Highly Sensitive, Fast-Responding, and Stable Photodetector Based on ALD-Developed Monolayer TiO2

In this paper, high-quality wafer-scale monolayer TiO
₂
films were synthesized via atomic layer deposition and their main characteristics were investigated. The deposited TiO
₂
monolayer films were subsequently utilized in photodetectors (PDs), which demonstrated considerable optoelectronic performance with ultrafast response (30 
μ
s) and recovery (63 
μ
s) time, high on/off ratio (220), good reversibility, and great long-term stability (less than 2% variation after 1000 cycles). The photoresponsivity (
R_λ
) and external quantum efficiency of 0.352 A/W and 109.12% were, respectively, attained at the incident laser power density of 118 mW/cm
²
(
$\lambda = \text{400}\; \text{nm}$
) and
$V_{{\rm{DS}}} = \text{1}\; \text{V}$
. These photoelectrical characteristics of the monolayer TiO
₂
-based PDs confirmed that this TiO
₂
nanostructure could be an excellent candidate for various smart and portable applications such as UV-detection devices, photoswitches, high-speed optical communications, and image sensors.