Optical, structural, and electrical properties of sputter-deposited SnOx thin films

• Preparation of p-type SnO films without heating by DC magnetron sputtering. • Post-annealing results in a phase transition from p-type SnO to n-type SnO2. • Post-annealing increases the bandgap, oxidizes the sample and causes grain growth. This study investigated the effect of deposition parameters on the properties of tin oxide (SnO x ) thin films deposited by direct current magnetron sputtering using a Sn metal target. As confirmed by optical bandgap, X-ray photoelectron spectroscopy, high-resolution X-ray diffraction and Hall effect measurements, as-grown samples deposited at 7.5 and 10% oxygen partial pressure (OPP) and post-annealed samples deposited at 5% OPP had a p-type SnO phase, whereas samples fabricated with 7.5 and 10% OPP and annealed at 400°C had a n-type SnO 2 phase. Post-annealing at 400°C increases the bandgap and injects more oxygen into the SnO x thin film, further oxidizing the sample. In addition, post-annealing greatly increased the carrier concentration of the SnO x thin film, which increased carrier scattering and, in turn, greatly reduced the mobility of the sample. The SnO x thin film deposited at 7.5% OPP and not heat treated showed the best p-type properties, with a Hall mobility of 5.11 cm 2 /Vs, a hole carrier concentration of 1.13 × 10 15 cm −3 , and a resistivity of 1082 Ωcm.