| AVS 65th International Symposium & Exhibition | |
| Thin Films Division | Monday Sessions |
| Session TF1-MoM |
| Session: | Precursors and Surface Reactions |
| Presenter: | Konner Holden, Oregon State University |
| Authors: | K. Holden, Oregon State University J.F. Conley, Jr., Oregon State University C.L. Dezelah, EMD Performance Materials |
| Correspondent: | Click to Email |
Nickel oxide (NiO), a wide band gap p-type oxide semiconductor, is of interest for applications in solar energy conversion [1], electrocatalysis [2], and as a tunnel barrier for metal/insulator/metal (MIM) diodes for infrared energy harvesting. Atomic layer deposition (ALD) is an ideal technique for the highly conformal, uniform thin films needed for these applications. Herein, we develop a new process for ALD of NiO using Ni(tBu2DAD)2 and O3.
ALD growth of metallic Ni has been demonstrated recently using Ni(tBu2DAD)2 and tert-butylamine [3]. ALD of metallic cobalt [4] and cobalt oxide [5] have been reported using Co(tBu2DAD)2 with formic acid and O3, respectively. Here, we report the use of Ni(tBu2DAD)2 and O3 for ALD of NiO. NiO was deposited in a Picosun Sunale R-150 using N2-purge-separated cycles of Ni(tBu2DAD)2 held at 140°C and an O3/O2 mixture of ~10%. NiO films were characterized using variable angle spectroscopic ellipsometry (VASE) and grazing-incidence x-ray diffraction (GIXRD).
A plot of thickness vs. temperature for depositions using 135 cycles of a 5/30/4/30 s Ni(tBu2DAD)2/N2/O3/N2 pulse sequence shows slightly decreasing growth with increasing temperature in the range of 175°C to 225°C (Fig. 1). In this temperature range, the refractive index is roughly constant at 2.38, consistent with reports for bulk and thin film NiO. Below 175°C, growth increases more steeply, likely due to condensation. Above 225°C, growth continues to decrease, due to desorption or possibly upstream precursor decomposition. A more detailed investigation of growth per cycle (GPC) versus temperature is underway. At 200°C, a linear GPC is observed, and saturating growth is observed for O3 pulses of 4 s and longer, using a 5/30/x/30 s sequence (Fig. 2), while softer saturation is observed for Ni(tBu2DAD)2 pulses of 1 s and longer using a x/30/4/30 s sequence and is under further investigation. A GIXRD scan of an ~18 nm thick film deposited at 200°C indicates polycrystalline cubic NiO (Fig. 3).
Atomic force microscopy (AFM), x-ray reflectivity (XRR) and x-ray photoelectron spectroscopy (XPS) characterizing surface morphology, density, and composition, respectively, will be discussed at the meeting as well as dielectric properties (leakage, breakdown strength, dielectric constant, etc.) revealed by metal/insulator/metal (MIM) test devices.
[1] S. Seo et al., Nanoscale 8, 11403 (2016).
[2] K. L. Nardi et al., Adv. Energy Mater. 5 (2015).
[3] M. M. Kerrigan et al., ACS Appl. Mat. & Interfaces. 10, 14200 (2018).
[4] J. P. Klesko, M. M. Kerrigan, and C. H. Winter, Chem. Mater. 28, 700 (2016).
[5] J. Kim et al., Chem. Mater. 29, 5796 (2017).