RECOIL IMPLANTATION OF ALPHA-SOURCES FOR THICKNESS MEASUREMENT OF THIN-FILMS

A sequence of radioactive decays can be used to implant alpha-emitting sources in substrates for thickness measurements of films grown on th em. Starting with Th-228, both direct recoil implantation of Ra-224 an d a two-stage recoil implantation of Pb-212 were performed. The thickn ess of germanium layers grown on gallium arsenide was determined by me asuring the energy loss of the alpha particles traversing them. The re sults were found to be consistent with those obtained by other methods . The special advantages of the present procedure are discussed.