Solution-processed p-type copper oxide thin-film transistors fabricated by using a one-step vacuum annealing technique

Copper oxide (CuxO) thin films were fabricated on SiO2/Si substrates by using a solution process. The coated CuxO gel films were treated using a vacuum annealing method at various temperatures (400-700 degrees C). X-ray diffraction results indicated that the vacuum annealing technique was effective in transforming CuO into Cu2O. Atomic force microscopy images showed that the mean grain size and the surface roughness of the resulting films increased with increasing annealing temperature. To verify the possibility of CuxO thin films as channel layers, the bottom gate structured thin film transistors (TFTs) were integrated. The electrical properties of the as-fabricated CuxO TFTs were improved with increasing processing temperature from 400 to 600 degrees C. The 600 degrees C-annealed CuxO TFT exhibited the best electrical performances, including a low threshold voltage of -3.2 V, a large field-effect mobility of 0.29 cm(2)V(-1)s(-1), a small subthreshold swing of 0.8 V dec(-1), and an on/off current ratio of 1.6 x 10(4), respectively. However, with increasing annealing temperature, the electrical properties of the CuxO TFTs were degraded dramatically. These results suggest that solution-processed CuxO TFTs achieved by using a one-step vacuum annealing technique could potentially be used for high-performance p-type electronic devices, which represents a great step towards the further development of low-cost and all-oxide CMOS electronics.