description fig1 16 illustrate various methods of forming field emission tips according to the present invention it should be understood that the illustrations are not meant to be actual views of any particular field emission device but are merely idealized representations which are employed to more clearly and fully depict the formation of field emission tips of the present invention than would otherwise be possible additionally elements common to fig1 16 retain the same numerical designation fig1 4 illustrate one embodiment for forming field emission tips according to the present invention as shown in fig1 an etch mask material such as a photoresist material is patterned by photolithography to define an etch mask element 104 on a substrate 102 such as a wafer of semiconductor material e g silicon or a silicon on insulator soi type substrate such as a silicon on glass sog or silicon on sapphire sos substrate the substrate 102 may also be conductive material layered over a dielectric substrate not shown the substrate 102 is then anisotropically etched by dry etch techniques such as physical sputtering or plasma etching to form from the substrate 102 and under etch mask element 104 a vertical column 106 of substantially constant cross section and exhibiting substantially vertical sidewalls 107 relative to a plane of substrate 102 as shown in fig2 for example the anisotropic etch may be a plasma dry etch conducted at a power of about 250 watts at a pressure of about 85 mtorr and employing an etchant gas mixture comprising hydrobromic acid hbr gas delivered at a rate of about 10 sccm and chlorine gas cl 2 delivered at a rate of about 60 sccm the etch mask element 104 is removed from the.