Effects of gate underlap on electronic properties of conventional single-material-gate CNTFET (C-CNTFET) and heteromaterial-gate CNTFET (HMG-CNTFET) are investigated theoretically in a quantum kinetic model.The model is based on twodimensional non-equilibrium Green's functions (NEGF) solved self-consistently with Poisson's equations.It shows that intrinsic cutoff frequency of C-CNTFETs reaches a few THz.In addition,a comparison study was performed about C-and HMG-CNTFETs.Calculated results show that,C-CNTFETs with longer underlap have better switching speed but less on/off current ratios.For HMG-CNTFET,gate underlap improves sub-threshold performance and switching delay times,and decreases output conductance significantly.

Ballistic performance of single-material-gate and triple-material-gate graphene nanoribbon field effect transistors (GNRFETs) with various doping profiles is studied in a quantum kinetic model based on non-equilibrium Green's functions (NEGF) solved self-consistently with Poisson's equations.It shows that triple-material-gate GNRFET with linear doping (TL-GNRFET) exhibits significant advantage in reducing SCEs and DIBL effects,as well as achieving better subthreshold slope and better on/off current ratio.In addition,asymmetric gate underlap is also discussed.It is revealed that as top and bottom gates are both shifted towards source on/off state current performance is improved.

A computing method for image reconstruction of electronic density rearrangement from the compton scattering data is presented.The well-posedness of the discrete problems is discussed.Some numerical experiments of interest given here show that the method is efficient.

A physical model is presented for linear coupling of microwave pulses into apertures in cavities. The numerical simulation method of FDTD and absorbing boundary conditions are dis cussed. We calculate coupling processes of microwave pulses into apertures with various size and different positions, and an alyse the dependence of coupling on aperture size and polarization direction of the incident field.