| AVS 61st International Symposium & Exhibition | |
| Thin Film | Monday Sessions |
| Session TF+PS-MoA |
| Session: | ALD Surface Reactions and Precursors |
| Presenter: | Adriaan Mackus, Stanford University |
| Authors: | A.J.M. Mackus, Stanford University R.W. Johnson, Stanford University W.-H. Kim, Stanford University S.F. Bent, Stanford University |
| Correspondent: | Click to Email |
In recent years there is increasing interest in atomic layer deposition (ALD) processes that go beyond traditional AB cycles to enable the deposition of alloyed, doped, or ternary materials. The composition of a ternary material can be tuned by mixing the cycles of two different AB processes in a certain ratio ((AB)n(CD)m). However, in practice, the composition and the growth rate tend to deviate from what is expected based on the cycle ratio n/m, whereas the formation of a certain crystallographic phase strongly depends on the mixing of ALD cycles and post-deposition anneal conditions. A detailed understanding of how to deposit ternary metal oxides with control of composition and crystallographic phase is currently lacking.
In this work, the material zinc tin oxide (ZTO) has been selected as a model system for studying ternary metal oxide ALD, motivated by its applications as transparent conducting oxide (TCO)1 or buffer layer2 in solar cells. For these applications it is important that ZTO consists of earth-abundant non-toxic elements, and therefore has the potential to replace indium-based TCOs or Cd-based buffer layers. ZTO films were deposited by combining the ALD processes of ZnO from diethylzinc (DEZn) and water, and SnO2 from tetrakis(dimethylamido)tin (TDMASn) and water.1,3 Synchrotron-radiation X-ray diffraction (SR-XRD) has been performed at the Stanford Synchrotron Radiation Lightsource (SSRL) to investigate the crystallographic phase of the films as a function of composition, cycle ratio, and anneal conditions. It was found that the zinc orthostannate (Zn2SnO4) phase forms upon high-temperature annealing, thereby confirming the deposition of ZTO. In addition, Fourier transform infrared spectroscopy (FTIR) was employed to elucidate the surface chemistry of the ZTO ALD process.
1. Mullings et al., Thin Solid Films 556, 186 (2014)
2. Lindahl et al., Prog. Photovolt: Res. Appl. 21, 1588 (2013)
3. Mullings et al., J. Vac. Sci. Technol. A 31, 061503 (2013)