Device design and optimization of CNTFETs for high-frequency applications

Carbon nanotube (CNT) field-effect transistors (FETs) have recently reached high-frequency (HF) performance similar to that of silicon RF-CMOS at the same gate length despite a tube density and current per tube that are far from the physical limits and suboptimal device architecture. This work reports on an investigation of the optimal device design for practical HF applications in terms of cut-off frequencies, power gain, and linearity. Different fundamental designs in the gate contact arrangement are considered based on a 3D device simulation of both CNTs and contacts. First, unit cells with a single CNT and minimal contact sizes are compared. The resulting simulation data are then extended toward a structure with two gate fingers and realistic contact sizes. Corresponding parasitic capacitances, as well as series and contact resistances, have been included for obtaining realistic characteristics and figures of merit that can be used for comparison with corresponding silicon RF MOSFETs. Finally, a sensitivity analysis of the device architecture with the highest performance is performed in order to find the optimal device design space.

Performance Analysis of Mixed-Wall CNT Interconnects Using Colliding Bodies Optimization Technique

In recent years, carbon nanotube (CNT) interconnects have emerged as a potential alternative to copper interconnects due to their several magnificent properties. Due to fabrication issues, realization of densely packed CNTs with uniform diameters in a bundle structure is difficult to achieve. Consequently, it is advantageous to obtain a combination of CNTs with non-uniform diameters in the bundle, thereby leading to a densely packed mixed-wall CNT bundle (MWCB). In a MWCB structure, tube density plays a major role to determine the parasitic elements associated with the interconnects. For this, prospectively, colliding bodies optimization (CBO) technique has been incorporated. It is inferred from the study that the overall crosstalk noise, delay, and power dissipation of MWCB interconnect with higher tube density (i.e., obtained using CBO technique) are lesser than other CNT structures. Henceforth, it is determined from the proposed work that prospective CBO technique for advanced MWCB structure is highly efficient and effective for on-chip interconnects in IC designs.

Apparent molar volumes, Vф, of calcium acetate (Ca(Ch3COO)2(aq)) at 273.15 to 353.15 K and pressures up to 100 MPa

Pressure, density and temperature (p, ?, T) data and apparent molar volumes, V?o, of aqueous calcium acetate solutions Ca(CH3COO)2(aq) over a wide range of temperatures from 273.15 to 353.15 K, pressures up to p = 100 MPa and molalities m, of 0.04918, 0.09367, 0.23797, 0.36365, 0.85923, 1.06930, 1.35223 and 1.81668 mol?kg-1 of Ca(CH3COO)2 are reported. The combined expanded uncertainty of the density (?) measurements at the 95 % confidence level with a coverage factor of k = 2 was estimated to be Uc(?) = ?0.3 kg?m?3. The measurements were realized with an Anton Paar DMA HPM vibration tube density meter. The system was calibrated using double-distilled water, aqueous NaCl solutions, methanol, toluene and acetone. An equation of state for fitting of the (p, ?, T) data of aqueous calcium acetate was developed as a function of pressure, temperature and molality. After a thorough analysis of literature values and validity of the constructed equation of state, various thermophysical properties, such as isothermal compressibility, isobaric thermal expansibility, differences in isobaric and isochoric heat capacities, thermal pressure coefficient and internal pressure at the investigated state parameter intervals were calculated.

Piezoelectric Properties of 1-3 Piezoelectric Tubular Composites

The piezoelectric coefficients of 1-3 piezoelectric tubular composites are studied. Taking into account the non-uniform electric field distribution in piezoelectric tube, the piezoelectric coefficients as functions of volume fraction, aspect ratio, tube density and matrix materials were discussed. By means of finite element software, the relationship between piezoelectric coefficients and ceramic volume fraction was derived to validate theoretical results. This research provides theoretical guidance and basis for the design of 1-3 piezoelectric tubular composites.

Aligned Carbon Nanotube Polymer Composites

Carbon nanotube (CNT) polymer nanocomposites are promising new materials with a unique combination of mechanical and transport properties. As physical properties such as mechanical behavior, dielectric relaxation, thermal and electrical conductivities depend strongly on morphological structures of composites, we illustrate in this study the structure/property relationship in vertically aligned CNT (VACNT)/polymer nanocomposites. We have prepared VACNT/polystyrene composites and characterized their morphologies and properties. We have reported previously the continuous variation of alignment order along the height of CNT, which remain unaltered upon forming composites as revealed by small angle neutron scattering (SANS). Nanoindentation shows that both the elastic modulus and hardness vary along the CNT growth direction due to the varying tube density, alignment order and entanglement.