1. Cluster Beam Evaporation: Bottom Up technique

2. what is cluster: Few hundred to few dozens of atoms together(bound by some forces) are called as cluster( cluster bombing)
Nanoparticles are nucleated at cluster stage
Almost everything forms cluster and the diversity is vast
On the exploration of cluster, C60 was discovered
In between bulk and molecular/atomic
Properties are accordingly differ than bulk and depend on mole./atomic constituents

5. clusters Can have net charge Or no charge ( neutral cluster)
(Ionic cluster)
Or no charge
( neutral cluster)
Aggregate of atoms/mole. Form cluster are bound by forces, Metallic, covalent, ionic, hydrogen or Van der Waals

6. clusters Cluster contain well defined number of transition metal atoms
have unique chemical, electronic and magnetic properties
Properties vary dramatically with number of constituent atoms, type of element and the charge on the cluster

9. Clusters formation: surface fraction of atoms
surface used to be more reactive and active for any reactions/catalysis
On Bulk /cm3= 1023 atoms
On the surface of this cube, only 1.5x1016 atoms,
Fraction of atoms on surface is 1 in
Hence they (fraction of surface atoms)do not influence(properties) much in bulk

10. Clusters formation: surface fraction of atoms
On the surface of this cluster, Fraction of atoms on surface can be of the order of 1
This makes a significant change in the properties
Fraction of atoms F=4/n1/3 , n is the number of atoms in cluster
F=0.3 if n=1000
F=0.2 if n=10,000
F=0.04 if n=1000,000

11. What changes with number of constituents

12. What changes with size of clusters

15. Low density (half of bulk) Generally highly porous
Cluster assembled films are formed by the deposition of these clusters on to a solid substrate
Low density (half of bulk)
Generally highly porous
CBD

16. What is the CBD? Cluster Beam Deposition (CBD)
Method that deposits nanoparticles as a type of cluster on substrate
High degree of purity and exact nanoparticle size control
Figure 2. Schematic showing the deposition of patterned films(SEM)

17. Gas phase Clusters are generated in cluster sources Its possible to produce intense cluster beams of any materials Cluster include species exist only in gas phase or condensed phase or in both
Laser vaporization flow condensation source
Pulsed arc cluster ion source
Laser ablation cluster source
Supersonic( free jet) nozzle source
Knudsen cell (effusive source)
Ion sputtering source
Magnetron sputtering Source
Gas aggregation/ smoke source
Liquid metal ion source

19. Vacuum evaporation thin film technique( cluster having high F, are highly active and will react if not produced in vacuum)
Thin film is deposited at wafer(rotatable to have uniform film) in vacuum ( as clusters are highly reactive when precursor is evaporated

23. Laser Vaporization Using laser energy to heat sample particles
highly localized heating(due to small laser spot) and rapid cooling( with background gases)
Shematic diagram of the Laser reactors
TEM of the iron ultrafine particles
Majima et al. (1994) Jpn. J. Appl. Phys. 33,

25. Control on cluster growth as density
reduces drastically in vacccum

29. How can nanoparticles be deposited on a substrate?
Gas phase nanoparticle formation and growth
Formation and growth processes of objects relevant for CBD follow the same physical and chemical mechanisms as any gas-phase particle synthesis process.
1. Particle formation
2. Particle growth

30. How can nanoparticles be deposited on a substrate?
1. Particle formation
The starting material can be vaporized from a hot source into a low density inert gas employing Joule heating, thermal plasma or laser ablation.
(1)Homogeneous nucleation:
Cooling of the vapor rapidly leads to super-saturation followed by homogeneous nucleation and the formation of first product clusters.[1] A criterion to determine the formation path of a cluster is its thermodynamically critical diameter,
the Kelvin diameter d1,C :Qa
: Surface tension
: Molecular volume of the cluster
: Boltzmann constant.
: Dimensionless saturation ratio at temperature T
1.Granqvist C G and Buhrman R A (1976)

31. How can nanoparticles be deposited on a substrate?
Critical diameter of cluster << Diameter of a single molecule of the product species
-A nucleus is stable and there will be no growth or shrinkage by condensation or evaporation and the particle will form by coagulation
Critical diameter of cluster >> Diameter of a single molecule of the product species
A nucleus is unstable and particles are formed by homogeneous nucleation:
balanced condensation and evaporation of molecules to and from clusters of the
product species.
(2)Coagulation (collision):
It is applied to particle growth in combination with coalescence.
2.K Wegner and P Piseri (2006)

32. How can nanoparticles be deposited on a substrate?
2. Particle growth
The newly formed particles continue to grow either by surface growth (addition
of atoms or molecules to the particle) or by coagulation (inelastic particle–particle collisions) which is usually followed by coalescence.
Coagulation describes particle–particle collisions due to
Brownian motion or other mechanisms such as shear or
electrostatic forces. Particle growth by coagulation has to
be distinguished between collisions in the free molecular
regime (particle diameter dp smaller than the mean free path
of the gas λ) and in the continuum regime (dP>>λ).
(1).Coagulation (collision)
2.K Wegner and P Piseri (2006)

33. How can nanoparticles be deposited on a substrate?
The classical theory for Brownian coagulation of monodisperse spheres in the continuum regime at temperature T is used to calculate dp [3] (Neglecting the particle morphology and the spread of the particle size distribution):
: Initial particle diameter
: Initial particle concentration
: Dynamic viscosity of the gas
: Residence time
If the particle diameter is much smaller than the mean free path of the gas, as is usually the case with clusters, the coagulation theory in the free molecular regime has to be applied. (Neglecting the spread of the particle distribution and the morphology):
: Total volume of particles per unit volume of
gas
: Density of the particles
3.Friedlander S K (2000)

34. How can nanoparticles be deposited on a substrate?
Self-preserving size distributions [3]
:Particles that grow by Brownian coagulation typically reach asymptotic distributions
tSPSD: Time to reach the self-preserving size distribution in the free molecular
regime.[4]
3.Friedlander S K (2000)
4.Wegner K and Walker B(2002)

35. How can nanoparticles be deposited on a substrate?
Surface growth
Surface growth consists of a first step of molecule or atom transport to the surface of an already-formed particle and a second step involving a chemical reaction or a phase change at the particle surface. Especially during the first stages of particle formation from supersaturated vapour, surface growth can be significant as the initially formed clusters act as condensation seeds for the remaining vapour. By controlling the supersatura- tion at a low level, particle nucleation can be slowed down while the rate of surface growth by vapour deposition can be increased
2.K Wegner and P Piseri (2006)

36. How can nanoparticles be deposited on a substrate?
The rate of change of the particle diameter dp at temperature T by vapor deposition in the free molecular regime is given by [3]:
: Volume of the transported molecule in the
particle phase
:Partial pressure of the gas or vapor topical far from the particle
: Partial pressure at the particle surface obtained
from the equilibrium vapor pressure
: Fuchs–Sutugin factor for bridging the free molecular with the continuum regime [41]
3.Friedlander S K (2000)

37. How can nanoparticles be deposited on a substrate?
In the continuum regime, the rate of change of the particle diameter is [3]:
: Diffusion coefficient of the gas or vapor
: Fuchs–Sutugin factor for bridging the
continuum with the free molecular regime
3.Friedlander S K (2000)

38. How to get nanoparticles’ formation (method)-
How to get nanoparticles’ formation (method) (1)Supersonic beam cluster
1.Nanostructured TiO2 films were grown by
depositing clusters produced by a pulsed
microplasma cluster source (PMCS), in high
vacuum conditions.
2.Particles with different masses have different
inertia so that a spatial separation takes place and
the particles are deposited in different regions of
the collecting surface, called impactor.
3.Oxidation of titanium clusters constituting the
films takes place immediately after exposition to
the air,due to the high reactivity of titanium and to
the high porosity of the cluster-assembled films.
Ref. E.Barborini,I.N.Kholmanov(2002)
Fig.2.TEM image showing the nanostructure
of the film:Grains with size below 10 nm are
randomly assembled to constitute a porous
structure such as those typical of the ballistic
aggregation regime.

39. How to get nanoparticles’ formation-
How to get nanoparticles’ formation (2)Low energy cluster beam deposition
1.XPS, Auger, and EELS spectroscopies
confirm that the LECBD technique in
UHV allows us to produce
nanostructured silicon films with a rather
low oxygen contamination. In the
deposited size range under consideration
in our experiments (below 300 atoms) the
general behavior of the film is comparable
to amorphous silicon
2.The silicon nanograins are partially
connected by their dangling bonds
leading to a minimization of their total
numbers. In addition, cluster surface
reconstructions involving the formation of
oddmembered rings is at the origin of
dangling bond minimization.
Ref.P.Melinon P.Keghelian (1997)
Specific electronic properties
The x-ray photoelectron spectroscopy technique (XPS), associated with the Auger electron spectroscopy (AES), and the electron energy loss spectroscopy (EELS) techniques are applied on samples in ultrahigh vacuum conditions (UHV) for the investigation of the electronic structure.

40. How to get nanoparticles’ formation (method)-
How to get nanoparticles’ formation (method) (2)Low energy cluster beam deposition
Magnetic properties
The structural properties and the magnetic behavior of pure SmCo5 cluster assembled lms prepared by the LECBD technique, and SmCo5 clusters embedded in a silver matrix
A slight increase of the magnetic anisotropy in the mixed SmCo5
cluster films compared to the pure Co-cluster ones.
Ref. M. Negrier, J.Tuaillon-Combes (1999)