A method for fabricating a periodic dielectric structure which exhibits a photonic band gap. Alignment holes are formed in a wafer of dielectric material having a given crystal orientation. A planar layer of elongate rods is then formed in a section of the wafer. The formation of the rods includes the step of selectively removing the dielectric material of the wafer between the rods. The formation of alignment holes and layers of elongate rods and wafers is then repeated to form a plurality of patterned wafers. A stack of patterned wafers is then formed by rotating each successive wafer with respect to the next-previous wafer, and then placing the successive wafer on the stack. This stacking results in a stack of patterned wafers having a four-layer periodicity exhibiting a photonic band gap.

A method for fabricating a periodic dielectric structure which exhibits a photonic band gap. Alignment holes are formed in a wafer of dielectric material having a given crystal orientation. A planar layer of elongate rods is then formed in a section of the wafer. The formation of the rods includes the step of selectively removing the dielectric material of the wafer between the rods. The formation of alignment holes and layers of elongate rods and wafers is then repeated to form a plurality of patterned wafers. A stack of patterned wafers is then formed by rotating each successive wafer with respect to the next-previous wafer, and then placing the successive wafer on the stack. This stacking results in a stack of patterned wafers having a four-layer periodicity exhibiting a photonic band gap.

A field-emission structure suitable for large-area flat-panel televisions centers around an insulating porous layer (24A) that overlies a lower conductive region (22) situated over insulating material of a supporting substrate (20). Electron-emissive filaments (30) occupy pores (28) extending through the porous layer. A conductive gate layer (34A) through which openings (36) extend at locations centered on the filaments typically overlies the porous layer. Cavities (38) are usually provided in the porous layer along its upper surface at locations likewise centered on the filaments. In fabricating the structure, the pores are preferably formed by etching charged-particle tracks. Electrochemical deposition is employed to selectively create the filaments in the pores. Self-alignment of the gate openings to the filaments is achieved with charged-particle track etching and/or further electrochemical processing.

A gated electron-emitting device contains a multiplicity of electron-emissive elements, each formed with a pedestal (98) and an overlying cone (941). In each electron-emissive element, the base diameter of the cone is greater than the element, the base diameter of the cone is greater than the diameter of the pedestal. With the pedestal being electrically conductive, the cone may be electrically resistive. Alternatively, each electron-emissive element can be an elongated element (30B) that reaches a maximum diameter at a point between, and spaced apart from, both ends of the element.