Formation of dark spatial optical solitons in planar waveguides produced by implantation of light ions into Fe- or Cudoped X cut lithium niobate wafers is experimentally studied. The implantation both of protons and O3+-ions results in the excellent waveguide layers with their thickness about 3 microns and optical losses less than 1 dB/cm. The soliton states at light wavelengths of 532 nm and 633 nm are developed due to the self-defocusing photorefractive- photovoltaic nonlinearity of lithium niobate. Extraordinarily polarized light beams are used in experiments to form dark solitons and to probe the soliton-induced waveguide channels. Steady-state dark photovoltaic spatial solitons have been realized in both, H+- implanted and O 3+- implanted planar waveguides at optical powers from 10 to 100 microwatts. The storage time of soliton-induced channel waveguides makes up at least some hours without special illumination of a planar waveguide and they may be erased within some seconds in a case of their permanent readout with stronger light beams. The possibility to form more complicated channel waveguide structures in regimes of dark spatial solitons is also demonstrated. © 2008 SPIE.