射频磁控溅射ZnO薄膜的结构和光学特性

Structural and Optical Properties of ZnO Thin Films Grown by RF Reactive Magnetron Sputtering

采用射频 (RF)反应磁控溅射法在n Si(0 0 1)衬底上外延生长ZnO薄膜。XRD谱测量显示出较强的 (0 0 2 )衍射峰 ,表明ZnO薄膜为c轴择优取向生长的。室温PL谱测量观察到了较强的紫外光发射和深能级发射。

ZnO,a wide direct-gap semiconductor, attracts as much attention as GaN in optoelectronics research field. ZnO not only has the same crystal structure as GaN, but also has strong exciton binding energy of 60meV which is 2.4 times to that of GaN. ZnO films have been grown by many methods, such as chemical vapour deposition (CVD), molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD). We adopt sputtering for the growth of ZnO films. Sputtering methods have several advantages. They can deposit large area films of well controlled compositions economically and the growth rate is high enough for thick films and low enough for ultrathin films by changing the sputtering rate. ZnO films were deposited on (001) silicon substrate by radio frequency (r.f.) magnetron sputtering. Gas flux ratio of O 2 to Ar and the RF power is 3∶1 and 600W, respectively. The sputtering time was 40min. The substrates were rotated and heated to 200℃ during the sputtering. The X-ray diffraction (XRD) patterns of the sample showed sharp diffraction peak for ZnO(002) ,which indicate that as-sputtered film were highly c-axis oriented. The sample grown under the conditions could generate strong luminescence of ZnO. The band edge emission and deep level emission were observed in photoluminescence (PL) spectra at room temperature.