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

Abstract

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 (ppO 2) 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 cm 2 /Vs) and n-type (22.20 cm 2 /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.

Electrical Properties of a p‐SnOx/n‐SnOx Diode on a Flexible Polyimide Substrate

“…Also, the mobility in our flexible diode is almost eight times higher. Finally, when comparing our diode on glass [ 25 ] against our flexible diode (this work), we observed that the turn‐on voltage diminished from 4.70 to 2.24.…”

“…The p‐SnO x and n‐SnO x films were annealed to increase their crystallinity structure and carrier concentration, at 180 °C for 30 min in air at atmospheric pressure using a tubular furnace. [ 25 ] To prevent a short circuit, an insulating layer of Al 2 O 3 (100 nm in thickness) was deposited between p‐SnO x and ITO using atomic layer deposition. After open via toward the p‐SnO x , the assembly of the diode was completed with an ITO film (150 nm in thickness) deposited by radio‐frequency magnetron sputtering at 70 W.…”

“…Our previous work described the experimental conditions to obtain p‐ and n‐type SnO x thin films by DC magnetron sputtering. [ 25 ] In brief, the growth of p‐type SnO x thin films was achieved by varying the oxygen partial pressure (ppO 2 ) between 4.8% and 9.5%, whereas for n‐type materials, the range was 15.3% to 18.5%. Having studied the effect of the ppO 2 on the growth of the films, the optimal ppO 2 values to obtain p‐ and n‐type SnO x films were 8.0% and 18.5%, respectively.…”