Electrical properties and topography of SnO ₂ thin films prepared by reactive sputtering

A scanning tunneling microscopy study of the topology of thin films of SnO₂ has been conducted. The films were deposited using dc reactive magnetron sputtering on microscope slides heated to 150°C. No annealing treatments were needed. For films of 125 Å to 2000 Å, the grain size was proportional to the thickness of the films. A study of the O₂ partial pressure showed that films made with a pressure in the 10^-6 Torr range gave a quasi-amorphous film. For films made with higher O₂ partial pressure, the grain size increased. Scanning tunneling microscopy showed a good crystallinity for these films. The transparency was greater than 95% in the 400-800 nm wavelength region for films 125 A thick. We obtained a film resistivity of 4.5 × 10^-3 Ω cm, a carrier concentration of 8.9 × 10¹⁹ cm^-3 and a Hall mobility of 20.77 cm² V^-1 s^-1. With a relatively good resistivity in the 10^-3 Ω cm range and a mobility around 18 cm² V^-1 s^-1, we made films having a carrier concentration adjustable by one order of magnitude in the 10¹⁹ cm^-3 range.