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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Ar plasma treated ZnON transistor for future thin film electronics

To achieve high-mobility and high-reliability oxide thin film transistors (TFTs), ZnON has been investigated following an anion control strategy based on the substitution of oxygen with nitrogen in ZnO. However, as nitrogen possesses, compared to oxygen, a low reactivity with Zn, the chemical composition of ZnON changes easily, causing in turn a degradation of both the performance and the stability. Here, we have solved the issues of long-time stability and composition non-uniformity while maintaining a high channel mobility by adopting the argon plasma process, which can delay the reaction of oxygen with Zn–O–N; as a result, owing to the formation of very fine nano-crystalline structure in stable glassy phase without changes in the chemical composition, the material properties and stability under e-radiation have significantly improved. In particular, the channel mobility of the ZnON TFTs extracted from the pulsed I−V method was measured to be 138 cm{sup 2}/V s.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

High-mobility thin film transistors with neodymium-substituted indium oxide active layer

Thin-film transistors (TFTs) with neodymium-substituted indium oxide (InNdO) channel layer were demonstrated. The structural properties of the InNdO films as a function of annealing temperature have been analyzed using X-ray diffraction and transmission electron microscopy. The InNdO thin films showed polycrystalline nature when annealed at 450 °C with a lattice parameter (cubic cell) of 10.255 Å, which is larger than the cubic In{sub 2}O{sub 3} film (10.117 Å). The high-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy showed that no Nd{sub 2}O{sub 3} clusters were found in the InNdO film, implying that Nd was incorporated into the In{sub 2}O{sub 3} lattice. The InNdO TFTs annealed at 450 °C exhibited more excellent electrical properties with a high mobility of 20.4 cm{sup 2} V{sup −1} s{sup −1} and better electric bias stability compared to those annealed at 300 °C, which was attributed to the reduction of the scattering centers and/or charge traps due to the decrease of the |Nd3d{sub 5/2}{sup 5}4f{sup 4}O2p{sup −1}〉 electron configuration.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

A thermalization energy analysis of the threshold voltage shift in amorphous indium gallium zinc oxide thin film transistors under positive gate bias stress

Thin film transistors (TFTs) employing an amorphous indium gallium zinc oxide (a-IGZO) channel layer exhibit a positive shift in the threshold voltage under the application of positive gate bias stress (PBS). The time and temperature dependence of the threshold voltage shift was measured and analysed using the thermalization energy concept. The peak energy barrier to defect conversion is extracted to be 0.75 eV and the attempt-to-escape frequency is extracted to be 10{sup 7} s{sup −1}. These values are in remarkable agreement with measurements in a-IGZO TFTs under negative gate bias illumination stress (NBIS) reported recently (Flewitt and Powell, J. Appl. Phys. 115, 134501 (2014)). This suggests that the same physical process is responsible for both PBS and NBIS, and supports the oxygen vacancy defect migration model that the authors have previously proposed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Metal-induced crystallization of amorphous zinc tin oxide semiconductors for high mobility thin-film transistors

Transition tantalum induced crystallization of amorphous zinc tin oxide (a-ZTO) was observed at low temperature annealing of 300 °C. Thin-film transistors (TFTs) with an a-ZTO channel layer exhibited a reasonable field-effect mobility of 12.4 cm{sup 2}/V s, subthreshold swing (SS) of 0.39 V/decade, threshold voltage (V{sub TH}) of 1.5 V, and I{sub ON/OFF} ratio of ∼10{sup 7}. A significant improvement in the field-effect mobility (up to ∼33.5 cm{sup 2}/V s) was achieved for crystallized ZTO TFTs: this improvement was accomplished without compromising the SS, V{sub TH}, or I{sub ON/OFF} ratio due to the presence of a highly ordered microstructure.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Boost up the electrical performance of InGaZnO thin film transistors by inserting an ultrathin InGaZnO:H layer

This study examined the electrical performance of bilayer channel InGaZnO:H/InGaZnO thin-film transistors (TFTs). The field-effect mobility and bias stress stability of the InGaZnO device were improved by inserting the hydrogenated InGaZnO ultrathin layer compared to the pure InGaZnO single channel layer device. As a consequence, a high field-effect mobility of 55.3 cm{sup 2}/V s, a high on/off current ratio of 10{sup 8}, a threshold voltage of 0.7 V, and a small sub-threshold swing of 0.18 V/decade have been achieved. The X-ray photoelectron spectroscopy and low-frequency noise analysis suggest that these desirable properties should be attributed to the ultrathin InGaZnO:H layer, which could provide suitable carrier concentration and reduce the average trap density near the channel and insulator layer interface. Meanwhile, the channel conductance of the bilayer device is controlled by thick InGaZnO layer through formation barrier energy for electron transport at the interface of InGaZnO:H and InGaZnO layer. These improved electrical properties have represented a great step towards the achievement of transparent, high performances, and low-cost metal oxide TFTs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

InN thin-film transistors fabricated on polymer sheets using pulsed sputtering deposition at room temperature

Indium nitride (InN) is potentially suitable for the fabrication of high performance thin-film transistors (TFTs) because of its high electron mobility and peak electron velocity. However, InN is usually grown using a high temperature growth process, which is incompatible with large-area and lightweight TFT substrates. In this study, we report on the room temperature growth of InN films on flexible polyimide sheets using pulsed sputtering deposition. In addition, we report on the fabrication of InN-based TFTs on flexible polyimide sheets and the operation of these devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Homogeneous double-layer amorphous Si-doped indium oxide thin-film transistors for control of turn-on voltage

We fabricated homogeneous double-layer amorphous Si-doped indium oxide (ISO) thin-film transistors (TFTs) with an insulating ISO cap layer on top of a semiconducting ISO bottom channel layer. The homogeneously stacked ISO TFT exhibited high mobility (19.6 cm{sup 2}/V s) and normally-off characteristics after annealing in air. It exhibited normally-off characteristics because the ISO insulator suppressed oxygen desorption, which suppressed the formation of oxygen vacancies (V{sub O}) in the semiconducting ISO. Furthermore, we investigated the recovery of the double-layer ISO TFT, after a large negative shift in turn-on voltage caused by hydrogen annealing, by treating it with annealing in ozone. The recovery in turn-on voltage indicates that the dense V{sub O} in the semiconducting ISO can be partially filled through the insulator ISO. Controlling molecule penetration in the homogeneous double layer is useful for adjusting the properties of TFTs in advanced oxide electronics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Improving positive and negative bias illumination stress stability in parylene passivated IGZO transistors

The impact of a parylene top-coating layer on the illumination and bias stress instabilities of indium-gallium-zinc oxide thin-film transistors (TFTs) is presented and discussed. The parylene coating substantially reduces the threshold voltage shift caused by continuous application of a gate bias and light exposure. The operational stability improves by 75%, and the light induced instability is reduced by 35%. The operational stability is quantified by fitting the threshold voltage shift with a stretched exponential model. Storage time as long as 7 months does not cause any measurable degradation on the electrical performance. It is proposed that parylene plays not only the role of an encapsulation layer but also of a defect passivation on the top semiconductor surface. It is also reported that depletion-mode TFTs are less sensitive to light induced instabilities. This is attributed to a defect neutralization process in the presence of free electrons.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Topological field theory with Haagerup symmetry

Here, we construct a (1 + 1)d topological field theory (TFT) whose topological defect lines (TDLs) realize the transparent Haagerup $\mathscr{H}$ 3 fusion category. This TFT has six vacua, and each of the three non-invertible simple TDLs hosts three defect operators, giving rise to a total of 15 point-like operators. The TFT data, including the three-point coefficients and lasso diagrams, are determined by solving all the sphere four-point crossing equations and torus one-point modular invariance equations. We further verify that the Cardy states furnish a non-negative integer matrix representation under TDL fusion. While many of the constraints we derive are not limited to this particular TFT with six vacua, we leave open the construction of TFTs with two or four vacua. Finally, TFTs realizing the Haagerup $\mathscr{H}$ 1 and $\mathscr{H}$ 2 fusion categories can be obtained by gauging algebra objects. This article makes a modest offering in our pursuit of exotica and the quest for their eventual conformity.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Expeditious, scalable solution growth of metal oxide films by combustion blade coating for flexible electronics

Metal oxide (MO) semiconductor thin films prepared from solution typically require multiple hours of thermal annealing to achieve optimal lattice densification, efficient charge transport, and stable device operation, presenting a major barrier to roll-to-roll manufacturing. Here, we report a highly efficient, cofuel-assisted scalable combustion blade-coating (CBC) process for MO film growth, which involves introducing both a fluorinated fuel and a preannealing step to remove deleterious organic contaminants and promote complete combustion. Ultrafast reaction and metal–oxygen–metal (M-O-M) lattice condensation then occur within 10–60 s at 200–350 °C for representative MO semiconductor [indium oxide (In 2 O 3 ), indium-zinc oxide (IZO), indium-gallium-zinc oxide (IGZO)] and dielectric [aluminum oxide (Al 2 O 3 )] films. Furthermore, wafer-scale CBC fabrication of IGZO-Al 2 O 3 thin-film transistors (TFTs) (60-s annealing) with field-effect mobilities as high as ~25 cm 2 V –1 s –1 and negligible threshold voltage deterioration in a demanding 4,000-s bias stress test are realized. Combined with polymer dielectrics, the CBC-derived IGZO TFTs on polyimide substrates exhibit high flexibility when bent to a 3-mm radius, with performance bending stability over 1,000 cycles.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Plasmon-enhanced photocurrent of Ge-doped InGaO thin film transistors using silver nanoparticles

Germanium-doped indium-gallium oxide (GIGO) thin film transistors (TFTs) decorated with silver (Ag) nanoparticles (NPs) were prepared to study the plasmon effect. GIGO films of various thicknesses were deposited on SiO{sub 2}/Si substrates, and Ag NPs (∼25 nm in diameter) were formed using a thermal evaporator and a postannealing process. The Ag NPs effectively absorbed light in the wavelength range of 500 and 600 nm, which corresponds to the plasmonic effect. Due to the plasmon resonance of Ag NPs, a significantly enhanced photocurrent was observed on the devices. The current increased by 348% with exposure to light when the Ag NPs were formed at the interface between the 10-nm-thick GIGO film and SiO{sub 2} substrate. The increased photocurrent revealed the presence of strong coupling between the localized plasmon and electrical carrier of the devices. The results show that the photocurrent of GIGO TFTs can be greatly enhanced when the plasmonic Ag NPs are located in the channel region of the devices.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Stable organic thin-film transistors

Organic thin-film transistors (OTFTs) can be fabricated at moderate temperatures and through cost-effective solution-based processes on a wide range of low-cost flexible and deformable substrates. Although the charge mobility of state-of-the-art OTFTs is superior to that of amorphous silicon and approaches that of amorphous oxide thin-film transistors (TFTs), their operational stability generally remains inferior and a point of concern for their commercial deployment. We report on an exhaustive characterization of OTFTs with an ultrathin bilayer gate dielectric comprising the amorphous fluoropolymer CYTOP and an Al2O3:HfO2 nanolaminate. Threshold voltage shifts measured at room temperatureovertimeperiods upto5.9×105 s do not vary monotonically and remain below 0.2 V in microcrystalline OTFTs (mc-OTFTs) with field-effect carrier mobility values up to 1.6 cm2 V-1 s-1. Modeling of these shifts as a function of time with a double stretched-exponential (DSE) function suggests that two compensating aging mechanisms are at play and responsible for this high stability. The measured threshold voltage shifts at temperatures up to 75°C represent at least a one-order-of-magnitude improvement in the operational stability over previous reports, bringing OTFT technologies to a performance level comparable to that reported in the scientific literature for other commercial TFTs technologies.

42 ENGINEERING↗
DOE OSTI2019

P‐23: Enhancement in the Mobility and the Stability of Solution‐Processed Zinc‐Tin Oxide Thin‐Film Transistors Using Alkali Metal Superoxide

We have studied how to improve the mobility and stability of solution processed zinc‐tin oxide thin‐film transistors (ZTO TFTs) simultaneously using multifunctional potassium superoxide precursor. Potassium cations in the potassium superoxide precursor acts as a shallow donor in the ZTO thin film to improve the carrier concentration (electron), which allows the potassium‐doped ZTO TFT to exhibit high mobility. Then, the anion of the precursor exists as a superoxide radical, and it showed the effect of reducing the oxygen vacancy in the process of forming the oxide thin film Consequently, potassium‐doped ZTO TFT using potassium superoxide precursor exhibited improved mobility and stability, showing an increase in the mobility from 5.11 to 8.36 cm 2 /Vs and a decrease in the threshold voltage shift from 4.65 to 3.36 V under a negative bias temperature illumination stress test conducted over 5,000 sec..

Jung, Tae Soo↗
DOE OSTI2024

Nozzle-Free Printing of CNT Electronics Using Laser-Generated Focused Ultrasound

Printed electronics have made remarkable progress in recent years and inkjet printing (IJP) has emerged as one of the leading methods for fabricating printed electronic devices. However, challenges such as nozzle clogging, and strict ink formulation constraints have limited their widespread use. To address this issue, a novel nozzle-free printing technology is explored, which is enabled by laser-generated focused ultrasound, as a potential alternative printing modality called Shock-wave Jet Printing (SJP). Specifically, the performance of SJP-printed and IJP-printed bottom-gated carbon nanotube (CNT) thin film transistors (TFTs) is compared. While IJP required ten print passes to achieve fully functional devices with channel dimensions ranging from tens to hundreds of micrometers, SJP achieved comparable performance with just a single pass. For optimized devices, SJP demonstrated six times higher maximum mobility than IJP-printed devices. Furthermore, the advantages of nozzle-free printing are evident, as SJP successfully printed stored and unsonicated inks, delivering moderate electrical performance, whereas IJP suffered from nozzle clogging due to CNT agglomeration. Moreover, SJP can print significantly longer CNTs, spanning the entire range of tube lengths of commercially available CNT ink. The findings from this study contribute to the advancement of nanomaterial printing, ink formulation, and the development of cost-effective printable electronics.

47 OTHER INSTRUMENTATION↗
DOE OSTI2011

Suppression in the negative bias illumination instability of Zn-Sn-O transistor using oxygen plasma treatment

This study examined the effect of oxygen plasma treatment on light-enhanced bias instability in Zn-Sn-O (ZTO) thin film transistors (TFTs). The treated ZTO TFT exhibited only a threshold voltage (V{sub th}) shift of -2.05 V under negative bias illumination stress (NBIS) conditions, whereas the pristine device suffered from a negative V{sub th} shift of 3.76 V under identical conditions. X-ray photoelectron spectroscopic analysis revealed that the oxygen vacancy defect density was diminished via the oxygen plasma treatment. This suggests the V{sub th} degradation under NBIS is due to photo-transition of oxygen vacancy defects.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Enhanced stability against bias-stress of metal-oxide thin film transistors deposited at elevated temperatures

Transparent zinc-tin-oxide (ZTO) thin film transistors (TFTs) have been prepared by DC magnetron sputtering. Compared to reference devices with a channel deposited at room temperature and subsequently annealing at 400 deg. C, a substantially enhanced stability against bias stress is evidenced for devices with in-situ substrate heating during deposition (400 deg. C). A reduced density of sub-gap defect states in TFT channels prepared with in-situ substrate heating is found. Concomitantly, a reduced sensitivity to the adsorption of ambient gases is evidenced for the in-situ heated devices. This finding is of particular importance for an application as driver electronics for organic light emitting diode displays.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Recovery from ultraviolet-induced threshold voltage shift in indium gallium zinc oxide thin film transistors by positive gate bias

The effect of short-duration ultraviolet (UV) exposure on the threshold voltage (V{sub th}) of amorphous indium gallium zinc oxide thin film transistors (TFTs) and its recovery characteristics were investigated. The V{sub th} exhibited a significant negative shift after UV exposure. The V{sub th} instability caused by UV illumination is attributed to the positive charge trapping in the dielectric layer and/or at the channel/dielectric interface. The illuminated devices showed a slow recovery in threshold voltage without external bias. However, an instant recovery can be achieved by the application of positive gate pulses, which is due to the elimination of the positive trapped charges as a result of the presence of a large amount of field-induced electrons in the interface region.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Double-metal-gate nanocrystalline Si thin film transistors with flexible threshold voltage controllability

We fabricated nano-crystalline Si (nc-Si:H) thin-film transistors (TFTs) with a double-metal-gate structure, which showed a high electron-mobility (μ{sub FE}) and adjustable threshold voltages (V{sub th}). The nc-Si:H channel and source/drain (S/D) of the multilayered TFT were deposited at 375 °C by inductively coupled plasma chemical vapor deposition. The low grain-boundary defect density of the channel layer is responsible for the high μ{sub FE} of 370 cm{sup 2}/V-s, a steep subthreshold slope of 90 mV/decade, and a low V{sub th} of −0.64 V. When biased with the double-gate driving mode, the device shows a tunable V{sub th} value extending from −1 V up to 2.7 V.

77 NANOSCIENCE AND NANOTECHNOLOGY↗