Effect Of Li And Cu Co-doped NiO Thin Films On Photoelectric Properties

Transparent conductive oxide(TCO)film materials organically combine the transparency and conductivity of substances and have become the focus of exploration by a wide range of researchers.Nickel oxide(NiO)is a p-type wide band gap semiconductor with a typical 3d electronic energy band structure,and NiO thin films are widely used in optoelectronic devices due to their excellent optoelectronic properties.At present,the mechanism of co-doping regulation of the conductivity of NiO thin films is still unclear and needs to be further explored.To this end,in this paper,the preparation of unintentionally doped,Li-doped and Cu-Li co-doped NiO thin films on Si substrate and sapphire substrate were carried out by sol-gel method,and the influence of doping method,doping concentration,annealing temperature and annealing time on the structure and optoelectronic properties of NiO thin films were systematically researched.The main research works and conclusions are as follows.1.The effects of doping concentration,annealing temperature and time on the electrical conductivity,grain size and optical properties of NiO:Li films were researched.The experiments show that the conductivity of NiO:Li films is p-type,and the resistivity diminish and then stabilizes as the concentration of Li doping enhanced,the grain size enlarges and then diminish,and gradual reduction of film transmittance.Therefore,Li doping improves the electrical conductivity of the film.When the annealing temperature elevates,the resistivity of the film reduces and then enlarges,the transmittance gets larger,and the electrical properties of the film deteriorate by prolonging the annealing time.the NiO:10%Li film prepared by high temperature annealing at 500? for 1 h grows selectively along the(200)crystal direction,the maximum grain size is about 20 nm,the optical band gap is 3.56 eV,the cavity carrier concentration is 5.82×1015crm-3 at room temperature,the resistivity is about 3.04×103?·cm at minimum,while the mobility is essentially constant at about 0.353cm2/V·s.2.Cu-Li co-doped NiO thin films were successfully prepared by 10%Li doping.The experimental results show that Cu-Li co-doped NiO thin films have no impurity phase formation and grow along the(200)crystal direction.Cu and Li are successfully mixed into the NiO thin films,and Cu and Li replace Ni2+ as substitutions of doping ions.Therefore,after Cu-Li co-doping,the amount of Ni2+ is increased and the hole concentration is further increased.3.The influence of Cu-Li co-doping,annealing temperature and time on the optoelectronic properties of NiO thin films were study ed.The results indicate that the Cu-Li co-doped NiO films are p-type conductive at room temperature,the maximum grain size of 3%Cu-10%Li co-doped NiO films prepared by high temperature annealing at 500? for 1h is about 21.9 nm,the transmittance in the visible range is about 70%,the optical band gap is 3.48 eV,the cavity carrier concentration increases from 5.82×1015cm-3 to 1.79×1017cm-3,the resistivity is minimized to about 32.50?·cm,and a significant increase in mobility of about 1.074cm2/V·s.