Room-Temperature Fabrication of High ... - ACS Publications

Subscriber access provided by Warwick University Library

Article

Room-temperature fabrication of high-performance amorphous In-GaZn-O/Al2O3 thin-film transistors on ultra-smooth and clear nanopaper Honglong Ning, Yong Zeng, Yudi Kuang, Zeke Zheng, Panpan Zhou, Rihui Yao, Hongke Zhang, Wenzhong Bao, Gang Chen, Zhiqiang Fang, and Junbiao Peng ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b07525 • Publication Date (Web): 02 Aug 2017 Downloaded from http://pubs.acs.org on August 3, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Room-temperature fabrication of high-performance amorphous In-Ga-Zn-O/Al2O3 thinfilm transistors on ultra-smooth and clear nanopaper Honglong Ning1, Yong Zeng1, Yudi Kuang2, Zeke Zheng1, Panpan Zhou2, Rihui Yao1*, Hongke Zhang1, Wenzhong Bao3*, Gang Chen2, Zhiqiang Fang1,2,4*, Junbiao Peng1 1. State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 Guangdong, China. 2. State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640 Guangdong, China. 3. State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China. 4. Key Laboratory of Pulp and Paper Science & Technology of Ministry of Education/Shandong Province, Qilu University of Technology, Jinan 250353 Shandong, China. Email: [email protected], [email protected], [email protected] Abstract Integrating biodegradable cellulose nanopaper into oxide thin-film transistors (TFTs) for next generation flexible and green flat panel displays has attracted great interests because it offers a viable solution to address the rapid increase of electronic waste that poses a growing ecological problem. However, a compromise between device performance and thermal annealing remains an obstacle for achieving high-performance nanopaper TFTs. In this study, a highperformance bottom-gate IGZO/Al2O3 TFT with a dual-layer channel structure was initially fabricated on a highly transparent, clear, and ultra-smooth nanopaper substrate via conventional physical vapor deposition approaches, without a further thermal annealing processing. Purified nanofibrillated cellulose with a width of approximately 3.7 nm was used to prepare nanopaper with excellent optical properties (92% transparency, 0.85% transmission haze) and superior surface roughness (Rq is 1.8 nm a 5×5 µm2 scanning area). More significantly, a bilayer channel structure (IGZO/Al2O3) was adopted to fabricate high performance TFT on this nanopaper substrate without thermal annealing and the device exhibits a saturation mobility of 15.8 cm2/Vs, an Ion/Ioff ratio of 4.4×105, a threshold voltage (Vth) of -0.42V, and a subthreshold swing (SS) of 0.66V/dec. The room-temperature fabrication of high-performance IGZO/Al2O3 TFTs on such nanopaper substrate without thermal annealing treatment brings industry a step closer to realizing inexpensive, flexible, lightweight, and green paper displays. Key words: cellulose nanofiber nanopaper, ultra-smooth, thin-film transistor, IGZO semiconductor, electrical properties

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Introduction Thin-film transistors (TFTs) are the fundamental building blocks for state-of-the-art flat panel displays (FPDs) that are extensively used in consumer electronic products like smart phones, portable laptops, and wearable devices.1-5 As the consumers’ insatiable appetite for newer and more elegant-looking devices grows and device lifecycle decreases that results in a huge amount of electronic waste, the next-generation FPDs require TFTs to be flexible, cheap, lightweight, and biodegradable.6-9 A feasible and economical solution to fulfilling these requirements is embodied by the incorporation of cellulose nanofiber nanopaper into TFTs. Nanopaper, a cutting-edge variety of paper initially invented by Nogi et.al in 2009,10 exhibited the advantages of biodegradability, renewability, highly optical transparency (~90% at 550 nm), strong tensile strength (100-300MPa), good Young’s modulus (7-30GPa), low coefficient of thermal expansion (5-10ppm/K), excellent solvent resistance, nano-scale surface roughness (several to dozens of nanometers), and good barrier properties beyond the traditional properties of common paper.9, 11-21 These attractive properties enable the nanopaper to apply in high-tech fields in which the use of common paper is untenable. Many efforts have been devoted to fabricating TFTs on conventional paper substrates,22-26 however, only several publications reported on the fabrication of nanopaper TFTs. Zhu et.al. first demonstrated organic field-effect transistors (FETs) on highly transparent and flexible nanopaper made of nanofibrillated cellulose (NFC) in 2013.13 Since then, a variety of organic semiconductors and fabrication strategies have been implemented to improve the electrical properties (mobility, Ion/Ioff ratio, subthreshold swing (SS), etc.) and environmental stability of TFTs on nanopaper substrates.27-29 While progresses have been made for nanopaper TFTs based


Page 2 of 25

Page 3 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


on organic semiconductors, their low mobility (a maximum mobility of ~1 cm2/Vs) and operational instability are challenging for high-resolution and large-area FPD applications. Recently, oxide TFTs have received growing attention due to their high carrier mobility, good electrical uniformity, low processing temperature, and potentially affordable cost.7, 30-33 InGa-Zn-O (IGZO) transistors on nanopaper simultaneously acting as the substrate and as the gateinsulating layer were demonstrated for the first time by Fortunato et.al.34 The nanopaper FETs based on IGZO possessed a much higher mobility (µsat >7 cm2/Vs) than organic transistors. Besides, the saturation mobility could be further increased up to 16 cm2 V−1 s−1 by reducing the pH value of the nanopaper to 5.5.35 These oxide TFTs on nanopaper exhibited good electrical properties. However, IGZO TFTs on nanopaper generally required a further thermal annealing process to achieve the desired level of mobility, which was impractical for flexible large-area electronic devices. Moreover, using nanopaper not only as substrate but also as insulating layer for IGZO transistor could increase device defects during fabrications. Electrolyte gated multilayer two-dimensional (2D) nanomaterials such as MoS2 were also applied as channel material for the fabrication of FETs on nanopaper without an annealing procedure, but no mobility was presented in relevant publications.36-38 In this work, we present a high-performance IGZO/Al2O3 TFT on a highly transparent, clear, and ultra-smooth nanopaper substrate for the first time, to the best of our knowledge, by using conventional physical vapor deposition (PVD) methods, without a further thermal treatment. Original NFC isolated from wood pulp by the combination of 2,2,6,6-tetramethylpiperidine-1oxyl (TEMPO) treatment and homogenization was purified by centrifugation to remove the nanofibril bundles with large dimensional size. The obtained homogeneous NFC dispersion was then used to prepare ultra-smooth nanopaper with a high transparency and low transmission haze



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 25

by a casting process. Furthermore, a bi-layer structure of the channel layer was employed to fabricate high-performance IGZO/Al2O3 TFTs on this nanopaper substrate without thermal annealing treatment. The successful room temperature fabrication of high-performance TFTs on nanopaper substrates brings industry a step closer to realizing inexpensive, flexible, lightweight, and green paper displays.

Results and Discussion The excellent mechanical, optical, anti-solvent, thermal, and barrier properties of nanopaper enable it to be a potential substrate for electronic devices.10,

13, 14, 28, 39, 40

Among these

characteristics, the transmission haze and surface roughness of nanopaper is of significance for its application in display industry. The morphology of NFC plays a significant role in the transmission haze and surface topography of nanopaper for electronic devices. To achieve suitable NFC, TEMPO pretreatment coupled with a homogenization procedure was utilized to efficiently disintegrate NFC from wood fibers; the morphology of isolated NFC is shown in Figure 1a. We can see from the atomic force microscopy (AFM) image that there are some obvious fibril bundles with widths from several dozens of nanometers to hundreds of nanometers in isolated NFC, resulting from incomplete homogenization of the wood fibers. These large-size fibril bundles, accounting for 5-6% by weight in the original NFC, will have a negative effect on surface roughness and transmission haze.21, 37, 41 Therefore, in the current study, a centrifugation procedure was applied to remove these bundles; the morphology of purified NFC after centrifugation is displayed in Figures 1b and 1c, indicating an average fiber diameter of approximately 3.7 nm. Figure 1d shows, from left to right, the visual appearances of water, original NFC dispersion, and purified NFC dispersion. The purified NFC dispersion seems as clear as the water, and the


Page 5 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


lettering behind the samples can be observed clearly by the naked eye. However, the original NFC dispersion looks slightly hazy due to the existence of fibril bundles. This phenomenon can be further confirmed by conducting light scattering testing on the three samples. In our test, a horizontal green laser (532 nm) incident from the right-hand side passed through the three distinct samples. No light is observed in water, but for samples containing NFC, the green laser light is visible due to the Tyndall effect. Compared to the original NFC dispersion, the purified NFC dispersion demonstrates a weak light scattering behavior because of the removal of large fibril bundles (as shown in Figure 1e). The homogeneous purified NFC was then utilized to prepare highly transparent, clear, and ultra-smooth nanopaper for TFTs by a casting process that was dried at a temperature of 40 °C and a relative humidity of 50% in a constant temperature and humidity chamber (detailed information appears in experimental part below). Figure 2a exhibits a piece of as-prepared nanopaper that exhibited a high transparency and clarity similar to glass or transparent plastic films. The tensile strength and thermogravimetric analysis of the obtained nanopaper are shown in Figure S2 and S3, respectively. The surface roughness of a nanopaper substrate is crucial for the operational performance of the electronics applied on it. In general, functional layers within electronics have a thickness of only several nanometers or dozens of nanometers, and thus the high surface roughness could lead to bad device performance or even an inactive device.

The surface topography of as-prepared nanopaper was evaluated by AFM. As shown in Figure 2b, the average root-mean-square (RMS) roughness of nanopaper is approximately 1.8 nm over a 5×5 µm2 region, which is close to the RMS of conventional glass and plastic films, such as polyimide. Scanning electron microscopy (SEM) was used to further characterize the



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

surface texture of nanopaper. As shown in Figure 2c, there are no obvious convex or concave spots on the nanopaper surface over an area measuring several square millimeters. The same can be concluded by examining the area of the nanopaper in the red box in Figure 2c under magnification; such zoomed-in SEM image indicating superior surface smoothness, is presented in Figure 2d. Moreover, substrates with both high transparency and low transmission are desirable for bottom emissive displays.42 A total optical transparency of more than 85% over the visible wavelength range and a transmission haze of less than 1% are typically required for display applications.43 Figure 2e and f demonstrate the optical transmittance and transmission haze, respectively, of the obtained ultra-smooth nanopaper. The nanopaper realized in this work had a transparency of approximately 92% over 400-800 nm and a transmission haze of ~0.85%. A bottom-gate inverted-staggered structure was adopted to prepare an IGZO/Al2O3 TFT on a transparent, clear, and ultra-smooth nanopaper substrate (thickness 40 µm) by the PVD method at room temperature; the cross-sectional schematic of the TFT is presented in Figure 3a. The source/drain, gate electrodes, bilayer channel layer, and gate insulator were all defined by shadow masks. A ~170-nm-thick Al layer was chosen for source/drain electrodes and an 80-nmthick Al layer was used for the gate electrode. While a 400-nm-thick Al2O3 film served as the gate insulator (Figure 3c). Stacked IGZO/Al2O3 films (~13.5 nm) acted as n-channel active layer, with channel length approximately 600 µm (Figure 3b). Figure 3d shows a high-resolution TEM image of the stacked IGZO/Al2O3 channel layer. As the TEM image shows, the IGZO/Al2O3 bilayer channel presents a wavy configuration, and a magnified image of it indicates the aggregation of metal elements, which is further verified by element-mapping analysis of elemental indium, gallium, and zinc element (Figure 3e). To explain the wavy structure of the channel layer, the surface topographies of the buffer layer,


Page 6 of 25

Page 7 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


insulating layer, and channel layer (from bottom to top) were characterized by AFM analysis. As shown in Figure 3f, the average RMS surface roughness of buffer layer is approximately 7 nm, but when the IGZO/Al2O3 channel layer was deposited on the insulating layer (RMS roughness: 9.5 nm), its RMS roughness increased to 12.70 nm, showing an increment of almost 81% relative to the buffer layer. The rapid increase of RMS roughness may have contributed to the wavy structure of the channel layer. We are planning to further optimize the RMS roughness for each functional layer in the future. The electrical properties of a bottom-gate inverted-staggered IGZO/Al2O3 TFT on nanopaper substrate were analyzed by an Agilent semiconductor parameter analyzer 4155C (Agilent Corp., Santa Clara, CA, USA), and its output and transfer characteristics are displayed in Figures 4a and b, respectively. The as-prepared nanopaper TFT exhibits a saturation mobility of 15.8 cm2/Vs, a threshold voltage (Vth) of -0.42 V, an SS of 0.66 V/dec, and an Ion/Ioff ratio of 4.4×105. Currently, glass and polyimide (PI) are two types of predominant commercial substrates for TFTs. To compare the performance of an IGZO/Al2O3 TFT on a glass or PI substrate with that on nanopaper, their output and transfer characteristics were measured. The basic properties of nanopaper, PI, and glass are displayed in Table S1. Figure 4c shows the output characteristics of IGZO/Al2O3 TFTs fabricated on different substrates. A clear pinch-off and current saturation behavior is observed in IGZO/Al2O3 TFTs on a glass or a PI at high VD, which confirms that the operation of TFTs follows the standard field-effect-transistor theory. However, there is no pinchoff for IGZO/Al2O3 TFT on a nanopaper substrate at a VG of 20 V due to VD = VD(sat) < VG-Vth. The transfer characteristics of IGZO/Al2O3 TFTs with a width-to-length ratio=(500 µm)/(600 µm) fabricated on three different substrates are shown in Figure 4d. Hysteresis-free behavior is observed for IGZO/Al2O3 TFTs based on a glass or a PI substrate, while obvious



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

hysteresis exists in IGZO/Al2O3 TFTs based on a nanopaper substrate. The hysteresis is attributed to hole/electron trapping or to donor-like defect creation.44 This is in agreement with the result listed in Table 1, that an IGZO/Al2O3 TFT on nanopaper has the largest SS, 0.66 V. Furthermore, as shown in Figures 3(c) and (d), it is easy to absorb H2O and O2 from surrounding environment due to the high roughness of each layer. As reported, the hysteresis of TFT could be caused by H2O or O2 electrochemical reactions.45 The dieletric layer was sputtered Al2O3 with a capacitance of 21 nF/cm2, while the insulator was anodized Al2O3:Nd insulator with a capacitance of 38 nF/cm2 for an IGZO/Al2O3 TFT on a glass or a PI substrate (see Figure S1 in the Supporting Information). The saturation mobility (µsat) of IGZO/Al2O3 TFTs on a glass, PI, and nanopaper substrate is 19.9, 17.6 and 15.8 cm2/Vs, respectively. The µsat of an IGZO/Al2O3 TFT on a nanopaper substrate is nearly as good as that on glass and PI substrates and sufficient to fulfill the needs of displays; thus, there is significant application potential of nanopaper TFTs in displays. The electrical properties in a linear region are related to the source/drain contact properties. To investigate the source/drain contact properties of different substrates in IGZO/Al2O3 TFTs, output characteristics and the derivative of the output curves (dID/dVD) in a zoom-in plot of linear region (VD=0-5 V) are displayed in Figures 5a-c. Plotting VD-(dID/dVD) curves can better reveal the current crowding. A TFT with current crowding exhibits a nonlinear behavior in its VD-(dID/dVD) curves, which indicates a non-Ohmic source/drain contact.46 As shown in Figures 5b and c, the differential conductance decreased linearly with VD, which reveals that there is no current crowding in IGZO/Al2O3 TFTs on glass and PI substrates.47 However, as shown in Figure 5a, the differential conductance decreased nonlinearly with VD, which indicates the existence of current crowding in IGZO/Al2O3 TFTs on a nanopaper substrate.


Page 8 of 25

Page 9 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1 Performance parameters comparison of IGZO/Al2O3 TFTs based on different substrates (glass, PI, and nanopaper) with a width-to-length ratio=(500 µm)/(600 µm) µsat SS Ci Ion Ioff 2 -1 Substrate (cm V s (V/dec Ion/Ioff (nF/cm2) (A) (A) 1 ) ) IGZO/ Glass 38 19.9 0.3 1.3×10-4 2.9×10-12 4.4×107 Al2O3 PI 38 17.6 0.24 6.1×10-5 4.7×10-12 1.2×107 TFTs Nanopaper 21 15.8 0.66 5.0×10-5 1.1×10-10 4.4×105

As shown in figure 6a, high off-state current is responsible for the deterioration of the on/off current ratio for IGZO/Al2O3 TFTs on a nanopaper substrate. The off-state drain current is derived from two possible primary leakage paths, involving leakage current in the channel and/or through the gate insulator.48 Because of wide-band-gap (3.25 eV) and unipolar electrical properties, the IGZO channel layer exhibits extremely small leakage, which is lower than that of the polysilicon or amorphous hydrogenated silicon channel layers. This can be affirmed by the indication in Table 1 that Ioff is as low as 10-12 A for an IGZO/Al2O3 TFT on a glass or a PI substrate. As shown in Figures 5a and b, the insulator leakage (10-8 A) of the nanopaper substrate is two orders of magnitude higher than that (10-10 A) of glass or PI substrates. This result indicates the fact that the high Ioff value is related to the leakage current through the gate insulator, which depends on the quality of insulator thin film. Figure 6c shows the evolution of transfer characteristics as a function of the applied stress time under positive bias stress (PBS) with VG=5V for an IGZO/Al2O3 TFT on a nanopaper substrate. The stress-induced hump effect is observed; that is, the TFT shifts in the positive direction at high VG, while the hump shifts in the negative direction in the subthreshold regime.49 The hump effect is related to edge effects, which can cause trapping of more electrons at the edges, thus creating a hump due to the higher electric field.50 However, this phenomenon only occurs in top-gate coplanar-structured TFTs rather than bottom-gate inverted-staggered



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

structured TFTs,49 which can exclude edge effects. The self-heating effect could cause a hump effect for TFTs with large channel widths (> 100 um).51 Furthermore, the hump effect increases with increasing self-heating stress time. Obviously, the hump does not increase when the stress time increases from 3600 to 7200 s as shown in Figure 6c, which reveals the exclusion of self-heating effects on hump. Moreover, the negative shift of Vth is attributed to hole trapping, and, therefore, the hump effect could be related to the migration of positively charged, mobile particles under PBS, such as zinc interstitial ions and oxygen vacancies.49, 52 The oxygen chemistry state is characterized by x-ray photoelectron spectroscopy (XPS) and shown in Figure 6d. The peaks at 530.2eV，531eV and 532eV are attributed to O2- ions surrounded by metal atoms (M-O-M), oxygen vacancies (VO), and loosely bound oxygen (M-OR) involving adsorbed O2, H2O and CO2. VO ionization (V2+ O ) easily occurs by trapping electrons and the migration of V2+ O could lead to the negative shift of Vth. As shown in Figure 6(d), the concentration of VO is very high, which could result in the hump effect under PBS.

Conclusion In summary, we initially fabricated high-performance TFTs using the IGZO/Al2O3 bilayer films as an n-channel active layer on highly transparent, clear, and ultra-smooth nanopaper substrates by conventional PVD methods, without a further thermal treatment. The large-size bundles in the original NFC dispersion were removed by centrifugation, and the purified NFC obtained was then used to prepare the nanopaper for TFTs by a casting procedure. The asprepared nanopaper possessed a transparency of 92% at 550 nm, a transmission haze of 0.85% at 550 nm, and an average RMS roughness of 1.8 nm over a 5×5 µm2 scanning area. In addition, a


Page 10 of 25

Page 11 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


bi-layer channel structure (IGZO/Al2O3) was adopted to fabricate high-performance TFTs on the nanopaper substrate without thermal annealing, and the devices exhibited excellent operating characteristics, i.e., a saturation mobility of 15.8 cm2/Vs), an Ion/Ioff ratio of 4.4×105, a threshold voltage Vth of -0.42V, and a subthreshold swing of 0.66V/dec. The successful room temperature fabrication of high-performance oxide TFTs on transparent, clear, and ultra-smooth nanopaper without thermal treatment sheds light on the realization of inexpensive, flexible, lightweight, and green paper displays. Experimental Section Preparation of Nanofibrilated Cellulose and Nanopaper NFC was disintegrated from bleached eucalyptus pulp (Arauco Eucalyptus, Chile) by a combination TEMPO/NaBr/NaClO system and homogenization. TEMPO-oxidized pretreatment and homogenization of eucalyptus pulp were conducted according to our previous method.15, 53 The obtained original NFC dispersion was centrifuged at 5000 rpm for 20min to remove the large fibril bundles. The as-prepared purified NFC dispersion was then poured onto a 15×15 cm2 glass slide and dried at 40°C and 50% elative humidity in a constant-temperature and -humidity chamber for 46h. After drying, the formed NFC film was detached from the glass using a thin, sharp knife for characterization and TFT fabrication. The grammage of as-prepared nanopaper was approximately 40g/m2. For more information about this nanopaper, please see Table S2 in supporting information. Device Fabrication The fabrication of oxide TFTs was carried out on the aforementioned highly transparent, clear, and ultra-smooth nanopaper. A 130-nm-thick SiO2 thin film, serving as buffer layer to



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

block the penetration of water or O2 into the functional layers of TFTs, was deposited on the surface of the nanopaper by radio-frequency (RF) magnetron sputtering with a power of 100 W and pressure of 1 mTorr. An 85-nm-thick Al gate electrode was then deposited with a steel mask by direct-current (DC) magnetron sputtering with a power of 100 W and pressure of 1 mTorr, followed by RF magnetron sputtering of an Al2O3 gate insulator with a pressure of 1 mTorr under a pure argon atmosphere (the RF power was 120 W). The channel layer is the stacked bilayer structure of IGZO (the target being In:Ga:Zn:O=1:1:1:1 (in atomic ratio) and an Al2O3 thin film. The thickness of the IGZO layer is 10 nm, which was prepared by pulsed DC magnetron sputtering with a pulsed duration of 20 µs and a pulsed frequency of 1 kHz. The gases introduced were argon and oxygen with a volume ratio of 100:5. The DC sputtering power and pressure were 120 W and 1 mTorr, respectively. The Al2O3 thin film deposition process was identical to that of the gate insulator, except for the sputtering time. The thickness of Al2O3 film is 3.5 nm, which was controlled by sputtering time. As shown in Figure 3(a), a bottom-gate invertedstaggered structured TFT was completed after a 170-nm-thick aluminum (Al) film was evaporated in an Edwards thermal evaporator to act as the source/drain electrodes. Each layer was deposited through a metal shadow mask, except the buffer layer. The channel width and length were 500 µm and 600 µm, respectively, as shown in Figure 3b. All devices were prepared at room temperature without thermal annealing process. The saturation mobility was extracted by transfer characteristics with high VD:13 d I! ! ) d V! 𝐶! 𝑊

2L( 𝜇!"# =


Page 12 of 25

Page 13 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Here, Ci is the capacitance of the insulator layer, W and L are the channel width and length, respectively. The subthreshold swing (SS) indicates the necessary to increase ID by one decade[13]:

Acknowledgement Honglong Ning thanks the funding from National Key R&D Program of China (Grant 2016YFB0401504), Science and Technology Project of Guangdong Province (Grant 2014B090915004 and 2016B090907001), and NSFC (No.U1601651). Zhiqiang Fang would like to acknowledge financial support from the Training Program of State Key Laboratory of Pulp and Papermaking Engineering (2016PY01, 201709), the Fundamental Research Funds for the Central Universities (2015ZM156), the Foundation (No. KF201619) of Key Laboratory of Pulp and Paper Science and Technology of Ministry of Education/Shandong Province of China. Wenzhong Bao acknowledges the support of the National Key Research and Development Program (2016YFA0203900) Supporting information The detail information of capacitance values of Al2O3 insulator layer, the tensile strength and TGA curve of transparent, clear, and ultra-smooth nanopaper. A comparison of nanopaper, PI, and glass for electronic applications. Basic properties of transparent, clear, and ultra-smooth nanopaper. Additional information



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Completing financial interests: The authors declare no competing financial interests.

References 1. Lee, S.; Nathan, A. Subthreshold Schottky-Barrier Thin-Film Transistors with Ultralow Power and High Intrinsic Gain. Science 2016, 354, 302-304. 2. Rembert, T.; Battaglia, C.; Anders, A.; Javey, A. Room Temperature Oxide Deposition Approach to Fully Transparent, All‐Oxide Thin‐Film Transistors. Adv. Mater. 2015, 27, 6090-6095. 3. Kwon, G.; Kim, K.; Choi, B. D.; Roh, J.; Lee, C.; Noh, Y. Y.; Seo, S. Y.; Kim, M. G. Kim C. Multifunctional Organic‐Semiconductor Interfacial Layers for Solution‐Processed Oxide‐ Semiconductor Thin‐Film Transistor. Adv. Mater. 2017, 29, 1607055 (1-7) 4.Park, J. S.; Maeng, W. J.; Kim, H. S.; Park, J. S. Review of Recent Developments in Amorphous Oxide Semiconductor Thin-Film Transistor Devices. Thin Solid Films. 2012, 520, 1679-1693. 5.Street, R. A. Thin‐Film Transistors. Adv. Mater. 2009, 21, 2007-2022. 6. Nakagaito, A. N.; Nogi, M.; Yano, H. Displays from Transparent Film of Natural Nanofibers. MRS Bull. 2010, 35, 214-218. 7. Tan, M, J.; Owh, C.; Chee, P. L.; Kyaw, A. K. K.; Kai, D.; Loh, X.J. Biodegradable Electronics: Cornerstone for Sustainable Electronics and Transient Applications. J. Mater. Chem. C. 2016, 4, 5531-5558. 8. Nomura, K.; Ohta, H.; Takagi, A.; Kamiya, T.; Hirano, M.; Hosono, H. Room-Temperature Fabrication of Transparent Flexible Thin-Film Transistors Using Amorphous Oxide Semiconductors. Nature 2004, 432, 488-492. 9. Irimia, V. M. "Green" Electronics: Biodegradable and Biocompatible Materials and Devices for Sustainable Future. Chem. Soc. Rev. 2014, 43, 588-610. 10. Nogi, M.; Iwamoto, S.; Nakagaito, A. N.; Yano, H. Optically Transparent Nanofiber Paper. Adv. Mater. 2009, 21, 1595-1598. 11. Fukuzumi, H.; Saito, T.; Iwata, T.; Kumamoto, Y.; Isogai, A. Transparent and High Gas Barrier Films of Cellulose Nanofibers Prepared by TEMPO-Mediated Oxidation. Biomacromolecules 2009, 10, 162. 12. Eichhorn, S. J.; Dufresne, A.; Aranguren, M.; Marcovich, N. E.; Capadona, J. R.; Rowan, S. J.; Weder, C.; Thielemans, W.; Roman, M.; Renneckar, S.; Gindl, W.; Veigel, S.; Keckes, J.; Yano, H.; Abe, K.; Nogi, M.; Nakagaito, A. N.; Mangalam, A.; Simonsen, J.; Benight, A. S.; Bismarck, A.; Berglund, L. A.; Peijs, T. Review: current international research into cellulose nanofibres and nanocomposites. J. Mater. Sci. 2010, 45, 1-33. 13. Huang, J.; Zhu, H.; Chen, Y.; Preston, C.; Rohrbach, K.; Cumings, J.; Hu, L. Highly Transparent and Flexible Nanopaper Transistors. ACS Nano 2013, 7, 2106-2113. 14. Zheng, G.; Cui, Y.; Karabulut, E.; Wagberg, L.; Zhu, H.; Hu, L., Nanostructured Paper for Flexible Energy and Electronic Devices. MRS Bull. 2013, 38, 320.


Page 14 of 25

Page 15 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


15. Kuang, Y.; Chen, G.; Ming, S.; Wu, Z.; Fang, Z. Solvent Resistance of 2, 2, 6, 6Tetramethylpiperidine-1-Oxyl (TEMPO) Treated Cellulose Nanofiber Film for Flexible Electronics. Cellulose 2016, 23 (3), 1979-1987. 16. Belbekhouche, S.; Bras, J.; Siqueira, G.; Chappey, C.; Lebrun, L.; Khelifi, B.; Marais, S.; Dufresne, A. Water Sorption Behavior and Gas Barrier Properties of Cellulose Whiskers and Microfibrils Films. Carbohydr. Polym. 2011, 83, 1740-1748. 17. Lavoine, N.; Desloges, I.; Dufresne, A.; Bras, J. Microfibrillated Cellulose–Its Barrier Properties and Applications in Cellulosic Materials: A Review. Carbohydr. Polym. 2012, 90, 735. 18. Yagyu, H.; Saito, T.; Isogai, A.; Koga, H.; Nogi, M., Chemical Modification of Cellulose Nanofibers for the Production of Highly Thermal Resistant and Optically Transparent Nanopaper for Paper Devices. ACS Appl. Mater. Interfaces 2015, 7, 22012-22017. 19. Sehaqui, H.; Zhou, Q.; Ikkala, O.; Berglund, L. A., Strong and Tough Cellulose Nanopaper with High Specific Surface Area and Porosity. Biomacromolecules 2011, 12 (10), 3638-3644. 20. González, I.; Alcalà, M.; Chinga-Carrasco, G.; Vilaseca, F.; Boufi, S.; Mutjé, P. From Paper to Nanopaper: Evolution of Mechanical and Physical Properties. Cellulose 2014, 21, 2599-2609. 21. Zhu, H.; Parvinian, S.; Preston, C.; Vaaland, O.; Ruan, Z.; Hu, L. Transparent Nanopaper with Tailored Optical Properties. Nanoscale 2013, 5, 3787-3792. 22. Shao, F.; Feng, P.; Wan, C.; Wan, X.; Yang, Y.; Shi, Y.; Wan, Q., Multifunctional Logic Demonstrated in a Flexible Multigate Oxide‐Based Electric‐Double‐Layer Transistor on Paper Substrate. Adv. Electron. Mater. 2017, 3, 1600509 (1-7). 23. Jiang, J.; Sun, J.; Dou, W.; Zhou, B.; Wan, Q. In-Plane-Gate Indium-Tin-Oxide Thin-Film Transistors Self-Assembled on Paper Substrates. Appl. Phys. Lett. 2011, 98, 113507 (1-3). 24. Fortunato, E.; Correia, N.; Barquinha, P.; Pereira, L.; Gonçalves, G.; Martins, R. HighPerformance Flexible Hybrid Field-Effect Transistors Based on Cellulose Fiber Paper. IEEE Electron Device Lett. 2008, 29, 988-990. 25. Lim, W.; Douglas, E. A.; Norton, D. P.; Ren, F.; Heo, Y. W.; Son Y. S.; Yuh, J. H. LowVoltage Indium Gallium Zinc Oxide Thin Film Transistors on Paper Substrates. Appl. Phys. Lett. 2010, 96, 053510 (1-3). 26. Lim, W.; Douglas, E. A.; Kim, S. H.; Norton, D. P.; Pearton, S. J.; Ren, F.; Shen, H.; Chang, W. H. High Mobility InGaZnO4 Thin-Film Transistors on Paper. Appl. Phys. Lett. 2009, 94, 072103 (1-3). 27. Hassinen, T.; Alastalo, A.; Eiroma, K.; Tenhunen, T. M.; Kunnari, V.; Kaljunen, T.; Forsstrom, U.; Tammelin, T. All-Printed Transistors on Nano Cellulose Substrate. MRS Adv. 2016, 1, 645-650. 28. Fujisaki, Y.; Koga, H.; Nakajima, Y.; Transparent Nanopaper-Based Flexible Organic ThinFilm Transistor Array. Adv. Funct. Mater. 2014, 24, 1657-1663. 29.Wang, C.-Y.; Fuentes-Hernandez, C.; Liu, J.-C.; Dindar, A.; Choi, S.; Youngblood, J. P.; Moon, R. J.; Kippelen, B. Stable Low-Voltage Operation Top-Gate Organic Field-Effect Transistors on Cellulose Nanocrystal Substrates. ACS Appl. Mater. Interfaces 2015, 7, 48044808. 30. Martins, R.; Ahnood, A.; Correia, N.; Pereira, P.; Barros, R.; Barquinha, P.; Costa, R.; Ferreira, M.; Nathan, A.; Fortunato, E. Recyclable, Flexible, Low‐Power Oxide Electronics. Adv. Funct. Mater. 2013, 23, 2153-2161. 31. Fortunato, E.; Barquinha, P.; Martins, R; Oxide Semiconductor Thin‐Film Transistors: A Review of Recent Advances. Adv. Mater. 2012, 24, 2945-2986.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

32. Nomura, K.; Ohta, H.; Ueda, K.; Kamiya, T.; Hirano, M.; Hosono, H. Thin-Film Transistor Fabricated in Single-Crystalline Transparent Oxide Semiconductor. Science. 2003, 300, 12691272. 33. Sun, Y.; Rogers, J. A. Inorganic Semiconductors for Flexible Electronics. Adv. Mater. 2007, 19,1897-1916. 34. Gaspar, D.; Fernandes, S. N.; De Oliveira, A. G.; Fernandes, J. G.; Grey, P.; Pontes, R. V.; Pereira, L.; Martins, R.; Godinho, M. H.; Fortunato, E. Nanocrystalline Cellulose Applied Simultaneously as the Gate Dielectric and the Substrate in Flexible Field Effect Transistors. Nanotechnology 2014, 25, 094008. 35. Pereira, L.; Gaspar, D.; Guerin, D.; Delattre, A.; Fortunato, E.; Martins, R. The Influence of Fibril Composition and Dimension on the Performance of Paper Gated Oxide Transistors. Nanotechnology. 2014, 25, 094007. 36. Bao, W.; Fang, Z.; Wan, J.; Dai, J.; Zhu, H.; Han, X.; Yang, X.; Preston, C.; Hu, L. Aqueous Gating of Van Der Waals Materials on Bilayer Nanopaper. ACS Nano. 2014, 8, 10606-10612. 37. Fang, Z.; Zhu, H.; Bao, W.; Preston, C.; Liu, Z.; Dai, J.; Li, Y.; Hu, L. Highly Transparent Paper with Tunable Haze for Green Electronics. Energy Environ. Sci. 2014, 7, 3313-3319. 38. Tao, J.; Fang, Z.; Zhang, Q.; Bao, W.; Zhu, M.; Yao, Y.; Wang, Y.; Dai, J.; Zhang, A.; Leng, C., Super‐Clear Nanopaper from Agro‐Industrial Waste for Green Electronics. Adv. Electron. Mater. 2017, 3, 1600539 (1-7). 39. Hu, L. B.; Zheng, G. Y.; Yao, J.; Liu, N. A.; Weil, B.; Eskilsson, M.; Karabulut, E.; Ruan, Z. C.; Fan, S. H.; Bloking, J. T.; McGehee, M. D.; Wagberg, L.; Cui, Y., Transparent and Conductive Paper from Nanocellulose Fibers. Energy Environ. Sci. 2013, 6, 513-518. 40. Zhu, H.; Xiao, Z.; Liu, D.; Li, Y.; Weadock, N. J.; Fang, Z.; Huang, J.; Hu, L. Biodegradable Transparent Substrates for Flexible Organic-Light-Emitting Diodes. Energy Environ. Sci. 2013, 6, 2105-2111. 41. Hsieh, M.-C.; Koga, H.; Suganuma, K.; Nogi, M., Hazy Transparent Cellulose Nanopaper. Sci. Rep. 2017, 7, 41590 (1-7). 42. MacDonald, W. A., Engineered Films for Display Technologies. J. Mater. Chem. 2004, 14, 4-10. 43. Zhu, H.; Luo, W.; Ciesielski, P. N.; Fang, Z.; Zhu, J. Y.; Henriksson, G.; Himmel, M. E.; Hu, L. Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications. Chem. Rev. 2016, 116, 9305-9374. 44. Hwang, D. K.; Lee, K.; Kim, J. H.; Im, S.; Park, J. H.; Kim, E. Comparative Studies on the Stability of Polymer Versus SiO2 Gate Dielectrics for Pentacene Thin-Film Transistors. Appl. Phys. Lett. 2006, 89, 093507 (1-3). 45. Qu, M.; Li, H.; Liu, R.; Zhang, S. L.; Qiu, Z. J. Interaction of Bipolaron with the H2O/O2 Redox Couple Causes Current Hysteresis in Organic Thin-Film Transistors. Nat. Commun. 2014, 5, 3185 (1-7). 46. Fung, T. C.; Abe, K.; Kumomi, H.; Kanicki, J. Electrical Instability of RF Sputter Amorphous In-Ga-Zn-O Thin-film Transistors. J. Disp. Technol. 2009, 5, 452-461. 47. Kim, W. S.; Moon, Y. K.; Lee, S.; Kang, B. W.; Kwon, T. S.; Kim, K. T.; Park, J. W. Copper Source/Drain Electrode Contact Resistance Effects in Amorphous Indium–Gallium–Zinc‐ Oxide Thin Film Transistors. Phys. Status Solidi RRL. 2009, 3, 239-241. 48. Wager, J. F.; Yeh, B.; Hoffman, R. L.; Keszler, D. A. An Amorphous Oxide Semiconductor Thin-Film Transistor Route to Oxide Electronics. Curr. Opin. Solid State Mater. Sci. 2014, 18, 53-61.


Page 16 of 25

Page 17 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


49. Mativenga, M.; Seok, M.; Jang, J. Gate Bias-Stress Induced Hump-Effect in Transfer Characteristics of Amorphous-Indium-Galium-Zinc-Oxide Thin-FiLm Transistors with Various Channel Widths. Appl. Phys. Lett. 2011, 99, 122107 (1-3). 50. Valletta, A.; Gaucci, P.; Mariucci, L.; Fortunato, G.; Templier, F. “Hump” Characteristics and Edge Effects in Polysilicon Thin Film Transistors. J. Appl. Phys. 2008, 104, 124511(1-6). 51. Mativenga, M.; Choi, M. H.; Jang, J.; Mruthyunjaya, R.; Tredwell, T. J.; Mozdy, E.; KosikWilliams, C. Degradation Model of Self-Heating Effects in Silicon-on-Glass TFTs. IEEE Trans. Electron Devices. 2011, 58, 2440-2447. 52. Kim, Y.-M.; Jeong, K.-S.; Yun, H.-J.; Yang, S.-D.; Lee, S.-Y.; Kim, Y.-C.; Jeong, J.-K.; Lee, H.-D.; Lee, G.-W. Investigation of Zinc Interstitial Ions as the Origin of Anomalous StressInduced Hump in Amorphous Indium Gallium Zinc Oxide Thin Film Transistors. Appl. Phys. Lett. 2013, 102, 173502 (1-3). 53. Fang, Z.; Zhu, H.; Preston, C.; Han, X.; Li, Y.; Lee, S.; Chai, X.; Chen, G.; Hu, L. Highly Transparent and Writable Wood All-Cellulose Hybrid Nanostructured Paper. J. Mater. Chem. C 2013, 1, 6191-6197.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 1. Characterizations of NFC disintegrated from wood pulp. AFM height images of (a) original NFC and (b) purified NFC. Fibril bundles are marked with red circles. (c) A Transmission electron microscopy (TEM) image showing the fiber morphology of purified NFC with an average fiber diameter of approximately 3.7 nm. (d) Visual appearance of water, purified NFC dispersion, and original NFC dispersion (from left to right). (e) Light scattering behavior of water, purified NFC dispersion, and original NFC dispersion when a horizontal green light passes from left to right with regard to the viewing perspective.


Page 18 of 25

Page 19 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. Characterization of ultra-smooth and clear nanopaper made of purified NFC dispersion by a casting process. (a) A photograph of optically transparent and clear nanopaper detached from glass. (b) An AFM height image of nanopaper substrate for thin-film transistor. Rq denotes the average RMS roughness of nanopaper over a 5×5 µm2 scanning area. (c) Top-view SEM image of nanopaper and (d) a zoom-in image for the red box of (c). (e) Total optical transparency (92% at 550 nm) and (f) transmission haze (0.85% at 550 nm) of the nanopaper.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 3. (a) Cross-sectional schematic of a bottom-gate inverted-staggered IGZO/Al2O3 TFT on a nanopaper substrate. (b) An optical image of a single bottom-gated device with a width-tolength ratio of 500:600 µm. (c) SEM image showing the cross-sectional structure of TFT on nanopaper. (d) High-resolution TEM images of stacked IGZO/Al2O3 channel layer. (e) In, Ga, and Zn element mappings in IGZO active layer. (f) AFM height images of buffer layer, insulating layer, and active layer. Scale bar is 400 nm.


Page 20 of 25

Page 21 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. (a) Output and (b) transfer characteristics of a bottom-gate inverted-staggered IGZO/Al2O3 TFTs on nanopaper, and a comparison of (c) output and (d) transfer characteristics of IGZO/Al2O3 TFTs based on glass and PI substrates with a width-to-length ratio=(500 µm)/(600 µm).



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 5. Zoom-in plot of a linear region (VD=0-5 V) and of the (dID/dVD)-vs-VD characteristics of an IGZO/Al2O3 TFT on (a) nanopaper, (b) PI, and (c) glass.


Page 22 of 25

Page 23 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6. IG-VD curves of IGZO/Al2O3 TFTs on (a) nanopaper and (b) PI and glass substrates. (c) Evolution of transfer characteristics as a function of the applied stress time under PBS (VG = 5V) for IGZO/Al2O3 TFTs on a nanopaper substrate. (d) O1s photoelectron spectra (XPS) of IGZO/Al2O3 TFTs on a nanopaper substrate.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table of Content

In this study, we adopt a bilayer channel structure to fabricate high-performance IGZO/Al2O3 thin-film transistor on a transparent, clear, and ultra-smooth cellulose nanopaper substrate by conventional physical vapor deposition, without a further thermal annealing processing. The obtained device presents a saturation mobility of 15.8 cm2/Vs, an Ion/Ioff ratio of 4.4×105, a threshold voltage (Vth) of -0.42V, and a subthreshold swing (SS) of 0.66V/dec.


Page 24 of 25

Page 25 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table of Content

In this study, we adopt a bilayer channel structure to fabricate high-performance IGZO/Al2O3 thin-film transistor on a transparent, clear, and ultra-smooth cellulose nanopaper substrate by conventional physical vapor deposition, without a further thermal annealing processing. The obtained device presents a saturation mobility of 15.8 cm2/Vs, an Ion/Ioff ratio of 4.4×105, a threshold voltage (Vth) of -0.42V, and a subthreshold swing (SS) of 0.66V/dec.


Room-Temperature Fabrication of High ... - ACS Publications

Recommend Documents