Structure and Morphology of Reactively Sputtered In_0.9Sn_0.1O_x Layers

Abstract

In this work, the influence of the discharge parameter oxygen partial pressure during reactive magnetron sputtering on the structure and morphology of In_0.9Sn_0.1O_x films is investigated. The oxygen partial pressure was varied in order to deposit In_0.9Sn_0.1O_x films with 0 ≤ x ≤ 1.76. The composition x was measured by Rutherford backscattering (RBS). For low x values, these films are metallic and opaque, while at x ≈ 1.5 the layers exhibit good properties as transparent and conducting electrodes. Further increase in x leads to transparent insulating films. The morphology of the films, investigated by SEM, shows significant variations with the composition x. While the metallic films consist of coarse globular grains, made up of polycrystalline indium-tin, a small addition of oxygen leads to nearly amorphous metal-oxide mixtures with smooth surfaces. Around x ≈ 1.5 the films are polycrystalline with the cubic In₂O₃ bixbyite structure and show a resistivity minimum. The cross sectional morphology of these films exhibits a columnar structure of broad bundles (≈250 nm), composed of narrow needle-like crystallites of about 20 nm diameter. At very high oxygen partial pressures, the grain size decreases while the strain and the resistivity increase significantly.