Preparation And Optical And Magnetic Properties Of ZnTiO₃ Films Doped With Co And Fe

Zinc titanate?ZnTiO₃?materials have excellent microwave dielectric properties and have been applied in d eVices such as dielectric resonators in mobile communication equipment,gas sensors,pigments and thin film solar cells.At the same time,zinc titanate is also a wide bandgap semiconductor,and the doping of magnetic elements may make it a new dilute magnetic semiconductor material.Most of the existing studies on zinc titanate focus on its nano,powder and bulk materials,and pure phase ZnTiO₃ is difficult to obtain,so its optical,electrical and magnetic reports are still scarce.In addition,changing the stoichiometry of the material or elemental doping will change the physical properties of the material.In view of this,in order to further explore and improve the physical properties of ZnTiO₃ film,we have carried out element doping of ZnTiO₃ and study its optical,electrical and magnetic properties.In addition,Fe-based chalcogenides have received extensive attention due to their excellent properties.Co and Fe are in the same period and have similar properties.Therefore,we tried to prepare CoTe₂-based single crystals and studied their physical properties in order to obtain some intentional result.The CoTe₂ single crystal exhibits paramagnetism,and Fe doping may be change its magnetic properties.In this paper,Co and Fe doped zinc titanate films were prepared by sol-gel method,and Fe-doped CoTe₂ single crystal were grown by self-flux method.The main contents are as follows:1.Co-doped ZnTiO₃ films were deposited on a Si substrate by a sol-gel method.X-ray diffraction ?XRD?results revealed that all the samples are hexagonal structures of pure phase.With the increase of Co concentration,the lattice constant a gradually increases,while the lattice constant c decreases;X-ray photoelectron spectroscopy results display that Co²⁺ions exist in the current samples;The Raman spectrum of the samples further indicates that all samples are pure phase H-ZnTiO₃;The results of atomic force microscopy?AFM?indicate that as the Co doping increases,the surface roughness of the films decreases and the grain size becomes larger;The parent ZnTiO₃ film showed weak ferromagnetism,while the doped samples figured significant ferromagnetism at room temperature.As the Co concentration increases,ferromagnetism gradually increases,which is related to the magnetic ion-induced bound magnetic polaron in the samples;According to the Adachi dielectric function model,the elliptically polarized spectrum of the samples were processed to obtain the optical constant,the forbidden band width and the film thickness of the samples.At 532 nm,the refractive index n of the samples becomes larger as the Co doping concentration increases,the optical band gap E_OBGBG and Co content x belongs to the relationship of E_OBG=?4.37-2.66*x?;With the Co content increases,the average oscillator intensity E₀ and the average array wavelength S₀ of the sample decrease,while the electro-optic parameter E₀/S₀ becomes larger.In addition,Co-doped ZnTiO₃ films on quartz substrate were prepared.XRD results point that all films are hexagonal phase ZnTiO₃;The UV-Vis-NIR transmission spectrum display that as the Co concentration increases,the absorption edge of the samples moves toward the low energy end;The forbidden band width of the samples from the Tauc's law is gradually decreased as the Co concentration increases.In addition,we also measured the non-linear Z-scan spectrum of the sample,which may have nonlinear optical effects.2.The Fe-doped ZnTiO₃ films with hexagonal phase on Si substrate was prepared by sol-gel method.The XRD results demonstrate that the diffraction peak intensity of?110?and?104?increases with the increase of doping concentration;The results of AFM present that as the Fe increases,the surface roughness of the films decreases and the grain size becomes larger;The undoped ZnTiO₃ film dispalyes almost no magnetic properties,and the doped samples showed obvious ferromagnetic order,and the magnetic properties of the samples increased with the increase of Fe concentration;Additionally,we did study on Fe-doped ZnTiO₃ thin films grown on quartz substrates.The XRD results showed that all the films are the hexagonal phase of ZnTiO₃;The UV-Vis-NIR spectroscopy study of the samples illustrated that the absorption edge of the films shifted to the low energy end with the increase of the Fe concentration;The value of the forbidden band of the samples obtained according to Tauc law is gradually decreased as the Fe concentration increases,which is similar to the case of Co-doped ZnTiO₃ films on a quartz substrate.According to the Cauchy dispersion model,we processed the transmission spectrum of the sample between400-800 nm to obtain the refractive index and extinction coefficient of the sample.3.Te is used as a flux to grow larger CoTe₂ and Fe-doped CoTe₂ single crystals;XRD results showed that all single crystals are orthogonal structure with Pnmm space group;Electrical transport measurements were performed on nominal composition x=0.03 Fe-doped sample,which exhibited metallic-like behavior;Using the Bloch-Grüneisen theory to study the electrical transport,the results show that the conductivity may be derived from the in-band electronic transition;The magnetic susceptibility-temperature relationship of the sample indicates that it has a paramagnetic behavior,but at around 40 k,a weak peak appears in the curve,indicating that the sample may have antiferromagnetic behavior.