DETERMINATION OF W AND Ta CONTAMINATIONS IN Nb THIN FILMS
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
A sensitive, quantitative method of analyzing thin films of Nb, NbO, NbSi for minute W and Ta contaminations is based on neutron activation of specially prepared samples. The Nb film is deposited on an Si wafer having a number of small windows with an area of about 6 x 6 mm and an Si thickness of 2 to 3 mm (such wafers being obtained by back-etching after B-doping to the desired window thickness). The film-covered windows (with a known quantity of Nb) are then stamped from the wafer and placed in a sample vessel which is subjected together with a calibrated reference mass of pure W and Ta to a high flux of thermal neutrons in a nuclear reactor. The neutrons activate (n, ) reactions in W-187 and Ta-182g with a high radiative capture cross-section.