| AVS 57th International Symposium & Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF+SE-WeM |
| Session: | Glancing Angle Deposition (GLAD) I |
| Presenter: | J.M. LaForge, University of Alberta, Canada |
| Authors: | J.M. LaForge, University of Alberta, Canada M.T. Taschuk, University of Alberta, Canada M.J. Brett, University of Alberta, Canada |
| Correspondent: | Click to Email |
Zinc oxide possesses a combination of properties, including semiconductor electronic behaviour, optical transparency, and piezoelectricity, that make it an interesting candidate for energy scavenging, photovoltaics, and chemical sensing applications (1, 2). Several unique nanostructures may be formed with ZnO, with a variety of growth methods that exploit the difference in surface energy between the low-index crystal faces of the wurtzite ZnO crystal leading to preferential growth along the c-axis.
Glancing angle deposition (GLAD) is assumed to operate effectively under conditions of limited surface diffusion so that growth occurs from geometric shadowing of an incoming particle flux. While amorphous GLAD films are typical, there are numerous crystalline films reported in the literature, including ZnO (3). This suggests that in certain material systems growth kinetics play a role in GLAD growth. However, the conditions under which GLAD produces crystalline films has not been thoroughly investigated or explained.
We have selected ZnO to investigate these issues for two reasons: first, the technological applications outlined above, and second, to explore the material growth properties which can produce crystalline structures. This makes it an ideal candidate for studying nanostructure morphology and crystal properties as a function of process parameters, including deposition rate, pitch and throw distance. Optimal growth conditions for zinc oxide nanorod films occurred for pitch values in the vicinity of 1 nm to 10 nm. Study of the post aspect ratio and areal post density suggests that typical GLAD growth occurs for deposition rates <0.005 nm sec-1 and that growth kinetics begin to contribute significantly at deposition rates >0.01 nm sec-1. . Films deposited at pitch values between 0.001 nm to 6.5 µm are crystalline and textured, and greater texturing is achieved for conditions of decreased surface diffusion.
(1) Wang, Z. L. Journal of Physics: Condensed Matter. 2004, 16, R829-R858.
(2) Ye, C.; Fang, X.; Hao, Y.; Teng, X.; Zhang, L. The Journal of Physical Chemistry. B. 2005, 109, 19758-65.
(3) Teki, R.; Parker, T.; Li, H.; Koratkar, N.; Lu, T.-M.; Lee, S. Thin Solid Films. 2008, 516, 4993-4996.