Heat treatment of conductive polymer buffer layers results in increased resistance and thus improved interpixel isolation in polymer light emitting device arrays. In one embodiment, a metal organic chemical vapor deposition process is used to deposit a Group III-nitride film on a plurality of substrates within a processing chamber. A high resistivity region is adjacent each end of the toner thin layer forming region on the developing roll. An attachment structure operably connects the guide tools to the bone screws.