The Woodruff School

SUMMARY

Unique pathways to “direct-write” nanofabrication are possible using focused electron beam induced deposition (FEBID), owing to its capability of generating and directing the appropriate energy electrons to facilitate a wide range of (electro)chemical reactions in gas, liquid and solid phases. This proposal is based on a recent discovery of a new approach to FEBID, made in the course of preliminary work, by using the nano-electrospray delivery of liquid phase precursors (Nano Letters, 15, 8385 (2015)). This new technique, hereafter referred to as NESA-FEBID, enables important new capabilities by (1) dramatically increasing the growth rate of deposition/etching, (2) enabling deposition of composite materials and alloys with tailored electromechanical properties, and (3) fabrication of new, truly 3D topologies of nanostructures that are fundamentally out of reach of current gas-phase FEBID techniques. The mechanism of liquid-phase FEBID is mostly unknown, and currently limited understanding of process fundamentals is a roadblock to advancing NESA-FEBID, thus necessitating an in-depth fundamental study as proposed here.

At the foundation of the proposed research approach is a controlled-current liquid electrochemical cell, in which the transport (currents) of all charged species (precursor ions, solvent ions, incoming beam electrons and outgoing reduction reaction electrons) are measured and dynamically controlled in-situ. Quantification of the precursor thermodynamic state variables and charge conversion processes allows for probing the kinetic pathways, using NESA-FEBID as a unique experimental platform to drive the experimental inquiries and answer the following questions: (1) What are the interactions between two major types of reactions that occur in the liquid phase - electrochemical reduction and solvent radiolysis/decomposition and role of different energy electrons in mediating these interactions?; (2) What is the influence of heterogeneous vs. homogeneous reactions on the nucleation and directed growth/assembly of materials?

Basic insights and experimental/computational tools resulting from this project will enable discovery and validation of new methods for improving the growth rate, resolution, and composition/phase control of FEBID of 3D-complex hierarchical materials with atomic scale control, and will be essential for transforming FEBID into a truly powerful additive nanomanufacturing tool with broad applications.

SUBJECT:	Ph.D. Proposal Presentation

BY:	Jeffrey Fisher

TIME:	Wednesday, April 6, 2016, 9:30 a.m.

PLACE:	MRDC Building, 4211

TITLE:	Nanoelectrospray-Assisted Focused Electron Beam Induced Deposition (NESA-FEBID) of 3D Nanostructures using Liquid Phase Precursors

COMMITTEE:	Dr. Andrei Fedorov, Chair (ME) Dr. Steven Danyluk (ME) Dr. Samuel Graham (ME) Dr. Peter Kottke (ME) Dr. Younan Xia (BME)

SUMMARY Unique pathways to “direct-write” nanofabrication are possible using focused electron beam induced deposition (FEBID), owing to its capability of generating and directing the appropriate energy electrons to facilitate a wide range of (electro)chemical reactions in gas, liquid and solid phases. This proposal is based on a recent discovery of a new approach to FEBID, made in the course of preliminary work, by using the nano-electrospray delivery of liquid phase precursors (Nano Letters, 15, 8385 (2015)). This new technique, hereafter referred to as NESA-FEBID, enables important new capabilities by (1) dramatically increasing the growth rate of deposition/etching, (2) enabling deposition of composite materials and alloys with tailored electromechanical properties, and (3) fabrication of new, truly 3D topologies of nanostructures that are fundamentally out of reach of current gas-phase FEBID techniques. The mechanism of liquid-phase FEBID is mostly unknown, and currently limited understanding of process fundamentals is a roadblock to advancing NESA-FEBID, thus necessitating an in-depth fundamental study as proposed here. At the foundation of the proposed research approach is a controlled-current liquid electrochemical cell, in which the transport (currents) of all charged species (precursor ions, solvent ions, incoming beam electrons and outgoing reduction reaction electrons) are measured and dynamically controlled in-situ. Quantification of the precursor thermodynamic state variables and charge conversion processes allows for probing the kinetic pathways, using NESA-FEBID as a unique experimental platform to drive the experimental inquiries and answer the following questions: (1) What are the interactions between two major types of reactions that occur in the liquid phase - electrochemical reduction and solvent radiolysis/decomposition and role of different energy electrons in mediating these interactions?; (2) What is the influence of heterogeneous vs. homogeneous reactions on the nucleation and directed growth/assembly of materials? Basic insights and experimental/computational tools resulting from this project will enable discovery and validation of new methods for improving the growth rate, resolution, and composition/phase control of FEBID of 3D-complex hierarchical materials with atomic scale control, and will be essential for transforming FEBID into a truly powerful additive nanomanufacturing tool with broad applications.