1. MMethods for singleethods for single
crystal growthcrystal growth
SSUMEET S.UMEET S. CCHAVANHAVAN
M.SC.- II SEM-IIIM.SC.- II SEM-III
2. CContentontent
1.1. CCRYSTAL GROWTH FROM LIQUID SOLUTION.RYSTAL GROWTH FROM LIQUID SOLUTION.
- FLUX GROWTH- FLUX GROWTH
- TEMPERATURE GRADIENT METHODS.- TEMPERATURE GRADIENT METHODS.
2.2. CCRYSTAL GROWTH FROM VAPOUR PHASE.RYSTAL GROWTH FROM VAPOUR PHASE.
- EPITAXIAL GROWTH METHODS.- EPITAXIAL GROWTH METHODS.
3. FLUX GROWTHFLUX GROWTH
-- IIn contrast to the other methods in which meltedn contrast to the other methods in which melted
solid substance that have the same composition as thesolid substance that have the same composition as the
melt.melt.
-- FFlux growth method involves the growth of crystalslux growth method involves the growth of crystals
from solvent of different compositon to give crystals.from solvent of different compositon to give crystals.
4. -- TThe solvent may be the one of the constituents of thehe solvent may be the one of the constituents of the
desired crystal.desired crystal.
E.g. : crystalization of salt hydrate crystals usingE.g. : crystalization of salt hydrate crystals using
water as a solvent.water as a solvent.
-- TThe solvent may be entirely seperate liquid element orhe solvent may be entirely seperate liquid element or
compound in which the crystal of intrest are partiallycompound in which the crystal of intrest are partially
soluble.soluble.
EE.g : SiO.g : SiO22 and various high melting silicates may beand various high melting silicates may be
precipitated from low melting borate or halide melts.precipitated from low melting borate or halide melts.
5. -- IIn these cases, the solvent melts are sometimesn these cases, the solvent melts are sometimes
reffered to as fluxes, since they effectively reduce thereffered to as fluxes, since they effectively reduce the
M.P.M.P. OOf the crystals by the considerable amount.f the crystals by the considerable amount.
- The method has been used to grow crystals of- The method has been used to grow crystals of
beta-allumina and acid electrolytes using borax flux.beta-allumina and acid electrolytes using borax flux.
6. TEMPERATURE GRADIENT METHODTEMPERATURE GRADIENT METHOD
(HYDROTHERMAL TECHNIQUE)(HYDROTHERMAL TECHNIQUE)
-- Hydrothermal synthesis involves heating reactants inHydrothermal synthesis involves heating reactants in
water/steam at high pressures and temperatures.water/steam at high pressures and temperatures.
-- TheThe water has two functions, as a pressure-water has two functions, as a pressure-
transmitting medium and as a solvent, in which thetransmitting medium and as a solvent, in which the
solubility of thesolubility of the reactants is Preactants is P..TT..-dependent.-dependent.
7. - R- Reacteactaant and water are placednt and water are placed
inside a PTFE-lined cylinderinside a PTFE-lined cylinder oror
‘bomb’ which is either sealed or‘bomb’ which is either sealed or
connected to an externalconnected to an external
pressure control.pressure control.
-- TheThe cylindercylinder is placed in an oven,is placed in an oven,
usually at a temperature in the rangeusually at a temperature in the range
100–500 ◦C.100–500 ◦C.
-- Pressure is controlledPressure is controlled either externally or by theeither externally or by the
degreedegree ofof filling in a sealedfilling in a sealed cylinder.cylinder.
8. Pressure–temperature relations for water at constant volume.Pressure–temperature relations for water at constant volume.
-- Dashed curves represent pressuresDashed curves represent pressures developed inside a closeddeveloped inside a closed
vessel;vessel;
- N- Numbers represent the percentage filling of the vessel byumbers represent the percentage filling of the vessel by
water at ordinarywater at ordinary P,T.P,T.
9. - B- By making use of the P–T ‘phase diagram’y making use of the P–T ‘phase diagram’
curve AB is the saturatedcurve AB is the saturated steam curve and separatessteam curve and separates
water (above) from steam (below)water (above) from steam (below)..
- A- At temperatures above 374 ◦C,t temperatures above 374 ◦C, point B, waterpoint B, water
is in the supercritical condition and there is nois in the supercritical condition and there is no
distinction between liquid and vapour statesdistinction between liquid and vapour states..
10. -- FFor the growth of single crystal by hydrothermalor the growth of single crystal by hydrothermal
method, it is neccessary to add a mineralizer.method, it is neccessary to add a mineralizer.
MMineralizer is any compound that speeds up to itsineralizer is any compound that speeds up to its
crystalization.crystalization.
- It is usually operates by increasing the solubility of- It is usually operates by increasing the solubility of
the solute through the formation of soluble species thatthe solute through the formation of soluble species that
would not usually be present in water.would not usually be present in water.
11. CRYSTAL GROWTH FROM VAPOUR PHASECRYSTAL GROWTH FROM VAPOUR PHASE
(EPITAXIAL GROWTH METHOD)(EPITAXIAL GROWTH METHOD)
-- Single crystal in the form of thin layers are oftenSingle crystal in the form of thin layers are often
required for application in electronic devices and specialrequired for application in electronic devices and special
methods may be needed for their applications.methods may be needed for their applications.
- The use of seed crystal in other methods implies on- The use of seed crystal in other methods implies on
orientation relationship between two growing crystalsorientation relationship between two growing crystals
and seed.and seed.
- The crystal may grow epitaxially or topotaxially.- The crystal may grow epitaxially or topotaxially.
12. Vapour-phase transportVapour-phase transport
-- The essential feature of this method is the formationThe essential feature of this method is the formation
of a volatile, unstable intermediate that contains at leastof a volatile, unstable intermediate that contains at least
one of the elements in the desired final product. Theone of the elements in the desired final product. The
method may be used to grow single crystals.method may be used to grow single crystals.
-- The method consists of a tube, usually of silica glass,The method consists of a tube, usually of silica glass,
with the reactantswith the reactants A, at oneA, at one end, which is sealed eitherend, which is sealed either
under vacuum or with a small amount of theunder vacuum or with a small amount of the
transporting agenttransporting agent BB..
13. -- IIn the epitaxial growth of thin layers, oriented growthn the epitaxial growth of thin layers, oriented growth
of crystals occurs on the surface of the substrate.of crystals occurs on the surface of the substrate. TThehe
substrate may be crystal of the same or similarsubstrate may be crystal of the same or similar
composition or it may be an entirely different materialcomposition or it may be an entirely different material
whoes lattice parameters at its surface, match those ofwhoes lattice parameters at its surface, match those of
the growing crystals to within few percent.the growing crystals to within few percent.
- The chemical reaction may or may not be takes place- The chemical reaction may or may not be takes place
in vapour phase.in vapour phase.
14. -- IIn this deposition it is carried out on a substrate twon this deposition it is carried out on a substrate two
dimentionally hence, it is known as epitaxial growth.dimentionally hence, it is known as epitaxial growth.
E.g – deposition of silicon from silane or chlorosilane.E.g – deposition of silicon from silane or chlorosilane.
SiHSiH44(g) carrier gas Si(s) + 2H(g) carrier gas Si(s) + 2H22(g)(g)
SiClSiCl44(g) + 2H(g) + 2H22(g) Si(s) + 4HCl(g) Si(s) + 4HCl
