The structural, optical and morphological properties of CaF2 thin films by using Thermionic Vacuum Arc (TVA)

In this study, calcium fluoride (CaF2) thin films have been prepared by Thermionic Vacuum Arc (TVA) technique on glass substrates. In this technique CaF2 thin films are produced by condensing the plasma of anode material generated in the TVA setup under high vacuum conditions on glass substrates. Crystal structures as well as optical and surface properties of CaF2 antireflective (AR) coated thin films were investigated. X-ray diffraction (XRD) measurements showed that amorphous CaF2 thin films were formed. Optical and surface properties of CaF2 films have been studied based on optical transmittance, reflectance, refractive index and atomic force microscopy imaging (AFM). Our results also show that CaF2 coated samples exhibit lower reflectance (R). From our optical studies, we have observed that CaF2 thin films have high AR properties.TUBITAK (108M608); ESOGU Scientific Research Commission (200819045

Electrochromic properties of graphene doped Nb2O5 thin film

Electrochromic device plays a key role in energy efficiency management and modern display technology. As a cathodic coloration material, Nb2O5 is one of the important material used in the electrochromic device. The capacity of a layer is related with the intercalation and deintercalation behavior. Graphene Doping is a promising process for the high-capacity ion storage application. Graphene is a two-dimensional material and it possesses excellent mechanical and electrical properties. In this paper, graphene doped Nb2O5 thin films have been deposited onto ITO coated glass substrate by a thermionic vacuum arc (TVA) technique. The coloring efficiency has been calculated as 91 and 56 cm(2) C-1 at 414 and 550 nm, respectively. The transmittance variation of graphene doped Nb2O5 layer have determined as 42%. According to the Raman spectroscopy, the peaks for orthorhombic phase of Nb2O5 and graphene bands have been observed. According to obtained results, graphene is a promising dopant material for the high performance electrochromic device with Nb2O5 active layer.Eskişehir Osmangazi Üniversitesi (201719041

Optical and surface properties of LiFePO

LiFePO4 thin films with thickness values of 65 nm and 70 nm were deposited onto glass substrates by RF magnetron sputtering, using a LiFePO4 target in the argon atmosphere. A comprehensive study of the optical properties was performed and the dispersions of the constants were determined. The transmittance and absorbance spectra were measured in the wavelength range of 400−1000 nm. The films showed optical transmittance over 90% in the visible range. The optical band gap value of the films was evaluated as 3 eV. The refractive index value of the films is 1.63 at λ = 550 nm. AFM micrographs indicate smooth surface with low values ofroot mean square roughness. Contact angle measurements of several testing liquids were used to characterize each sample in terms of wettability. The films are hydrophilic as observed from contact angle measurements. The surface free energy of the film surfaces and their components (dispersive and polar) were calculated from the contact angle data using the different theories available in the literature

Investigation of photodetector performance based on methylammonium lead halide perovskites/reduced graphene oxide heterostructure

The remarkable advancements achieved in the field of perovskite materials have spurred the development of photodetectors, playing a pivotal role in diverse optoelectronic applications. Among these, heterostructured perovskite-based photodetectors have emerged as a superior choice, surpassing the performance capabilities of their pure perovskite counterparts. This study presents the fabrication of an rGO/MAPbI3 heterostructured photodetector via the spin-coating technique. A comprehensive structural analysis of the device was conducted, encompassing X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Current–voltage (I–V) and capacitance–voltage (C–V) measurements, performed under various illumination conditions as well as in the absence of light, unequivocally demonstrate the photodiode characteristics of the device. The data reveal a direct correlation between illumination intensity and both current and capacitance, substantiating the photodetector’s responsiveness. Notably, the calculated photosensitivity values S (%) of the Al/Gra/p-Si device, measured under a reverse bias of − 2 V, exhibit a range, varying from 42,000 to 79,300%. Furthermore, observations suggest a decrease in series resistance with increasing illumination intensity, while the ideality factor and barrier height values show an opposite trend. In addition, frequency-dependent measurements divulge a decrease in capacitance as the frequency escalates. These findings can be elucidated through the interactions involving light-induced charges at the interface between the rGO oxide layer and the semiconductor, coupled with the dynamic fluctuations in quasi-Fermi levels within the state of equilibrium