臺灣博碩士論文加值系統

本論文主耍在研究熱穩定性極佳的 YBa(2)Cu(4)O(8) 超導體,及其低歐姆
接觸電極的製作技術, 並藉由熱處理及 Ag(2)O 的添加探討其對接觸界面
特性的影響。其重耍結果如下: 1.以硝酸鹽熱分解法製備 YBa(2)Cu(4)
O(8) 超導體時, 在燒結前添加 Ag(2)O , 將有助於 YBa(2)Cu(4)O(8)
相的穩定及形成,且具有可使製程簡化及增加樣品的導電性等優點。 2.適
當溫度的熱處理, 將可有效改善 Y(0.9)Ca(0.1)Ba(2)Cu(4)O(8)/Ag接觸
系統原本未退火前之半導體的非歐姆接觸界面, 成為金屬性的歐姆接觸。
在退火條件 600 C,1小時通氧處理下具有最低接觸電阻率；其室溫接觸電
阻率為 4.55 * 10(-5) ohm.cm(2),而超導時之接觸電阻率,則低於
10(-8) ohm.cm(2)。 3.Y(0.9)Ca(0.1)Ba(2)Cu(4)O(8) + 25 wt.% Ag(2)
O/Ag 接觸系統中不須額外的熱處理, 便可使界面完全呈現金屬性, 且具
有低的歐姆接觸電阻率；其室溫接觸電阻率 1.57 * 10(-4) ohm.cm(2)
,而超導時之接觸電阻率 4.60 * 10(-8) ohm.cm(2)。 4.Y(0.9)Ca(0.1)
Ba(2)Cu(4)O(8) + 25 wt.% Ag(2)O/Ag 接觸系統仍可藉適當溫度的熱處
理, 有效改善界面特性, 得到便低歐姆接觸電阻率。且 25 wt% Ag(2)O/
Ag 的添加,將可降低所使用的熱處理溫度至 400 c, 並且得到比未添加的
樣品( 600 c 熱處理 )具更低的歐姆接觸電阻率；在 400 c, 1 小時通氧
退火條件處理下,其室溫接觸電阻率為2.76 *10(-5) ohm.cm(2) 而超導時
之接觸電阻率, 由未經熱處理的樣品便可達 4.60 * 10(-8)ohm.cm(2)來
看,應遠低於 10(-8) ohm.cm(2)。 5.由 SEM 之 X 光剖面線分析得知,
添加 Ag(2)O 樣品的接觸電阻率比未添加低者主耍原因,是由於樣品內界
面附近的 Ag, 往界面擴散所致, 而且其擴散程度與退火條件有很大關係
。在 400 C, 在 1小時通氧退火條件下,恰使樣品內界面附近的 Ag, 往界
面擴散至界面處, 而形成極低電阻的金屬性緊密接觸。 6.Ag 電極對
1-2-4 超導體而言, 為一優良的歐姆接觸金屬；尤其在 YBa(2)Cu(4)
O(8) 添加 Ag(2)O 時, 便是一絕佳電極材料。

The topics of this thesis are devoted to study the
YBa(2)Cu(4)O(8) superconductor with excellent thermal stability
of oxygen content and technique for the fabrication oflow ohmic
contact electrodes, and to discuss the influence on the charac-
teristic of metal-contacted interface by thermal annealing and
the addition of Ag(2)O. The important results are as follows:
1.A low-resistance ohmic contact forY(0.9)Ca(0.1)Ba(2)Cu(4)O(8)
+ 25 wt.% Ag(2)O/Ag interface can be even achieved withoutany
thermal annealing. The lowest contact resistivity is 1.57 *10
(-4) ohm.cm(2) at 300 K and 4.60 * 10(-8) ohm.cm(2) at 77 k.
2.The characteristics of Y(0.9)Ca(0.1)Ba(2)Cu(4)O(8) +25 wt.%
Ag(2)O/Ag interface can be improved by suitable heat
treatment. The optimal annealing condition is at 400 C for 1h
under 1 atm oxygen presure. 3.From thr results of x-ray line
profile of SEM,the reason for the contact resistivity of
specimen with Ag(2)O addition is lower than that of Ag(2)O
free system may be due to the Ag of specimen diffuse to the
interface. The degree of diffusion strongly depends on the
annealing temperature.While the spec- imen is heated at 400 C
for 1h under 1 atm oxygen presure,the Ag of specimen is just
connected to the Ag electrode, result- ing the formation of
lowest-resistance ohmic contact. 4.Ag is an excellent candidate
for practical electrode material on YBa(2)Cu(4)O(8),
especially YBa(2)Cu(4)O(8) with addition of Ag(2)O.