RUI: Regenerative Electroless Etching for the Production of Si Nanostructures

纳米结构硅在消费产品、纳米医疗和充电电池等领域的应用，将受益于经济地生产对国家繁荣至关重要的新技术所需的千克至吨规模的多孔硅粉。化学蚀刻，这是一种公认的具有工业潜力的电化学工艺，但需要在重现性、可控性、纯度、成本和规模方面取得进展。这项研究将开发一种新的电化学工艺，称为再生化学刻蚀(ReEtching)，这是一种新的化学湿法刻蚀概念，具有生产纳米结构和分层结构半导体的能力。反萃取是一种使用一种氧化剂连续再生反应混合物中低浓度第二氧化剂的方法，该反应混合物用于反应。这些研究将把化学蚀刻从不可重复的过程转变为一种可以产生任意厚度的均匀多孔膜、产生任意长度的柱状颗粒、产生结晶或非晶柱、产生中孔内具有纳米孔或在大孔内具有纳米孔的分级多孔性材料的过程。这项工作是在一个主要是本科院校进行的，具有很强的国际成分，为参与研究的本科生提供了独特的国际研究体验。再生化学刻蚀(ReEtching)是一种无电湿法刻蚀工艺，具有生产纳米结构和分层结构半导体的能力。重新刻蚀生产纳米结构半导体的过程中，氧化剂(OX1)被用作催化剂，以促进半导体和第二氧化剂(OX2)之间的反应，而第二氧化剂在第一反应中不起反应。OX2用于再生能够引发刻蚀的OX1。反应程度由OX2的加入量控制，反应速度由OX2的注入速度控制。一个具体的例子是通过在HF(AQ)中与V2O5(催化剂)和H2O2(再生剂)反应制备高发光的纳米多孔硅粉末。因为它便于控制反应速度而不受反应程度的影响，所以重刻具有以前无法达到的处理能力。这笔赠款将把化学蚀刻从一种不可重复的过程转变为一种可以产生任意厚度的均匀多孔膜、产生任意长度的柱状颗粒、产生晶体或非晶柱、产生中孔内有纳米孔或大孔内有纳米孔的分级多孔性材料的过程。这些介观到纳米的结构将通过光致发光进行表征，并与材料的结构参数相关联。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Applications of nanostructured silicon in, e.g., consumer products, nanomedicine and rechargeable batteries, would benefit from economical production of porous silicon powder on the kilogram-to-ton scale needed in new technologies essential for national prosperity. Electroless etching, which is an electrochemical process that is recognized possessing industrial potential but requiring advances in its reproducibility, controllability, purity, cost and scaling. This research will develop a new electrochemical process called regenerative electroless etching (ReEtching), a new concept in electroless wet etching with the capability of producing nanostructured and hierarchically structured semiconductors. ReEtching is a method in which one oxidant is used to continuously regenerate a low concentration of a second oxidant in the reaction mixture which is used in the reaction. These investigations will transform electroless etching from an irreproducible procedure into a process that can produce homogeneous porous films of arbitrary thickness, produce pillared particles of arbitrary length, produce either crystalline or amorphous pillars, produce hierarchical porous materials with nanopores inside of mesopores or nanopores inside of macropores. This work is carried out in a primarily undergraduate institution with strong international components providing the undergraduates involved in the research a unique international research experience.Regenerative electroless etching (ReEtching) is a electroless wet etching process with the capability of producing nanostructured and hierarchically structured semiconductors. ReEtching produces nanostructured semiconductors in a process which an oxidant (Ox1) is used as a catalytic agent to facilitate reaction between a semiconductor and a second oxidant (Ox2) that would be unreactive in the primary reaction. Ox2 is used to regenerate Ox1, which is capable of initiating etching. The extent of reaction is controlled by the amount of Ox2 added and the rate of reaction is controlled by the injection rate of Ox2. A specific example is the production of highly luminescent, nanocrystalline porous Si powder through reaction with V2O5 (the catalytic agent) and H2O2 (the regeneration agent) in HF(aq). Because it facilitates control the rate of reaction independent of the extent of reaction, ReEtching possesses previously unattainable processing capabilities. This grant will transform electroless etching from an irreproducible procedure into a process that can produce homogeneous porous films of arbitrary thickness, produce pillared particles of arbitrary length, produce either crystalline or amorphous pillars, produce hierarchical porous materials with nanopores inside of mesopores or nanopores inside of macropores. These meso-to-nanostructures will be characterized by photoluminescence and correlated with the materials structural parameters. Extension to other semiconductors will be developed.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.