The structural and magnetic properties of Cr-doped ZnO thin films

• Main Authors: Cheng-wen Hsu, 徐政文
• Other Authors: Yu-min Hu
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/s6c925

碩士 === 國立高雄大學 === 應用物理學系碩士班 === 97 === In this thesis, we report effects of different growth atmospheres, such as Ar、Ar+N2 and Ar+O2, growth temperature and sputtering powers of Cr and ZnO targets on the crystal structural, surface morphological, optical, electrical, and magnetic properties of Cr-doped ZnO films. All of the film samples were deposited using the magnetron co-sputtering method. The aim of this work is to examine the possibility, as well as to the origin and mechanism, of room-temperature ferromagnetism in Cr-doped ZnO films. Our results showed that as the PWCr is higher than 4 W, little amounts of the Cr2O3 phase appear in the Cr-doped ZnO film and at the same time the ferromagnetic signal is weaken. It is worthy noting that for all Cr-doped ZnO films gown under the Ar+O2 atmosphere, no Cr2O3 phase can be observed and the optical bandgap will increase with an increase in the Cr content. The estimated optical bandgaps of Cr-doped ZnO films are observed to be inversely proportional to the crystallite sizes calculated from the XRD results. For the low Cr content, the ferromagnetic signals of Cr-doped ZnO films grown under the Ar or Ar+O2 atmospheres, or at the lower temperature, are stronger than those of films grown under the Ar+N2 atmospheres, or at the higher temperature. Based on the PL results, we suggest that both little amounts of Cr and the existence of zinc vacancies are necessary for the presence of room-temperature ferromagnetism in Cr-doped ZnO films. Moreover, the electrical resistivity of the insulating Cr-doped ZnO film increases with the Cr content. In general, the resistivities (~ 104 Ωcm) of samples deposited under the Ar+N2 atmosphere are lower than those (~ 105 Ωcm) of samples deposited under the Ar+O2 atmosphere. Resistivity of the films which growth in Ar+N2 is lower than the films which growth in Ar+O2 and low temperature.