Variation in the properties of ZnO:Al films grown by using atomic layer deposition with the precursor-pulse ratio

Aluminium-doped ZnO(ZnO:Al) films on glass substrates at a temperature of 200 .deg. C were grown by using atomic layer-controlled deposition with diethylzinc (Zn(C2H2)2; DEZn), water (H2O) and trimethylaluminium (Al(CH3)3; TMA) as precursors. The growth was accomplished by the sequential precursor reactions 'DEZn precursor -> Ar purge -> H2O precursor -> Ar purge -> TMA precursor' and by repeating the entire cycle with different pulse ratios of TMA to DEZn. As the cycle ratio of TMA to DEZn (TMA/DEZn) was increased, the resistivity of the films decreased and the roughness increased. In the case of a TMA/DEZn pulse ratio of 1 to 10, the film had a resistivity of 9.7 x 10-4 Ω·cm and a roughness of 2.25 nm(rms) while in the case of only DEZn injection, the film had a resistivity of 3.5 x 10-3 Ω·cm and a roughness of 1.07 nm(rms). The transmittances of the films were in excess of 76 % for all samples with a better performance corresponding to the respective wave range.