The Doping Effect And Properties Of P-type Oxides Semiconductor CuCrO₂with Delafossite Structure

Transparent conductive oxide (TCO) thin films with good electrical conductivity and high visible light transmittance have been widely used in the field of optoelectronic devices, such as solar cells, flat panel display. So far, n-TCO materials have been more widely studied than p type materials. It is known that transparent semiconductor devices need p-type TCO materials with high performance. In this paper, the pure and doped CuCrO2powders prepared by sol-gel method, in which the doped elements are Mg, Zn and Ca. similarly CuCrO2ceramic samples ware prepared by pressing and sintering. The effects on the structure, optical and electrical properties of the samples were investigated by X-ray diffraction, scanning electron microscopy, UV-Vis spectrophotometer, semi-conductor test instrument. The main results were as follow:1). Pure CuCrO2powders were prepared by sol-gel and calcined at750℃for7h, and the powders with single phase show a delafossite structure (space group R3-m). When calcined at750℃,with the increase of calcined time, the particles size of CuCrO2powders increases from200nm to4.5um.Their average optical band-gap is about3.22eV.With the increase of calcined temperature, the optical band gap of CuCrO2powders slightly increases.2). CuCrO2ceramic samples were obtained by pressing and sintering the powders. As the pressure increases, the compact density and the conductivity of ceramic samples increases. Pressed at600MPa, the density of the samples increases from3.95g/cm3before sintering to4.89g/cm3after sintering, which is about89.1%of the theory density of CuCrO2. However, the pressure is550MPa, the conductivity of CuCrO2ceramic samples gets to the maximum about3.6×10-3S/cm.3). Mg, Zn and Ca ware doped into CuCrO2powder prepared by sol gel process. When the amount of doping elements is suitable, the lattice structures CuCr1-xMxO2(M=Mg, Ca, Zn) powders remain3R structure, otherwise there will occur impurity phase, for example, CuO, CaCr2O4, ZnCr2O4, etc.4). With the increase of the doping content, the visible light absorbance of CuCr1-xMxO2(M=Mg, Ca, Zn) powders increases, and the band gap width decreases. The average band gap width of the CuCr1-xMxO2(M=Mg, Ca, Zn) was3.03eV,3.01eV,3.09eV respectively. The conductivity of the ceramic samples firstly increases then decreases. The conductivity of the CuCro.97Mgo.03O2ceramic sample gets to the maximum about18.9S/cm.5). CuCr1-x-yMgxNyO2(N=Zn、Ni) samples co-doped with Mg and N elements remain delafossite structure. The conductivity of CuCr0.97Mg0.0N0.02O2ceramic sample was20.2S/cm. slightly larger than the conductivity of CuCr0.97Mg0.03O2ceramic sample.6). In the temperature range from200to300K, with the decrease of temperature,The resistance of the ceramic samples of CuCrO2and the doping decreases, which is consistent to semiconductor conduction mechanism. The thermal activation model of carriers is consistent to Arrhenius law.