Paper SE-ThP4
Influence of Substrate Temperature on Reactive-sputtered Tin-nitride Thin Films Prepared by Glancing Angle Deposition

Thursday, October 23, 2008, 6:00 pm, Room Hall D

1. Introduction Properties of tin-nitrogen compounds have not been recognized in detail. Tin-nitride was reported to exhibit a spinel structure (Sn₃N₄) at low temperature, while tin-nitride films deposited at high temperature showed a zinc blende (SnN) structure. As one of the properties of tin nitride, we found that amorphous tin-nitride (a-SnN) films prepared by reactive ion plating show an erectrochromic (EC) phenomenon, which is a reversible color change of materials induced by applying a burst of electrical charge. We have reported that the EC phenomenon occurs due to the change of surface adsorption at indium nitride film, so that the color-change efficiency is strongly influenced by surface area. Moreover, it is influenced by crystallinity. Therefore, both the expansion of surface area and the improvement of crystallinity are important. In this study, we aim to investigate the properties of reactive-sputtered tin-nitride thin film prepared by glancing angle deposition (GLAD). 2. Experimental procedure The tin-nitride films were prepared by using a conventional rf magnetron sputtering system. After evacuation of a deposition chamber under 1×10^-3 Pa, high-purity N₂ gas was introduced into the chamber up to 1 Pa. Then rf power (13.56MHz, 75W) was applied to a metallic tin target of 4N purity. The angle of a substrate holder against the sputtered tin flux was set at 0° and 85°. In-plane rotation condition of the substrate holder was controlled by a motor. We used both Si (100) single crystal wafers and glass plates as substrates. The substrate temperature was controlled by a halogen spot heater. Crystallinity and microstructure of the films was characterized by an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). 3. Results In the case of non-heating substrates, we confirmed that both the samples deposited at 0° (sample A) and at 85° (sample B) have the spinel (Sn₃N₄) crystal phase. The cross-sectional surfaces of the sample A showed a dense columnar structure. EC characterization revealed that the sample A shows no EC phenomenon. On the other hand, the microstructure of the sample B is quite similar to the microvillus structure of small intestine, which consists of isolated nanocolumns. The sample B showed small EC phenomenon, which may due to the surface area much expanded than that of the sample A.