24 research outputs found
CHARACTERIZATION OF RF AND DC MAGNETRON REACTIVE SPUTTERED TiO 2 THIN FILMS FOR GAS SENSORS
This study presents the technology for prep
aring and characterization of titanium oxide
thin films with proper
ties suitable for gas sensors. For
preparing the samples the reactive
radio frequency (RF) and direct current (DC) magnetron sputtering methods were used.
The composition and microstructure of the films were studied by X-ray photoelectron
spectroscopy (XPS), X-ray diff
raction (XRD) and Raman spectroscopy, the surface of the
films was observed applying high-resolution scanning electron microscopy (SEM). For
measuring the thickness and identifying the refractive indices of the films laser
ellipsometry was used. The research was focuse
d on the sensing behavior of the sputtered
titania thin films applying quartz crystal microbalance (QCM) method, which allows
detection of mass changes in the nanogram range. Prototype QCM sensors with TiO
2
thin
films were made by our team and tested for sensitivity to NH
3
and NO
2
. These films even
in as-deposited state and without heating th
e substrates show good sensitivity. Additional
thermal treatment is not necessary, making manufacturing of QCM gas sensor simple and
cost-effective, as it is fully compatible with the technology for producing the initial
resonator. The sorption is fully reversible and the studied TiO
2
films are stable, which
makes them capable for meas
urements for long terms
Characterization of thin MoO3 films formed by RF and DC-magnetron reactive sputtering for gas sensor applications
The present work discusses
a
technology f
or deposition and characterization of
thin
molybdenum oxide (MoO
x
,
MoO
3
)
films
studied
for gas sensor applications.
T
he samples
were
produced by
reactive radio
-
frequency (RF) and direct c
urrent (DC) magnetron sputtering.
The
composition and microstructure of the
films were studied by XPS
, XRD and Raman
spectroscopy, the
morphology
,
using
high resolution SEM. T
he research
was
focused on the
sensing
properties
of the sputtered
thin
MoO
3
films.
Highly sensitive gas sensor
s were
implemented
by depositing
films
of various thicknesses
on quartz resonators.
Making use of
the quartz crystal microbalance (QCM) method
,
the
se
sensors we
re capable
of
detect
ing
chan
ges in the molecular range.
Prototype QCM structures
with thin
MoO
3
films were tested
for sensitivity to NH
3
and NO
2
.
E
ven in as
-
deposited state and without heating
the substrates,
these films
show
ed
good sensitivity
.
Moreover
,
no
a
dditional thermal treatment is necessary,
which makes
the production
of
such
QCM gas sensor
s
simple and cost
-
effective, as it is fu
lly
compatible wit
h the technology for producing t
he initial resonator
.
Đą
he films are sensitive
at
room temperature and can
reg
ister concentrations
as
low as 50 ppm
. The sorption is fully
reversible
, the
films are stable and capable
of
long
-
term
measuremen
ts
WO3 nanopaticles and PEDOT:PSS/WO3 composite thin films studied for photocatalytic and electrochromic applications
Photocatalytic properties of h-WO3 nanoparticles obtained by annealing and h-WO3 nanorods prepared by hydrothermal method
Characterization of PLD grown WO3 thin films for gas sensing
Tungsten trioxide (WO3) thin films were grown by pulsed laser deposition (PLD) with the aim to be applied in gas sensors. The films were studied by atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and profilometry. To study the gas sensing behavior of these WO3 films, they were deposited on quartz resonators and the quartz crystal microbalance (QCM) method was applied to analyze their gas sensitivity. Synthesis of tetragonal-WO3 films starting from a target with predominantly monoclinic WO3 phase was observed. The films deposited at 300 degrees C presented a surface topology favorable for the sorption properties, consisting of a film matrix with protruding craters/cavities. QCM prototype sensors with such films were tested for NO2 sensing. The PLD grown WO3 thin films show good sensitivity and fast reaction at room temperature, even in as-deposited state. With the presented technology, the manufacturing of QCM gas sensors is simple, fast and cost-effective, and it is also suitable for energy-effective portable equipment for on-line monitoring of environmental changes. (C) 2017 Elsevier B.V. All rights reserved
Optical measurements of electrophoretic suspension kinetics
Electrophoretic deposition (EPD) was originally used for formation of coatings, e. g. in the automotive industry.
Recently EPD is successfully utili
zed for thin film preparation with an app
lication in the optics and electronics. This
paper investigates the process of the suspension formation and aggregation by ultraviolet and visible spectroscopy (UV-
VIS) spectroscopy and Dynamic Light Scattering (DLS) methods. The suspensions were formed by a precipitation of
solution of poly[2-methoxy-5-(3
âČ
,7
âČ
-dimethyloctyloxy)-1,4-phenylenevinylene]
in toluene using acetonitrile as a
precipitator. It could be concluded that the progressive suspension particle growth observed by DLS affects regularly
the first derivative of the UV-VIS spectra. By a comparison of the results obtained by both methods it could be seen that
UV-VIS spectroscopy combined with the
spline method could be successfully used
for an estimation of electrophoretic
suspensions