Fabrication and charaterization of YBCO photodetectors

• Main Authors: Cheng, Yung-Feng, 鄭永豐
• Other Authors: Chu, Ann-Kuo;H Chou
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/11975541932459163854

碩士 === 國立中山大學 === 光電(科學)研究所 === 84 === The free-precipitation YBCO films have been grown from the t- arget with different density by off-axis sputtering technique at some certain deposition conditions. Their criyical temper- ature(Tco) can be varied from 76.1 to 84.13 K. These films e- xhibit an extremely smooth surface with a rms roughness less than 5 nm. The films grown by different conditions and from laser ablation technique have many precipitations on the samp- le surface. Films with different surface morphologies have b- een used to study the dependence of the bolometric effect to the precipitation on the films. We used the conventional pho- tolithography and wet etching to pattern YBCO films in the de- sired bolometer structure. In this thesis, we have constructed three different types of bolometers: The first is a microbridge- type device , the second is a microbrige-type of a superconductor-insulator-supercondu- ctor (SIS) junction device , and the third is a meander-type device . These bolometers exhibit Tco from 69.6 to 87.2 K and transition width from 1.8 to 3 K. The Tco of the precipitation- free microbridge can be tuned by applying different bias currents , which resulted in a tunable operation temperature of the photo- detector in 77.35 K and leads it to be more economic and in applications. When a bias current of 8 mA and a low power sity of 0.08 J/cm2-sec He- Ne laser chopped at 2 Hz were applied the microbridge at 77.35 K, a high responsivity of 2300 V/W was btained. We also found that the film with less precipitates will results in better the thermal conduction, and a larger The photoresponse of the signals decay exponentially with the pitation coverages. The meander-type bolometer have a high sponse signal than the microbridge one.This is due to its higher esistance and better coupling efficiency. However, SIS bolometer as a wider stable operation temperature in comparison to type device.