Espiau de Lamaestre R, Majimel J, Jomard F, Bernas H
CSNSM/CNRS, Université Paris Sud, 91405 Orsay Campus, France.
J Phys Chem B. 2005 Oct 20;109(41):19148-55. doi: 10.1021/jp0527047.
Lead chalcogenide (PbS, PbSe, and PbTe) nanocrystals were synthesized by sequential implantation of Pb and one of the chalcogen species into pure silica. The implantation energy and fluence were chosen so that the implantation profiles practically overlap at a depth approximately 150 nm with a maximum concentration of about 0.3 atom %. Annealing for 1-8 h at 850-900 degrees C triggers nanocrystal growth, which is monitored by high-resolution (HRTEM) and conventional transmission electron microscopy (TEM), secondary-ion mass spectrometry (SIMS), and Rutherford backscattering spectrometry (RBS). Striking differences are found in the depth distributions and microstructures of the resulting nanocrystals. We show that the differing chemical interactions of Pb and chalcogens (between each other and with silica) play a crucial role in chalcogenide nucleation and growth. Using available information on chalcogen redox states in silicate glass, we propose a nonclassical nucleation and growth mechanism consistent with our experimental results. The complex chemistry involved at the microscopic level is shown to impair control over the nanocrystal size distribution. Finally, PbS nanocrystal-doped silica is shown to emit intense photoluminescence (PL) in the 1.5-2 microm wavelength range, an effect that we relate to the above nucleation and growth scheme.
通过将铅和一种硫族元素依次注入纯二氧化硅中来合成硫族化铅（硫化铅、硒化铅和碲化铅）纳米晶体。选择注入能量和注量，使得注入分布在深度约150 nm处实际重叠，最大浓度约为0.3原子%。在850 - 900℃下退火1 - 8小时会引发纳米晶体生长，通过高分辨率（HRTEM）和传统透射电子显微镜（TEM）、二次离子质谱（SIMS）以及卢瑟福背散射光谱（RBS）对其进行监测。在所得纳米晶体的深度分布和微观结构中发现了显著差异。我们表明，铅和硫族元素之间（彼此之间以及与二氧化硅之间）不同的化学相互作用在硫族化物的成核和生长中起着关键作用。利用关于硅酸盐玻璃中硫族元素氧化还原态的现有信息，我们提出了一种与我们的实验结果一致的非经典成核和生长机制。结果表明，微观层面涉及的复杂化学过程会影响对纳米晶体尺寸分布的控制。最后，掺硫化铅纳米晶体的二氧化硅在1.5 - 2微米波长范围内发射出强烈的光致发光（PL），我们将这种效应与上述成核和生长机制联系起来。
