Hsueh-Yung Chao

Field-emission properties of novel palladium nanogaps for surface conduction electron-emitters

We explore novel nanometer-scale gaps with different widths in palladium (Pd) thin-film strips using hydrogen absorption under high-pressure conditions and different temperatures. Both the experimental measurement and numerical calculation are conducted to examine the electron conduction properties of the newly proposed surface conduction electron-emitters (SCEs). It is shown that this novel structure exhibits a high emission efficiency, so that a low turn-on voltage of 40 V for an SCE with a 30 nm nanogap is obtained. A calibrated model is adopted to predict the effects of the emitter thickness and different material work functions on emission current with different width of nanogaps. It is found that the heightened thickness increases the emission current. However, it tends to saturate for smaller nanogaps. The decrement of work function is proportional to the increase in emission current, which is independent of the width of nanogap.

Effect of Process Variation on Field Emission Characteristics in Surface-Conduction Electron Emitters

In this paper, we explore the effect of process variation on field emission characteristics in surface-conduction electron emitters. The structure of Pd thin-film emitter is fabricated on the substrate and the nanometer scale gap is formed by the focused ion beam technique. Different shapes of nanogaps due to the process variations are investigated by the experiment and three-dimensional Maxwell particle-in-cell simulation. Four deformation structures are examined, and it is found that the type 1 exhibits high emission efficiency due to a stronger electric field around the apex and larger emission current among structures. The electron emission current is dependent upon the angle of inclination of surface. Hydrogen plasma treatment is also used to increase the edge roughness of the nanogap and thereby dramatically improve the field emission characteristics. For the nanogap with a separation of 90 nm, the turn-on voltage significantly reduces from 60 to 20 V after the hydrogen plasma treatment.

P-102: Three-Dimensional Simulation of Novel Surface Conduction Electron-Emitters

We for the first time explore a novel structure of Pd thin-film emitter fabricated on the substrate with various gaps ranging from 30 nm to 90 nm. with the 3D electromagnetic particle-in-cell (PIC) simulation, we study the conducting mechanism and driving current for the new device with one palladium field emission emitter. Compared with the experimental data, our calibrated simulation predicts a high emission efficiency of the investigated device structure. It is found that the turn-on voltage is about 50V and a very high electron emission current of 0.1 mA is estimated at the anode voltage of 80 V for one emitter. The novel structure of surface conduction electron-emitter (SCE) has the advantages of the simple fabrication and the high emission efficiency. Based upon the numerical procedure, we are currently investigating the emission efficiency for more advanced structures of SCE.

Integral equation solvers for real world applications - some challenge problems

This paper presents some real world applications and problems for integral equation solvers (IES). Integral equation solvers are, in general, more complex to implement compared to differential equation solvers (DESs). This is due to the need for the Greens function method, which generally involves the evaluation of singular integrals. Moreover, due to the dense matrix system, acceleration solution methods have to be invoked before IESs are competitive with differential equation solvers. Also, linearity of the media has to be assumed before frequency-domain and Greens function techniques can be used. In contrast to DESs, the advantage of IESs, lies in the smaller number of unknowns and favorable scaling properties for memory and CPU requirements. DESs are simple to implement, but usually exhibit worse scaling properties when applied to surface scattering problems. The presence of grid-dispersion error worsens their scaling properties for large scale computing. On the other hand, DESs in the time domain can easily account for nonlinear phenomena. Hence, for an area replete with nonlinear physics, such as computational mechanics or computational fluid dynamics, DESs outrank integral equation solvers in popularity. The advantages of IESs in EM make them popular for solving a number of scattering problems. This is especially so when they have been accelerated with fast algorithms

A Linear-Time Algorithm for Extracting Tree and Loop Bases in Computational Electromagnetics

In this paper, we propose a novel loop extraction algorithm that significantly outperforms other computational electromagnetics methods. Since the algorithm does not involve loop independence tests and the rejection of candidate loops, it is also more efficient than the polynomial-time loop extraction algorithms. Further tests demonstrate that our algorithm can find a spanning tree and associated subminimal loops in linear time for a donut structure consisting of many holes

Effect of process variation on field emission characteristic in surface conduction electron-emitters

In this work, we explore the effect of process variation on field emission characteristics in surface conduction electron-emitters. The structure of palladium thin-film emitter is fabricated on the substrate and the nanometer scaled gap is formed by the focused ion beam (FIB) technique. Different shapes of nanogaps due to the process variations are investigated by the experiment and 3D Maxwell particle-in-cell simulation. Four deformation structures are examined, and it is found that the Type 1 exhibits high emission efficiency due to a stronger electric field around the apex and larger the emission current among structures. The electron emission current is dependent upon the angle of inclination of surface.

Automatic generation of passive equivalent circuits for broadband microstrip antennas

In this paper, we propose an efficient method for extracting passive equivalent circuits of broadband antennas. To fully automate the extraction, the vector fitting in B. Gustaven and A. Semlyen (1999) is modified such that the order of the rational approximation can be determined automatically for a given error bound. Then, the approximation is corrected by quadratic programming for enforcing passivity. The passive model is further synthesized by RLC components using algorithms in G. Antonini (2003). As a result, simulated or measured frequency responses of a broadband antenna can be fit with minimum fitting error over a wide range of frequencies.

Review of multi-scale electromagnetic modeling

This paper reviews various methods to solve multi-scale problems ranging from low-frequency methods to very high-frequency methods.

Equivalent Circuit Extraction for Passive Devices

In this study, a minimal equivalent circuit extraction scheme is provided for passive elements such as interconnects and packages. Instead of common poles, the non-common poles are used as the dominant poles of each frequency response when approximating those frequencies into a rational form. An illustration is given to show the relation between the electrical lengths of the interconnects/packages and the corresponding dominant poles. Finally, a three-port interconnect is used to validate the proposed approach. The circuit extracted by the proposed scheme has fewer components than the circuit from the conventional scheme, and decreases the computational load of the circuit simulation.

13.3: Novel Surface Conduction Electron Emitter (SCE) Nanogaps for Field Emission Displays

A novel nanometer scaled gap in palladium thin film strip was prepared by hydrogen absorption under high pressure conditions, and implemented in the fabrication of the surface conduction electron emitter (SCE) for flat panel display applications. The lattice constant increase in the Pd due to the phase transformation from the α-phase to the β-phase after hydrogen absorption, a large compressive stress occurred to the Pd thin film. with a proper geometric arrangement of the Pd/Pt/Ti emitter electrode of the SCE structure, a single nanogap per SCE device was prepared. Finite element analysis was carried out to study the hydrostatic stress distribution in the thin film emitter structure after Pd hydrogenation, and thereby the optimized thickness of thin film electrodes of the emitter was determined for the nanogap fabrication. The novel SCE emitter had an inclined protrusion structure on the cathode, which greatly enhance the local electrical field and improve electron beam focusing. The experimental measurement and theoretical analysis show that field emission properties of the novel SCE are superior to conventional SCE with the coplanar cathode.