A method of forming a shallow trench isolation has the steps of: forming a plurality of trenches in a semiconductor substrate; forming an oxide liner on the bottom and sidewall of each trench; and thermal annealing in a nitrogen-containing atmosphere to dope nitrogen elements in the oxide liner. Each of the display panels is mounted proximate a roadway or other public venue and is optically visible to persons traveling along the roadway or otherwise in the public venue. The first optional layer coating consists typically of a pigmented coating bound together with a synthetic or natural binder and is applied in sufficient quantity to level and densify the surface of a given substrate.