Thin film technology has been developed primarily
for the need of the integrated circuit industry.
Thin films cannot exist by itself; it needs substrate
to adhere to.
Thin film can be treated as two dimensional
specimens because the third dimension namely
the thickness is very small .
Thin film is created through atomic/molecular
In CVD process the substrate is exposed to one
or more volatile precursors, which react or
decompose on the substrate surface to produce the
Physical deposition uses mechanical or
thermodynamic means to produce a thin film of
The most convenient and powerful tool for
the structural study is electron diffraction and
diffraction effect provides information regarding the
nature of these films, their crystal structures, lattice
parameters, grain size etc.
Electrical conductivity of a film is many
orders of magnitude smaller than that of bulk
material and is generally characterized by a
negative temperature coefficient of resistivity
Optical Properties of Thin Film:
Optical measurements constitute the most
important means of determining the band
structures of semiconductors.
Optical measurements can also be used to study
Thin Film Drug Delivery
Thin Film Transistor
Dye Sensitized Solar Cell
Applications in Metallurgical Coatings
Zinc oxide is an inorganic compound with the formula
ZnO. It usually appears as a white powder, nearly
insoluble in water.
Crystal structure of ZnO
At ambient pressure and temperature, ZnO
crystallizes in the wurtzite structure, hexagonal
ZnO bond also possesses very strong ionic
character, and thus ZnO lies on the borderline of
ionic and covalent compound.
Synthesis of K- doped ZnO thin film by double dip
Structural analysis by XRD.
Particle size determination
Determination of cell parameters.
Measurement of thin film surface resistivity.
Optical analysis by photoluminescence
The well cleaned substrate was first immersed in
the sodium zincate bath for 10 sec (first dip) and
then dipped in hot water for the same duration
ZnSO4+4NaOH Na→ 2ZnO2+Na2SO4+2H2O
In order to improve the gas sensing properties, metal
ions can be doped onto ZnO thin films.
The doped thin films have the following advantages:
Working temperature can be decreased.
Response time for sensing can be decreased.
Sensitivity can be increased.
The sensitivity for low concentration gas can be
The structural properties of film were studied by X-
ray diffraction analysis using powder diffract meter
XRD is non- destructive method that reveals
detailed information about the chemical
deposition, crystallographic and microstructure of
all types of natural and manufactured materials.
The constructive interference can take place when
the Bragg law is satisfied:
2dhkl sinθ = nλ
θ is the glancing angle of incident x-rays.
λ is the incident wavelength.
dhkl is the interplanar distance.
n is any integer corresponding to spectral order.
For wurtzite structure,
hkl = [4/3((h2
+ hk + k2
)] + (l/c)2
Photoluminescence describes the phenomenon of
light emission from any form of matter after the
absorption of photons (electromagnetic radiation).
In a typical PL experiment, a semiconductor is
excited with a light-source that provides photons
with energy larger than the band gap energy.
It is a measure of materials surface inherent resistance
to current to flow.
This electrical resistance is proportional to the samples
length and the resistivity and inversely proportional to
the samples cross sectional area.
R = ρl/A
R = Resistivity
A= cross – sectional area
L = length
The resistance of ZnO thin film is measured using
Keithley 2100 6 ½ Digital Multimeter which can
measure mega ohm range.
X – ray powder diffraction may be used to
measure the average crystal size in a powdered
FWHM is the full width of the peak at the half of
maximum value of intensity. For full width half
maximum (FWHM), β = x2 – x1 .Debye Sherrer
formula is used to calculate the grain size of the
crystal, grain size D is given by
D = 0.9λ/ βcosθ
β = value of full width in radians
λ =incident wavelength
θ = diffraction angle at which peak occurs.
Cell parameter Standard cell
Sample Average particle size
Resistance at room temp
3% 17.48 5
5% 26.85 2
1.Samples of K- doped ZnO thin films were synthesized by double
2.Phase determination of sample was done by XRD technique.
From XRD analysis the sample was found to be phase pure.
3.Average particle size of thin film is calculated. It was found that
as the doping percentage increases particle size also increases.
4.Cell parameters of the film were determined and it is in
agreement with the standard values.
5.Resistance of the samples is measured. As doping concentration
increases resistance was found to be decreased.
6.Optical analysis is done by photoluminescence studies and it was
found that intensity of visible light emission peak was
significantly enhanced with increasing K concentration.
7.By doping particle size of the sample was found to be increased
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