Sintered By Field Assisted Sintering Technology And The Films Deposited By Magnetron Sputtering

Antimony doped tin oxide (ATO) film as a new kind of transparent conductiveoxides, has many superior properties, such as low cost and nontoxic, wide band gap(3.6eV), high electrical conductivity, high transparency in visible light, goodchemical stability, which makes ATO film the most probable substitution materialsfor tin doped indium oxide (ITO) film. Magnetron sputtering deposition is the mostwidely used coating method in industry. However, ATO ceramic target is difficult tobe densified because of the volatilization for SnO2at high temperature (>1100oC) andits evaporation condensation mechanism during sintering process. Low density ofATO ceramic target restricts the enhancement of electrical and optical properties ofATO film.Therefore, in this paper, magnetron sputtering deposited ATO transparentconductive oxide films were set as the research object. In view of the point that thehigher the target density, the better the performance of films, and in order to solve theproblem of low density for ATO ceramic targets, ATO nanoparticles prepared bynonhydrolytic sol-gel process were used as raw material because nanoparticles canreduce the sintering activation energy and improve the sintering driving force; FieldActivated Sintering Technology with low sintering temperature and short sinteringtime was used to restrain the volatilization of SnO2and prepare the ATO ceramictarget with high density; magnetron sputtering was used to prepare ATO films and theeffect of target density on the composition, structure and properties of ATO filmswere firstly studied.Firstly, the absolute ethyl alcohol instead of benzene methanol was used assolvent and oxidant, and then nonhydrolytic sol-gel process was used to prepare ATOnanoparticles with high crystallize and controllable Sb doping content. By studyingthe complexing agent content on the composition and structure of ATO nanoparticles,the best proportion of citric acid (as the complexing agent) was determined as citricacid to metal mol ratio is2. Under this proportion, when Sb doping content variesfrom0at.%to30at.%, Sb was successfully cooperated into SnO2lattice, and ATO nanoparticles were prepared with controllable Sb doping content and no Sb surfacesegregation. ATO nanoparticles are good crystalline with grain size of about20nm.Secondly, the as-synthesis ATO nanoparticles were used as raw material andATO ceramic target with high density were prepared using field activated sinteringtechnology. By studying the effect of sintering parameters (sintering temperature,heating rate and sintering pressure), Sb doping content and sample size on themicrostructure and density of ATO ceramics, the optimum sintering conditions wasinvestigated; by analyzing the structure evolution of ATO ceramic during fieldactivated sintering, and using ANSYS software to numerical simulate the electricaland thermal distribution, sintering mechanism of ATO ceramic was build; then, onthe basis of ATO ceramics with high density, the effect of Sb doping content andgrain size on the electrical properties of ATO ceramics were illustrated. The resultssuggest that, under the optimum sintering conditions (sintering temperature is1000oC,sintering rate is100oC/min, sintering pressure is40MPa, holding time is3min), thedensity of ATO ceramic is all above95%when Sb doping content increases from1at.%to10at.%. When Sb doping content is5at.%, the density of ATO ceramic is ashigh as99.2%. Field activated sintering shows obvious size effect: when the samplesize is small with a diameter of20mm, the structure of ATO ceramic is homogenousand the density is high; while when the sample size is large with a diameter above50mm, the structure of ATO ceramic is inhomogeneous and the density is low. Whenextending the holding time to30min, the ATO ceramic with a diameter of50mm,density of98.1%,5at.%Sb doping content and homogenous structure are obtained.Field activated sintering mechanism of ATO ceramic can be expressed as twosintering stages. The electrical resistivity of ATO ceramic first decreases thenincreases with the increasing of Sb content, and decreases with the increaseing ofgrain size. When the Sb doping content is5at.%, grain size is50nm, ATO ceramicshows the lowest electrical resistivity of4.4310-3cm.Finally, ATO film with low electrical resistivity and high transmition weredeposited by magnetron sputtering. By studying the composite and structure variationof ATO ceramic target with different density before and after sputtering, andrevealing the effect of target density on the composite, structure and properties ofATO films, the relationship between relative density of ATO ceramic target and properties of ATO film was illustrated; using ATO ceramic with high density astarget, the effects of magnetron sputtering parameters (annealing treatment, oxygenpartial pressure, substrate temperature, sputtering power) on the composite, structureand properties of ATO films were studied and ATO film with enhanced propertieswas obtained. The results suggest that, under the same magnetron sputteringconditions, commercial ATO target with low density is easy to form nodules and theSb content and Sb5+/Sb3+ratio of ATO film prepared by commercial target is low.Sintered ATO target with high density is easier to control the Sb doping content ofATO thin film and is propitious to prepare ATO film with high carrier concentration,low electrical resistivity and high transmittance. When the oxygen partial pressure isO2/(O2+Ar)=10%, deposition temperature is300oC, sputtering power is300W,annealing atmosphere is air, the ATO film using high density ceramic as a targetshows lowest electrical resistivity of1.2110-3·cm, and average opticaltransmittance of89.76%.