Ion implantation for doping of polyacetylene film is described. An ion implanter is used for implantation and the conditions for potassium implantation are: ion beam energy 10-30 KeV

fluence 1×1015-1×1017 ions/cm2

and beam current about 2μA. The pristine (CH)x film emerged a little of p-type semiconductor characteristics because of residual catalyst or oxygen. Apparent doping effects were observed in those films implanted with K ions as a n-type electron-donating dopants. Current-voltage characteristic of a p-n junction produced and the resulting diode characteristics are stable for more than a week in the open air. The depth pro-file of implanted K ions in a polyacetylene film obtained by Rutherford Backscattering Spe-ctrometry (RBS) shows a Gaussian distribution centred around a few thousand A.