Diana Shvydka, Ph.D - The University of Toledo

PHYSICS OF THIN FILMS/DEVICES
Thin film device fabrication
Fabricated compound semiconductor thin films and solar cell devices using rf-sputtering
and pulsed laser deposition techniques. Samples of intentionally varied properties were
used for electrical and optical studies aimed at optimization of complete PV device
performance.
AFM/STM studies
Established the phenomenon of temporal chaos in micro-scale current-voltage
characteristics of thin-film devices: AFM current exhibits stochastic behavior in addition to
the spot-to-spot variation. This research illuminates the microscopic physics of electron
transport through thin-film and nano-particle barriers.
Shunting and dielectric breakdown
This ongoing effort is aimed at understanding the nature of dielectric breakdown in the
modern nano-scale devices (MOS transistors) and relating this phenomenon to the omnipresent
shunting effects in thin-film photovoltaics. This resulted in two recent publications
in PRB and APL, and clearly has potential for more significant papers.
Piezo-photovoltaic coupling
Uncovered the phenomenon of piezo-photovoltaic coupling and related to the morphology
of the CdS film.
Nano-dipole photovoltaics
Developed new thin-film photovoltaic device principle, where the electric field is created
by a set of nanoparticles imbedded into a light-absorbing matrix. Utility patent application
has been filed.
Corrosion resistant protective tunneling layer
Recently filed a utility patent for a new principle of corrosion resistant electrode based on
the physical phenomenon of quantum tunneling rather than on the electrode chemistry.
Optical properties
Applied transmission-reflection and photoluminescence (PL) measurements to study the
near-band edge properties of CdSxTe1-x ternary system for films of different compositions
at room temperature and, at 10K; identified features related to defects and compositional
disorder. Systematically applied a below-band-gap PL excitation technique to elucidate the
effects of different steps in solar cell production.
Non-local photovoltaic response
Found the effect of non-local photovoltaic response to a scanning laser beam in CdTe/CdS
solar cells. The degree of non-locality depends on the device lateral resistance and laser
beam power, and can be as long as 1 meter in finished devices. Associated with the nonlocal
response are also features in PL mapping where different excitation powers lead to
different map topologies.
Bias-dependent photoluminescence
Discovered the effect of external bias on PL intensity in thin-film CdTe PV (later verified
for thin-film CIGS PV by other groups): PL suppression under reverse bias, increase with
moderate forward bias and subsequent saturation is extremely sensitive to device
degradation. The phenomenon is shown to result from the competition between the field-
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