Facilities
Deposition
Physical Vapor Deposition
We deposit thin films using physical vapor deposition
(PVD). In PVD, the material (in the form of powder or pellets) is evaporated to
make the thin film. The material can be evaporated using three techniques:
·
Electron
beam evaporation
·
Thermal
evaporation using resistive heating of a metallic boat
·
Thermal
evaporation using a ceramic crucible.
The
choice of any of these three techniques depends on the material to be
deposited. The thickness of the film can be controlled using a thickness
monitor. The substrates can be rotated and heated up to 300 oC.
In addition, reactive evaporation (using controlled
atmospheres of oxygen, nitrogen and other gases) can be achieved. Moreover,
co-evaporation (simultaneous evaporation from more than one source) can be
achieved. All PVD process take place in the fully-automated Leybold
L-560 box coater.
Pulsed Laser Ablation
Thin films can also be deposited using pulsed
laser ablation (evaporation). In this technique, the energy
required to evaporate the material is supplied by powerful laser pulses. The
most important advantage of this technique is that it is versatile, it can work
with almost any material. In addition, the chemical composition of the film is
very close to the starting material. Currently, we use a UV pulsed excimer
laser (Lambda Physik COMPEX Pro 102).
Characterization
Atomic Force Microscope
The atomic force microscope
(AFM) or scanning force microscope (SFM) is a very high-resolution type of
scanning probe microscope, with demonstrated resolution of fractions of a
nanometer, more than 1000 times better than the optical diffraction limit. The
AFM is one of the foremost tools for imaging, measuring and manipulating matter
at the nanoscale. The term 'microscope' in the name is actually a misnomer
because it implies looking, while in fact the information is gathered by
"feeling" the surface with a mechanical probe. Piezoelectric elements
that facilitate tiny but accurate and precise movements on (electronic) command
enable the very precise scanning. (© Wikipedia the free encyclopedia)
We are using the Veeco Innova
diSPM.
Surface
Profilometer
Stylus
profilers employ a simple measurement technique.
A
conical diamond tip stylus (with a radius ranging from 0.2µm to 25µm) scans
across the surface at a very light stylus force. As a sample moves under the
stylus and the stylus encounters various surface features, vertical motion of
the stylus is detected by an LVDT, and this signal is converted into
two-dimensional data. This data is presented as a profile or cross section of
the sample surface, and provides extremely accurate and repeatable step height
measurements of vertical features.
We are using an AMBIOS XP-2
surface profilometer to measure the thickness of films.
UV-VIS-NIR
Spectrophotometer
The Jasco V-570 is a double
beam scanning spectrometer with two monochromators which cover the
wavelength range of 190-2500 nm. Both gratings and detectors are changed
automatically and the user can select the wavelength at which the changeover
occurs. The spectrometer is capable of performing transmittance, absorption and
reflectance measurements of solid and liquid sample. These measurements are
used to extract the optical properties of the materials.
Spectrofluorometer
Fluorescence is the emission of light. This emission can be
stimulated by heat, electron bombardment, or high-energy photons. This process
may also be referred to as luminescence. Luminescence of thin films can yield
information on their bandgaps and defects. Luminescence processes are
especially important in thin films intended for optoelectronic applications,
such as light detectors and emitters. In our lab, we use the Shimadzu RF-5301 PC spectrofluorometer. It can also be
used with liquid sample. For high resolution spectra, we have installed an MMR
refrigerator to cool the samples down to 80 K.
Electrical Measurements
This system is used to measure the resistivity, sheet
resistance and carrier concentration. It can work both at room temperature as
well as liquid nitrogen temperature (77 K).
The system is fully automated and
computer-controlled.
This system is used to measure the sheet resistance
and resistivity. It is computer-controlled with variable load to insure contact
to the sample surface.
Gas
Sensing
A gas-mixing chamber wherein the monitored gas (e.g.
CO) could be mixed with normal air to a controlled concentration (i.e. parts
per million of the monitored gas) has been fabricated and is in use (see the
image here). The chamber is coupled to another chamber
wherein measurement of change in resistance of the sensor can be carried out as
a function of the concentration of the monitored gas.
The resistance measurement chamber coupled to the
gas-mixing chamber is also shown on the right.
The gas sensor and the heater for the sensor has been mounted on a
common flange as shown in the second figure. Varying the magnitude of the
applied voltage to the heating element controls the temperature of the sensor.
Measurement of sensitivity and selectivity of pure
and catalyst added metal oxide thin film gas sensors for different gas such as
CO, CO2, SO2 etc.
at various temperatures and different concentrations of the monitored gas mixed
with normal air can be carried out.
KFUPM Facilities
In addition to the above facilities, we benefit form
various facilities available at KFUPM. These include: X-ray photoelectron
spectroscopy (XPS), X-ray diffraction (XRD), X-ray fluorescence (XRF), energy
dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and Fourier
transform infrared spectroscopy (FTIR).
