The Electrical Transport Properties And Magnetic Properties Of ZnO Based Materials

ZnO is a n-type semiconductor with wide band gap,high transmittance in visible region and high exciton binding energy.By doping aluminum element,the conductivity increases several orders of magnitudes.In addition,ZnO possesses non-toxic,abundant and low cost,particularly thermal stability and chemical stability in hydrogen plasma.Therefore,ZnO has been extensively studied.The researchers focus on the growth of high quality films,there is still lack of systematic studies on their electrical transport properties,especially the low temperature electron scattering mechanisms.At the same time,room temperature ferromagnetism in semiconductors has attracted much attention and has been found in many materials.But the prepared products are impure,which may affect the accuracy of measurement.Therefore,it is necessary to find a preparation method with pure products.In this paper,Al-doped ZnO(AZO)films are treated by annealing.We measure the structure,morphology,magnetic properties and electrical transport properties of AZO films and systematically investigate the low temperature electron scattering mechanisms.Simultaneously,the pulsed laser ablation is a simple and green method with pure products.ZnO nanoparticles are grown by using nanosecond pulse laser.We measure the structure,morphology,optical and magnetic transport properties and study the ferromagnetic in ZnO nanoparticles.For the AZO films,the temperature coefficient of resistivity is positive at relative high temperatures,and the carrier concentration is almost invariable with temperature from 300 down to 2 K,indicating that the films possess degenerate semiconductor characteristics in electrical transport properties.We study the dephasing mechanism of films,and found that the scattering mechanisms are different in the films annealed at different temperatures.That is to say,the electron-phonon scattering dominates dephasing mechanism in the unannealed films;both electron-phonon scattering and small-energy-transfer electron-electron scattering dominate dephasing mechanism in the films with relative low annealing temperature;the small-energy-transfer electron-electron scattering solely dominates dephasing mechanism in the films with relative high annealing temperature.We have observed the room temperature ferromagnetism in the ZnO nanoparticles.The nanoparticles are wurtzite structure and contain only Zn and O elements,indicating that the nanoparticles are pure and have no impurities.In other words,ferromagnetism is not caused by impurities.Considering defects occur in ZnO nanoparticles,we think that the room temperature ferromagnetism is related to defects.