I. Sieber et al., ELECTRON-MICROSCOPIC CHARACTERIZATION OF REACTIVELY SPUTTERED ZNO FILMS WITH DIFFERENT AL-DOPING LEVELS, Thin solid films, 330(2), 1998, pp. 108-113
Highly conductive and transparent ZnO:Al films for solar cell applicat
ions were deposited by reactive co-sputtering of Zn and Al from separa
te targets onto silicon substrates. The structure of the films was cha
racterized with FE-SEM and HREM. Films with Al-doping levels up to 5 a
t.% show a columnar structure. The columnar grains are mainly composed
of ZnO in the hexagonal wurtzite structure. The single grains consist
of mutually tilted parts. Stacking faults and twins were observed. Al
influences the growth of nuclei of columnar grains. Near the interfac
e nanocrystallites of different phases were discovered. At the ZnO/Si
interface an amorphous silicon oxide layer was formed. The nanocrystal
line region grows with increasing Al-doping level. Above an Al concent
ration of 5 at.% the films exhibit a nanocrystalline structure. (C) 19
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