Abstract: N-type semiconducting diamond is disclosed, which is intrinsically, i.e., at the time of diamond formation, doped with n-type dopant atoms. Such diamond is advantageously formed by chemical vapor deposition from a source gas mixture comprising a carbon source compound for the diamond, and a volatile precursor compound for the n-type impurity species, so that the n-type impurity atoms are doped in the diamond film in situ during its formation. By such in situ formation technique, shallow n-type impurity atoms, e.g., lithium, arsenic, phosphorous, scandium, antimony, bismuth, and the like, may be incorporated into the crystal lattice in a uniform manner, and without the occurrence of gross lattice asperities and other lattice damage artifacts which result from ion implanation techniques. A corresponding chemical vapor deposition method of forming the n-type semiconducting diamond is disclosed.

Abstract: A printed background pattern for a document is described, wherein the pattern masks a copy indicator which is revealed upon making a copy of the pattern using a digital optical scanning means. The background pattern comprises an area of microprinting with a type size having a line resolution of about 20% to about 80% of the resolving power of the scanning means. Preferably, the type size is less than 100 .mu.m. An area of solid line printing is provided within the microprinting which defines the copy indicator. The solid lines have a visual value approximating that of the microprinting so as to be masked therein, and the solid lines are capable of resolution by the digital scanning means.

Abstract: Method of preparing a contoured plate by selectively hardening a photopolymer plate in a zone which is adjacent the lower surface of the plate and increases continuously in thickness from one portion of the plate to another by a first exposure of the upper surface of the plate to a quantity of light energy which increases continuously per unit area of the surface from said one portion of the plate to the other. Discrete portions of the upper surface of the plate are masked in the portions on which it is desired to form a recessed design, and the non-masked portions of the plate are hardened by a second exposure of its upper surface to light energy, so that the masked portions remain unhardened from their upper surface to the upper region of said hardened zone. The unhardened portions are removed to provide a recessed design in the upper surface of the plate. The design varies continuously in depth independently of the width of the design.