John G. Ekerdt
Dick Rothwell Endowed Chair in Chemical Engineering
Associate Dean for Research in Engineering

Office:	CPE 4.468	Mailing Address:
Phone:	(512) 471-4689	The University of Texas at Austin
Fax:	(512) 471-7060	Department of Chemical Engineering
Email:	ekerdt@che.utexas.edu	1 University Station C0400
UT Mail:	C0400	Austin, TX 78712-0231

ChE 372 Course Web Site

Presentation Made to Prospective Graduate Students Spring 2008

Focus:
Surface and interface reaction kinetics, and the chemistry of electronic materials growth.

Figure 1: (click image to enlarge)We are exploring ways to passivate the surfaces of silicon nanoparticles and realize particle size dependent photoluminescence (PL) for supported Si nanocrystals. Borrowing from the chemistry of adsorbates on single crystal surfaces, chemical passivants, such as adsorbed deuterium, are under investigation. The images above show the desorption of D (c) from Si nanocrystals (a) that demonstrates the ways D adsorbs on nanocrystals, and the PL (b) shows that D-passivation of nanocrystals leads to efficient recombination.

Figure 2: (click image to enlarge) We study the growth of ultra thin (less than 9 nm) amorphous metal films. Guided by first-principles calculations in collaboration with Prof. Hwang, this research examines the role of alloying elements, such as phosphorus and boron, in stabilizing an amorphous microstructure for ruthenium, cobalt, nickel and palladium films. The research objectives are an understanding of the enabling reactions and processes that will lead to the thinnest possible continuous film, and to an ultra thin film with amorphous character.

Research:

The focus of my research is on the surface, growth and materials chemistry of metal, oxide and ferroelectric ultra thin films, and of silicon nanostructures, and on the kinetics and chemistry of lignin depolymerization. The former programs are motivated by applications in electronic materials. The research programs are highly interdisciplinary and involve collaborations with faculty in chemical engineering, physics, and electrical engineering, and researchers in industry.

Metal films find applications in sensors, optics and microelectronics, and as the critical dimensions or size of the applications and systems decrease, the metal film’s thickness will decrease to tens of atomic diameters at most and must have a specific microstructure. Our program seeks to describe how films form, with an emphasis on nucleation and island coalescence, the evolution of interfacial layers that bind the film to the substrate, how properties of bulk materials scale with thickness, and precisely how short range order is preserved as the film thickness approaches thicknesses that are 5-15 times the characteristic dimension of the Veronoi polyhedra.

The research on silicon alloy nanoparticle growth chemistry on dielectric surfaces seeks to understand how to grow nanoparticles of a particular diameter and density, and how to precisely position these nanoparticles on the surface. The key is to control nucleation and the uncouple nucleation and growth processes. We have explored the chemistry and kinetics of nanoparticle growth in detail on silicon dioxide and have identified the chemical structure of the defect site where nucleation occurs. Our focus is to determine the chemical properties of the defects on additional, technically relevant dielectrics surfaces, such as hafnium dioxide, and to manipulate the surface passivation and surface states of the nanoparticles to improve their properties.

The research on dielectric and ferroelectric films seeks to understand the chemical reactions responsible for atomic layer deposition growth and the interfacial reactions responsible for forcing the films to remain amorphous or to grow in a crystalline form. Studies with hafnia and zirconia are exploring the thermodynamic stability of the various phases and the role of homogeneously distributed aliovalent ions, such at La, and nanolaminates of La in changing the crystallization temperature and stabilizing the amorphous phase. Studies with ferroelectrics explore homoepitaxy and heteroepitaxy of perovskite films using molecular beam epitaxy and atomic layer deposition and the role of the growth surface termination and methods to enhance wetting/spreading to realize two dimensional epitaxial growth.

Lignin is one of the major components of lignocellulosic biomass and its resilience towards chemical attack is one of the major hurdles for biomass processing. Our work targets homogeneous and heterogeneous base-catalyzed routes to hydrogenolysis of oxygen bonds that comprise the backbone of lignin. Studies employ ionic liquids and model compounds, such as guaiacylglycerol-ß-guaiacyl ether, and seek to develop the kinetics and reaction pathways of depolymerization.

Selected Publications

• Time-to-failure Analysis of 5 nm Amorphous Ru(P) as a Copper Diffusion Barrrier (L. B. Henderson and J. G. Ekerdt) Thin Solid Films 517, 1645-1649 (2009).
• Germanium Interactions with Si-etched Silicon Dioxide (W. A. Winkenwerder and J. G. Ekerdt), Surface Science 602, 3071-3076 (2008).
• Film continuity and interface bonding of thin boron carbo-nitride films on Ge(100) and Si(100) (P. R. Fitzpatrick and J. G. Ekerdt), J. Vacuum Science and Technology A 26(6), 1397-1406 (2008).
• Effects of P in amorphous CVD Ru-P alloy films for barrier/seed application in Cu metallization (Jinhong Shin, Hyun-Woo Kim, Kyriacos Agapiou, Richard A. Jones, Gyeong S. Hwang, and John G. Ekerdt) Journal of Vacuum Science and Technology A 26, 974-979 (2008).
• Investigation of Volmer-weber growth mode kinetics for germanium nanoparticles on hafnia (S. S. Coffee and J. G. Ekerdt) J. Applied Physics 102, 1149129-(1-7) (2007).

 

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