GROWTH OF PBS THIN-FILMS FROM NOVEL PRECURSORS BY ATOMIC LAYER EPITAXY

Two lead tert-butoxide complexes (1) [Pb(OBu(t))(2)](m), (m=3 or 2 in the solid and gaseous phase, respectively) and (2) Pb4O(OBu(t))(6) wer e used as precursors for atomic layer epitaxy (ALE) deposition of PbS thin films. The growth on soda lime glass, with and without an alumina coating, was studied by varying the source furnace and the substrate temperatures as well as the total number of cycles. Pb(thd)(2) (3) and Pb(dedtc)(2) (4) were used for comparison while H2S served in all exp eriments as the sulfur source. The films obtained were smooth and gene rally highly crystalline. The substrate temperature had a strong effec t on the growth rate of PbS thin films. Nevertheless, in the self-cont rolled region of ALE growth the tert-butoxide complexes gave a signifi cantly higher growth rate than the other source chemicals, with a maxi mum of 0.9 Angstrom per cycle at 150 degrees C. Upon sublimation 1 is converted to 2, which contains four Pb atoms in a tetrahedral arrangem ent; this may cause the higher growth rate. Thermogravimetry/different ial thermal analysis curves and mass spectrometric data were measured for all precursors. As the butoxide and thd complexes (1-3) are therma lly unstable the useful ALE prosessing windows (temperature/pressure) are narrow compared to the much more stable dedtc complex (4).