Reactive pulsed laser deposition and laser induced crystallization of SnO2 transparent conducting thin films

Transparent conducting SnO2 thin films with a thickness between 1000–2000 A were deposited on glass, quartz and silicon substrates using standard pulsed laser deposition techniques with two different targets (Sri and SnO2) and with three different laser wavelengths (1.06, 0.532 and 0.266 μ) from a Q-switched Nd: YAG laser. Tin dioxide films with optical transmission over most of the visible spectrum exceeding 80% were obtained using a Sn target and a background oxygen pressure of 20 Pa. The electrical resistivity (ρ) depended strongly on the substrate temperature during deposition, with the lowest values ofρ of about 10−2 Ω-cm obtained when the substrate was maintained at 400°C during deposition. Using SnO2 targets, predominantly amorphous phase SnO2 films were deposited on Si substrates and then transformed into polycrystalline Sn3O4 by laser induced crystallization (λ = 1.06 μm). Whereas these later films were essentially non-conducting as deposited (ρ > 400 Ω-cm), the electrical resistivity was permanently reduced after laser induced crystallization by a factor greater than 1000 to a value of approximately 4 × 10−1 Ω-cm.