SnO_x thin films with tunable conductivity for fabrication of p–n homo-junction

Tin oxide (SnO_x) has been widely used for the fabrication of transparent and flexible devices because of its excellent optical and electronic properties. In this work, we established a methodology for the synthesis of SnO_x thin films with p-type and n-type tunable conductivity by direct currecnt (DC) magnetron sputtering. The SnO_x thin films changed from p-type to n-type by increasing the relative oxygen partial pressure (ppO₂) from 4.8% to 18.5% and by varying the working pressure between 1.8 and 2.5 mTorr. The SnO_x thin films were annealed at 160°C, 180°C, and 200°C for 30 min to promote the formation of the desired crystalline structures. At the annealing temperature of 180°C in air ambient, the SnO_x thin films showed a tetragonal structure with Sn traces. Having found the optimal conditions, we deposited both types of SnO_x thin films with the same tetragonal structure and similar chemical stoichiometry. Also, the conditions to obtain thin films with the highest mobility values for p-type (1.10 cm²/Vs) and n-type (22.20 cm²/Vs) were used for fabricating the device. Finally, the implementation of a SnO_x-based p–n diode was demonstrated using transparent SnO_x thin films developed in this work, illustrating their potential use in transparent electronics.