铒铥共掺氧化锌薄膜近红外宽带发射及变温行为的研究

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 (⁴I_13/2 → ⁴I_15/2) 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 ℃ 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 ℃ 升高到1000 ℃, 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 ℃ 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.

Near infrared broadband from Er-Tm codoped zinc oxide and temperature-dependent properties

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, Er^{3+ 4}I_13/2 →⁴I_15/2, Tm^{3+ 1}G₄ → ³F₂ and Tm^{3+ 3}F₄ → 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 ℃ are nearly constant, while the ratios increase sharply above 1000 ℃. 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.