| Budget Amount *help |
¥5,600,000 (Direct Cost: ¥5,600,000)
Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1985: ¥5,100,000 (Direct Cost: ¥5,100,000)
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| Research Abstract |
<Ta_2O_5> thin films have been used for forming thin-film capacitors and, more recently, for optical wave-guides and for antireflection coating on solar cells. These application are essentially based on the high chemical stability of this oxide and especially on its optimum optical properties such as a high refractive index and a very low absorption coefficient for light. In previous works, the <Ta_2O_5> thin films were obtained by the thermal oxidation of a tantalum film evaporated onto a substrate, rf sputtering, and reactive dc sputtering. All <Ta_2O_5> thin films obtained in previous work were amorphous, and were not single crystals.
In this research, We have clarified next three points that
(1) the <Ta_2O_5> thin films are fabricated by the planar-magnetron reactive DC diode sputtering method. These kind of films such as oriented, amorphous and polycrystalline can be fabricated by varying the sputtering condition. Especially, the oriented film is one axis oriented film where the x-axis of <beta> - <Ta_2O_5> belonging to point group " m " is grown perpendicular to the substrate. Furthermore the film shows piezoelectric properties and is a new piezoelectric film which has not been reported thus far.
(2) In the oriented <Ta_2O_5> thin film, the maximum electromechanical coupling coefficient <K^2> for the surface acoustic wave is 1.54% at hk=1.6. The propagation loss of the SAW is 13.3 dB/cm at 131 MHz when the fused quartz substrate is used.
(3) The first-order TCD of the oriented <Ta_2O_5> thin film is zero. The second-order TCD is 0.148 ppm/ <C^2> at hk=1.78 for the fused quartz substrate and is 0.052ppm/ <C^2> at hk=1.27 for the PYREX substrate, respectively.
The <Ta_2O_5> film is chemically stable and may supply SAW device with good temperature characteristics. The fabrication of <Ta_2O_5> thin film with more excellent properties is expected.
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