Thin films of 1-2 mum amorphous solid electrolytes, (1-x)LiBO2-xLi(2)SO(4) (LiBSO), were fabricated by RF magnetron sputtering with a wide range of compositions, i.e. x = 0.4-0.8, which are beyond the glass-forming region by conventional melt quenching method. The ionic conductivity of the electrolyte at room temperature increased with x and showed a maximum at x = 0.7, about 2.5 x 10(-6) S/cm. For higher x, (x > 0.7), the conductivity began to decrease due to the partial crystallization. In addition, the electrolyte was stable up to 5.8. V vs. Li/Li+. LiBSO thin film electrolyte was incorporated into Li/TiS2 microbattery, showing a good cycling performance. (C) 2003 Elsevier Science B.V. All rights reserved.