Poorani Gnanasambandan1,2,Renaud Leturcq1
Luxembourg Institute of Science and Technology1,University of Luxembourg2
Poorani Gnanasambandan1,2,Renaud Leturcq1
Luxembourg Institute of Science and Technology1,University of Luxembourg2
Zinc tin oxide being abundant and non-toxic has varied applications from gas sensors, thin film transistors, to window and buffer layers in thin film solar cells, etc. The synthesis of zinc tin oxide (ZTO) by atomic layer deposition (ALD) has been widely studied with different Sn precursors and reactants [1][2]. Atomic layer deposition of ternary materials by mixing two binary ALD processes has its challenges [3]; the composition and growth rates of ternary materials deviate from that of the binary processes due to various factors, including the interaction between different precursors.<br/>Previous studies aimed to understand deeper the ZTO ALD processes, by investigating the underlying surface chemistry of the precursors, influence of substrate temperature and constructing analytical models from observed deviations in the growth rate [4][5][6]. Still there remains a need for a consistent model that explains the nonidealities observed in the growth of ZTO by ALD under various processing conditions.<br/>We study atomic layer deposited Zn<sub>1-x</sub>Sn<sub>x</sub>O with x varying from 0.1 to 0.4 by optimizing the growth conditions with varying deposition temperatures and supercycle parameters such as pulse ratios and bilayer period. We analyze the deviation of growth rate and composition of ZTO from the respective binary ALD processes. We find that the composition of [Sn]/([Sn]+[Sn]) has a strong dependence on the deposition temperature in contradiction to Ref. [6]. We aim to achieve precise control over the composition and demonstrate the effect of doping on the band alignment, electrical and optical properties in order to optimize low-temperature deposition of zinc tin oxide as buffers for low bandgap CIGSe absorbers.<br/>[1]. Lee, Yun Seog, et al. "Ultrathin amorphous zinc-tin-oxide buffer layer for enhancing heterojunction interface quality in metal-oxide solar cells." Energy & Environmental Science 6.7 (2013): 2112-2118<br/>[2]. Salome, Pedro MP, et al. "Influence of CdS and ZnSnO Buffer Layers on the Photoluminescence of Cu(In, Ga)Se<sub>2 </sub>Thin Films." IEEE Journal of Photovoltaics 7.2 (2017): 670-675.<br/>[3]. Markus, Adriaan JM, et al. "Synthesis of doped, ternary, and quaternary materials by atomic layer deposition: a review." <i>Chemistry of Materials</i> 31.4 (2018): 1142-1183.<br/>[4]. Markus, Adriaan JM, et al. "Incomplete elimination of precursor ligands during atomic layer deposition of zinc-oxide, tin-oxide, and zinc-tin-oxide." The Journal of chemical physics 146.5 (2017): 052802<br/>[5]. Mullings, Marja N., et al. "Thin film characterization of zinc tin oxide deposited by thermal atomic layer deposition." Thin Solid Films 556 (2014): 186-194.<br/>[6]. Lindahl, Johan, et al. "The effect of substrate temperature on atomic layer deposited zinc tin oxide." Thin Solid Films 586 (2015): 82-87.