Investigations On The Preparation And Property Of ZnO Based Dilute Magnetic Semiconductor Thin Films By PLD

DMS (diluted magnetic semiconductor) can directly integrated with the existing semiconductor devices due to the application of both the electronic charge and spin nature, and can be used to manufacture high-density information memory, logic devices and the spin-polarized light transmitter of ultra-low energy consumption, which are optical, electrical and magnetic integrated new devices. Diluted magnetic semiconductor is a spin-polarized semiconductor, usually diluted magnetic semiconductor is a semiconductor material with the incorporation of a small number of the 3d transitional elements, which not only has ferromagnetism but also maintain its semiconductor properties at the same time. Dietl and others predicted that the Curier temperature of several ferromagnetic semiconductor materials, including ZnO and GaN-based compounds, may reach room temperature by mean-field theory approximation. It is under the influence of this prophecy that research in ZnO based diluted magnetic semiconductor, also known as the 3d-group elements doped ZnO-based materials, has become one of the hot spots in recent years.Zinc oxide (ZnO) is a direct wide band-gap compound semiconductor materials with E_g = 3.37 eV at room temperature and the exciton binding energy of up to 60 meV, so its excitons can be stable under room temperature and even above. ZnO is an ideal material for laser diodes( LDs), light-emitting diodes (LEDs) and such kind semiconductor devices. ZnO also has good thermal stability, low epitaxial growth temperature, strong anti-radiation ability, besides ZnO has many advantages involving non-toxic and relatively low cost. Since to the polarized growth characteristics of ZnO, transition metal ions can be easily doped into ZnO to prepare good performance dilute magnetic semiconductors, and ZnO-based materials has become a major diluted magnetic semiconductor research materials in recent years.In this thesis, based on the introduction of past and current research on ZnO-based diluted magnetic semiconductor materials and devices, transition metal ions doped ZnO thin films are prepared by PLD on the Si (100),quartz and glass substrates. The main research work are as follows: 1. Co element single doped ZnO thin film preparation and characterization. Co-doped ZnO thin films were grown by PLD on Si(100) substrates. By changing substrate temperatures and pressures,we seek for proper growth conditions for Co doped ZnO thin films and to study how the crystal quality affects the magnetic properties. We find that magnetism is very sensitive to growth temperature, but we find no regular correlation with the growth temperature.2. To enhance the saturation magnetization as well as Curie temperature of diluted magnetic semiconductor materials, Co, Mn co-doped ZnO thin films were prepared by PLD,and its morphology and magnetic properties were characterized with a little discussion on the magnetic mechanism,however, there is no increasement in saturation magnetization, which may result from the reduction of Co incorporation and the increasement of dopants, which enhance the antiferromagnetic coupling.3. In order to study what is the carrier's influence on the magnetic properties,so that to figure out where comes the magnetism,Co doped ZnO thin films grown in an atmosphere of nitrous oxide and Co,Ga co-doped ZnO thin films in oxygen atmosphere were prepared,respectively, which have different types of conductivity. The film's morphology and structure, electrical properties, magnetic properties were characterized to explore magnetism sources of diluted magnetic semiconductor materials. By contrast,it seems that p-type electrical environment is more conducive to the generation of room temperature magnetism.