Organic single crystals growth and characterization

conference presentation

1. ICMES 2014-
Paper ID- H026A

2. Crystal Growth
Art
Science
Technology

4. Importance of Single Crystals
76,000 crystals of PbWO
4
is
used in the Compact Muon
Solenoid (CMS) Detector.
Large Hadron Collider

6. F = kx + k'x
2
+ k"x
3
+ k"'x
4
+ . . .

8. SECOND HARMONIC GENERATION

9. NEED FOR NEW MATERIALS

10. Organic materials – Relevance

11. For optical applications a nonlinear material should have
the following characteristics (Nalwa and Miyata 1997).
 
(i)a wide optical transparency domain
(ii) large nonlinear figure of merit for frequency conversion
(iii)
 high laser damage threshold
(iv)
 be readily available in large single crystals
(v)
  wide phase matchable angle
(vi)
 ability to process into crystals, thin films
(vii) ease of fabrication
(viii)
 nontoxicity and good environmental stability
(ix) high mechanical strength and thermal stability and
(x)
  fast optical response time

12. CRYSTAL GROWTH METHODS
 
Crystal growth needs the careful control of phase change. There are three main
categories of crystal growth methods.
Growth from the solid: S S processes involving solid – solid

phase transitions
Growth from the solid or meltL S Processes involving liquid –
solid phase transitions
Growth from the vapour V SProcesses involving vapour –
solid phase transitions

13. MOLECULAR BEAM EPITAXY TEMPERATURE
OSCILLATION
METHOD
POLYMORPHIC
PHASE TRANSITION
STRAIN
ANNEAL
HALIDE
TRANSPORT
PROCESS
ZONE HEATING
VACUUM
EVAPORATION
SUBLIMATION
CHEMICAL
VAPOUR
DEPOSITION
VAPOUR
PHASE
EPITAXY
GAS
TRANSPORT
PROCESS
GAS PHASE
REACTION
SOLID STATE
DIFFUSION
REACTIONS
SINTERING
SKULL
MELTING
DIRECTIONAL
FREEZING
NORMAL
FREEZING
COOLED
SEED
ZONE
MELTING
FLOAT ZONE
MELTING
CRYSTAL
PULLING
PEDESTAL
PULLING
AUTOMATED CRYSTAL
PULLING
PLASMA
MELTING
ORGANIC
SOLUTION
GROWTH
SHAPE
CONTROLLED
CRYSTAL PULLING
ELECTRO
CRYSTALLIZATI
ON
AQUEOUS
SOLUTION
GROWTH
HYDROTHERMAL
GROWTH
GEL GROWTH
FLUX
GROWTH
ACCELERATED
CRUCIBLE
GROWTH
LIQUID PHASE
EPITAXY
LIQUID
ENCAPSULATION
PULLING
FLAME
FUSION
MOLTEN METAL
SOLUTION
GROWTH
VAPOUR LIQUID
SOLID GROWTH
VAPOUR
PHASE
GROWTH
SOLID STATE
GROWTH
SOLUTION
GROWTH
MELT
GROWTH
 

14. Growth from Melt
Crystal growth from melt is probably the most widely
practiced commercial process for growing single crystals. All the
methods of growth from melt rely on cooling the liquid below its
freezing point. If care is exercised, single crystals can be made to
grow which will otherwise end up with polycrystalline mass.
The technique by which this is done can be split
into three:
 
Czochralski technique
 
Bridgman technique
 
Verneuil technique

15. In the Czochralski method the melt is
contained in a crucible but the crystals are
grown at the free top surface of the melt so
that there is no contact between the crystal
and the crucible. In this method as the crystal
grows, it is slowly pulled upwards so that the
solid - liquid interface is just above the level of
the liquid surface. The melt temperature and
pulling rate depend upon the rate at which the
heat is removed and they can be changed
independently. By the rotation of the crucible
and the crystal, asymmetries in the
temperature gradient of the melt are reduced
and a better mixing of the melt is achieved.
Crystals such as sapphire and silicon have
been grown by this method.
Czochralski technique

16. In the Bridgman technique the melt is contained in a sealed crucible and is progressively
frozen from one end which can be achieved by :
 
1. Moving the crucible down the temperature gradient (or)
 
2. Moving the furnace over the crucible (or)
 
3. By keeping both the furnace and the crucible stationary and cooling
the furnace
 
So that the freezing isotherm moves steadily through the originally molten charge. The
latent heat of solidification, which is evolved as the crystal grows, is removed by conduction
through the crystal and the crucible. In this method, atleast some part of the solid-liquid
interface is in contact with the crucible. The advantage of this technique is that the shape of
the crystal can be controlled by the crucible while the disadvantage lies in fact that the crystal
gets strained and the melt-crystal-crucible contact can result in the nucleation of differently
aligned crystals.  

Bridgman method

17. Schematic of Bridgman technique

18.  
The principle of this method is based on the concepts of solubility and
supersaturation.
In the low temperature solution growth the methods used to produce the required
supersaturation are
 the slow cooling of the solution
 the slow evaporation of the solvent
 the establishment of a temperature gradient
between a relatively hot zone containing un
dissolved solid and a cooler zone in which the crystal grows.
The growth of crystals from solution is possible in two different ways :
  1. low temperature solution growth and
2. high temperature solution growth

Growth from Solution

19.  High purity of material is an essential prerequisite for crystal growth.
 Purification – recrystallisation
After choosing the solution method for growth, suitable choice of solvent
is necessary.The solvent must be chosen, taking into account the
following factors
 
a)
        a good solubility for the given solute
b)
        a good temperature co-efficient
of solute solubility
c)
        less viscosity
d)
        less volatility
e)
        less corrosion and non-toxicity
f)
         small vapour pressure and
g)
        cost advantage
 
Schematic representation CTB
MATERIAL PURIFICATION and SOLVENT SELECTION

20. X-RAY DIFFRACTION
FT-IR SPECTROSCOPY
RAMAN SPECTROSCOPY
MASS SPECTRUM
EDAX
UV-VIS SPECTROSCOPY
SHG STUDIES
DIELECTRIC STUDIES
THERMAL STUDIES
OPTICAL ASSESSMENT

21. Benzaldehyde 4 nitro Phenyl Hydrazone
By following the procedures of Vogel
There is a weak intermolecular hydrogen bonding between
NH group and p-nitro Group which leads to nonlinear optical properties
in this crystal
monoclinic crystal system with space group Cc,
a=6.102Å , b= 23.291 Å, c= 8.512 Å,
CHO
NH
H
2N
NO
2
C
H
N
N
H
NO
2
H
+

22. Intermolecular Hydrogen
Bonding
FTIR SPECTRUM

23. 1000 2000 3000
200
400
600
800
1000
1200


R
a
m
a
n

I
n
t
e
n
s
i
t
y
Wavenumber (cm
-1
)

24. UV-Vis Spectrum of BPH
400 600 800100012001400160018002000
1.2
1.3
1.4
1.5
1.6
1.7
A
b
s
o
r
b
a
n
c
e
Wavelength (nm)

OVERTONES OF
NO2 GROUP

25. Factor
group
species
C
s
Benzaldehyde
4-nitro phenylhydrazone
C
1
site
C
C
1 site
H
C
1 site
N
C
1 site
O
C
1 site
Optical
modes
Acoustic
modes
Activity
Internal
modes
External
modes
Benzaldehyde 4-nitro phenylhydrazone
C
1 site
IR Raman
A’ 162 6T, 6R 78 66 18 12 174 01 T
x, T
y

xx, 
yy, 
zz,

xy
A” 162 6T, 6R 78 66 18 12 174 02 T
z

yz,

xz
Total
modes
324 12T, 12R 156 132 36 24 348 03
FACTOR GROUP ANALYSIS -SUMMARY
The BPH crystallizes in the orthorhombic system, with Cc

space group. As there are 29 atoms in
the unit cell (Z=4), there are 348 branches to phonon dispersion curves. The representation of

total of all vibrations can be decomposed according to the irreducible representation of the
point group as ­
total
=173A

+ 172 A apart from three acoustic modes (acou = A

 + 2 A) are
included that correspond to the block transitions of the crystal. The formal classification of
fundamental mode predicts 324 internal vibrations which can be distributed as (162A+ 162 A)
and 24 external modes such as (6A+6A) translational, (6A+6A) vibrational modes

26. Comparison of SHG signal energy output
The efficiency of BPH crystal is higher than
KDP and Urea counterparts
Input
power
mJ/ pulse
KDP
mV
Urea
mV
BPH mV
1.9 9.0--- 162 mV
3.0 ---100 213 mV