D. Liu

Bio: D. Liu is an academic researcher from New Jersey Institute of Technology. The author has contributed to research in topics: Silicon & Field electron emission. The author has an hindex of 4, co-authored 5 publications receiving 327 citations.

Formation of silicon tips with <1 nm radius

Abstract: Electron emitters in vacuum microelectronic devices need sharp tips in order to permit electron emission at moderate voltages A method has been found for preparing uniform silicon tips with a radius of curvature less than 1 nm These tips are formed by oxidation of 5‐μm‐high silicon cones through exploitation of a known oxidation inhibition of silicon at regions of high curvature

Atomically sharp silicon and metal field emitters

Abstract: A method is described for forming atomically sharp silicon tips of less than 10-15 degrees half-angle by utilizing a known oxidation inhibition at regions of high curvature; equally sharp silicon wedges are now made in a similar fashion. The sharp silicon tips serve as the starting point for forming sharp tips of W, beta -W and gold. Field emission data from silicon emitters are compared with Fowler-Nordheim modelling and emission as a function of emitter-anode distance is described. >

Fabrication of wedge‐shaped silicon field emitters with nm‐scale radii

Abstract: Wedge‐shaped field emitters may have some advantages over conical tip emitters as electron sources in vacuum microelectronic devices. A method has been developed to make atomically sharp wedge‐shaped silicon through use of dry etching and dry oxidation. Transmission electron microscopy studies show that silicon wedge emitters can be made with wedge radius and angle at 1 nm and 60°, respectively, by repeated oxidation in oxygen at 950 °C.

Fabrication of self-aligned gated field emitters

Abstract: Reports a new self-aligned process to form gated field emitters including an evaluation of dielectrics and field emission measurements. This process offers advantages including gate opening control down to 0.25 mu m diameter without electron-beam writing assistance, a planar structure, and thick dielectric for capacitance reduction. The current-voltage characterization of the gated field emitter follows Fowler-Nordheim behavior. Leakage characteristics of various dielectric materials are measured and described.

Gated micrometer-size electron field emitters

Abstract: Summary form only given. A procedure has been developed for making arrays of gated micrometer-size electron field emitters from silicon with some advantages over similar processes developed elsewhere. One-micron-high emitters are made with radii as small as 1 nm, and with self-aligned flat gate electrodes with low capacitance and with the circular gate opening controlled to submicrometer diameter independently of the tip height. Emission measurements show expected Fowler-Nordheim behavior, with the Fowler-Nordheim curves (I/V/sup 2/ versus 1/V) parallel but displaced along the 1/V axis for different tips. The field factor K (where E=K*V) is derived from the measured slope, and the emission area is derived from K, the Fowler-Nordheim equation, and an assumed work function. >

Advances in atomic force microscopy

Abstract: This article reviews the progress of atomic force microscopy in ultrahigh vacuum, starting with its invention and covering most of the recent developments. Today, dynamic force microscopy allows us to image surfaces of conductors and insulators in vacuum with atomic resolution. The most widely used technique for atomic-resolution force microscopy in vacuum is frequency-modulation atomic force microscopy (FM-AFM). This technique, as well as other dynamic methods, is explained in detail in this article. In the last few years many groups have expanded the empirical knowledge and deepened our theoretical understanding of frequency-modulation atomic force microscopy. Consequently spatial resolution and ease of use have been increased dramatically. Vacuum atomic force microscopy opens up new classes of experiments, ranging from imaging of insulators with true atomic resolution to the measurement of forces between individual atoms.

Powering an Inorganic Nanodevice with a Biomolecular Motor

Abstract: Biomolecular motors such as F 1 –adenosine triphosphate synthase (F 1 -ATPase) and myosin are similar in size, and they generate forces compatible with currently producible nanoengineered structures. We have engineered individual biomolecular motors and nanoscale inorganic systems, and we describe their integration in a hybrid nanomechanical device powered by a biomolecular motor. The device consisted of three components: an engineered substrate, an F 1 -ATPase biomolecular motor, and fabricated nanopropellers. Rotation of the nanopropeller was initiated with 2 mM adenosine triphosphate and inhibited by sodium azide.

Novel cold cathode materials and applications

Abstract: Field emission (FE) is based on the physical phenomenon of quantum tunneling, in which electrons are injected from the surface of materials into vacuum under the influence of an applied electric field. A variety of field emission cold cathode materials have been developed to date. In this review, we shall focus on several kinds of novel cold cathode materials that have been developed in the past decade. These include materials for microfabricated field-emitter arrays, diamond and related films, carbon nanotubes, other quasi one-dimensional nanomaterials and printable composite materials. In addition, cold cathode materials have a wide range of applications such as in flat panel displays, high-power vacuum electronic devices, microwave-generation devices, vacuum microelectronic devices and vacuum nanoelectronic devices. Applications are in consumer goods, military industries and also space technology. A comprehensive overview of the various applications is presented. Recently, recognizing the strong possibility that vacuum nanoelectronic devices using quasi one-dimensional nanomaterials, such as carbon nanotubes may emit electrons with driving voltages comparable to that of a solid-state device, there is a growing interest in novel applications of such devices. With such exciting opportunities, there is now a flurry of activities to explore applications far beyond those considered for the conventional hot cathodes that operate on thermionic emission. We shall discuss the details of a number of fascinating potential applications.

Efficient field emission from ZnO nanoneedle arrays

Abstract: Well-aligned arrays of ZnO nanoneedles were fabricated using a simple vapor phase growth. The diameters of the nanoneedle tips are as small as several nanometers, which is highly in favor of the field emission. Field-emission measurements using the nanoneedle arrays as cathode showed emission current density as high as 2.4 mA/cm2 under the field of 7 V/μm, and a very low turn-on field of 2.4 V/μm. Such a high emission current density is attributed to the high aspect ratio of the nanoneedles. The high emission current density, high stability, and low turn-on field make the ZnO nanoneedle arrays one of the promising candidates for field-emission displays.

Vacuum microelectronic devices

Abstract: In this review/tutorial paper, we cover the history, physics, and current status of vacuum microelectronic devices. First we overview the performance requirements of vacuum microelectronic devices necessary for them to replace, or fill voids left by, solid state devices. Next we discuss the physical characteristics of micro-field-emission sources important to device applications. These characteristics include fundamental features, such as current-voltage data and noise, in addition to engineering considerations, such as life expectancy and procedures for tube assembly. We conclude with a review of a wide variety of demonstrated and proposed devices based on vacuum microelectronic principles, including electron guns, microwave tubes, and flat-panel displays. >