摘要:

Characteristics of a conical field emission gun (FEG) are measured and discussed. The field emission current from a W emitter is found to obey the Fowler–Nordheim (FN) equation. An expression was given describing the dependence of the mean work function on the curvature radius at the vertex of the emitter. Using scanning electron microscopy, a radius of 1500 Å was measured with which the slope of the FN plot yielded a mean work function of 4.8 eV. The initial value of the emission current, obtained after cleaning the tip by flashing, decays with time due to an increase of the work function caused by the adsorption of residual gases. The measured time dependent mean emission current was interpreted as a weighted superposition of local field emissions from the W(310), (100), (110), (111), and (112) planes. This interpretation resulted in a mean work function of 4.6 eV in good agreement with the value determined from the FN plot. For an accelerating voltage of 15 keV and an emission current of 8 μA after flashing, the dependence of the probe current on the extraction voltage was measured. ForVacc/Vex=1,an angular current density of(41±4) μA/srwas found. Similar measurements of the dependence of the probe current on the ratioVacc/Vex(accelerating voltage/extraction voltage) made 3 h after flashing yielded(20±6) μA/srforVacc=Vex.The transfer efficiency defined as the ratio between probe current and emission current was found to be 0.4%–0.3%.

ISSN:1071-1023    

DOI:10.1116/1.590286

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A simple empirical circuit model, which can be incorporated into circuit simulation programs such asSPICE, for a field emission triode is developed. The model is based on the Fowler-Nordheim (FN)J-Erelationship but takes into account the space charge effect and the exponential-like charge distribution on the surface of the tip of the device. A procedure is also developed to extract the parameters of the model.

ISSN:1071-1023    

DOI:10.1116/1.590241

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

An improved finite difference method is used to study the field emitter arrays in both diode and triode modes. In the simulation, the boundary of the emitter can be fitted with irregular meshes. The emission performance of the emitter array is analyzed in this article. Simulation results show that the electric field at tips in the emitter array is not uniform. The emission currents from tips are also different. Due to the influence of the interaction and fringe field, the emission currents from tips near the edge of the array are larger than that from tips on the center part of the array. However, the presence of the gate can reduce the interaction between neighboring tips in the triode structure. Thus, it is possible to achieve a higher current density in the triode mode.

ISSN:1071-1023    

DOI:10.1116/1.590287

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A low temperature plasma-promoted chemical vapor deposition (PPCVD) process has been developed for the growth of tantalum (Ta) from the halide source tantalum pentabromide(TaBr5),using hydrogen as reducing agent, for incorporation in emerging integrated circuitry (IC) copper metallization schemes. Ta films were produced at substrate temperatures of 400–450 °C, reactor working pressures of 0.6–0.7 Torr, hydrogen carrier flow rate of 50 sccm, hydrogen reactant flow rates between 200 and 1200 sccm, and plasma power ranging from 20 to 100 W, corresponding to a power density of 0.11–0.55 W/cm2. The films were subsequently characterized by Auger electron spectroscopy (AES), Rutherford backscattering (RBS), x-ray diffraction (XRD), atomic force microscopy (AFM), four-point resistivity probe, scanning electron microscopy (SEM), and cross-section SEM. These studies indicated that the Ta films thus produced were carbon and oxygen free, contained bromine concentration below 2.5 at. %, and exhibited better than 75% step coverage in nominally 0.6 μm, 2.5:1 aspect ratio, trench structures.

ISSN:1071-1023    

DOI:10.1116/1.590288

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The patterning of phosphor screens was carried out using a lithographic technique and electrophoretic deposition of phosphor particles for high-resolution field emission display applications. The electrophoretic deposition and photolithography steps were established. Patterned phosphor screens were fabricated by controlling process parameters such as electrophoretic deposition rate in combination with a well-controlled photoresist process in order to achieve proper pixel size with clear boundaries.

ISSN:1071-1023    

DOI:10.1116/1.590289

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Already at coverages as low as 0.005 monolayer of potassium on room temperature Si(111)7×7 surfaces, atomic resolution is gradually lost when imaging the surface with scanning tunneling microscope at positive sample bias, giving rise to bright triangles over the faulted halves of the 7×7 unit cells and dark triangles above the unfaulted halves. We suggest that this is due to potassium atoms that are picked up by the tip fromKislands at the surface, as is evident by the observed lowering of the tunneling energy barrier. This phenomenon vanishes upon thermal desorption ofKislands or upon exposure to 0.1 L oxygen.

ISSN:1071-1023    

DOI:10.1116/1.590290

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We have studied theTcdegradation of epitaxialYB2Cu3O7−x(YBCO) films on (100)LaAlO3substrates implanted with 100 keVO+ions at different conditions. The influence of Au mask thickness and the implantation doses on the film characteristics have been investigated systematically. YBCO bridges have been modified by local oxygen ion implantation at optimal condition through a narrow trench in an Au/photoresist mask, which was fabricated formed by focused ion beam milling and reactive ion etching. The critical current and normal resistance of the modified bridges were found to be characteristic of superconductor/normal/superconductor Josephson junction behavior. Microwave irradiation of the junctions resulted in Shapiro steps in theI–Vcharacteristics.

ISSN:1071-1023    

DOI:10.1116/1.590291

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

In order to investigate the reflow characteristics of copper, copper was deposited on hole and trench patterns by metal organic chemical vapor deposition and it was annealed in nitrogen and oxygen ambients with the annealing temperatures ranging from 350 to550 °C.Upon annealing in an oxygen ambient at higher than 450 °C, copper was reflowed into the trench patterns whose line- width and aspect ratio were 0.2 μm and 4:1, respectively. Copper oxide was found with a thickness of less than a fifth of the total film thickness. The resistivity of the copper film increased when reflow occurred. It is thought that the reflow of copper in an oxygen ambient takes place because of enhanced surface diffusion.

ISSN:1071-1023    

DOI:10.1116/1.590292

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.590293

出版商:American Vacuum Society    

年代:1998

数据来源: AIP