Structural, Chemical, Optical, and Electrical Evolution of SnO_x Films Deposited by Reactive rf Magnetron Sputtering

Abstract

In this paper, SnO(x) films were produced by reactive radio frequency magnetron sputtering under various oxygen partial pressure (P(O)) in conjunction with a thermal annealing at 200 °C afterwards. The obtained SnO(x) films were systematically studied by means of various techniques, including X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, spectroscopic ellipsometry, and Hall-effect measurement. The structural, chemical, and electrical evolution of the SnO(x) films was found to experience three stages: polycrystalline SnO phase dominated section with p-type conduction at P(O) ≤ 9.9%; amorphous SnO(2) phase dominated area at P(O) ≥ 12.3%, exhibiting n-type characteristics; and conductivity dilemma area in between the above mentioned sections, featuring the coexistence of SnO and SnO(2) phases with compatible and opposite contribution to the conductivity. The polycrystalline to amorphous film structure transition was ascribed to the enhanced crystallization temperature due to the perturbed structural disorder by incorporating Sn(4+) into the SnO matrix. The inversion from p-type to n-type conduction with P(O) variation is believed to result from the competition between the donor and acceptor generation process, i.e., the n-type behavior would be present if the donor effect is overwhelming, and vice versa. In addition, with increasing P(O), the refractive index decreased from 3.0 to 1.8 and the band gaps increased from 1.5 to 3.5 eV, respectively.

Extremely Sensitive Dependence of SnOx Film Properties on Sputtering Power

“…Clear SnO peaks were observed after annealing at 200~300 °C, but SnO 2 rather than SnO should be the dominant phase in the film because separate TFTs sputtered and annealed under the same conditions all showed n-type conduction. SnO 2 is amorphous at this temperature and cannot be detected by XRD3536, but can be confirmed by XPS as shown in Fig. 2.…”

Sputtering Deposition of P-Type SnO Films with SnO2 Target in Hydrogen-Containing Atmosphere

“…These binding energies and chemical shifts well agree with the results previously reported. 19,20 In increasing the H 2 gas ratio from 0% to 25%, peaks of the Sn (a) XPS spectra in the Sn 3d 5/2 core-level region for SnO X films deposited with varied H 2 gas ratios. Deconvoluted Sn 0 , Sn 2+ , and Sn 4+ components (purple, red, and blue lines, respectively) to fit measured Sn 3d 5/2 core-level spectra are also shown.…”

Magnetron-Sputtered SnO Thin Films for p-Type and Ambipolar TFT Applications

“…23 It was suggested that the crystalline structure transition from polycrystalline to amorphous results from the involvement of Sn 4+ in the SnO matrix, which boosts the structural disorder and consequently increases the crystallization temperature. 23 Fig . 2 shows the dependency of Hall mobility and carrier concentration on different P O .…”

“…In this region, the amorphous SnO 2 phase is considered to dominate other phases. 23 The conversion from p-type conduction to high resistivity and then to n-type conduction with P O is believed to mainly originate from the competition between the donor and acceptor generation process. 23 Specifically, for the SnO-dominated films, the majority carriers are holes originated from acceptors.…”