Date of Graduation

12-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Chemical Engineering

Advisor

Donald K. Roper

Committee Member

Bob Beitle

Second Committee Member

Shannon L. Servoss

Third Committee Member

Rick Ulrich

Fourth Committee Member

Surendra P. Singh

Keywords

Applied sciences; Electroless plating; Gold nanoparticles; Gold thin film; Mass transfer in thin film deposition; Real time monitoring; Surface plasmon resonance

Abstract

The scientific and industrial demand for controllable thin gold (Au) film and Au nanostructures is increasing in many fields including opto-electronics, photovoltaics, MEMS devices, diagnostics, bio-molecular sensors, spectro-/microscopic surfaces and probes. In this study, a novel continuous flow electroless (CF-EL) Au plating method is developed to fabricate uniform Au thin films in ambient condition. The enhanced local mass transfer rate and continuous deposition resulting from CF-EL plating improved physical uniformity of deposited Au films and thermally transformed nanoparticles (NPs). Au films and NPs exhibited improved optical photoluminescence (PL) and surface plasmon resonance (SPR), respectively, relative to batch immersion EL (BI-EL) plating. Suggested mass transfer models of Au mole deposition are consistent with optical feature of CF-EL and BI-EL films.

The prototype CF-EL plating system is upgraded an automated scalable CF-EL plating system with real-time transmission UV-vis (T-UV) spectroscopy which provides the advantage of CF-EL plating, such as more uniform surface morphology, and overcomes the disadvantages of conventional EL plating, such as no continuous process and low deposition rate, using continuous process and controllable deposition rate. Throughout this work, dynamic morphological and chemical transitions during redox-driven self-assembly of Ag and Au film on silica surfaces under kinetic and equilibrium conditions are distinguished by correlating real-time T-UV spectroscopy with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) measurements. The characterization suggests that four previously unrecognized time-dependent physicochemical regimes occur during consecutive EL deposition of silver (Ag) and Au onto tin-sensitized silica surfaces: self-limiting Ag activation; transitory Ag NP formation; transitional Au-Ag alloy formation during galvanic replacement of Ag by Au; and uniform morphology formation under controlled hydraulic conditions.

A method to achieve the time-resolved optical profile of EL Au plating was devised and provided a new transitional EL Au film growth model which validated mass transfer model prediction of the deposited thickness of ¡Ü100 nm thin films. As a part of the project, validation of mass transfer model, a spectrophotometric method for quantitative analysis of metal ion is developed that improves the limit of detection comparable to conventional instrumental analysis.

The present work suggests that modeling, fabrication and characterization of this novel CF-EL plating method is performed to achieve an ultimate purpose: developing a reliable, inexpensive wet chemical process for controlled metal thin film and nanostructure fabrication.

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