Study On Properties Of ZrW₂O₈ Thin Films Prepared By Radio Frequency Magnetron Sputtering

Negative thermal expansion (NTE) material, ZrW₂O₈, which exhibits large isotropic negative thermal expansion over its entire stability range from 0．3K to 1050K, has been paid particularly attention in material field recently. ZrW₂O₈ have very important practical applications in micro-electronics, optics, communication, medical fields and so on. Recently, the study of preparation and property of ZrW₂O₈ powders and bulks has been matured, but the study of ZrW₂O₈ thin film is only in initial step. The synthesis of ZrW₂O₈ film and its property were studied in this paper.In this paper, as-deposited thin film was prepared by Radio frequency magnetron sputtering using ZrW₂O₈ ceramic target and the ceramic target compounded with ZrO₂ and WO₃ powder as targets. On the base of preliminary studies, ZrW₂O₈ film of high purity was obtained by optimizing sputtering parameters and annealing technology. The phase and the surface morphology of the film were studied using X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). The thermal expansion property, dielectric property and transmission property were studied by temperature XRD, Analyzers and Spectrophotometer, respectively.The results indicated that the precursors films prepared by different as-deposited films were amorphous, the structure and the purity of the obtained ZrW₂O₈ film will be influenced by the heating process. ZrW₂O₈ film with good crystallization could be obtained by heated at 740℃for 3min in quick cooling, and its purity can be enhanced by increasing the heating time. But the pure ZrW₂O₈ film without ZrO₂ and WO₃ can not be obtained at 740℃by any way. Pure ZrW₂O₈ film could be obtained at 1200℃for 8 min by quick cooling using different precursor film.The surface of the obtained precursor film is smooth without crystal grain. The crystal grain of the ZrW₂O₈ film heated at 740℃grow up obviously, the size is average. The crystal grain of ZrW₂O₈ film obtained by quick cooling is small, the structure is condensed.ZrW₂O₈ film shows excellent negative thermal expansion property, its thermal expansion efficient is-10．08×10^-6 K^-1 from room-temperature to 700℃. Dielectric constants of ZrW₂O₈ film is 10 during the higher frequency. ZrW₂O₈ film shows good transmission during the visible spectrum and infrared spectrum.