Field effect transistor from individual trigonal Se nanowire

Trigonal Se nanowires (NWs) were fabricated through a high-yield chemical solution process. The morphology and structural characterization of the Se NWs were investigated using transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and x-ray diffraction (XRD). The results indicated that the Se NWs grow along the crystallographic c-axis, the direction of which is parallel to the helical chains of Se atoms. Single Se NW field effect transistor (FET) devices were prepared through photolithographic patterning. The device performance shows that the Se NWs are p-type semiconductors displaying mobility up to 30?cm(2)?V(-1)?s(-1). This finding on the Se NW FETs has broad implications and provides very useful fundamental information necessary for future applications in the fabrication of high-quality NW FETs and other electronic devices.     

Miniature circulators

Recent work on moderate-bandwidth and broadband miniature circulators is reviewed. The lumped-element design approach is the basis of a discussion of the size-bandwidth tradeoff. It is pointed out that a tradeoff situation exists with respect to size and insertion loss because ohmic losses in the coupling structure become dominant as the size of the circulators is reduced. The problems of achieving circulator performance over very broad frequency bands in circulators of moderate size are discussed for coplanar and microstrip circulators. The lumped-element approach is primarily applicable to circulators operating at relatively low frequencies and for relatively small bandwidths (up to 50%, for instance). The distributed-field approach has broader validity since it is not restricted by any assumption about the size of the ferrite disk. The application of this approach to broadband miniature circulators operating over the 6- to 18-GHz band is discussed     

The quantum interference effect transistor

We give a detailed discussion of the quantum interference effect transistor (QuIET), a proposed device which exploits the interference between electron paths through aromatic molecules to modulate the current flow. In the off state, perfect destructive interference stemming from the molecular symmetry blocks the current, while in the on state, the current is allowed to flow by locally introducing either decoherence or elastic scattering. Details of a model calculation demonstrating the efficacy of the QuIET are presented, and various fabrication scenarios are proposed, including the possibility of using conducting polymers to connect the QuIET with multiple leads.     

并五苯场效应晶体管的研制

以X射线衍射仪（XRD）研究了在硅表面形成并五苯多晶薄膜晶体结构，通过原子力显微镜（AFM）分析了在二氧化硅表面形成并五苯多晶薄膜的形貌。以热氧化的硅片作为绝缘栅极，并五苯作为有缘层，采用底接触结构，研制场效应晶体管。经过测试得到其场效应迁移率为1．23cm^2/Vs，开关电流比＞10^6。     

On the flicker noise of ferrite circulators for ultra-stable oscillators

The flicker noise of the ferrite circulator is a critical element in ultra-stable microwave oscillators, in which the signal reflected from the input of the reference cavity is exploited to stabilize the frequency. This paper explains why the circulator noise must be measured in isolation mode, proposes a measurement scheme, and provides experimental results. The observed flicker spans from -162 to -170 dB[rad2]/Hz at 1 Hz off the 9.2 GHz carrier, and at +19 dBm of input power. In the same conditions, the instrument limit is below -180 dB[rad2]/Hz. Experiments also give information on the mechanical stability of the microwave assembly, which is in the range of 10(-11) m. The measurement method can be used as the phase detector of a corrected oscillator; and, in the field of solid-state physics, it can be used for the measurement of random fluctuations in magnetic materials.     

PN-junction diode behavior based on polyaniline nanotubes field effect transistor

Polyaniline (PANI) nanotubes configured as a field effect transistor (FET) exhibits a p–n junction diode behavior. The forward-bias current can be modulated by a gate voltage; turning on at negative gate voltage and turning off at positive gate voltage. An energy band diagram model has been proposed to explain the rectifying effect of the PANI nanotubes FET (PNT-FET). All the four different forward bias conduction mechanisms of a typical p–n junction diode can be identified for this PNT-FET using a semi-log graph to confirm this resemblance.     

High mobility field effect transistor from solution-processed needle-like tellurium nanowires

Well-dispersed and uniform needle-like tellurium nanowires (NWs) have been fabricated in high yield by an environmentally-friendly hydrothermal method. It is found that beta-cyclodextrin ligands and reaction temperature play a great role on the morphology of Te NWs. Uniform needle-like Te NWs can only be obtained at suitable concentration of beta-CD and reaction temperature. A possible mechanism for the formation of the needle-liked Te NWs is discussed based on the experiment results briefly. High quality single Te NW field effect transistors are prepared through photolithographic patterning. By optimizing electrode and surface treatments, the NW FET has a high carrier mobility of 299 cm2V(-1)s(-1), which is the highest value ever reported for Te NW-based FETs. The performance is influenced by purity, crystallinity, surface species of NWs and metal contacts of NW device.     

Ultimate performance limitations of high-power ferrite circulators and phase shifters

The power-handling capability of circulators and phase shifters in rectangular waveguide is analyzed. It is shown that an appropriate measure of the suitability of microwave ferrites for high-power applications is given by the "high-power figure of merit"F_{hp}* = 4piMgamma^{2}h_{crit}/omega^{2}mu'. Here γ is the gyromagnetic ratio, hcritthe critical RF field, ω the (angular) frequency,mu"the imaginary part of the diagonal component of the permeability tensor. In applications to nonlatching devices,Mis the saturation magnetization; in applications to latching devices it is the remanent magnetization. The figures of merit of various rare-earth substituted garnets are reported. The figures of merit obtained to date are approximately 2. Theoretical analysis indicates that significantly larger figures of merit can be Obtained only at the cost of reducing the saturation magnetization. It is concluded that for circulators using theH-plane configuration and having an insertion loss of 0.5 dB the maximum attainable peak power level is of the order of 50 MW. For latching twin slab phase shifters (E-plane configuration) having an insertion loss of 1 dB the maximum attainable peak power level is estimated to be 80 kW.     

场效应管X射线剂量增强的实验测量

为了实验精确测量场效应管的X射线剂量增强系数,介绍了如何改进剂量增强系数实验测量的方法和实验测量装置,以及实验测量的详细过程.得到了两种不同类型场效应管的辐照数据,根据实验数据计算了其剂量增强系数.剂量增强效应十分明显,IRF540场效应管在阈电压1.5 V时相对剂量增强系数为16,IRF9530要小些,在阈电压为4v时相对剂量增强系数约7.5.     

A carbon nanotube field effect transistor with a suspended nanotube gate

We investigate theoretically field effect transistors based on single-walled carbon nanotubes (CNTFET) and explore two device geometries with suspended multiwalled carbon nanotubes (MWNT) functioning as gate electrodes. In the two geometries, a doubly or singly clamped MWNT is electrostatically deflected toward the transistor channel, allowing for a variable gate coupling and leading to, for instance, a superior subthreshold slope. We suggest that the proposed designs can be used as nanoelectromechanical switches and as detectors of mechanical motion on the nanoscale.     

In-situ detection of C-reactive protein using silicon nanowire field effect transistor

Label-free, sensitive, and real-time c-reactive protein (CRP) sensor was fabricated using p-type silicon nanowire (SiNW) based structures configured as field effect transistors (FET) using the conventional 'top-down' semiconductor processes. The width of SiNWs were distributed 80 nm to 400 nm. Among them to improve signal-to-noise ratio and sensitivity of SiNW FET, 221 nm-SiNW was chosen for biosensing of CRP. Antibody of c-reactive protein (anti-CRP) was immobilized on the SiNW surface through polydimethylsiloxane (PDMS) microfluidic channel for detection of CRP. Specific binding of CRP with anti-CRP on the SiNW surface caused a conductance change of SiNW FET and various injections from 10 and 1 microg/ml to 100 ng/ml solutions of CRP resulted in the conductance changes from 39 and 25 to 16%, respectively. Label-free, in-situ and very sensitive electrical detection of CRP was demonstrated with the prepared SiNW FET.     

A novel fabrication method for the nanoscale tunneling field effect transistor

Tunneling Field Effect Transistors (TFETs) are considered as a candidate for low power applications. However, most of TFETs have been researched on only for long channels due to the misalignment problem that occurs during the source/drain doping process in device fabrication. Thus, a new method is proposed for the fabrication of TFETs in nanoscale regions. This proposed fabrication process does not need an additional mask to define the source/drain regions, and makes it possible to form a self-aligned source/drain doping process. In addition, through TCAD simulation, the electrical characteristics of a TFET with dopant engineering and a rounded gate edge shape for a higher on/off current ratio were investigated. As a result, the TFET showed the properties of a larger on-current, a lower average subthreshold swing (58.5 mV/dec), and a 30-fold smaller leakage current compared to the conventional TFET The TFET with dopant engineering and a rounded gate edge shape can also be fabricated simply through the proposed fabrication process.     

Observation of a long-range action effect in ion-bombarded GaAs transistor structures

Changes in the carrier concentration and mobility in the active layers of Schottky-barrier field-effect transistors are observed when the structures are bombarded with argon ions on the nonworking side of the GaAs substrate. Pis’ma Zh. Tekh. Fiz. 25, 50–53 (August 26, 1999)     

High mobility polymer gated organic field effect transistor using zinc phthalocyanine

Organic thin film transistors were fabricated using evaporated zinc phthalocyanine as the active layer. Parylene film prepared by chemical vapour deposition was used as the organic gate insulator. The annealing of the samples was performed at 120 °C for 3 h. At room temperature, these transistors exhibit p-type conductivity with field-effect mobilities ranging from 0·025–0·037 cm²/Vs and a (I _on/I _off) ratio of ～10³. The effect of annealing on transistor characteristics is discussed.     

Transient charge accumulation in pentacene field effect transistor with silver electrode

Time-resolved microscopic optical second harmonic generation (TRM-SHG) imaging was employed to study a transient charge accumulation in top-contact pentacene field effect transistor (FET) with Ag electrodes. It was demonstrated that the SHG signal at the edge of the Ag electrode decayed but remained in a steady state depending on biasing condition. An electric field formed in pentacene layer below Ag electrode activates the SHG, indicating the insufficient accumulation of injected carriers in the FET channel. By using the TRM-SHG technique transient change of the carrier density in the OFET is obtained.     

Bidirectional optical add-drop multiplexer based on Bragg gratings and circulators

We propose and demonstrate a bidirectional optical add-drop multiplexer for use in single-fiber bidirectional networks. With effective use of multiport circulators, fiber-Bragg gratings, and a single amplifier element, the new structure can add and/or drop channels in both directions and achieves more than 16 dB of bidirectional gain. The device utilizes Bragg gratings and light absorber to remove Rayleigh backscattered and reflected light at the input stage.