Influence of Oxygen on Zinc Oxide Films Fabricated by Ion-Beam Sputter Deposition

Abstract

In this study, zinc oxide films were deposited by an ion-beam sputter deposition in various oxygen partial pressures at room temperature. The films changed the structures from amorphous to polycrystalline with increasing the oxygen partial pressure ( O 2 ). The optimal O 2 was found at 1.2 × 10 −4 Torr because the film prepared at the oxygen partial pressure had the lowest resistivity and the highest transparence in the visible light region. The lowest resistivity results from a great number of oxygen vacancy sites formed on the polycrystalline surface as exposed to the atmosphere. Moreover, the film has the highest XRD peak intensity, smallest FWHM diffraction peak, smallest -spacing, and smallest biaxial stress.

Comparison of the Optical and Electrical Properties of Al-Doped ZnO Films Using a Lorentz Model

“…The deposition rate reduced with increasing P O 2 as a result of ZnO oxide formation on the surface of the metallic Zn target; the optimal P O 2 was found when the deposition rate no longer showed a clear decrease [30]. An optimal oxygen-deficient state was exhibited in the film deposited at P O 2 = 0.12 mTorr [15]. Moreover, the ZnO-i films deposited at P O 2 > 0.1 had an average transmittance superior to 80% in the visible and near-IR regions, with a transmittance close to zero in the UV range, as shown in Figure 3.…”

“…The ZnO-i film's structures changed from the amorphous to the crystalline state, illustrating only the fitted X-ray diffraction (XRD) peak (002). In Figure 4a, the 2θ value (where θ is the Bragg diffraction angle) changes from 33.96 • to 34.11 • with increasing P O 2 when P O 2 > 0.1 mTorr, owing to the self-assembly property of the ZnO-i film [15,31]. The grain size mostly decreased with increasing P O 2 > 0.1 mTorr.…”

“…By adjusting the distance H between the Zn target and the center of the ion beam, the ratio of the Al sputtering area to the total sputtering area (marked with a red ellipse, as shown in Figure 1) could be changed to control the amount of Al dopant in the deposited AZO film on the B270 glass and Si wafer substrates. The transmittance in the UV/visible/near-IR regions, crystalline structures, surface roughness, surface morphology and cross-section structure, atomic percentages (at.%), electrical resistivity (ρHall), free electron carrier concentration (NHall), and mobility (μHall) of the films were reviewed from our previous studies [15][16][17][18][19].…”

“…As shown in Figure 5 with green circles ( ms was 6.3 ± 4.7 mΩ cm. The ZnO-i films y of 2.40 ± 0.12 mΩ cm [15]. However, the o a CTO film for commercial use.…”

“…This study includes reviewed data from our previous studies [15][16][17][18][19], wherein AZO films were investigated using spectroscopic ellipsometry with a parametric model containing two Lorentz oscillators. The model assumes that the response of the electron carrier driven by the electric field in the film is similar to that of a mass harmonically driven by a spring combined with a dissipative force.…”