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Journal ArticleDOI

Low-voltage pentacene organic field-effect transistors with high-κ HfO2 gate dielectrics and high stability under bias stress

02 Dec 2009-Applied Physics Letters (American Institute of Physics)-Vol. 95, Iss: 22, pp 223302
TL;DR: In this article, a low-voltage pentacene organic field effect transistors are demonstrated with high-κ hafnium dioxide gate dielectrics grown by atomic layer deposition at 200 °C.
Abstract: Low-voltage pentacene organic field-effect transistors are demonstrated (operating voltage of −3 V) with high-κ hafnium dioxide gate dielectrics grown by atomic layer deposition at 200 °C. A high hole mobility of 0.39 cm2/V s with low threshold voltage (<−0.5 V) and low subthreshold slope of 120 mV/dec is achieved with a HfO2 dielectric layer modified with a phosphonic acid based treatment. A high value of 94.8 nF/V s is obtained for the product of mobility and capacitance density. The devices show excellent bias stress stability with or without the phosphonic acid at the HfO2 gate dielectric surface.
Citations
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Journal ArticleDOI
TL;DR: Although the complexity of OFET, OLED, and OPV makes revealing their structure-property relationships difficult, a cooperative approach incorporating virtual ML, human consideration, and fast experimental screening may help to navigate growth and development in the organic electronics field.
Abstract: Organic electronics such as organic field-effect transistors (OFET), organic light-emitting diodes (OLED), and organic photovoltaics (OPV) have flourished over the last three decades, largely due to the development of new conjugated materials. Their designs have evolved through incremental modification and stepwise inspiration by researchers; however, a complete survey of the large molecular space is experimentally intractable. Machine learning (ML), based on the rapidly growing field of artificial intelligence technology, offers high throughput material exploration that is more efficient than high-cost quantum chemical calculations. This review describes the present status and perspective of ML-based development (materials informatics) of organic electronics. Although the complexity of OFET, OLED, and OPV makes revealing their structure-property relationships difficult, a cooperative approach incorporating virtual ML, human consideration, and fast experimental screening may help to navigate growth and development in the organic electronics field.

41 citations

Journal ArticleDOI
TL;DR: It has been demonstrated that the low processing temperature of amorphous STO makes it the most suitable gate dielectric for flexible and transparent organic devices to operate under low voltage.
Abstract: We report that the pervoskite material, strontium titanate (STO) can be used as a gate dielectric layer of flexible and low voltage organic field effect transistor (OFET). The crystallinity, dielectric constant, and surface morphology of STO films can be controlled by the engineering of the growth condition. Under optimized growth condition, amorphous films of STO show a much better gate dielectric compared to other gate dielectrics used to date, with very small leakage current density for flexible and low voltage (<5 V) OFETs. The amorphous STO film decreases the interface trap density at organic/dielectric interface substantially. Pentacene transistors with amorphous STO gate dielectric show high mobility of 2 cm(2)/(V s), on/off ratio of 10(6), subthreshold swing of 0.3 V/dec and low interface trap density. Similarly excellent performance has been obtained in copper phthalocyanine (CuPc) based OFETs with on/off ratio ∼10(5) and carrier mobility ∼5.9 × 10(-2) cm(2)/(V s). Moreover, the operating voltage (∼5 V) has been reduced by more than one order of magnitude. It has been demonstrated that the low processing temperature of amorphous STO makes it the most suitable gate dielectric for flexible and transparent organic devices to operate under low voltage.

32 citations

Journal ArticleDOI
TL;DR: In this article, stable organic field effect transistors (OFETs) with an ultra-thin HfO2 gate insulator deposited directly on top of rubrene single crystals by atomic layer deposition (ALD) are presented.
Abstract: We have produced stable organic field-effect transistors (OFETs) with an ultra-thin HfO2 gate insulator deposited directly on top of rubrene single crystals by atomic layer deposition (ALD). We find that ALD is a gentle deposition process to grow thin films without damaging rubrene single crystals, as results these devices have a negligibly small threshold voltage and are very stable against gate-bias-stress, and the mobility exceeds 1 cm2/V s. Moreover, the devices show very little degradation even when kept in air for more than 2 months. These results demonstrate thin HfO2 layers deposited by ALD to be well suited as high capacitance gate dielectrics in OFETs operating at small gate voltage. In addition, the dielectric layer acts as an effective passivation layer to protect the organic semiconductor.

29 citations

Journal ArticleDOI
TL;DR: In this article, a low operating voltage (<2 V) organic field effect transistor (OFET) using phenylhexyltrichlorosilane (PTS) self-assembled monolayer (SAM) dielectric and copper phthalocyanine (CuPc) as semiconductor with improved mobility and threshold voltage stability was demonstrated.
Abstract: A low operating voltage (<2 V) organic field-effect transistor (OFET) using phenylhexyltrichlorosilane (PTS) self-assembled monolayer (SAM) dielectric and copper phthalocyanine (CuPc) as semiconductor with improved mobility (0.035 cm2 V−1 s−1) and threshold voltage stability was demonstrated. This device showed better performance when compared to an OFET with octyltrichlorosilane (OTS-8) SAM dielectric. The improved mobility was attributed to the 2D growth mode of CuPc on PTS SAM because of surface energy matching between the two, whereas CuPc film on OTS-8 showed a 3D growth mode with larger grain boundary density. The higher threshold voltage stability of OFETs on PTS SAM was attributed to the efficient coverage and screening of trap centres at dielectric/semiconductor interface due to stronger intermolecular linking and formation of closely packed surface by the bulky phenyl end groups. Decrease in grain boundaries offered by 2D growth of CuPc for electron and hole trapping was also found to be another reason for improved threshold voltage stability. The results indicated that the nature of the end group of SAM dielectric, surface chemistry of dielectric and initial growth mode of semiconductors are all responsible for improvement in threshold voltage stability and enhanced performance of OFET.

24 citations

References
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Journal ArticleDOI
TL;DR: Flexible active-matrix monochrome electrophoretic displays based on solution-processed organic transistors on 25-μm-thick polyimide substrates based on 1,888 transistors are demonstrated, which are the largest organic integrated circuits reported to date.
Abstract: At present, flexible displays are an important focus of research1,2,3 Further development of large, flexible displays requires a cost-effective manufacturing process for the active-matrix backplane, which contains one transistor per pixel One way to further reduce costs is to integrate (part of) the display drive circuitry, such as row shift registers, directly on the display substrate Here, we demonstrate flexible active-matrix monochrome electrophoretic displays based on solution-processed organic transistors on 25-μm-thick polyimide substrates The displays can be bent to a radius of 1 cm without significant loss in performance Using the same process flow we prepared row shift registers With 1,888 transistors, these are the largest organic integrated circuits reported to date More importantly, the operating frequency of 5 kHz is sufficiently high to allow integration with the display operating at video speed This work therefore represents a major step towards 'system-on-plastic'

1,577 citations

Journal ArticleDOI
TL;DR: In this article, the properties of low-temperature Al2O3 ALD films were investigated versus growth temperature by depositing films on Si(100) substrates and quartz crystal microbalance (QCM) sensors.
Abstract: Al2O3 films were deposited by atomic layer deposition (ALD) at temperatures as low as 33 °C in a viscous-flow reactor using alternating exposures of Al(CH3)3 (trimethylaluminum [TMA]) and H2O. Low-temperature Al2O3 ALD films have the potential to coat thermally fragile substrates such as organic, polymeric, or biological materials. The properties of low-temperature Al2O3 ALD films were investigated versus growth temperature by depositing films on Si(100) substrates and quartz crystal microbalance (QCM) sensors. Al2O3 film thicknesses, growth rates, densities, and optical properties were determined using surface profilometry, atomic force microscopy (AFM), QCM, and spectroscopic ellipsometry. Al2O3 film densities were lower at lower deposition temperatures. Al2O3 ALD film densities were 3.0 g/cm3 at 177 °C and 2.5 g/cm3 at 33 °C. AFM images showed that Al2O3 ALD films grown at low temperatures were very smooth with a root-mean-squared (RMS) roughness of only 4 ± 1 A. Current−voltage and capacitance−voltage...

1,274 citations

Book
01 Jan 1996
TL;DR: Semiconductor Models -- A General Introduction, Field Effect Introduction -- the J-FET and MESFET, and Electrostatics -- Mostly Qualitative Formulation.
Abstract: I. SEMICONDUCTOR FUNDAMENTALS. 1. Semiconductors -- A General Introduction. General Material Properties. Crystal Structure. Crystal Growth. 2. Carrier Modeling. The Quantization Concept. Semiconductor Models. Carrier Properties. State and Carrier Distributions. Equilibrium Carrier Concentrations. 3. Carrier Action. Drift. Diffusion. Recombination -- Generation. Equations of State. Supplemental Concepts. 4. Basics of Device Fabrication. Fabrication Processes. Device Fabrication Examples. R1. Part I Supplement and Review. Alternative/Supplemental Reading List. Figure Sources/Cited References. Review List of Terms. Part I Review Problem Sets and Answers. IIA. PN JUNCTION DIODES. 5. PN Junction Electrostatics. Preliminaries. Quantitative Electrostatic Relationships. 6. PN Junction Diode -- I-V Characteristics. The Ideal Diode Equation. Deviations from the Ideal. Special Considerations. 7. PN Junction Diode -- Small-Signal Admittance. Introduction. Reverse-Bias Junction Capacitance. Forward-Bias Diffusion Admittance. 8. PN Junction Diode -- Transient Response. Turn-Off Transient. Turn-On Transient. 9. Optoelectronic Diodes. Introduction. Photodiodes. Solar Cells. LEDs. IIB. BJTS AND OTHER JUNCTION DEVICES. 10. BJT Fundamentals. Terminology. Fabrication. Electrostatics. Introductory Operational Considerations. Performance Parameters. 11. BJT Static Characteristics. Ideal Transistor Analysis. Deviations from the Ideal. Modern BJT Structures. 12. BJT Dynamic Response Modeling. Equivalent Circuits. Transient (Switching) Response. 13. PNPN Devices. Silicon Controlled Rectifier (SCR). SCR Operational Theory. Practical Turn-on/Turn-off Considerations. Other PNPN Devices. 14. MS Contacts and Schottky Diodes. Ideal MS Contacts. Schottky Diode. Practical Contact Considerations. R2. Part II Supplement and Review. Alternative/Supplemental Reading List. Figure Sources/Cited References. Review List of Terms. Part II Review Problem Sets and Answers. III. FIELD EFFECT DEVICES. 15. Field Effect Introduction -- the J-FET and MESFET. General Introduction. J-FET. MESFET. 16. MOS Fundamentals. Ideal Structure Definition. Electrostatics -- Mostly Qualitative. Electrostatics -- Quantitative Formulation. Capacitance-Voltage Characteristics. 17. MOSFETs -- The Essentials. Qualitative Theory of Operation. Quantitative ID - VD Relationships. ac Response. 18. Nonideal MOS. Metal-Semiconductor Workfunction Difference. Oxide Charges. MOSFET Threshold Considerations. 19. Modern FET Structures. Small Dimension Effects. Select Structure Survey. R3. Part III Supplement and Review. Alternative/Supplemental Reading List. Figure Sources/Cited References. Review List of Terms. Part III Review Problem Sets and Answers. Appendix A. Elements of Quantum Mechanics. Appendix B. MOS Semiconductor Electrostatics -- Exact Solution. Appendix C. MOS C-V Supplement. Appendix D. MOS I-Vsupplement. Appendix E. List of Symbols. Appendix M. MATLAB Program Script.

1,048 citations

Journal ArticleDOI
TL;DR: In this article, a pentacene organic thin-film transistor (OTFT) driven active matrix organic light-emitting diode (OLED) displays on flexible polyethylene terephthalete substrates were fabricated.
Abstract: We have fabricated pentacene organic thin-film transistor (OTFT) driven active matrix organic light-emitting diode (OLED) displays on flexible polyethylene terephthalete substrates These displays have 48×48 bottom-emission OLED pixels with two pentacene OTFTs used per pixel Parylene is used to isolate the OTFTs and OLEDs with good OTFT yield and uniformity

577 citations

Journal ArticleDOI
05 Jul 2005
TL;DR: Progress is reported on in developing materials, processes, and devices for the realization of ultralow-cost printed RFID tags using novel pentacene and oligothiophene precursors for pMOS and ZnO nanoparticles for nMOS.
Abstract: Printed electronics provides a promising potential pathway toward the realization of ultralow-cost RFID tags for item-level tracking of consumer goods. Here, we report on our progress in developing materials, processes, and devices for the realization of ultralow-cost printed RFID tags. Using printed nanoparticle patterns that are subsequently sintered at plastic-compatible temperatures, low-resistance interconnects and passive components have been realized. Simultaneously, printed transistors with mobilities >10/sup -1/ cm/sup 2//V-s have been realized using novel pentacene and oligothiophene precursors for pMOS and ZnO nanoparticles for nMOS. AC performance of these devices is adequate for 135-kHz RFID, though significant work remains to be done to achieve 13.56-MHz operation.

501 citations