摘要:
采用磁控共溅射技术制备了铒铥共掺杂氧化锌发光薄膜.通过优化退火温度,实现了薄膜的近红外平坦宽带发射,总带宽可达到～500 nm,覆盖了光通信S+C+L+U区波段.此发射带由Er3+的1535 nm (4I13/2→4I15/2)发射峰及Tm3+的1460 nm (3H4→3F4),1640 nm (1G4→3F2),1740 nm (3F4→3H6)发射峰组成.研究表明：退火温度低于800?C时,没有观察到薄膜样品明显的光致发光现象；随着退火温度从800?C升高到1000?C, I1640/I1535发射峰强度比从0.2升高到0.3, I1740/I1535发射峰强度比从0.5降低到0.4,发射峰强度比均基本保持稳定；当退火温度高于1000?C时, I1640/I1535发射峰强度比从0.3升高到0.6, I1740/I1535发射峰强度比从0.4升高到0.8,发射峰强度比均急剧增加.变温行为表明：随着温度从10 K逐渐升高到300 K,谱线的总带宽基本不变,在340—360 nm之间；Tm3+在1640和1740 nm处的发射峰强度分别降低了2/3和1/2, Er3+在1535 nm的发射峰强度增大了1.2倍.这是因为随着温度的升高,声子数目增多, Er3+与Tm3+离子之间发生能量传递的概率不断变大,并且在Tm3+离子之间没有发生交叉弛豫现象.
Abstract:
Er-Tm codoped ZnO thin film is synthesized by co-sputtering from separated Er, Tm, and ZnO targets. A flat and broad emission band is achieved in a range of 1400–2100 nm by optimizing annealing temperature, and the observed 1460, 1540, 1640 and 1740 nm emission bands are attributed to the transitions of Tm3+: 3H4→3F4, Er3+ 4I13/2→4I15/2, Tm3+1G4→ 3F2 and Tm3+ 3F4→ 3H6 transitions, respectively, which cover S, C, L, U bands. The intensity ratios of 1640 to 1535 nm and 1740 to 1535 nm below 1000 ?C are nearly constant, while the ratios increase sharply above 1000 ?C. The temperature dependence of photoluminescence (PL) spectrum is studied under 10–300 K. With increasing the operation temperature, the bandwidth of broadband is nearly invariable (340–360 nm), and the Tm3+ PL emission intensities of 1640 nm and 1740 nm from Er-Tm co-doped ZnO thin film decrease by a factor of 1.5 and 2, respectively. Moreover, the 1535 nm emission intensity is increased by a factor of 1.2. This phenomenon is attributed to the complicated energy transfer (ET) processes involving both Er3+ and Tm3+ and the increase of phonon-assisted ET rate with temperature as well. And the cross relaxation between Tm3+ ions does not occur.
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