Research And Optoelectronic Properties Of ZnO Thin Films Prepared By Sol-gel Doped

Zinc oxide (ZnO) is a kind of high performance Ⅱ-Ⅵ compound semiconductor.Its energy-gap is3.37eV at room temperature, As one of the new member of the third generation semiconductors, its exciton binding energy is60meV and usually it has the hexagonal wurtzite.ZnO thin films have good property in optical property, electric property, magnetic property, gas sensitive property and photoelectric property, etc. These excellent properties make it have widely use, such as in LCD, magnetism recorder, thin film resistors, sensors, ultraviolet detectors, pressure sensitive resistors, stealth materials. Therefore zinc oxide has important position in the semiconductor industry and optoelectronic industry.Based on consulting a large amount of scientific research literature about the zinc oxide and combining with the actual situation of our laboratory, the doped ZnO thin films are prepared by sol-gel method and the photoelectric properties of these doped ZnO thin films are investigated. The experimental contents and results are shown as follows:1. First of all, the intrinsic zinc oxide thin films are prepared on silicon substrate through sol-gel method and then investigate the influence of the order of reagent, mixing temperature, aging condition, pretreatment temperature and annealing temperature on the sol and the films’ quality.The optimum process conditions of the intrinsic ZnO thin film is:Zn2+0.75mol/L, aging temperature60℃, aging time48h, pretreatment temperature150℃, pretreatment time15min, the annealing temperature650℃and annealing time2h. Under this process condition, the prepared thin films is preferred of C axes and the surface is flat and dense.2. Based on the optimum process conditions of the intrinsic thin films, the ZnO thin films with different doped elements and different concentration are prepared. The doped elements are Co, Cu, Cd, La, respectively. The doping concentration are2%,5%,8%, respectively.The ZnO thin films’crystal structure, surface morphology and luminescent properties and electrical properties are investigated.3. The results show that the doping concentration of different doping elements will affect the luminescent properties and electrical properties of ZnO thin films. In terms of luminescent property, these all have three photoluminescence peaks, but the strength of the peaks are different.(1) The ultraviolet light emitting peak is around375nm,(2) the green light emitting peak is near520nm or near570nm.(3) the faint red light emitting peak is around725nm. In the electrical properties, because the Co, Cu, Cd, La’s ion radius are different from zinc’s ion radius, so Co, Cu, Cd, La doped thin films changes differently in electrical property.When Co doping concentration is5%, the resistivity of thin film is minimum (2.48×102Ω·cm). When Cu doping concentration is5%, the resistivity of thin film is minimum (4.16×102Ω·cm). When Cd doping concentration is2%, the resistivity of thin film is minimum (3.38X103Ω·cm). When La doping concentration is8%, the resistivity of thin film is minimum (1.17×103Ω·cm).