1. Ultrathin, Smooth, and Stable
Doped Silver Films
Tom George, Electrical Engineering, San Jose State University
NNIN REU Site: Lurie Nanofabrication Facility
PI: Professor Jay Guo, Mentor: Cheng Zhang
Department of Electrical Engineering and Computer Science – University of Michigan, Ann Arbor
Introduction
Silver(Ag) is preferred for use in many optoelectronic applications
because it is transparent, highly conductive, and has low loss in the
visible and NIR regions. However, Ag atoms grow in a 3D island mode on
dielectric substrates, resulting in a rough and even un-continuous surface
when the deposited film thickness is less than 15nm. To achieve an
ultrathin, smooth, and stable Ag film, it was recently discovered that Ag
can be doped with aluminum(Al), which makes up around 5% of the
entire thin film composition. The purpose of this project was to investigate
the effects of other metal dopants, such as titanium(Ti) and chrome(Cr),
on thin Ag film formations.
Methods and Materials
 Investigate other metal dopants such as Ti and Cr
 Characterize the fabricated Ti-doped Ag and Cr-doped
Ag films in terms of their surface morphologies, sheet
resistances, and optical properties, etc.
 Explore the mechanisms of doped metallic atoms
helping ultra-thin Ag film growth
Objectives
Results
Conclusion
References
[1] An Ultrathin, Smooth, and Low-Loss Al-Doped Ag Film and Its Application as
a Transparent Electrode in Organic Photovoltaics. Adv. Mater., 26: 5696–5701.
DOI:10.1002/adma.201306091
[2] Ultrasmooth and Thermally Stable Silver-Based Thin Films with
Subnanometer Roughness by Aluminum Doping, ACS Nano 2014 8 (10),
10343-10351
DOI: 10.1021/nn503577c
I would like to thank my mentor Cheng Zhang and PI Professor Guo
for their mentorship. Also to Sandrine Martin, Pilar Herrera-Fierro, and
Nadine Wang for their guidance and support. Also, this work would not
have been possible without the LNF staff especially David Sebastian
and Brian Armstrong. I am grateful to the National Nanotechnology
Infrastructure Network and the National Science Foundation for
providing this opportunity
 Kurt.J.Lesker Lab 18 Sputtering tool used for
thin film deposition
 Deposition on Fused Silica and SiO2/Si
samples
 Ag target set at a fixed power
 Ti and Cr targets power swept from low to
high values to determine optimal co-
deposition condition
 Film thickness and optical properties
measured using J.A. Woollam ellipsometer
 Film surface morphologies characterized by
Scanning Electron Microscopy and Atomic
Force Microscope
 Doping of both Ti and Cr promote the growth of thin and
smooth silver films
 Ti-doped Ag and Cr-doped Ag are not as good as Al-
doped Ag in terms of sheet resistance and optical
properties, but are viable alternatives
 Further testing include film stability as well as effects of
other doping metals
9nm Ti-doped Ag
• Al forms enhanced nucleation sites over the substrate
• Capping layer is formed when sample is brought into an oxygen
ambient environment
• Enhanced nucleation sites and capping layer results in ultrathin,
smooth, and stable film
 RMS surface roughness:
0.549nm
 Sheet Resistance: 51 𝛺
𝑠𝑞
 Ti optimum power: 150W
 RMS surface roughness:
0.709nm
 Sheet Resistance: 25 𝛺
𝑠𝑞
 Cr optimum power: 60W
9nm Cr-doped Ag
Ag film growth Al-doped Ag film growth
Kurt.J.Lesker Lab18
Inside Lab 18
Acknowledgments