International Journal of Engineering Trends and Technology- Volume4Issue3- 2013
SURVEY OF SYNTHESIS OF HIGH-KGATE
DIELECTRICFOR MULTIGATE MOSFETS
Aswathy Paul, I.Flavia Princess Nesamani
ECE Department, Karunya University
Coimbatore,India
Abstract— Continued downscaling of complementary
metal-oxide-semiconductor field effect transistor
resulted in short channel effects. The alternate device
FinFET controls the SCE as well as it is compatible
with high K dielectric materials. High dielectric
constant (high-k) gate materials act as alternatives to
SiO2 in sub 50nm technology. In this paper we have
surveyed all the techniques relevant to synthesis of two
high K materials titanium di oxide and zirconium di
oxide in order to propose a new synthesis method for
finding the nanoparticle size being formed and it
further application in FinFET devices and memory
applications.
Keywords— Chemical Synthesis methods, Survey,
High-K Dielectric, ZrO2, TiO2.
I.INTRODUCTION
The search for high dielectric constant gate dielectric
materials for finFET device beyond 50nm technology
has stimulated important research activities in both
conventional and unconventional electronics. High-k
dielectric nature of memories is particularly
important in the well-established silicon electronics
industry. As the technology scales down to avoid the
problems associated with lithography and gain new
device structures that are used for next generation
technology such as Double Gate(DG) MOSFETs[1].
Previously, this goal has been achieved by
developing new optical lithography tools, photo resist
materials, and critical dimension etch processes [2].
Despite the advances in these process technologies,
device performance in scaled devices will be
compromised because the traditional materials used
for fabrication i.e., silicon and silicon dioxide have
reached their fundamental material limits. Therefore,
continuing scaling will require the introduction of
new materials like ZrO2 and TiO2. Despite a number
of excellent properties, SiO 2 suffers from a relatively
low dielectric constant (k = 3.9). Because high gate
dielectric capacitance is necessary to enable the
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required drive currents for sub micrometer devices
and because capacitance for a film is proportional to
k and inversely proportional to gate dielectric
thickness (d), the SiO2 layer thickness must be
reduced accordingly to scaled device dimensions.
Because of the large band gap of SiO2 (9 Ev) and low
density of traps and defects in the bulk, the leakage
current through the dielectric layer is normally very
low. However, for ultrathin SiO 2 films this is no
longer the case[2].
High leakage currents will invariably compromise the
device performance as well as dissipate large
amounts of power. It is therefore obvious that SiO 2 as
deposited with current methods will soon reach its
limit as a gate dielectric for all kinds of low power
applications. Although higher power dissipation may
be tolerable with some high performance processors,
it quickly leads to problems for mobile devices. The
major limitation for thin oxides are reduced lifetime,
increased operation temperatures considerably
increase the gate leakage. The oxide reliability thus
remains one of the other major issues in CMOS
scaling. It is therefore clear that to meet nextgeneration device requirements, the solution is
represented by using thicker dielectric layers of
materials having permittivity’s higher than that of
SiO2 like ZrO 2 /HfO 2 with dielectric constant ranging
from 23 – 25 and TiO2 with80 .
II.LITERATURE SURVEY OF SYNTHESIS
TECHNIQUES OF HIGH-K GATE DIELECTRIC
MATERIALS
During the past decade, many methodologies have
been developed to prepare high-k gate dielectrics[3].
They can be categorized into two major approaches
based on the reaction mechanism during the
preparation: CVD (chemical vapor deposition)- and
PVD-based process. CVD-based approaches mainly
include metal-organic chemical vapor deposition
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(MOCVD), plasma-enhanced chemical vapor
deposition (PECVD), atomic-layer chemical vapor
deposition (ALCVD), and photo-assisted CVD
synthesis. These growth methods provide more
flexible synthesis process and an alternative to
achieve lower cost. Among these methods, ALCVD
is considered as promising method, since this is the
only feasible method to control thickness down to
nanometer range and composition of metal oxide
ultrathin films in a layer-by-layer fashion. However,
among these deposition techniques, one of the serious
problems is the interfacial layer growth due to the
oxidization of the Si substrate surface, which is
brought about in excess O 2 ambient at elevated
temperature. CVD processes are also suffering from
contaminants that need to be removed by a high
temperature deposition or a post deposition annealing.
But PVD-based sputtering has been pursued to
prepare high-k films due to its simple process, high
purity and low cost ownership. And also PVD-based
process shows easily controllable growth of low-k
interfacial layer at low temperature and
compositional consistency between the target and the
deposited film.
Synthesis based on PVD sputtering can be divided
into four different methods depicted as follows:
(1) Traditional reactive sputtering pursued to deposit
high-k dielectrics.
(2) Plasma oxidation of sputtered metal films.
Compared to other deposition methods ,plasma
oxidation offers a low temperature processing and
blocks the diffusion of oxygen content from the
ambient, which prevents the reaction of interfacial
layer. PVD[3]combined with plasma oxidation of
sputtered metallic films will have the possibility in
obtaining the high-quality high-k gate dielectric thin
films. Different from the reactive sputtering, after
metal layer deposition, the wafers were ex-situ
transferred to plasma oxidation chamber, and the
deposited metal layer was oxidized by Ar/O2 plasma
generated in the chamber.
(3) Combination of thermal oxidation and PVD.
This method avoids the further oxidation of the
interfacial layer and suppresses the growth of the
interfacial layer. In our group, we have obtained
high-k ZrO2 gate dielectrics through the in-situ
thermal oxidation of sputtered Zr metallic thin films.
(4) Pulse laser deposition (PLD).
Compared with other deposition techniques such as
sputtering and conventional vapour deposition
techniques, PLD technique has some advantages in
preliminary study of new high-k materials, for
instance, its being rapidly conducted and
compositional consistency between a target and
deposited films.
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III. MATERIALS AND METHODS
In this survey, we have studied about the papers
which dealt with the synthesis of High- K dielectric
material such as ZrO 2 and TiO2 so that it can be used
in MultiGate FINFET to reduce the Short Channel
Effects and these materials can be utilized as an
alternative to SiO2 in the near Fabrication process.
A .Titanium Dioxide
R.Vijayalakshmi et al[4] use sol-gel for synthesizing
Titanium Dioxide.Titanium Isopropoxide(TTIP) was
dissolved in ethanol and distilled water was added to
the solution in molar ratio of Ti:H 2O =1:4.Nitric acid
is used to adjust pH. The solution was vigorously
stirred for 30minutes in order to form sols. After
aging for 24hrs,the sols were transformed into gels.
In order to obtain nanoparticles,the gels were dried at
120oC for2hr.Then the dry gel was sintered at 4500C
for 2hrs to obtain nanocrystalline.
Agnes.et.al[5]prepared a stock solution with Ti41 ion
concentration of 0.7 mol L21 was prepared by dilution
of TiCl4 in HCl (3 mol ) solution. 5 ml of the stock
solution were introduced in 30 ml distilled water at
room temperature. No precipitation occurred. The pH
of the mixture was automatically fixed at a selected
value and kept constant by addition of NaOH (3 mol
L21) using a CombiTitreur 3D Metrohm apparatus.
The final volume of the mixture was adjusted with
distilled water or NaCl (3 mol ) to 50 mL in order to
obtain a TiCl4 ion concentration of 0.07 mol . Several
samples were prepared in the range pH 2 - 6.
Suspensions were aged in a stove at 60oC without
stirring. The solid was collected after centrifuging the
suspension just after the precipitation or after one day,
one week and one month of aging. The precipitate
was washed twice with water of the same pH as used
for the synthesis, and dried at room temperature.
Introduction of the TiCl4-HCl mixture in water
preheated at60 uC led to no detectable modification
of particles.
Montazeri et al[6] used all chemicals are of analytical
grade and were used without further purification. 0.2
moles (58.6 g) of tetraisopropylorthotitanate was
cooled in an ice-bath to decrease its condensation at
an early stage of the process. Then 0.2 moles (12 g)
of acetic acid was added all at once to it under
magnetic stirring at room temperature. The modified
precursor was stirred for about 15 min and 290 ml
water was quickly added to it with vigorous stirring
(800 rpm). During the addition, a white precipitate
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was formed. One hour of stirring was used to achieve
a complete hydrolysis reaction. After adding a
quantity of 6 ml or 8 ml of %65 nitric acid , the
mixture was heated from room temperature to 80 °C
and peptized for 90 min in order to prevent the
agglomeration of the particles present in the sol.
After cooling the resultant mixed suspension down to
room temperature, it was charged into an autoclave
and heated at different conditions in terms of
temperature and pressure.
S.N.Karthick et al[7] prepared two different TiO2
paste was prepared by the simple hydrothermal
technique using the commercial Degussa P25 powder
(sample A) and titanium isopropoxide(sample B).
The preparation of sample A requires 0.78 g of P25
powder was mixed in 60 ml of ethanol and followed
by the addition of 0.1 ml of acetic acid, 0.3 ml of
water and 2 ml of α-terpineol. Sample B was
prepared by 3 ml of titanium isopropoxide mixed
with 60 ml of ethanol followed by the addition of a
0.1 mL of acetic acid and 0.7 ml of water. Finally αterpineol was added slowly to the solution. The
solution was then heated at 2000C under
hydrothermal technique with vigorous stirring for
about 4 hours. After cooling 0.075 g of polyvinyl
pyrrolidone dissolved in ethanol were slowly added
to the above solution separately and heated in a hot
plate at 1000C for about 10 minutes with vigorous
stirring and cooled to room temperature. Then the
ethanol was evaporated using a solvent evaporator to
obtain a viscous TiO2 paste.
M.Askari et al[8] used the precursor solution as a
mixture of 5cc titanium isopropoxide, TTIP (97 %,
supplied by Aldrich Chemical) and 15cc Isopropanol
(99 %, supplied by Merck). A 250cc solution of
distilled water with varied pH was used as the
hydrolysis catalyst. The desired pH value of the
solution was adjusted by adding HNO3[15]. The gel
preparation process started when both solutions were
mixed together under vigorous stirring. Hydrolysis of
TTIP offered a turbid solution which heated up to 60
– 70 °C for almost 18 – 20 hours. The resultant
suspension was white-blue and opaque with high
viscosity[19]. The prepared precipitates were washed
with ethanol and dried for several hours at 100 °C
and finally annealed at a temperature ranging from
200 to 800 °C for 2 hours
.
R.D.Kale et al [9]used 1.02ml of hydrogen peroxide
in a round neck flask, into which 2.84ml of TIPT
under stirring was added at 5°C for 1 hour. The initial
pH of Hydrogen peroxidesolutions was adjusted to 9
by Ammonium Hydroxide. Yellow gel was observed
indicating the formation of peroxide complex of
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Titanium. To this 10 of ml n-hexane and 0.05gm
agaragar was added. White precipitate formed was
then filtered and washed first by distilled water and
then ethanol. It was dried at 50°C for 12 hour in oven
and then calcined at 550°C for 10 hour in muffle
furnace to get the white crystalline powder of Nano
TiO2 .
Prasoon Pal Singh et al[10] Take 100ml of tripled
distilled water in a 100 ml beaker and put the beaker
in an ice bath so that the vapours of Ti(OH)2
condensed and react properly for the nucleation and
growth of TiO2 nanoparticles. Add few amount of
hydrochloric acid in to water and then by using drop
casting technique, add drop by drop 10ml of TiCl4
liquid to the HCl added distilled water. Titanium
dioxide nanoparticles were prepared from titanium
tetrachloride and titanium isopropoxide in ethanol
and distilled water, the hydrolysis of the metal salt is
carried by in presence of little amount of
hydrochloric acid (HCl) or sodium hydroxide (NaOH)
the acidity of the solution is adjusted between PH-4
to PH-5, heat the solution at 80o -90o C while stirring
for about 2 to 3 hrs, white precipitate will form,
continuously heat the solution for few more hours till
it solvent is reduced to half, a white color particles is
settled down at the bottom of the beaker The solid
particles were filtered and washed subsequently by
water(500 ml) and ethanol (200 ml), and then dried at
room temperature for 12 hr.
V.Dutta.et.al[11] used different weight ratios of
Titanium iso-propoxide (precursor) and toluene
(solvent) which are mixed in inert atmosphere. The
weight ratios of titanium iso-propoxide are varied
from 5/100 to 60/100. The mixture is taken in Teflonlined stainless-steel autoclave and heated for different
time durations (4–24 h) with the reaction
temperatures varying from 180 to 240 0C[18]. The
products have been collected, washed thoroughly and
then dried in vacuum at 600C for 3 h.
Mike.et.al[12]studied anatase TiO2nanoparticles
which was prepared with a precursor solution
consisting of titanium tetraisopropoxide (TTIP),
Pluromic F127, hydrochloric acid (HCl), deionized
water, and ethanol. The molar ratio of TTIP : F127 :
HCl : H2O : Ethanol is 1 : 0.005 : 0.5 : 15 : 40.The
gel-like solution was first undergone hydrolysis at
40 0Cfor 24 hours then evaporated and dried at
1100Cfor another 24 hours. The white colored
powders were then calcinated at 400 0Cfor 6 hours.
The temperature ramping rate was approximately
0.3 0Cper minute, and the cooling rate was
approximately 1.50Cper minute. The product was
grinded into fine powder and set in vacuum for 1
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hour. Then it was filled with 20 atmospheric pressure
of 95% pure hydrogen gas in 2000Cfor 5 days.
Varun et al [13] used the titanium dioxide powder
was prepared by sol-gel process using titanium
isopropoxide,, as a precursor and ethanol as a solvent.
After dissolution of 11.2ml of TTIP in ethanol, a
solution of 0.73 ml water in ethanol was mixed and 1
mldiethenol amine added dropwise under continuous
stirring for 2h to realize a transparent sol. TTIP:
C2H5OH: H2O: C4H11NO2 molar ratio was set at
4:140:4:1. The sol was digested for 24h and dried
subsequently at 1000C for 10h, calcined for 2h
elevated temperatures, and cooled at a rate of ~ 8.3
0
C/min. Thermogravimetric[20] analysis (TGA) of
the dried sol-gel product was carried out by raising its
temperature at a rate of 4 0C/min from 50 0 to 8500C in
air to ascertain the conditions of TiO2 formation.
B. Zirconium Dioxide
Mohammed et al[14] used 1mmol Zirconium
Oxychloride,2mmol of benzyl alcohol was added to
drop-wise to form a gel. This was followed by
addition of 2mmol of sodium lauryl sulphate with
constant stirring. The product was dried at 200 0C for
5hours and calcined at temperature 600 0C for 5hours.
J.A.Wang et al [15]used Zirconium n-Butoxide(11ml)
was dissolved along with 32.5ml of absolute ethanol
under continues stirring. To the homogenous solution
was dropped the hydrolysis catalyst(NH4OH) until ph
reach 10.2ml of water were dropped and the new
solution was stirred until gelling. The gel was dried at
room temperature in a vacuum for 24h.Samples was
annealed for 4hr in air at 400,600 and 800 0C.
Lutz et al[16] conducted a reaction in 1g of
Zirconium Isopropoxide was taken in a Teflon vessel
and 6ml of analytical grade ethanol(99.8%).The
Teflon vessel was kept in a desiccators. The
precipitation of ZrO2 was initiated under moist
atmosphere induced by placing a petri dish filled with
water at bottom of desiccators. The diffusion
experiment was stopped after 12h,followed by the
addition of 25ml of NaOH aqueous solution .Then
the reaction was sealed into a stainless steel
hydrothermal bomb, which was heated to 180 0C for
18h.After the autoclave was cooled to room
temperature, the products were filtered and
repeatedly washed with 0.1M Nitric acid,1N HCl and
deionised water. After drying under vacuum a white
soft and fibrous powder was obtained.
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Lucia et al[17]prepared non-sulfated ZrO2according
to the following procedure. A 4.5 mol L-1
Ammonium Hydroxide aqueous solution was added
drop by drop, under stirring, to an aqueous solution
of ZrOCl2 with formation of a gel like precipitate,
until no more precipitation was observed. The
precipitate was filtered and thoroughly washed with
water until elimination of chloride in the washing
liquid. The precipitate was then dried in an oven for
24 h at 393 K. The solid zirconium hydroxide thus
obtained was calcinated at several temperatures (573,
673, 773 and 873 K) for 4 h in order to obtain the
ZrO2.
G.C.C.Costa et al [18]used starting materials as
zirconium hydroxide, scandium oxide , citric acid,
nitric acid , ethylene glycol , acrylamide , N,N′methylenebisacrylamide and ammonium persulfate.
Zirconium Hydroxide and Scandium Oxide were
first dissolved separately in a hot nitric acid solution
under stirring. After theirdissolution, the Zr4+ and
Sc3+ cations (Mx+)were complexed by the addition
of citric acid (CA) in the 1:1.2 ratio and the pH was
adjusted (3 to 5) just to dissolve completely the
species into a clear solution. Afterwards, the stock
solutions were mixed in the molar ratios
(0.90)Zr4+:(0.10) Sc3+ to obtain the solution.
Pavel et al [19] synthesized particles in an
externally heated tube flow reactor of length 55 cm
and i.d. 2.7 cm using two different nozzles at the inlet
for introducing the reaction mixture: a long nozzle of
length 25 cm and i.d. 2.0 cm and a short one 1.3 cm
long and of i.d. 1.2 cm. The deoxygenated, dry and
particle free nitrogen, used as a carrier gas, was
saturated with ZTBO vapor in an externally heated
saturator. The precursor concentration was controlled
by the flow rate through the saturator, whose
temperature was kept at 45°C. Saturated carrier gas
was then mixed with another stream of nitrogen and
fed axially into the center of the reactor through a
nozzle surrounded by a coaxial stream of nitrogen. In
hydrothermal experiments the mixing stream of
nitrogen was saturated with water vapor at laboratory
temperature. A mixture of gas and particles leaving
the reactor was cooled in a diluter by mixing with a
stream of nitrogen. Flow rates of individual gas
streams were controlled by electronic mass
flowmeters Tesla 306 KA/RA and the temperatures
of saturator and reactor by electronic temperature
controllers RLC T48. Samples of particles were
collected on Sterlitech Ag filters or deposited onto
carbon coated Cu grids by the point-to-plate
electrostatic precipitator.
Caili et al [20]used the gel which was washed with
deionized water in the precipitation method, thengel
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was washed with ethanol several times to remove
water involved in the hydrogel. The obtained alcogel
was put in an autoclave together with a certain
amount of ethanol. The temperature and pressure
(using N2) were increased to exceed the critical point
of ethanol (516 K, 6.3MPa), and the system was
maintained at the supercritical condition for 1 h. A N2
flow was used to bring the ethanol and water out of
the autoclave; meanwhile the temperature and
pressure were decreased to ambient conditions. The
obtained aerogel powder was calcined at desired
temperatures. The sample is marked as ZrO2(S).
Since the operation pressure, which is related to the
initial N2 pressure, would influence the density of the
ethanol fluid and the fluid density will influence the
structure and properties of zirconia, the dependence
of catalytic performances of zirconia on its
preparation pressures was examined. ZrO 2(S1),
ZrO2(S2) and ZrO2(S3) were prepared with the initial
N2 pressure being 3.5, 5.2 and 8.5MPa and were
calcined at the same temperature, 723 K.
K.Geethalakshmi et al[21] used chemicals zirconium
oxychlorideoctahydrate(ZrOCl2)
and
sodium
hydroxide (NaOH) for the preparation of nano ZrO 2.
Appropriate
amount
of
Zirconium
oxychlorideoctahydrate was dissolved in bi distilled
water using hot plate magnetic stirrer. Aqueous
solution of 2M NaOH was mixed in the above
mentioned precursor solution until the pH value
became 8. The precipitate was filtered after 15
minutes and was cleaned with water and acetone
many times and then it was dried at 100 °C overnight.
The calcination of the ZrO2sample thus prepared was
done at different temperatures 700°C/hr, 1000°C/hr
and 1200°C/hr. The as-prepared sample was coded as
Z0 and those calcined at 700°C/hr, 1000°C/hr and
1200°C/hr respectively are coded as Z1, Z2 and Z3.
A.Saberi et al[22] used Sucrose/fructose and PVA
were added to 0.1 M solution of zirconium hydroxide
which is prepared by solving 0.1 mole dried
zirconium hydroxide in 1 l nitric acid (64 wt.%)
solution. The molar ratio of zirconium cations to
chelating agents (sucrose/fructose) and PVA was
1:4:0.5 for sucrose and 1:8:0.5 for fructose. Then the
pH was adjusted to 1 by dropwise addition of diluted
nitric acid for 4 h.
The addition of nitric acid causes to break sucrose
into glucose and fructose. Also, this phenomenon
causes to prevent sucrose re-crystallization . The –
OH and –COOH groups of the decomposed products
promote binding of zirconia ions in homogeneous
solution. Subsequent heating at 80°C for 2 h on a hotplate stirrer causes complex formation of the zirconia
ions with sucrose or fructose. The solution was
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heated in an electrical oven at 200°C for 4 h. During
the heating process, the obtained gel converted to the
black foam mass. Finally, the obtained mass was
ground into powders and then calcined in an
electrical furnace at 500, 600 and 700°C for 1 h.
During the calcination process, the polymeric matrix
is decomposed to gases such as carbon dioxide and
water which this phenomenon causes to release a
large amount of heat. These produced gases prevent
the agglomeration of calcined powders.
Saeid et al[23] used initially, 2.58 g ZrOCl2·8H2O
and 4.80 g urea were dissolved in 20.0 ml CH3OH
under stirring to form a colourless solution. The
solution was transferred to a 20 ml Teflon-lined
stainless steel autoclave, which was heated by 200°C
and maintained at that temperature for 20 h. The
obtained white product was post-treated with
sulphuric acid solution (0.167 mmol) and then
calcined at 645°C.
IV.
ADVANTAGES
METHODS
ASSOCIATED
WITH
A .Titanium Dioxide
1. TiO2nanoparticles prepared via solgel route were
highly crystalline and had smaller crystallite size (~ 7
nm) as compared to the one prepared by
hydrothermal method (~ 17 nm). (R. Vijayalakshmiet
al,2012).
2.The method of synthesis of anatase is to adjust the
particle size at the nanometric scale. At this size scale,
the phonon confinement effect makes Raman
spectroscopya
very
useful
technique
for
characterizing particle size and crystallinity of the
material(Agnes et al).
3. XRD analysis was used to show that applied
hydrothermal treatment can facilely produce pure
anataseTiO2 and inhibits increase in the obtained
crystallite size. Crystallite sizes down to 7 nm could
be estimated by XRD line broadening technique.( M.
Montazeri-Pour etal,2012).
4.It was concluded that the performance of the paste
prepared from titanium isopropoxide using
hydrothermal technique is good compared to the
paste prepared from commercial TiO2.(Karthick et
al,2012).
5. A nanocrystalline TiO2 powder can be prepared by
the hydrolysis of titanium-isopropoxide alcoholic
solution and then peptization of the resultant
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suspension up to 70 °C for 20 hours.Powder
morphology in these criteria is almost spherical,
which is due to acidic condition thatprevents
agglomeration.(Askariet al,2006).
6.Nano TiO2 synthesized by different methods show
more or less same antimicrobial property. The
efficiency of antimicrobial activity increases with
increase in the concentration of nano particles and the
number of PEM deposited on the fibre surface.(Kale
et al,2012).
7. Nano-sized titanium dioxide TiO2powder has been
successfully prepared from its precursor titanium
tetrachloride and titanium (IV) isopropoxide (TTIP)
with hydrochloric acid using thermolysis technique in
which titanium tetra chloride react with double
distilled water at very lower temperature in acidic
medium. The amorphous TiO2 particles were
converted to anatasephase by calcining at
300 °C.(Prasoonet al,2012).
8.Nanocrystalline uniform sized TiO 2with average
particle size varied from 8 to 15 nm has been
synthesized by surfactant-free solvothermal method
using toluene as the solvent at low temperatures
(180–240 0C). Particle size, shape and crystallinity of
the nanoparticles are found to be dependent on the
reaction temperature, time and precursor to solvent
ratio.(V.Dutta et al,2007).
9.Anatase TiO 2 nanoparticles of 15 to 7nm size range
could be prepared by controlled dry time,calcinations
temperature, time, and amount of surfactant
used.(Mike et al,2011).
10. TiO2 nanoparticles of anatase phase with
controllable average size (d) 11-18 nm can
besynthesized by adjusting the time of calcination at
500 0 C of the dried sol – gel product. Theparticle
growth follows the relation d = α – β exp (t/τ).(Varunet al).
B. Zirconium Dioxide
1. Pure zirconium oxide nanoparticles were
successfully prepared by sol-gel method in nonaqueous medium. (Mohamed et al,2012).
2. Nanocrystalline zirconia can be synthesized
using precipitation method and sol-gel method with
low cost precursors.In both samples had tetragonal
and monoclinic phases coexist.(J.A.Wanget al,2001).
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3.
ZrO2 nanoparticles have been synthesized
using hydrothermal methods under mild conditions.
The morphology, structure and properties of as
synthesized nanoparticles were characterized using
HRTEM, XRD, Raman spectroscopy, UV-vis, PL
spectroscopy and BET measurements. The formation
of both, the monoclinic and the cubic polymorphs,
was confirmed by electron microscopy and Raman
spectroscopy.(Muhammad et al,2007).
4. Sulfated ZrO2 prepared by two different routes,
in onestep and in two steps, showed different
behaviors in the thermogravimetric analysis in the
region of sulfate mass loss and also in the Raman
spectra obtained after heating at several
temperatures.(Lucia et al,2007).
5. The procedure to prepare nanosized powders by
the polyacrylamide technique. A high value of
average specific surface area was obtained, 78 m2/g.
The nanosized particles are single crystalline, the
average particle size is 13 nm and the average value
of the crystallite size is 5 nm. (Costa et al,2008).
6. Zirconia particles were prepared by pyrolysis.
The produced particles consisted of two size modes.
The particle production and morphology were
remarkably affected by the choice of pyrolysis or
hydrolysis but also, to some extent, by nozzle
arrangement and the reactor temperature, precursor
concentration and flow rates used.(Pravelet al).
7. The acidic and basic properties of nanoscale
zirconia could be changed extremely by using
different preparation conditions and methods. Higher
pressure in SCFD method caused more basic sites on
zirconia surface. Both acidic and basic sites of the
catalysts are significant in the conversion of synthesis
gas to isobutene.(Caeliet al,2000).
8. Nano zirconium dioxide has been prepared
using co-precipitation process. The XRD result
confirms the pure monoclinic phase (m-ZrO2). The
phase purity is further ensured by FTIR spectra. The
band gap value of the sample is found to be 5.7 eV.
The dielectric constant of materials is due to the
electronic, ionic, dipolar, and surface charge
polarizations,
which
depend
on
the
frequencies.(Geethalakshmiet al,2012).
9. The
single-phase
tetragonal
zirconia
nanopowders had been prepared. The crystallite size
is in the range of 7-10 nm, and its particle size is
smaller than 50 nm in the sample that calcined
at500°C.(Saberiet al,2011).
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10. The average diameter of the ZrO2 nanoparticle
is 20nm and has a very narrow particle
distribution.(Saeidet al).
V. APPLICATIONS
The Titania(TiO2) finds its application as high K
dielectric, pigament, photo catalyst, UV absorber,
electronic data storage medium and Zirconia(Zr02) as
high K dielectric, ceramic additive, refractory
material, oxygen sensors, fuel cell membranes.
VI. CONCLUSION
The methods of synthesizing and characterization of
high-k dielectric materials were studied. In synthesis
most of the papers used either hydrothermal method
or sol-gel method. By the Sol-gel method, powders of
single and multiple component compositions can be
produced in a nanoscale particle size. In
characterization the techniques that can be adopted
are Scanning Electron Microscope, X-Ray
Diffraction, etc. Hence in our work, to synthesize
ZrO2 and TiO 2, we will use Sol gel method and the
characterization will be done through SEM and XRD.
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