B-doped　ZnO　thin　films　have　been　fabricated　on　fused　quartz　substrates　using　boron-ZnO　mosaic　target　by　pulsed-laser　deposition　technique,　and　the　mechanical　properties　have　been　studied　by　nanoindentation　continuous　stiffness　measurement　technique　and　transmission　electron　microscope　(TEM).　Nanoindentation　measurement　revealed　that　the　hardness　of　B-doped　ZnO　films,　9.32　+/-　0.90　to　12.10　+/-　1.00　GPa,　is　much　greater　than　that　of　undoped　ZnO　films　and　very　close　to　that　of　traditional　semiconductor　Si.　The　mean　transmittance　(%)　is　larger　than　81%　in　the　visible　range　(380-780　nm)　for　all　the　films,　and　the　Hall　effect　measurement　showed　that　the　carrier　density　is　around　2　x　10(20)　cm(-3)　and　the　resistivity　lower　than　3　x　10(-3)　Omega　cm.　TEM　characteristics　show　undoped　thin　films　have　more　amorphous　area　between　grains　while　the　B-doped　ZnO　films　have　thin　grain　boundaries.　We　suggest　that　the　grain　boundaries　act　as　the　strain　compensation　sites　and　the　decrease　in　thickness　of　grain　boundaries　enhances　the　hardness　of　the　B-doped　ZnO　films.　(c)　2006　Elsevier　B.V.　All　rights　reserved.