| AVS 55th International Symposium & Exhibition | |
| Thin Film | Monday Sessions |
| Session TF+NC-MoM |
| Session: | ALD of Hybrid Materials and ALD on 3D Nanostructures |
| Presenter: | G. Scarel, North Carolina State University |
| Authors: | G. Scarel, North Carolina State University G.K. Hyde, North Carolina State University J.C. Spagnola, North Carolina State University J.-S. Na, North Carolina State University B. Gong, North Carolina State University Q. Peng, North Carolina State University G.N. Parsons, North Carolina State University |
| Correspondent: | Click to Email |
Conformally coated 3D natural fibers are becoming important in various areas of catalysis, bio-scaffolds, drug delivery, energy storage and conversion applications. In this work we report on growth and characterization of inorganic coatings (Al2O3 and ZnO) on fibers including cotton and polypropylene. The coatings were prepared using low temperature (about 100 degree centigrade) ALD. We used tri-methyl aluminum and H2O for Al2O3 and di-ethyl zinc and H2O for ZnO. ALD is well known to produce conformal coatings on planar surfaces and deep trenches. However it is more difficult to establish and to characterize linear growth and conformality in complex 3D fibrous systems. We have developed a new method to evaluate linear growth and conformality on complex nano- and micro 3D structures. The method uses infrared spectroscopy to detect longitudinal optical (LO) modes in off-normal configurations (Berreman effect). These features pertain to ionic oxides and are sensitive to film thickness because they are generated by vibrations normal to the ionic oxide layer surface. We show that the height of a peak related to an LO mode grows linearly with the number of ALD cycles and that this linear behavior is related to the linearity of the growth on a planar Si(100) substrate. In addition, the angular behavior of the height of peaks related to LO modes in transmission infrared spectra can be related to the degree of coating conformality. In addition the data show that on 3D structures, especially on fibers, the number of incubation cycles needed before linear growth starts is even higher than on planar substrates. We investigate this phenomenon considering the structural, compositional, and the surface energy properties of the coated structures. The method we propose offers an easy non-local method to ascertain linear growth and conformality on complex 3D samples coated using ALD.