Silicon Nanowire Field-effect Transistors Research Articles

Ultrasensitive Electrical Detection of Hemagglutinin for Point-of-Care Detection of Influenza Virus Based on a CMP-NANA Probe and Top-Down Processed Silicon Nanowire Field-Effect Transistors.

Rather than the internal genome nucleic acids, the biomolecules on the surface of the influenza virus itself should be detected for a more exact and rapid point-of-care yes/no decision for influenza virus-induced infectious diseases. This work demonstrates the ultrasensitive electrical detection of the HA1 domain of hemagglutinin (HA), a representative viral surface protein of the influenza virus, using the top-down complementary metal oxide semiconductor (CMOS) processed silicon nanowire (SiNW) field-effect transistor (FET) configuration. Cytidine-5′-monophospho-N-acetylneuraminic acid (CMP-NANA) was employed as a probe that specifically binds both to the aldehyde self-aligned monolayer on the SiNWs and to HA1 simultaneously. CMP-NANA was serially combined with two kinds of linkers, namely 3-aminopropyltriethoxysilane and glutaraldehyde. The surface functionalization used was verified using the purification of glutathione S-transferase-tagged HA1, contact angle measurement, enzyme-linked immunosorbent assay test, and isoelectric focusing analysis. The proposed functionalized SiNW FET showed high sensitivities of the threshold voltage shift (ΔVT) ~51 mV/pH and the ΔVT = 112 mV (63 mV/decade) with an ultralow detectable range of 1 fM of target protein HA1.

Signal Enhancement of Silicon Nanowire Field-Effect Transistor Immunosensors by RNA Aptamer

Silicon nanowire field-effect transistors (SiNW-FETs) have been demonstrated as a highly sensitive platform for label-free detection of a variety of biological and chemical entities. However, detecting signal from immunoassays by nano-FETs is severely hindered by the distribution of different charged groups of targeted entities, their binding orientation, and distances to the surface of the FET. Aptamers have been widely applied as a recognition element for plentiful biosensors because of small molecular sizes and moderate to high specific binding affinity with different types of molecules. In this study, we propose an effective approach to enhance the electrical responses of both direct (6×-histidine) and sandwich (amyloid β 1–42) immunoassays in SiNW-FETs with R18, a highly negative charged RNA aptamer against rabbit immunoglobulin G (IgG). Empirical results presented that the immunosensors targeted with R18 expressed a significantly stabilized and amplified signal compared to the ones without this aptamer. The research outcome provides applicability of the highly negative charged aptamer as a bioamplifier for immunoassays by FETs.

Silicon Nanowires Field Effect Transistors: A Comparative Sensing Performance between Electrical Impedance and Potentiometric Measurement Paradigms.

Potentiometric sensors based on silicon nanowire field effect transistors (SiNW FETs) typically display exquisite sensitivities, but their bioanalytical implementation is limited due to the need for stringent measurement conditions and high-precision readout units. An alternative operation principle where SiNW FETs are operated in a frequency-domain electrical impedimetric approach is promising. However, to date only limited data is available in regard to the sensing performance and translational relevance of this novel approach in comparison to the standard charge detection paradigm. We demonstrate the feasibility of conducting electrical impedimetric FET measurements with a portable unit for the ultrasensitive detection of cancer biomarkers in biospecimens. Compared to standard potentiometric measurements, electrical impedimetric FET measurements yielded significant improvements in biosensing performances, including the limit of detection, sensing resolution, and dynamic range.

Cloning, expression, purification and interaction evaluation of 30 amino acids in C terminus of Clostridium perfringens toxin with its receptor Claudin-4

Oral vaccine is a strategy being the most interested about treatments of gastrointestinal infections because of many great benefits outweigh conventional injection vaccines. In order to resolve the dispersion of antigens in gastrointestinal surfaces, the immunological tolerance and also be capable to stimulate immune responses effectively, M cells are targeted for antigens delivery. A number of researches reported that 30 amino acids in C terminus of Clostridium perfringens toxin (CPE30) have a high affinity to Claudin-4 receptor presenting on M cells. It is highly indispensable to produce a resource for assessing of CPE30 binding ability so cpe30 gene was cloned into the pET-gfp plasmid by two restriction enzymes BamHI and NdeI on the E. coli DH5α strain. The expression and confirmation of the fusion protein CPE30-GFP which was induced by IPTG in E. coli BL21 (DE3) strain and assessed by SDS-PAGE and Western blot with 6xHis Taq antibody demonstrated that there was the over expression of CPE30 GFP fusion protein in the cytoplasm, mainly in the soluble form. Finally, CPE30-GFP was purified which the purity was approximately 92.3%. In vitro protein interaction measurement using silicon nanowire field-effect transistors (SiNW FETs) showed that CPE30-GFP had a good binding affinity with its receptor Claudin-4 (R4). This result laid the groundwork for the CPE30 interaction study with the M cell in vivo.

Neutralized chimeric DNA probe for the improvement of GC-rich RNA detection specificity on the nanowire field-effect transistor

Silicon nanowire (SiNW) field-effect transistors (FETs) is a powerful tool in genetic molecule analysis because of their high sensitivity, short detection time, and label-free detection. In nucleic acid detection, GC-rich nucleic acid sequences form self- and cross-dimers and stem-loop structures, which can easily obtain data containing signals from nonspecific DNA binding. The features of GC-rich nucleic acid sequences cause inaccuracies in nucleic acid detection and hinder the development of precision medicine. To improve the inaccurate detection results, we used phosphate-methylated (neutral) nucleotides to synthesize the neutralized chimeric DNA oligomer probe. The probe fragment originated from a primer for the detection of hepatitis C virus (HCV) genotype 3b, and single-mismatched and perfect-matched targets were designed for single nucleotide polymorphisms (SNP) detection on the SiNW FET device. Experimental results revealed that the HCV-3b chimeric neutralized DNA (nDNA) probe exhibited better performance for SNP discrimination in 10 mM bis-tris propane buffer at 25 °C than a regular DNA probe. The SNP discrimination of the nDNA probe could be further improved at 40 °C on the FET device. Consequently, the neutralized chimeric DNA probe could successfully distinguish SNP in the detection of GC-rich target sequences under optimal operating conditions on the SiNW FET device.

Top-down fabrication and electrical characterization of Si and SiGe nanowires for advanced CMOS technologies

Gate-all-around (GAA) silicon (Si) nanowires (NW) field effect transistor is today considered as a valuable alternative to FinFET architecture for advanced CMOS devices. Recent advances in characterization and integration have enabled the fabrication of nanowires with diameter below 10 nm. Although nanowires transistors with excellent electrostatic control can be achieved, the nanoscale dimensions induce quantum confinement effects and confer to nanowires electrical properties which differ from bulk Si. Then, low-field electron and hole mobility in Si NW transistors fabricated on (100) silicon-on-insulator (SoI) substrates have been measured over a wide range of NW width (8 nm ≤ W ≤ 220 nm) and height (6 nm ≤ Hfin ≤ 24 nm). A significant increase of hole effective mobility in thick and narrow Si NWs is evidenced along the [110] direction. In contrast, a decrease of NW width results in an electron mobility reduction. An electron mobility enhancement in n-FET NWs is achieved through the use of tensile strained-SoI (sSoI) substrates. As compared to unstrained-Si, +85% electron mobility enhancement is observed in uniaxially tensile strained-Si NW transistors. We have otherwise studied dual-channel CMOS co-integration, with Si channel n-FET and compressively-strained SiGe channel p-FET NWs. For p-FETs, the efficiency of compressive SiGe channels is evidenced for improving hole mobility in nanowires thanks to a Ge enrichment process. As compared to Si channel, the hole mobility is enhanced by 135% in p-FET NWs. Efficiency of compressive SiGe channel is evidenced for ultra-scaled p-FET NWs (LG = 15 nm) with +90% ION current improvement compared to Si. [110]-oriented NWs are shown to be the best candidates to improve electron and hole mobility under uniaxial tensile and compressive strain, respectively. Finally, in order to increase still further the drive current per layout footprint, GAA stacked-nanowire/nanosheet (NS) MOSFET are discussed in this paper. We will present intrinsic performance and design considerations of GAA structures that will allow to make this architecture a competitive solution for futures technology nodes. The key technological challenges (such as 3D integration process including inner spacer and strain engineering) will be discussed in relation to recent research results. We will show that more flexibility can be achieved with stacked-nanosheet transistors in order to manage power and performance optimization.

Temperature analysis of underlap GAA-SNWTs for analog/RF applications

In the present work, a comprehensive study of temperature on gate-all-around silicon nanowire FETs (GAA-SNWTs) with source/drain underlap is performed to investigate the influence of Air as spacer dielectric, on analog/RF behavior of the device. The transconductance gm of the device enhances when the temperature is dropped down to 100 K. Thus, the analog/RF figure-of-merit (FOM) of the device enhances, rendering the device suitable for low temperature, low-power high-frequency operations. For targeting low power applications, FOMs are elicited at 10 μA/μm. It is perceived that the intrinsic gain of the device is marginally altered for distinct spacer dielectric (Si3N4 and air). Frequencies like cut-off frequency (fT) and maximum oscillation frequency (fMAX) of air spacer dielectric based underlap GAA-SNWTs are enhanced by 2.15 times and 1.73 times respectively when the operating temperature is dropped down to 100 K from 400 K. This results in higher percentage improvement in RF-FOM in terms of transconductance frequency product (TFP), gain-frequency product (GFP), and gain transconductance frequency product (GTFP).

Detection of ultra-low protein concentrations with the simplest possible field effect transistor

Silicon nanowire (Si NW) sensors have attracted great attention due to their ability to provide fast, low-cost, label-free, real-time detection of chemical and biological species. Usually configured as field effect transistors (FETs), they have already demonstrated remarkable sensitivity with high selectivity (through appropriate functionalisation) towards a large number of analytes in both liquid and gas phases. Despite these excellent results, Si NW FET sensors have not yet been successfully employed to detect single molecules of either a chemical or biological target species. Here we show that sensors based on silicon junctionless nanowire transistors (JNTs), the simplest possible transistors, are capable of detecting the protein streptavidin at a concentration as low as 580 zM closely approaching the single molecule level. This ultrahigh detection sensitivity is due to the intrinsic advantages of junctionless devices over conventional FETs. Apart from their superior functionality, JNTs are much easier to fabricate by standard microelectronic processes than transistors containing p–n junctions. The ability of JNT sensors to detect ultra-low concentrations (in the zeptomolar range) of target species, and their potential for low-cost mass production, will permit their deployment in numerous environments, including life sciences, biotechnology, medicine, pharmacology, product safety, environmental monitoring and security.

Label-free detection of \u03b3-aminobutyric acid based on silicon nanowire biosensor

γ-Aminobutyric acid (GABA) is an important inhibitory neurotransmitter in the central nervous system (CNS), which acts as a major biomarker for neurological disorders such as Parkinson’s disease and Meningitis. To this end, the precise measurement of GABA molecule arisen as an important subject for the effective diagnosis and treatment of neurological disorders. However, yet highly sensitive biosensor systems which can analyze a wide range of GABA molecule in a fast response manner have not been reported. In this study, for the first time, a silicon nanowire field-effect transistor (FET) device based immunosensor was developed to detect GABA molecule. Zig-zag shaped silicon nanowires has been fabricated by electron beam lithography and the electrical property p-type FET device was validated through semiconductor analyzer. The optimal immobilizing condition of antibody against GABA molecule was determined by the fluorescent signal measurement. Various concentrations of GABA ranging from 970 fM to 9.7 μM were sensitively measured by conductance change on silicon nanowire-based through the immunoreactions. Further, owing to the ease of miniaturization and label-free system, we believe that the suggested device system has a potential to be utilized for an implantable biosensor to detect neurotransmitter in the brain and can create new opportunities in the field of diagnosis and treatment of neurological disorders.

Optimization of high-k composite dielectric materials of variable oxide thickness tunnel barrier for nonvolatile memory

<span>Downscaling the tunnel oxide thickness has become one of the innovative solutions to minimize the operational voltage with better the programming/erasing (P/E) operation time. However, the downscaling technique faces several challenges where the conventional SiO<sub>2</sub> tunnel layer has reached its limit. But a practical alternative has been introduced; Variable Oxide Thickness (VARIOT) technology in flash memory has been promising. VARIOT is one of tunnel barrier engineering technology for incorporating the high-k dielectric materials as a composite tunnel barrier. This paper presents the VARIOT concept to determine the optimum set of combination, the equivalent oxide thickness (EOT) and the low-k oxide thickness (T<sub>ox</sub>) for alternate high-k materials. Fowler-Nordheim (F-N) tunneling coefficients are also extracted for various combinations of VARIOT, where in this work ZrO<sub>2</sub>, HfO<sub>2</sub>, Al<sub>2</sub>O<sub>3,</sub> La<sub>2</sub>O<sub>3, </sub>and Y<sub>2</sub>O<sub>3 </sub>are used. The VARIOT optimization is conducted using 3-Dimensional (3D) Silicon Nanowire Field-Effect-Transistor (SiNWFET) device structure and simulated in TCAD Simulation tools. From the simulation results, it has found out that the high-k materials of La<sub>2</sub>O<sub>3 </sub>asymmetric stack is the excellent dielectric material among four (4) other dielectric materials; ZrO<sub>2</sub>, HfO<sub>2</sub>, Al<sub>2</sub>O<sub>3 </sub>and Y<sub>2</sub>O<sub>3</sub> for EOT=4nm and T<sub>ox</sub>=1nm. </span>

Towards pharmacological treatment screening of cardiomyocyte cells using Si nanowire FETs

Silicon nanowires (Si NWs) are the most promising candidates for recording biological signals due to improved interfacing properties with cells and the possibility of high-speed transduction of biochemical signals into detectable electrical responses. The recording of extracellular action potentials (APs) from cardiac cells is important for fundamental studies of AP propagation features reflecting cell activity and the influence of pharmacological substances on the signal. We applied a novel approach of using fabricated Si NW field-effect transistors (FETs) in combination with fluorescent marker techniques to evaluate the functional activity of cardiac cells. Extracellular AP signal recording from HL-1 cardiomyocytes was demonstrated. This method was supplemented by studies of the pharmacological effects of stimulations using noradrenaline (NorA) as a modulator of functional activity on a cellular and subcellular levels, which were also tested using fluorescent marker techniques. The role of calcium alteration and membrane potential were revealed using Fluo-4 AM and tetramethylrhodamine, methyl ester, perchlorate (TMRM) fluorescent dyes. In addition, chemical treatment with sodium dodecyl sulfate (SDS) solutions was tested. The results obtained demonstrate positive prospects for AP monitoring in different treatments for studies related to a wide range of myocardial diseases using lab-on-chip technology.

A new biosensor detection system to overcome the Debye screening effect: dialysis-silicon nanowire field effect transistor.

Background: A silicon nanowire field effect transistor biosensor has four advantages in the detection of small biomolecules. It is mark-free, immediately responsive, highly sensitive, and specific. However, because of environments with a high salt concentration, the Debye screening effect has been a major issue in biological detection.Objective: To overcome Debye screening effect, realize the clinical application of silicon nanowire field effect transistor and verify its specificity and sensitivity.Materials and methods: The test solution was desalted by miniature blood dialyzer, and then the tumor markers were detected by silicon nanowire field effect transistor.Results: Tumor markers in serum were detected successfully and their sensitivity and specificity were verified.Conclusion: This method was found to effectively promote the development of semiconductor materials in biological solution detection.

Low-temperature tunable radio-frequency resonator for sensitive dispersive readout of nanoelectronic devices

We present a sensitive, tunable radio-frequency resonator designed to detect reactive changes in nanoelectronic devices down to dilution refrigerator temperatures. The resonator incorporates GaAs varicap diodes to allow electrical tuning of the resonant frequency and the coupling to the input line. We find a resonant frequency tuning range of 8.4 MHz at 55 mK that increases to 29 MHz at 1.5 K. To assess the impact on performance of different tuning conditions, we connect a quantum dot in a silicon nanowire field-effect transistor to the resonator and measure changes in the device capacitance caused by cyclic electron tunneling. At 250 mK, we obtain an equivalent charge sensitivity of 43 μe/Hz when the resonator and the line are impedance-matched and show that this sensitivity can be further improved to 31 μe/Hz by re-tuning the resonator. We understand this improvement by using an equivalent circuit model and demonstrate that for maximum sensitivity to capacitance changes, in addition to impedance matching, a high-quality resonator with low parasitic capacitance is desired.

Wafer-scale HfO2 encapsulated silicon nanowire field effect transistor for efficient label-free DNA hybridization detection in dry environment

AbatractSilicon nanowire (SiNW) charge based biosensors are attractive for DNA sensing applications due to their compactness and large surface-to-volume ratio. Small feature size, low production cost, repeatability, high sensitivity and selectivity are some of the key requirements for biosensors. The most common e-beam manufacturing method employed to manufacture sub-nm SiNWs is both cost and time intensive. Therefore, we propose a highly reproducible CMOS industry grade low-cost process to fabricate SiNW-based field effect transistors on 4″-wafers. The 60 nm wide SiNWs reported in this paper are fabricated using the sidewall transfer lithography process which is a self-aligned-double-patterning I-line lithography process that also facilitates encapsulation of the SiNW surface with a thin HfO2 layer on which DNA probes are grafted to finalize the biosensors. Upon DNA hybridization, SiNW devices exhibit threshold voltage shift larger than the noise introduced by the exposition to saline solutions used for the bioprocesses. More specifically, based on a statistical analysis, we demonstrate that 85% of the tested devices exhibit a positive threshold voltage shift after DNA hybridization. These promising results make way for the monolithic integration of SiNW biosensors and CMOS circuitry to realize a point of care device which can offer reliable real time electrical readout.

Device Noise Reduction for Silicon Nanowire Field-Effect-Transistor Based Sensors by Using a Schottky Junction Gate.

The sensitivity of metal oxide semiconductor field-effect transistor (MOSFET) based nanoscale sensors is ultimately limited by noise induced by carrier trapping/detrapping processes at the gate oxide/semiconductor interfaces. We have designed a Schottky junction gated silicon nanowire field-effect transistor (SiNW-SJGFET) sensor, where the Schottky junction replaces the noisy oxide/semiconductor interface. Our sensor exhibits significantly reduced device noise, 2.1 × 10-9 V2 μm2/Hz at 1 Hz, compared to reference devices with the oxide/semiconductor interface operated at both inversion and depletion modes. Further improvement can be anticipated by wrapping the nanowire by such a Schottky junction, thereby eliminating all oxide/semiconductor interfaces. Hence, a combination of the low-noise SiNW-SJGFET device with a sensing surface of the Nernstian response limit holds promises for future high signal-to-noise ratio sensor applications.

Low-Noise Schottky Junction Trigate Silicon Nanowire Field-Effect Transistor for Charge Sensing

Silicon nanowire (SiNW) field-effect transistors (SiNWFETs) are of great potential as a high-sensitivity charge sensor. The signal-to-noise ratio (SNR) of an SiNWFET sensor is ultimately limited by the intrinsic device noise generated by carrier trapping/detrapping processes at the gate oxide/silicon interface. This carrier trapping/detrapping-induced noise can be significantly reduced by replacing the noisy oxide/silicon interface with a Schottky junction gate (SJG) on the top of the SiNW. In this paper, we present a tri-SJG SiNWFET (Tri-SJGFET) with the SJG formed on both the top surface and the two sidewalls of the SiNW so as to enhance the gate control over the SiNW channel. Both experiment and simulation confirm that the additional sidewall gates in a narrow Tri-SJGFET indeed can confine the conduction path within the bulk of the SiNW channel away from the interfaces and significantly improve the immunity to the traps at the bottom buried oxide/silicon interface. Therefore, the optimal low-frequency noise performance can be achieved without the need for any substrate bias. This new gating structure holds promises for further development of robust SiNWFET-based charge sensors with low noise and low operation voltage.

Temperature Characteristics of Silicon Nanowire Transistor Depending on Oxide Thickness

Among various sensing and monitoring techniques, sensors based on field effect transistors (FETs) have attracted considerable attention from both industry and academia. Owing to their unique characteristics such as small size, light weight, low cost, flexibility, fast response, stability, and ability for further downscaling, silicon nanowire field effect transistor (SiNW-FET) can serve as an ideal nanosensor. It is the most likely successor to FET-based nanoscale devices. However, as the dimensions (channel length and diameter) of SiNWT channel are shrinking down, electrical and temperature characteristics of SiNWTs should be affected, thereby degrading transistor performance. Although applications of SiNWTs as biological and/or chemical sensors have been extensively explored in the literature, less attention has been devoted to utilize such transistors as temperature sensors. Therefore, this paper characterizes the temperature sensitivity of SiNWT depending on the channel oxide thickness and also presents the possibility of using it as a nano-temperature sensor. The MuGFET simulation tool was used to investigate temperature characteristics of the nanowire. Current-voltage characteristics with different values of temperature and with different thickness of the nanowire gate (oxide thickness (TOX) = 1, 2, 3, 4, and 5 nm), were simulated. Metaloxide- semiconductor (MOS) diode mode connection was suggested for measuring the temperature sensitivity of SiNWT. Several operating voltages (0.25 to 5 V) with various working temperature (250 to 450 K) were investigated. The obtained results show that the highest temperature sensitivity was achieved by increasing oxide thickness to 5 nm. The impact of the considered temperature on SiNWT characteristics demonstrates the possibility of utilizing it as a temperature nanosensor.

Top-Bottom Gate Coupling Effect on Low Frequency Noise in a Schottky Junction Gated Silicon Nanowire Field-Effect Transistor

In this letter, strong low frequency noise (LFN) reduction is observed when the buried oxide (BOX)/silicon interface of a Schottky junction gated silicon nanowire field-effect transistor (SJGFET) is depleted by a substrate bias. Such LFN reduction is mainly attributed to the dramatic reduction in Coulomb scattering when carriers are pushed away from the interface. The BOX/silicon interface depletion can also be achieved by sidewall Schottky junction gates in a narrow channel SJGFET, leading to an optimal LFN performance without the need of any substrate bias.

Investigation of the performance of strain-engineered silicon nanowire field effect transistors (ɛ-Si-NWFET) on IOS substrates

In the current work, a design space for developing the performance enhanced strain-engineered Si nanowire field-effect-transistors has been provided. The fraction of insertion of the nanowire channel into the Insulator-on-Silicon substrate with judicious selection of high-k gate insulators is used as the key design parameter. The combined effect of fractional insertion and gate insulators results in inducing stress into the nanowire channel and, depending on their selection, it changes from tensile to compressive. Such induced-stress alters the existing inherent phononic-stress, leading to the modification of the carrier transport in the device channel. The carrier transport behavior in such partially embedded nanowire FETs has been modeled by incorporating the relevant stress-related effects into the indigenously developed self-consistent quantum-electrostatic framework. These equations are solved by employing the non-equilibrium Green's function formalism. The study shows the phonon scattering under tensile strain to occur at the expense of electron energy; however, the electrons can also gain energy during such scattering in compressive stress. Thus, the device current has been observed to increase with tensile stress and it achieves relatively smaller values when the inherent tensile phononic stress is balanced by the induced compressive stress. However, the current is finally observed to increase once the compressive stress overcomes the inherent tensile phononic stress. In general, the present devices exhibit promising Ion/Ioff ratio for all of the fractional insertions and gate dielectrics with a maximum Ioff of <10 nA/μm, threshold voltage of sub-0.3 V, gm of ∼104 µS/µm, sub-threshold swing of ∼100 mV/dec, and drain-induced-barrier-lowering of ∼100 mV/V.

Liquid-Gated Two-Layer Silicon Nanowire FETs: Evidence of Controlling Single-Trap Dynamic Processes.

We fabricate two-layer (TL) silicon nanowires (NW) field-effect transistors (FETs) with a liquid gate. The NW devices show advanced characteristics, which reflect reliable single-electron phenomena. A strong modulation effect of channel conductivity with effectively tuned parameters is revealed. The effect opens up prospects for applications in several research fields including bioelectronics and sensing applications. Our results shed light on the nature of single trap dynamics which parameters can be fine-tuned to enhance the sensitivity of liquid-gated TL silicon nanowire FETs.