Center for Nanoscale Science and Engineering (CeNSE), Department of Electrical and Computer Engineering, University of Kentucky, Lexington, KY 40506, USA.
Nanotechnology. 2010 Mar 19;21(11):115303. doi: 10.1088/0957-4484/21/11/115303. Epub 2010 Feb 22.
Nanoporous anodic aluminum oxide (AAO) has been used widely as a template for device fabrication. In many nanostructured electro-optical device designs, AAO grown on an ITO substrate is the desired configuration. However, a residual thin aluminum oxide barrier layer between ITO and the AAO pores remains and process non-uniformities during the template fabrication can cause serious problems in the quality of nanowires deposited later in these pores. It was observed that in many templates, even the pores closest to each other could have their barrier layer thicknesses differ by as much as 10-20 nm. In this paper, causes and remedies for this non-uniformity are investigated, including the effects of a thin Ti interlayer inserted between the ITO and AAO. Templates with different Ti layer thickness and annealing conditions were compared. Mechanisms for the formation of voids beneath the barrier layer were analyzed and studied experimentally. Reactive ion etch (RIE) was found to be the preferred method to mitigate process non-uniformities. Using the above methods, barrier-free AAO templates on ITO substrates were obtained; their thicknesses ranged from 200 to 1000 nm. The characteristics of CdS nanowires electrodeposited into the initial templates with non-uniform barrier layer thicknesses and into the processed, barrier-free templates were compared.
纳米多孔阳极氧化铝（AAO）已被广泛用作器件制造的模板。在许多纳米结构电光器件设计中，ITO 衬底上生长的 AAO 是理想的结构。然而，ITO 和 AAO 孔之间仍然存在一层薄的氧化铝阻挡层，并且在模板制造过程中的工艺不均匀性可能会导致以后沉积在这些孔中的纳米线的质量严重问题。在许多模板中观察到，即使彼此最接近的孔的阻挡层厚度也可能相差 10-20nm。本文研究了这种不均匀性的原因和补救措施，包括在 ITO 和 AAO 之间插入薄 Ti 夹层的影响。比较了具有不同 Ti 层厚度和退火条件的模板。分析和实验研究了阻挡层下形成空隙的机制。发现反应离子刻蚀（RIE）是减轻工艺不均匀性的首选方法。使用上述方法，获得了无阻挡层的 AAO 模板；其厚度范围从 200nm 到 1000nm。比较了 CdS 纳米线在初始阻挡层厚度不均匀的模板和经过处理的无阻挡层模板中的电沉积特性。
