1. A memristive device ( 400 ) comprising: a first electrode ( 405 ); a second electrode ( 425 ); a memristive matrix ( 415 ) interposed between said first electrode ( 405 ) and said second electrode ( 425 ); a porous dopant diffusion element ( 410 ) in physical contact with said memristive matrix ( 415 ) and in proximity to at least one of said first electrode ( 405 ) and said second electrode ( 415 ); and a first mobile dopant species, said first mobile dopant species moving through said porous dopant diffusion element ( 410 ) in response to a programming electrical field generated by said first electrode ( 405 ) and said second electrode ( 425 ), said programming electrical field altering a distribution of said first mobile dopant species within said memristive matrix ( 415 ).