Rouse Jason H, Ferguson Gregory S
Departments of Chemistry and Materials Science & Engineering, Lehigh University, Bethlehem, PA 18015-3172, USA.
J Am Chem Soc. 2003 Dec 17;125(50):15529-36. doi: 10.1021/ja036241z.
Silica films with controlled thickness and refractive index have been formed by the sequential adsorption of a cationic polyelectrolyte and silica sols. The conditions used to prepare the sol were varied, and allowed films with refractive indices as low as 1.16 to be obtained. The sequential adsorption technique allows the thickness of these films to be controlled in increments of 5-10 nm, depending on the desired refractive index. Scanning electron microscopy revealed that a low packing density of constituent silica particles was responsible for the low indices of these films. The as-adsorbed films are thermally robust; calcination at 500 degrees C resulted in only very small decreases in film thickness (by < or =1.8%) and refractive index (to as low as 1.14). After calcination, the silica films remained hydrophilic and sorbed water vapor from the atmosphere. As a result, the refractive indices of these films increased with increasing relative humidity (RH). The dependence of the refractive index on RH was eliminated by treating the calcined films with trimethylchlorosilane.
通过阳离子聚电解质和硅溶胶的顺序吸附，形成了具有可控厚度和折射率的二氧化硅薄膜。制备溶胶时所采用的条件有所变化，从而能够获得折射率低至1.16的薄膜。顺序吸附技术使得这些薄膜的厚度能够以5 - 10纳米的增量进行控制，具体取决于所需的折射率。扫描电子显微镜显示，组成二氧化硅颗粒的低堆积密度是这些薄膜折射率低的原因。吸附后的薄膜具有热稳定性；在500摄氏度下煅烧只会导致薄膜厚度非常小的减小（小于或等于1.8%）以及折射率降低（低至1.14）。煅烧后，二氧化硅薄膜仍保持亲水性，并从大气中吸附水蒸气。结果，这些薄膜的折射率随着相对湿度（RH）的增加而增大。通过用三甲基氯硅烷处理煅烧后的薄膜，消除了折射率对RH的依赖性。
