The validity of Kohlrausch law for the photocurrent transient and the role of N 2 /Ar flow ratio in photoconductivity of sputtered CoZnO

Abstract

Abstract Co:ZnO (CZnO) ferromagnetic semiconductor layers are coated on the surface of glass and Si substrates by Magnetron Sputter Deposition Method (MSDM) with variable N2/Ar gas flow ratio. N2/Ar flow ratio varies from 5 sccm to 20 sccm, keeping the Ar gas flow constant (at 30 sccm). Sample's surface topography-composition, structure and optic properties are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and ultraviolet–visible (UV/Vis) spectrophotometry. CZnO/p-Si structure exhibits both rectifying and photovoltaic behavior. Kohlrausch decay function is used to model the photocurrent transient curve and the associated relaxation process. The values of the photo charge density ( ρ p h ) and the relaxation time constant ( τ 0 ) are found to be 1.02 × 1011 Coul/cm−2 and 1.1 × 104 s, respectively. These findings suggest that CZnO/p-Si structure can be used in photodetector applications. The photoconductivity of the device can be tuned with the N2/Ar flow ratio since the property of CZnO thin films deposited from 3% Co doped ZnO target is dependent on the N2 and Ar atmosphere.