摘要:

In the effort to develop a high performance field emission cathode for application in microwave amplifiers, it is clear that the emitter structure should have a sharp emitter surface, a large emitter height, a small gate opening size, and a small emitter angle. We have developed a technique that fabricates knife‐edge field emission arrays (KEFEA) on (110) silicon wafers. KEFEA has an optimized structure meeting the requirements mentioned above. The emitter edge radius is about 250 Å or less, the emitter height is 8 μm, and the gate gap is ∼0.2 μm. Experiments have exhibited Fowler–Nordheim type field emission with gate‐to‐substrate bias voltage less than 50 V.

ISSN:0734-211X    

DOI:10.1116/1.587404

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A vacuum microdiode was fabricated with a silicon avalanche cathode and an on‐chip microanode. The image reverse process followed by proper heat treatment was employed to form a photoresist sacrificial layer in shaping a microanode. The distance of ∼3 μm between cathode and anode was achieved by adjusting the number of depositions of photoresist. On the top of the sacrificial layer, a multilayer (Al/TiW/Al) structure was deposited, which provided the microanode with good conductivity and mechanical strength. The dimension of the microanode was 8 (or 18) μm in width and more than 30 μm in length. TheI–Vcharacteristics of this vertical‐type microdiode demonstrated the enhancement of current emission due to a strong electric field at relatively low anode voltages.

ISSN:0734-211X    

DOI:10.1116/1.587405

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Field emission cathode arrays of Betsui type [K. Betsui, Technical Digest of the International Vacuum of Microelectronics Conference, Nagahama, Japan, 1991 (unpublished)] need an intermediate spacer layer with excellent insulator properties, i.e., ultrahigh resistivity, high breakdown voltage, excellent adhesion both to substrate and gate layer, low roughness, low dielectric constant, and sufficient long term stability. This study reports on an investigation of various fabrication methods for this insulating film in order to optimize its properties. Silicon and some compounds (a:Si, SiO, SiO2, SiOxNy) have been deposited by e‐beam or thermal evaporation and plasma enhanced chemical vapor deposition, respectively. These layers have been annealed or oxidized before deposition of the extraction gate layer. The structures have been characterized by means of capacitance measurements. The best results have been obtained with the deposition of pure silicon by e‐beam evaporation followed by an oxidization process. The method described in detail results in an insulator consisting of SiO2which exhibits excellent insulating properties (breakdown field strength 7 MV/cm). Field emission cathodes fabricated in this manner exhibit stable emission currents up to 1 μA/tip.

ISSN:0734-211X    

DOI:10.1116/1.587406

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The field emission characteristic of a Spindt‐type cathode, cleaned extensively in a hydrogen atmosphere while emitting, is considered. The maximum emission reached is about 800 μA. At high current levels theI–Vcurve clearly deviates from a Fowler–Nordheim behavior. This can be explained by the occurrence of space charge. Several models are considered to simulate the experimental results. The fit to the data is good except at the highest emission levels. In this region the difference between the measured currents and the simulation results is due to the neglect of the variation of the field on top of the tip in the presence of space charge.

ISSN:0734-211X    

DOI:10.1116/1.587407

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Square‐based pyramidal emitters formed by wet etching ofp‐type silicon wafers have been anodized to give a thin surface layer of porous silicon. At the surface of such material are very small fibrils with widths ≤3 nm. Field emission measurements from pyramidal cathodes of plain and anodized silicon show a dramatic improvement, when the porous silicon is present. In this case, average peak emission currents of 25 μA have been obtained with the highest measured being 90 μA, improved uniformity between cathodes was produced and emission began at lower voltages. It was found that plain cathodes too blunt to emit did so when covered in porous silicon. The reasons why such silicon fibrils improve emission are discussed.

ISSN:0734-211X    

DOI:10.1116/1.587408

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Realization of an easily manufacturable field emission device has been widely recognized as one of the keys to the widespread acceptance of vacuum microelectronics technology. Working to achieve this goal, many researchers have investigated edge emission cathodes similar to those developed by Grayetal. These efforts include work in the area of nonplanar edge emission devices reported by Weicholdetal. and devices reported by Itohetal. Based on that concept, this paper describes an improved nonplanar edge emission diode, suitable for monolithic integration. The structure described by Weichold has several interesting qualities, including the ability to easily define, nonphotolithographically, the anode to cathode spacing during the fabrication process. Additionally, the unique device geometry provides several advantages over traditional structures. Unfortunately, this device does not lend itself well to integration, due to the difficulty of making electrical contact to the cathode. An improved nonplanar diode design which addresses this issue has been conceived and manufactured. The new design has the additional advantage of relying only upon standard manufacturing techniques for its construction. Preliminary device testing has shown current–voltage characteristics that follow the Fowler–Nordheim model for cold field emission over several orders of magnitude of current. In this work, various cathode sizes are investigated and several cathode array sizes are tested.

ISSN:0734-211X    

DOI:10.1116/1.587366

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The properties of single silicon field emission microtriodes have been examined. Gate and collector currents were measured in a vacuum of 2×10−8Torr, and current–voltage, current–time, Fowler–Nordheim (I/V2versus 1/V), and triode characteristics were determined. The data showed that the electron emission followed Fowler–Nordheim behavior. Single emitters had turn‐on gate‐to‐cathode voltages (V) above 25 V (typically 50–90 V) and reproducible emission currents were measured in the range 5 pA–1 μA. Temporal fluctuations in emission current of 10%, 16%, and 40% were found for emission currents of 0.35, 50 nA, and 0.5 μA, respectively. The triode characteristics showed anIg/Icratio of 0.25% and higher. Transconductances were found to be 3×10−8Ω−1/tip. Electrostatic discharge and other device failure mechanisms have been observed and are described.

ISSN:0734-211X    

DOI:10.1116/1.587367

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

I–Vcharacteristics of silicon field emission diode and triode were investigated. The maximum emission current of 17 μA and the lowest onset voltage of 60 V were obtained by an array of 245 silicon tips. The typical reverse recovery time of the diode was 350 ps. The typical transconductance of the triode was about 10−7S. The fabrication processes for forming sharp silicon conical tips with a gate hole diameter 1 μm smaller than the corresponding oxide mask is described. The results of a high temperature activation process for improving emission characteristics of the device are presented. The stability and uniformity of the devices affected by the fabrication process and emission environment are also discussed in this paper.

ISSN:0734-211X    

DOI:10.1116/1.587368

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

By reversing the bias of a field emitter with a volcano‐shaped gate, it is demonstrated that emission occurs from the rim of the gate. The gate‐to‐emitter distance of this structure is defined by the thickness of the insulating film between the electrodes and not by expensive photolithographic techniques. By enlarging the gate diameter to printed circuit board‐type dimensions, in principle, low cost, large area field emitter arrays can be fabricated. The process is being demonstrated on a silicon substrates and initial emission data are being presented. The article concludes by demonstrating one transfer path of this technology onto an inexpensive glass substrate.  

ISSN:0734-211X    

DOI:10.1116/1.587369

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

In order to evaluate the potential of microtips in novel electron optics applications, the emission stability of a single tip was studied. It was found that after a few hours of ‘‘self‐shaping,’’ a tip may emit a very stable spot (for 700 nA of global emission, 7 min is reported without any change over 1 nA, and a couple of hours with less than ±1% change). Unfortunately, a period of instability may follow a period of stability. It was observed that the spot is composed of several subspots, each one having a much greater stability than the whole spot. These subspots are very likely to be emitted from independent nanoprotrusions or atoms, and changes in the emission occur because of motions of atoms and/or adsorption–desorption processes. It was concluded that, though the stability of an electron beam cannot be ‘‘infinite’’ as a laser beam is, very long periods of stability (hours) and high coherence of wave packets can be obtained, if work was done under very high vacuum (several 10−11mbar) and with a unique beam emitted from a single atomic site.

ISSN:0734-211X    

DOI:10.1116/1.587370

出版商:American Vacuum Society    

年代:1994

数据来源: AIP