Study On The Preparation And Property Of Transition Elements Doped ZnO Thin Films

Diluted magnetic semiconductor (DMS) has attracted great attention due to its potentialapplications in spintronics. Diluted magnetic semiconductors (DMSs) are formed by partialsubstitution of the cations of the host semiconductors with small amount of magnetictransition-metal (TM) ions such as V, Cr, Mn, Fe, Co, and Ni. With charge and spin degrees offreedom in a single substance, DMSs have attracted a great deal of attention in recent years asenabling materials in the emerging field of "spintronics", such as manufacture high-densityinformation memory, logic devices and the spin-polarized light transmitter of ultra-low energyconsumption, which are optical, electrical and magnetic integrated new devices.Among all theses oxides, ZnO belongs to the list of the most suitable building blockmaterials for spintronics application due to its abundance and environment friendly nature andalso due to its potential as a suitable optoelectronic material with a wide band gap (3.37 eV) anda high exciton binding energy (60 meV). ZnO has so many advantages, and was applied widelyand effectively. But there are many arguments for the origin of the magnetization. The main taskis to clearly the relationship between the carriers and the magnetization.In this thesis, based on the introduction of past and current research on ZnO-based dilutedmagnetic semiconductor materials and devices, transition metal ions doped ZnO thin films areprepared by PLD on the Si (100),quartz and glass substrates. The main research work are asfollows:The preparation and characterization of Ni doped ZnO thin films. The Ni doped ZnO thinfilms was prepared by PLD. By changing O₂ pressures and the content of Ni in the films, wesought for proper growth conditions for Ni doped ZnO thin films and studied the affects to themagnetic properties. Optimal conditions are as follows: the substrate tempreture is 500℃, the O₂pressure is 0.02 Pa, and the concentration of Ni is about 3at.%. When the Ni concentration isabove 5at.%, the existence of NiO phase in the films induces electric properties deterioratedand the visible light transmittance (400～800nm) decreased sharply resulting from the bindingenergy relaxation.N type Zn(Ni,Ga)O thin films and p type Zn(Ni,Na)O thin films were prepared by Ni-Ga codoping and Ni-Na codoping method and studied the influence of carrier type to theferromagnetism. We found that the Zn(Ni,Ga)O thin films have higher carrier concentration andlower magnetization. On the contrary, Zn(Ni,Na)O thin films are p type and with highermagnetization. We prepared p type Co-N codoped ZnO thin films using a technique of electroncyclotron resonance (ECR) N₂O plasma-enhanced pulsed laser deposition and observed asimilar result: Compared to the Co doped ZnO thin films prepared by the same method, the ptype film's magnetization becomes higher. So p type gives rise to the increasing ofmagnetization of Ni or Co doped ZnO thin films.