge-on orienta- tion and a large grain. Efective in-plane charge carrier Table 2 Device characteristics of OFETs with hybrid transport occurs due to the π–π stacking of pentacene dielectrics with the edge-on orientation and suppressed disordered 2 Dielectric Contact angle μsat (cm­ /Vs) SS (mV/ VTh (V) Ion/Iof regions with larger sized grains [26, 27]. PFPA with the (º) decade) pentafuorophenoxy end-group showed good device Al O < 10 0.05 345 2.18 ~ 105 performances comparable to PA-SAMs with the methyl 2 3 − HPA 102 0.35 151 1.71 ~ 106 terminal group due to the low surface energy and the − DDPA 105.5 0.41 173 1.83 ~ 106 accumulation of holes, which are majority carriers in − ODPA 109.8 0.58 135 1.84 ~ 106 the pentacene semiconductor, at the semiconductor- − PHDA 25.9 0.02 493 2.35 ~ 104 dielectric interface caused by fuorinated moieties. − MDPA 65.1 0.05 197 1.64 ~ 105 Tese results demonstrate that a hybrid dielectric based − PFPA 102 0.27 198 0.58 ~ 106 on a hydrophobic surface provides a powerful method − HUPA 28.5 0.03 196 1.95 ~ 105 to improve the device performance of OFETs. − In summary, low voltage operational OFETs below The contact angle (º), saturation feld efect mobility μ ­(cm2/Vs), subthreshold sat 4 V were successfully fabricated with hybrid dielec- slope SS (mV/decade), threshold voltage VTh (V), on–of current ratio Ion/Iof 2 tric flms. Hybrid dielectric flms were prepared using μsat ­(cm /Vs), SS (mV/decade), VTh (V) and Ion/Iof were calculated Jang et al. Nano Convergence (2018) 5:20 Page 7 of 8

Fig. 4 a Saturation feld-efect mobilities and b subthreshold slopes of hybrid dielectrics with various PA-SAMs as a function of the water contact angle

ALD and the consecutive assembly of various PA-SAMs Abbreviations OFETs: organic feld efect transistors; k: dielectric constant; ALD: atomic layer using simple spin-coating. Te water contact angles, deposition; Al2O3: alumium oxide; SAM: self-assembled monolayer; PA-SAM: capacitive densities and leakage current densities were phosphonic acid self-assembled monolayer; HPA: hexylphosphonic acid; measured for the characterization of the hybrid dielec- DDPA: dodecylphosphonic acid; ODPA: octadecylphosphonic acid; PHDA: phosphonohexadecanoic acid; MDPA: 12-mercaptododecylphosphonic acid; tric flms. Te methyl terminated alkyl-phosphates and PFPA: 12-pentafuorophenoxydodecylphosphonic acid; HUPA: 11-hydroxyun‑ PFPA have hydrophobic surfaces with a low surface decylphosphonic acid; MIS: metal–insulator-semiconductor; Ci: capacitive energy due to their non-polar end-functional groups. density; ti: thickness of insulator; IDS: the drain current; (IDS)sat: the drain current in saturation regime; μsat: the feld efect mobility in saturation regime; VTh: the Te dielectric constant k of the ­Al2O3 and PA-SAM threshold voltage; VDS: the source-drain voltage; VGS: the gate-drain voltage; SS: layers were extracted. Te OFETs were fabricated for substhreshold slope; Ion/Iof: on–of current ratio. the evaluation of the hybrid dielectrics for transistor Authors’ contributions applications. Te OFET with ODPA exhibited the high- TWK and SJ planned and supervised the project. SJ and TWK designed the est saturation mobility of 0.58 cm2/Vs among the PA- experiments. SJ performed the experimental work, data collection and data SAMs. Te edge-on orientation of pentacene, which analysis. DS optimized the ­Al2O3 deposition and measured water contact angles. SH confrmed the stoichiometry of ­Al2O3 through XPS. MK verifed was promoted by the lower surface energies of PA-SAM the amorphous phase of ­Al2O3 by XRD. All authors discussed the results and due to the non-polar end-groups, improved the carrier contributed to the manuscript preparation. All authors read and approved the conduction between the source-drain electrodes com- fnal manuscript. pared to bare ­Al2O3. PFPA showed a positive VT shift due to the accumulation of holes at the semiconductor- Acknowledgements dielectric interface. Tis hybrid dielectric platform can This work was supported by the Korea Institute of Science and Technology (KIST) institutional program. This work was partially supported by the National be compatible with low voltage transistor applications Research Foundation of Korea (NRF-2017M3A7B4049167). depending on the polarity of the solution processed and the vacuum deposited organic semiconductor. Competing interests The authors declare that they have no competing interests. Additional fle Availability of data and materials The datasets supporting the conclusions of this article are included within the Additional fle 1: Figure S1. (a) Optical microscopic image of our OFET article and its Additional fle 1. and MIS capacitor with a hybrid dielectric. (b) Gate leakage currents as a Funding function of the gate voltage (IGS-VGS) of the OFETs that include hybrid gate dielectrics with various PA-SAMs. Figure S2. Output characteristics as a Not applicable. function of the gate voltage (IDS-VGS) of the OFETs with hybrid dielectrics with various PA-SAMs (a) reference ­Al2O3 (b) HPA, (c) DDPA (d) ODPA, (e) PHDA, (f) MDPA, (g) PFPA and (h) HUPA. Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in pub‑ lished maps and institutional afliations. Jang et al. Nano Convergence (2018) 5:20 Page 8 of 8

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