Broadhead Eric J, Tibbetts Katharine Moore
Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States.
Langmuir. 2020 Sep 1;36(34):10120-10129. doi: 10.1021/acs.langmuir.0c01581. Epub 2020 Aug 21.
Laser processing is an emerging technique capable of synthesizing metal-silicon composite surfaces for various applications. However, little is known about the chemical composition of these laser-processed surfaces, and the reaction mechanisms leading to their formation are poorly understood. In this work, we report the formation of gold-silicon nanostructured surfaces through reactive laser ablation in liquid. Silicon wafers were immersed in pH-controlled solutions of KAuCl and processed with ultrashort laser pulses. Gold deposition on the silicon wafers was found to depend on the pH of the precursor solution: neutral solutions (pH ∼6.3) resulted in much higher gold deposition than acidic or basic solutions. Laser processing of silicon wafers in water followed by immersion in the KAuCl solution resulted in lower gold deposition. X-ray photoelectron spectroscopy and depth profiling showed the existence of both gold (Au) and gold-silicide (AuSi) phases on the surfaces. Under both types of processing conditions, the gold atomic fraction and gold-silicide content increased with depth to at least 150 nm into the surface of the silicon wafer, although significantly more gold and gold-silicide were formed when the silicon was ablated in KAuCl solution as compared to immersion in KAuCl after ablation in water. Based on these data and existing literature on laser processing of silicon, we propose mechanisms that explain the observed gold penetration depth and its deposition dependence on solution pH. The mechanistic understanding gained in this work may be useful for synthesizing a variety of metal-silicon composite surfaces through laser processing to prepare functional materials such as catalysts and surface-enhanced Raman spectroscopy substrates.
激光加工是一种新兴技术，能够合成用于各种应用的金属 - 硅复合表面。然而，对于这些激光加工表面的化学成分知之甚少，导致其形成的反应机制也了解不足。在这项工作中，我们报告了通过液体中的反应性激光烧蚀形成金 - 硅纳米结构表面。将硅片浸入pH值受控的KAuCl溶液中，并用超短激光脉冲进行处理。发现金在硅片上的沉积取决于前驱体溶液的pH值：中性溶液（pH ∼6.3）导致的金沉积比酸性或碱性溶液高得多。在水中对硅片进行激光加工，然后浸入KAuCl溶液中，会导致较低的金沉积。X射线光电子能谱和深度剖析表明，表面存在金（Au）和金硅化物（AuSi）相。在两种加工条件下，金原子分数和金硅化物含量都随着深度增加到硅片表面至少150 nm，尽管与在水中烧蚀后浸入KAuCl溶液相比，当硅在KAuCl溶液中烧蚀时形成的金和金硅化物明显更多。基于这些数据和关于硅激光加工的现有文献，我们提出了解释观察到的金渗透深度及其对溶液pH值的沉积依赖性的机制。这项工作中获得的机理理解可能有助于通过激光加工合成各种金属 - 硅复合表面，以制备功能材料，如催化剂和表面增强拉曼光谱基底。
