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Self-Assembly of Silver Nanowires on Silicon Substrates. James H. Craig, Jr. DMR-0511811. Fig. 2 SEM image Ag nanowires on Si(001). * One of the projects in the proposal, “Issues in Thin Film Growth on Group IV Semiconductors,” is the study of Ag nanowires.

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Self-Assembly of Silver Nanowires on Silicon Substrates

James H. Craig, Jr.


Fig. 2

SEM image

Ag nanowires

on Si(001)

* One of the projects in the proposal, “Issues in Thin Film Growth on Group IV Semiconductors,” is the study of Ag nanowires.

The objective of this research (performed in collaboration with the University

of Duisburg-Essen in Germany) is to understand the physical mechanism

that drives the growth of novel wire-shaped metallic islands on silicon

surfaces. Nanowires are of interest technologically because of their

potential for quantum device applications, and scientifically as they

provide a playground for studying the physics of quasi-1D systems.

* Figure 1 shows a series of Photo-emission electron microscopy

(PEEM) images displaying the self-assembly of a Ag nanowire

growing on an atomically clean silicon surface. The different

images in the figure are at different times with time increasing

from (a) to (c). Interestingly, the width of the growing nanowire

remains fixed while the ends of the wire grow without bound.

The crystalline shape of the nanowires and compact islands is

seen in the Scanning Electron Microscopy image of figure 2.

* Figure 3 shows a PEEM image of a silver nanowire during

thermal decay. The bright zones at each end of the wire

are due to silver atoms being fed onto the surface due

to increased temperature. Because the bright zones do

not extend from the wires’ side, silver atom diffusion is limited in that

direction. We attribute this kinetic limitation to localized Ag-induced step

bunching in the vicinity of the growing nanowires, and this effective one-

dimensional diffusion is responsible for producing the wire-like islands.



Fig. 1

PEEM images

of growing

Ag nanowire on

Si(001) at 600 C

Fig. 3

PEEM image

of Ag nanowire


thermal decay

at 650 C



Undergraduate Involvement in Thin Film Research

James H. Craig, Jr.


Undergraduate student Bret Kolditz

works on the STM.

Undergraduate students Julie Thompson and Steve Yeninas work on the HREELS system.

During the summer 2006 eight Bradley University undergraduate physics students participated in this research program mentored by one of the collaborating faculty members supported by the project. Each of these students became proficient at operation of one of the ultra-high vacuum systems in our research group and the associated surface analytical instrumentation. By the end of the ten week summer research period each student group was able to undertake independently the entire process of sample preparation; sample mounting in UHV; system bakeout; data acquisition; and data analysis. The students had the opportunity for "hands on" experience with a variety of instrumentation including: variable temperature UHV scanning tunneling microscope; X-ray and ultra-violet photoelectron spectroscopy; high resolution energy loss spectroscopy; Auger electron spectroscopy; and time-of flight surface mass spectroscopy. During the past year four students have served as presenters at two national meetings- AVS International Symposium in Boston, MA and "Surface Analysis 2006" in Albuquerque, NM. Two undergraduate students have co-authored two publications resulting from work on this NSF project. As a result of these opportunities the participating students have developed impressive research skills far in excess of that which would have been possible from purely classroom activities. Consequently, these students have developed rapidly as enthusiastic and passionate young scientists.