Showing papers on "Field effect published in 2010"
TL;DR: This article can reversibly switch between two distinct exchange-bias states by switching the ferroelectric polarization of BiFeO(3), an important step towards controlling magnetization with electric fields, which may enable a new class of electrically controllable spintronic devices and provide a new basis for producing electrically controlled spin-polarized currents.
Abstract: The control of magnetization by electric fields is important for applications in data storage and sensing. An efficient control of exchange bias by electric fields has now been achieved in thin-film devices in which a ferroelectric antiferromagnet is coupled to a ferromagnet.
628 citations
TL;DR: Recently, electric double layer transistors (EDLT), in which an ionic liquid or an electrolyte is used as a gate dielectric, have been the subject of intense research and rapidly increasing interest owing to the considerable amount of charge which can be provided by this technique.
Abstract: Field-effect transistors (FETs) are ubiquitous in our everyday life. Applying the fi eld-effect technique to new materials can lead not only to a modulation of their conductivity, but also to electrostatically driven phase transitions. [ 1–3 ] This method is particularly appealing for complex oxides, which exhibit a wide range of functional properties including metal-insulator (MI) transitions, colossal magnetoresistance and highT c superconductivity, all very sensitive to the level of electronic doping. The electric fi eld-effect approach seems thus to be a natural tool to try controlling and modifying reversibly the ground states of these materials. However, the required changes in carrier densities, which typically exceed 10 14 cm − 2 , [ 1 , 4 ] are diffi cult to induce with standard dielectrics. Recently, electric double layer transistors (EDLT), in which an ionic liquid or an electrolyte is used as a gate dielectric, have been the subject of intense research and rapidly increasing interest owing to the considerable amount of charge which can be provided by this technique. [ 5–7 ]
258 citations
TL;DR: The electronic and optoelectronic properties of FRGO FETs are found to be closely related to their bandgap energy, which has great application potential in the field of photodetection.
Abstract: Thin film field-effect phototransistors (FETs) can be developed from bandgap-tunable, solution-processed, few-layer reduced graphene oxide (FRGO) films. Large-area FRGO films with tunable bandgaps ranging from 2.2 eV to 0.5 eV can be achieved readily by solution-processing technique such as spin-coating. The electronic and optoelectronic properties of FRGO FETs are found to be closely related to their bandgap energy. The resulting phototransistor has great application potential in the field of photodetection.
201 citations
TL;DR: A mechanism for this transconductance hysteresis is proposed that involves water-related defects, formed during the hydration of the near-surface silanol groups in the bulk SiO(2), that can act as electron traps.
Abstract: We have studied the intrinsic doping level and gate hysteresis of graphene-based field effect transistors (FETs) fabricated over Si/SiO2 substrates. It was found that the high p-doping level of graphene in some as-prepared devices can be reversed by vacuum degassing at room temperature or above depending on the degree of hydrophobicity and/or hydration of the underlying SiO2 substrate. Charge neutrality point (CNP) hysteresis, consisting of the shift of the charge neutrality point (or Dirac peak) upon reversal of the gate voltage sweep direction, was also greatly reduced upon vacuum degassing. However, another type of hysteresis, consisting of the change in the transconductance upon reversal of the gate voltage sweep direction, persists even after long-term vacuum annealing at 200 °C, when SiO2 surface-bound water is expected to be desorbed. We propose a mechanism for this transconductance hysteresis that involves water-related defects, formed during the hydration of the near-surface silanol groups in the bulk SiO2, that can act as electron traps.
159 citations
TL;DR: In this paper, a detailed analysis of three-terminal field effect transistor-like devices using thin film VO2 as the channel layer is presented, where the gate is separated from the channel through an insulating gate oxide layer, enabling true probing of the field effect with minimal or no interference from large leakage currents flowing directly from the electrode.
Abstract: Electrostatic control of the metal-insulator transition (MIT) in an oxide semiconductor could potentially impact the emerging field of oxide electronics. Vanadium dioxide (VO2) is of particular interest due to the fact that the MIT happens in the vicinity of room temperature and it is considered to exhibit the Mott transition. We present a detailed account of our experimental investigation into three-terminal field effect transistor-like devices using thin film VO2 as the channel layer. The gate is separated from the channel through an insulating gate oxide layer, enabling true probing of the field effect with minimal or no interference from large leakage currents flowing directly from the electrode. The influence of the fabrication of multiple components of the device, including the gate oxide deposition, on the VO2 film characteristics is discussed. Further, we discuss the effect of the gate voltage on the device response, point out some of the unusual characteristics including temporal dependence. A re...
157 citations
TL;DR: In this article, an optical second-harmonic generation was employed to distinguish between the influence of field-effect passivation and chemical passivation through the measurement of the electric field in the c-Si space charge region.
Abstract: Al2O3 synthesized by plasma-assisted atomic layer deposition yields excellent surface passivation of crystalline silicon (c-Si) for films down to ∼5 nm in thickness. Optical second-harmonic generation was employed to distinguish between the influence of field-effect passivation and chemical passivation through the measurement of the electric field in the c-Si space-charge region. It is demonstrated that this electric field—and hence the negative fixed charge density—is virtually unaffected by the Al2O3 thickness between 2 and 20 nm indicating that a decrease in chemical passivation causes the reduced passivation performance for <5 nm thick Al2O3 films.
126 citations
TL;DR: The field effect control offers a more flexible and electrically compatible approach to regulate the DNA translocation through a nanopore for DNA sequencing.
Abstract: Field effect regulation of DNA nanoparticle translocation through a nanopore using a gate electrode is investigated using a continuum model, composed of the coupled Poisson−Nernst−Planck equations for the ionic mass transport and the Navier−Stokes equations for the hydrodynamic field. The field effect regulation of the DNA translocation relies on the induced electroosmotic flow (EOF) and the particle−nanopore electrostatic interaction. When the electrical double layers (EDLs) formed adjacent to the DNA nanoparticle and the nanopore wall are overlapped, the particle−nanopore electrostatic interaction could dominate over the EOF effect, which enables the DNA trapping inside the nanopore when the applied electric field is relatively low. However, the particle−nanopore electrostatic interaction becomes negligible if the EDLs are not overlapped. When the applied electric field is relatively high, a negative gate potential can slow down the DNA translocation by an order of magnitude, compared to a floating gate...
109 citations
TL;DR: In this article, a numerical simulation of the screening current-induced magnetic field for YBCO solenoids is presented. But the simulation is limited to the case of a single Y-coil.
Abstract: A numerical simulation method which deals with the screening current-induced magnetic field for YBCO coils, including the self field effect induced by the transport current, has been developed. The simulation agrees well with the experimental results for an YBCO solenoid. Based on the numerical simulation, the effect of coil shape on the screening current-induced magnetic field intensity for the YBCO coils has been investigated. The field was demonstrated to reach a maximum if the solenoid corresponds to the minimum-volume design; it amounts to as large as -18% of the central magnetic field. Two major problems must be considered for YBCO coils regarding the screening current: (a) a reduction in the central magnetic field by the screening current and (b) a temporal drift of the apparent magnetic field due to relaxation of the screening current by flux creep. It is suggested that the latter can be suppressed by a current sweep reversal technique.
93 citations
75 citations
TL;DR: In this article, the effect of the laser field on the nonlinear optical properties of a square quantum well under the applied electric field is investigated theoretically, and the calculations are performed in saturation limit using the density matrix formalism and the effective mass approach.
66 citations
TL;DR: In this article, a universal mobility model is obtained using a field effect technique and capacitancevoltage method for thin-film transistors (TFTs) in next-generation flat-panel displays.
Abstract: Amorphous In–Ga–Zn–O (α-IGZO) is expected for thin-film transistors (TFTs) in next-generation flat-panel displays but its intrinsic properties are not understood well and different mobility models have been applied to different films. This letter reports that a universal mobility model is obtained using a field-effect technique and capacitance-voltage method. Electrical characteristics of α-IGZO TFTs subjected to different annealing are reproduced using the mobility model and different trap densities. The present achievement will be a necessary basis to establish device and circuit simulators for α-IGZO-based electronic applications.
TL;DR: In this article, the role of the polarization gradient and intrinsic surface energy, interface dipoles, and free charges on polarization dynamics is explored, and the intrinsic field effects, which originated at the ferroelectric-semiconductor interface, lead to the surface band bending and result into the formation of depletion space charge layer near the semiconductor surface.
Abstract: Using Landau-Ginzburg-Devonshire approach we calculated the equilibrium distributions of electric field, polarization, and space charge in the ferroelectric-semiconductor heterostructures containing proper or incipient ferroelectric thin films. The role of the polarization gradient and intrinsic surface energy, interface dipoles, and free charges on polarization dynamics are specifically explored. The intrinsic field effects, which originated at the ferroelectric-semiconductor interface, lead to the surface band bending and result into the formation of depletion space-charge layer near the semiconductor surface. During the local polarization reversal (caused by the electric field of the nanosized tip of the scanning probe microscope) the thickness and charge of the interface layer drastically changes, in particular, the sign of the screening carriers is determined by the polarization direction. Obtained analytical solutions could be extended to analyze polarization-mediated electronic transport.
TL;DR: In this paper, the authors demonstrate the side gated field effect transistors individually controlled by local metal side gates, which can have on/off ratio comparable with that of the global back gate, and can be tuned in a large range by the back gate and/or a second side gate.
Abstract: We demonstrate ambipolar graphene field effect transistors individually controlled by local metal side gates. The side gated field effect can have on/off ratio comparable with that of the global back gate, and can be tuned in a large range by the back gate and/or a second side gate. We also find that the side gated field effect is significantly stronger by electrically floating the back gate compared to grounding the back gate, consistent with the finding from electrostatic simulation.
TL;DR: In this paper, the authors attributed the low field effect to a two-level electronic structure in a defect complex that contains Mg located on a Ti site, giving rise to underbonded oxide ions in the vicinity of the defect complex, that are readily ionised on application of a dc bias.
Abstract: The electrical conductivity of ceramics of composition Ba(Ti1−xMgx)O3−x: 0.00003 ≤ x ≤ 0.01 increases with time on application of a small dc bias voltage in the range 1 to 50 V cm−1 and at temperatures in the range 200 to 600 °C. The conductivity increase is reversible on removal of the dc bias. This low field effect is not observed in undoped BaTiO3, is intrinsic, is a property of the bulk material, is independent of atmosphere and electrode material, is not associated with charge injection into the BaTiO3 conduction band and differs from those of both varistors and memristors. The origin of the effect is attributed to a two-level electronic structure in a defect complex that contains Mg located on a Ti site, giving rise to underbonded oxide ions in the vicinity of the defect complex that are readily ionised on application of a dc bias. Conduction is predominantly p-type and therefore, holes located on oxygen, as O− ions, are more mobile than both electrons in Ti 3d levels and oxygen vacancies.
TL;DR: In this paper, the field effect modulation of ionic transport through an array of cylindrical nanopores fabricated in silicon-on-insulator substrates is demonstrated, and a numerical model based on Brownian dynamics reproduces the measured data.
Abstract: Results demonstrating the field effect modulation of ionic transport through an array of cylindrical nanopores fabricated in silicon-on-insulator substrates are presented. Pronounced modulation of the conductance is observed at low electrolyte concentrations when the electric double layers within the nanopores are overlapping. A numerical model based on Brownian dynamics reproduces the measured data.
TL;DR: The observation of built-in potentials makes an important connection between organic junctions and textbook descriptions of inorganic devices, and these kinds of potentials may prove to be controlling factors in charge separation efficiency in organic photovoltaics.
Abstract: The operation of organic diodes in solar cells and light-emitting displays strongly depends on the properties of the interfaces between hole- and electron-carrying organic semiconductors. Such interfaces are difficult to characterize, as they are usually buried under the surface or exist as an irregular “bulk heterojunction.” Using a unique fluorinated barrier layer-based lithographic technique, we fabricated a lateral organic p-n junction, allowing the first observation of the potential at an organic p-n interface simultaneously with the charge transport measurements. We find that the diode characteristics of the device (current output and rectification ratio) are consistent with the changes in the surface potentials near the junction, and the current-voltage curves and junction potentials are strongly and self-consistently modulated by a third, gate electrode. The generality of our technique makes this an attractive method to investigate the physics of organic semiconductor junctions. The lithographic technique is applicable to a wide variety of soft material patterns. The observation of built-in potentials makes an important connection between organic junctions and textbook descriptions of inorganic devices. Finally, these kinds of potentials may prove to be controlling factors in charge separation efficiency in organic photovoltaics.
TL;DR: In this paper, Cadmium sulfide thin film transistors were demonstrated as the n-type device for use in flexible electronics, where CdS thin films were deposited by chemical bath deposition (70°C) on either 100 nm HfO 2 or SiO 2 as the gate dielectrics.
Abstract: Cadmium sulfide thin film transistors were demonstrated as the n-type device for use in flexible electronics. CdS thin films were deposited by chemical bath deposition (70°C) on either 100 nm HfO 2 or SiO 2 as the gate dielectrics. Common gate transistors with channel lengths of 40-100 μm were fabricated with source and drain aluminum top contacts defined using a shadow mask process. No thermal annealing was performed throughout the device process. X-ray diffraction results clearly show the hexagonal crystalline phase of CdS. The electrical performance of HfO 2 /CdS-based thin film transistors shows a field effect mobility and threshold voltage of 25 cm 2 V -1 s -1 and 2 V, respectively. Improvement in carrier mobility is associated with better nucleation and growth of CdS films deposited on HfO 2 .
TL;DR: In this paper, a thermotropic liquid crystalline lutetium bisphthalocyanine sandwich complexes substituted with sixteen octyl chains are employed as active organic semiconducting layers in the fabrication of organic field effect transistors (OFET).
01 Nov 2010
TL;DR: In this article, the influence of dynamic temperature modulation on the selectivity of GasFETs has been investigated based on a diode coupled silicon carbide field effect transistor with platinum as catalytic gate material, and a suitable T-cycle for detection of typical exhaust gases (CO, NO, C 3 H 6, H 2, NH 3 ) was developed and combined with appropriate signal processing based on multivariate statistics, e.g. linear discriminant analysis (LDA).
Abstract: Based on a diode coupled silicon carbide field effect transistor with platinum as catalytic gate material, the influence of dynamic temperature modulation on the selectivity of GasFETs has been investigated. This operating mode, studied intensively for semiconductor gas sensors, is applied for the first time with gas sensors based on the field effect. A suitable T-cycle for detection of typical exhaust gases (CO, NO, C 3 H 6 , H 2 , NH 3 ) was developed and combined with appropriate signal processing based on multivariate statistics, e.g. linear discriminant analysis (LDA). Measurements have proven that several gases can be discriminated based on T-cycle data. Furthermore, quantitative determination of gases is also possible. In addition to varying the measurement conditions (e.g. background oxygen) experiments regarding stability and reproducibility were also carried out. Based on these preliminary studies the performance of field effect gas sensors can be enhanced considerably by T-cycling.
TL;DR: In this paper, the authors present results on the near-room temperature control of the magnetization of optimally doped La0.67Sr0.33MnO3 ultrathin films in vertical field effect devices, where they act as top or bottom electrodes.
Abstract: The control of the magnetization in ferromagnetic layers via electric fields is a hot topic in view of applications to the next generation of spintronic devices, where writing the magnetic information through current lines could be replaced by electric writing. Mixed valence manganites are good candidates for such a purpose because they present an intriguing coupling between ferromagnetism and charge ordering/doping which can be tuned by the application of an electric field. Here we present results on the near-room temperature control of the magnetization of optimally doped La0.67Sr0.33MnO3 ultrathin films in vertical field effect devices, where they act as top or bottom electrodes. In the latter case a slight decrease in the Curie temperature (∼5 K) is observed after application of 5×107 V/m, i.e., the maximum field preventing electric breakdown, compatible with the induced variation in the charge density and mixed valence within the Thomas Fermi screening length. These results indicate that electric fie...
TL;DR: An experimental proof of principle for a ternary multiplier realized in terms of the charge state of a single dopant atom embedded in a fin field effect transistor (Fin-FET).
Abstract: We provide an experimental proof of principle for a ternary multiplier realized in terms of the charge state of a single dopant atom embedded in a fin field effect transistor (Fin-FET). Robust reading of the logic output is made possible by using two channels to measure the current flowing through the device and the transconductance. A read out procedure that allows for voltage gain is proposed. Long numbers can be multiplied by addressing a sequence of Fin-FET transistors in a row.
29 Nov 2010-Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena
TL;DR: In this article, the authors demonstrate directed assembly of high quality solution processed single-walled carbon nanotube (SWNT) devices via ac dielectrophoresis using commercially available SWNT solutions.
Abstract: The authors demonstrate directed assembly of high quality solution processed single-walled carbon nanotube (SWNT) devices via ac dielectrophoresis using commercially available SWNT solutions. By controlling the shape of the electrodes, concentration of the solution, and assembly time, the authors are able to control the assembly of SWNTs from dense arrays down to individual SWNT devices. Electronic transport studies of individual SWNT devices show field effect mobilities of up to 1380 cm2/V s for semiconducting SWNTs and saturation currents of up to ∼15 μA for metallic SWNTs. The field effect mobilities are more than an order of magnitude improvement over previous solution processed individual SWNT devices and close to the theoretical limit. Field effect transistors (FET) fabricated from aligned two-dimensional arrays of SWNT show field effect mobility as high as 123 cm2/V s, which is three orders of magnitude higher than the solution processed organic FET devices. This study shows promise for commerciall...
TL;DR: In this paper, the authors examined the possibility of using Ti/Cu bilayer as source/drain electrodes for SiNx-passivated Hf-In-Zn-O (HIZO) thin film transistors by comparing their electrical properties with devices that use Mo electrodes.
Abstract: In this study, we examine the possibility of using Ti/Cu bilayer as source/drain electrodes for SiNx-passivated Hf–In–Zn–O (HIZO) thin film transistors by comparing their electrical properties with devices that use Mo electrodes. The Mo devices operate in depletion mode with a higher field effect mobility, while the Ti/Cu devices exhibit an improved subthreshold swing and operate in enhancement mode. Transmission electron microscopy characterization reveals the formation of an amorphous TiOx layer at the Ti/HIZO interface, which is suggested to be responsible for the disparate device characteristics in terms of contact resistance and threshold delay.
TL;DR: In this paper, the authors investigated the temperature-dependent behavior of a pentacene organic field effect transistor (OFET) by measuring dc current and voltage characteristics and the transient response of the OFET to a sharp voltage pulse applied at the source contact.
Abstract: We have investigated the temperature-dependent behavior of a pentacene organic field effect transistor (OFET) by measuring dc current and voltage characteristics and the transient response of the OFET to a sharp voltage pulse applied at the source contact. Standard transistor equations were used to extract the dc field-effect mobility, μFE, and the turn on time of the OFET was used to extract a dynamic mobility, μdynamic. Temperature dependent measurements were used to extract both field-effect and dynamic activation energies, Ea,FE and Ea,dynamic, over a range of effective gate voltages in order to vary the charge carrier density in the channel. We found that at higher temperatures μdynamic>μFE, while at lower temperatures μdynamic<μFE. We attribute this varying relationship between dynamic and field effect mobilities to the fact that μFE is an average mobility of all the charge carriers in the channel, while μdynamic is a measure of the mobility of the fastest charge carriers in the channel. We also fou...
TL;DR: In this article, a metal-oxide-semiconductor (MOS) photodetector with the high-k material enhanced deep depletion at edge was demonstrated, where the mechanism of saturated substrate injection current in MOS capacitor was adopted.
Abstract: Metal-oxide-semiconductor (MOS) photodetector with the high-k material enhanced deep depletion at edge was demonstrated. The mechanism of saturated substrate injection current in MOS capacitor was adopted. By building HfO2 based devices that with the direct observation of the enhanced edge charge collection efficiency due to fringing field effect in inversion, we are able to show a photodetector with 3000 times (ratio of photocurrent to dark current) improvement in sensitivity than the conventional SiO2 based tunneling photodiodes (approximate 100 times) in the visible.
TL;DR: Thin film transistors with a carbon nanotube network as a channel have been fabricated using grid-inserted plasma-enhanced chemical vapor deposition (PECVD) which has the advantage of preferential growth of the CNTs with semiconducting behavior in the I-V characteristics of CNT field effect transistors (CNT-FETs).
Abstract: Thin film transistors with a carbon nanotube (CNT) network as a channel have been fabricated using grid-inserted plasma-enhanced chemical vapor deposition (PECVD) which has the advantage of preferential growth of the CNTs with semiconducting behavior in the I–V characteristics of CNT field effect transistors (CNT-FETs). Taking advantage of the preferential growth and suppression of bundle formation, a large ON current of 170 µA mm − 1, which is among the largest in these kinds of devices with a large ON/OFF current ratio of about 105, has been realized in the relatively short channel length of 10 µm. The field effect mobility of the device was 5.8 cm2 V − 1 s − 1.
TL;DR: In this article, the effect of varying the thickness of poly(3-hexylthiophene) (P3HT) organic field effect transistors (OFETs) was studied.
Abstract: In this study, the conducting channel in poly(3-hexylthiophene) (P3HT) organic field effect transistors (OFETs) was investigated. The effect of varying the P3HT layer thickness on the OFET parameters was studied. The threshold voltage and the field effect mobility were determined from both the linear and saturation regime of the OFET output characteristics for all film thicknesses and the results are compared and discussed. A gated four probe technique was used to investigate the formation and evolution of the conducting channel by monitoring changes in potential at different points in the channel during measurement. It was found that the device performance of the OFETs was significantly influenced by the thickness of the P3HT layer. Bulk currents were found to dominate device performance for thicker P3HT layers.
TL;DR: In this paper, a low-voltage drive ZnO thin-film transistors with room-temperature radio frequency magnetron sputtering SiO 2 as the gate insulator were fabricated successfully on the glass substrate.
Patent•
06 Apr 2010TL;DR: The field effect transistor (FET) as discussed by the authors is a semiconductor device that uses single walled carbon nanotubes (SWCNTs) as the semiconducting material.
Abstract: Methods and apparatus for an electronic device such as a field effect transistor. One embodiment includes fabrication of an FET utilizing single walled carbon nanotubes as the semiconducting material. In one embodiment, the FETs are vertical arrangements of SWCNTs, and in some embodiments prepared within porous anodic alumina (PAA). Various embodiments pertain to different methods for fabricating the drains, sources, and gates.