Diffusion Properties of Tm3+ in Congruent LiNbO3 Crystal
Diffusion Properties of Tm3+ in Congruent LiNbO3 Crystal
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DOI：
10.1111/jace.12211
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发表时间：
2013-05
影响因子：
3.9
通讯作者：
De‐Long Zhang;Wen-Zhu Zhang;P. Hua;D. Yu;E. Pun
中科院分区：
文献类型：
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作者：
De‐Long Zhang;Wen-Zhu Zhang;P. Hua;D. Yu;E. Pun
研究了Tm~(3+)在同成分LiNbO_3晶体中的扩散特性，以及Tm~(3+)掺杂对LiNbO_3衬底折射率的贡献和Li的外扩散。在4个X切和4个Z切同组分的LiNbO_3衬底上局部涂覆了15-31 nm厚的Tm-金属薄膜，在不同温度(1030℃-1130℃)和不同时间(20-70 h)的环境空气中进行了不同时间的热处理，并在1311和1553 nm波长测量了晶体表面Tm~(3+)掺杂和无Tm~(3+)部分的折射率，根据测量的折射率估算了晶体表面Li2O的含量。结果表明，Tm~(3+)掺杂对衬底折射率的影响较小，对波导层折射率增加的贡献较小。掺Tm~(3+)表面的Li2O含量与无Tm~(3+)表面相同。Li的外扩散主要取决于扩散温度。在1100℃以下，锂的外扩散是不可测量的。在1130℃下，30小时的扩散过程可能会导致0.2-0.3%的Li2O含量轻微损失。用二次离子质谱仪研究了Tm~(3+)的扩散性质。结果表明，所有样品中扩散的Tm3+离子遵循互补的误差函数分布。根据测量的Tm~(3+)扩散谱，得到了扩散系数、扩散常数、活化能、溶解度、溶解度常数和溶液热等特征扩散参数，并与Er3+扩散的情况进行了比较。与Er~(3+)扩散相比，Tm~(3+)扩散表现出相似的各向异性和溶解度的温度依赖性。在扩散系数方面，在较低温度下，Tm3+的扩散系数比Er3+低，两者的扩散系数差随着温度的升高而减小，在1130℃时为零。
Diffusion properties of Tm3+ in congruent LiNbO3 crystal have been investigated, together with other two related issues, i.e., Tm3+-doping contribution to refractive index of LiNbO3 substrate and Li out-diffusion. Four X-cut and four Z-cut congruent LiNbO3 substrates locally coated with 15–31 nm-thick Tm-metal films were annealed in surrounding air under different temperatures of 1030°C–1130°C for different durations of 20–70 h. After anneal, refractive index at Tm3+-doped and Tm3+-free parts of crystal surface was measured at the wavelengths of 1311 and 1553 nm and surface Li2O contents were evaluated from measured refractive index. The results show that Tm3+ doping has a weak effect on substrate index and a small contribution to index increment in waveguide layer in comparison with Ti4+- or Zn2+ doping. The Li2O content at the Tm3+-doped surface equals that at the Tm3+-free surface. The Li out-diffusion depends mainly on the diffusion temperature. Below 1100°C, the Li out-diffusion is not measurable. At 1130°C, a 30-h diffusion procedure may cause 0.2–0.3 mol% slight loss of Li2O content. Secondary ion mass spectrometry was used to study the Tm3+ diffusion properties. The results show that the diffused Tm3+ ions in all samples follow a complementary error function profile. From measured Tm3+ profiles, characteristic diffusion parameters such as diffusivity, diffusion constant, activation energy, solubility, solubility constant, and heat of solution were obtained and discussed in comparison with the case of Er3+ diffusion. In comparison with Er3+ diffusion, the Tm3+ diffusion shows similar anisotropy and temperature dependence of solubility. In the aspect of diffusivity, under lower temperature the Tm3+ has a lower diffusivity than the Er3+, and their diffusivity difference reduces with the increased temperature and becomes null at 1130°C.