Influence of thickness on the structure and electrical, optical properties of N-doped SnO2 film

Abstract

N-doped SnO2 films with varying thickness (320, 420, 520, 620, and 720 nm) were deposited at 300oC in mixed – gas sputtering Ar/N (1:1) using DC magnetron sputtering. Influence of thickness on structure, optical constants (refractive index or extinction coefficient), and electrical properties were investigated by methods such as X-ray diffraction, Uv-Vis spectra, and Hall measurement. The results show that crystalline quality and optical constants improve with increasing thickness. Specifically, NTO – 620 film has the best crystal structure and maximum values ​​such as crystal size, refractive index, and carrier mobility, as well as the lowest extinction coefficient. Also, NTO films have a cubic structure with (111) peak as the preferred peak. Besides, the hole mobility increases with the increase of the thickness and reaches the maximum value of 14.95 cm2V-1s-1 for NTO – 620 films. The electrical properties of p-type NTO films were verified by X-ray electron spectroscopy (XPS) and I-V characteristic of p – NTO/n – Si heterojunction under illumination. P-type NTO – 620 films were fabricated on n-type Si substrate had a light-to-dark current ratio of 58 at - 6V, these results showed that p-type NTO films might have a promising future in optical sensors applications.