Solution-Processed SrOx-Gated Oxide Thin-Film Transistors and Inverters

In this paper, high-k strontium oxide (SrO
_x
) dielectric thin films were fabricated using simple and low-cost solution process. The formation and properties of SrO
_x
thin films annealed at various temperatures (400°C, 500°C, 600°C, and 700°C) were investigated using numbers of characterization techniques. The electrical analysis indicates that the insulating properties of SrOx thin films were improved with increasing annealing temperature. The post-annealing at temperatures higher than 400°C enables the SrO
_x
thin film, exhibiting low-leakage current density of ~10
^-8
A cm
^-2
at 3 V and the areal capacitance larger than 350 nF cm
^-2
at 20 Hz. To further explore the possible applications of solution-processed high-k SrOx thin films for thin-film transistors (TFTs), the indium oxide (In
₂
O
₃
) TFTs based on SrOx thin films were integrated for testing. The optimized In
₂
O
₃
/SrO
_x
TFT exhibits high performance with an average field-effect mobility of 5.61 cm
²
V
^-1
s
^-1
, a small subthreshold swing of 110 mV dec
^-1
, and a large on/off current ratio of 10
⁷
. To demonstrate the potential of In
₂
O
₃
/SrO
_x
TFT toward more complex logic applications, the unipolar inverter was further constructed and exhibited a high gain of 9.7. Importantly, all these device parameters were obtained at an ultralow operating voltage of 3 V, which represents a step toward portable, battery-driven, and low-power consumption electronics and circuits.