The Dielectric Properties Of Ti_1-2xAl_xNb_xO₂ Ceramics And Films

With the development of microelectronics technology and industry,many microelectronic devices are becoming more and more miniaturized and integrated.Materials with colossal permittivity?CP?in microelectronic devices,especially in dynamic random access memory?DRAM?which has a broad application prospect.Recently,?In+Nb?co-doped rutile TiO₂ was reported in Nat.Mater by Hu et al.which possessed colossal dielectric permittivity?>104?as well as low dielectric loss?<0.05?.The frequency-and temperature-independent dielectric properties observed over a wide frequency?100Hz-1MHz?and a wide temperature span?25K-450K?is very beneficial to the development and application of DRAM.In this paper,?In+Nb?co-doped rutile TiO₂ ceramic's dielectric properties was well explained by the effect of electron-pinned defect-dipoles clusters.Based on this theory,We studied the dielectric properties of?Al+Nb?co-doped anatase TiO₂ ceramic.We found that the ceramic also has good dielectric properties.Meanwhile,?Al+Nb?co-doped anatase TiO₂ thin film was fabricated on a Pt/Ti/SiO₂/Si substrate by pulsed laser deposition at room temperature.We also studied the thin film's dielectric properties,which also showed good dielectric properties.Details are as followed:?1?The?Al+Nb?co-doped anatase TiO₂ ceramics were prepared by conventional solid phase sintering.The concentration were 0.5%,1%,2% and 5%,respectively.The optimized annealing conditions for?Al+Nb?co-doped TiO₂ ceramics were 1,500? for 10 h under air atmosphere and the concentration was 2%.Accord to the sample's analysis of the microstructure,element valence,different temperature of dielectric properties,We found that the structure of ceramics transfrom anatase phase structure into rutile phase structure,and all the ceramics have very high density.Al³⁺and Nb⁵⁺ were doped into the Ti⁴⁺ sites instead of forming impurities.Al and Nb were distributed into the ceramics uniformly.Their dielectric properties have a very good frequency and temperature stability.At last,Series of?Zn?or Ag??+ Nb co-doped anatase TiO₂ ceramics were prepared by conventional solid phase sintering,we found that they also have good dielectric properties.Therefore,the effect of electron-pinned defect-dipoles clusters not only was applicable for symmetric valence state of doping ions?for example?In+Nb?or?Al+Nb?co-doped TiO₂ ceramics?but low valence state of doping ions?for example?Zn+Nb?or?Ag+Nb?co-doped TiO₂ ceramics?.The synthesis of such dielectric ceramics were beneficial to reduce the amount of doping and reduce the cost.?2?The Ti_0.96Al_0.02Nb_0.02O₂ thin film was fabricated on a Pt substrate by pulsed laser deposition at room temperature,Accord to the sample's analysis of microstructure,element valence and dielectric properties at room temperature,we found that the film was amorphous.?Al+Nb?modification of TiO₂-based materials resulted in obvious improvement of the dielectric properties.Dielectric constant of the amorphous Ti_0.96Al_0.02Nb_0.02O₂ thin film was increased to about twenty times as compared with intrinsic dielectric constant of pure Ti O₂?¹70?,reached 3182.Meanwhile,the dielectric loss of the doped amorphous TiO₂ was reduced significantly,to a minimum of 7.4%.The dielectric properties of the amorphous thin film have a high frequency stability.Temperature is an important index in microelectronics technology,low temperature can avoid the damage to the microelectronic devices,and we precisely deposited Ti_0.96Al_0.02Nb_0.02O₂ thin film at room temperature.In the semiconductor industry,which will improve efficiency and reduce cost.To sum up,doped TiO₂ thin film with high dielectric constant and low loss would be a great potential research.