The　polarity　of　the　ZnO　film　grown　on　sapphire　using　an　ultrathin　Ga　wetting　layer　has　been　investigated　by　electron　holography.　Spontaneous　polarization　of　the　ZnO　film　leads　to　localized　charges　in　the　surface,　which　change　the　potential　distribution　in　the　vacuum　side　of　the　film.　The　potential　distribution　depends　on　the　nature　of　the　bounded　charges　and　change　as　a　function　of　the　distance　from　the　film　surface.　By　studying　the　dependence　of　the　potential　change　on　the　distance　from　the　film　surface,　the　ZnO　film　with　very　thin　Ga　wetting　layer　is　determined　to　have　the　[0001]　polarity.　(C)　2004　American　Institute　of　Physics.