Microscopia Eletrônica de Varredura e
Nanoconformação com Feixe de Íons
Marcos Vasconcellos
Laboratório de Microanálise
[email protected]
www.if.ufrgs.br/~marcos
PGCIMAT 2010
Jeol JIB 4500
Multbeam
Http://nanolab.if.ufrgs.br
Feixe de
elétrons
MEV
Feixe de
íons
Ga
Microscopia eletrönica de varredura - modo de elétrons secundários
Supercondutores - monocristais em matrix policristalina
Grupo de resistividade elétrica if-ufrgs
Microscopia eletrönica de varredura - modo de elétrons secundários
TiVAl - TiN
Laboratório de Microanálise IF-UFRGS
Microscopia eletrönica de varredura - modo de elétrons retroespalhados
Pastilha de freio - filme de fricção
Laboratório de Microanálise IF-UFRGS
Silicon drift detector
Detetor de raios X característicos
256 x 256 = 65536 x 1s = 18 horas!!!!!!!
256 x 256 = 65536 x 100 ms = 1,8 horas
Al
Ba
Fe
O
O
S
Cu
BSE
C
Modos de operação
Imageamento
desbastamento
deposição
Imagem de elétrons secundários
Induzida por feixe de elétrons
Induzida por feixe de íons
Imagem de elétrons secundários
Induzida por feixe de elétrons
Induzida por feixe de íons
Contraste de canalização
do feixe de íons
15
20
25
FOCUSED ION BEAM
1. Equipamento
a. sistema de vácuo
b. liquid metal ion source – LMIS
c. coluna iônica
d. porta amostra
e. detetores
2. Interação íon-sólido
3. Fontes de gás (deposição e remoção)
4. Sistemas dual beam
5. Imageamento
6. Nanofabricação
7. Preparação de amostras para TEM
8. Tomografia
PGCIMAT 2010
1. Equipamento
Diagrama
b. fonte de íons
liquid metal ion source (LMIS)
Gallium (Ga)
(i) its low melting point (T,, = 29.8 "C) minimizes any reaction or interdiffusion
between the liquid and the tungsten needle substrate
(ii) Its low volatility at the melting point conserves the supply of metal and yields
a long source life;
(iii) its low surface free energy promotes viscous behaviour on the (usually W)
substrate;
(iv) its low vapor pressure allows Ga to be used in its pure form instead of in
the form of an alloy source and yields a long lifetime since the liquid will not
evaporate
(v) it has excellent mechanical, electrical, and vacuum properties, and
(vi) its emission characteristics enable high angular intensity with a small
energy spread.
two step process:
(i) The heated Ga flows and wets a W needle having a tip radius of - 2-5 pm.
Once heated, the Ga may remain molten at ambient conditions for weeks due to
its super-cooling properties. An electric field (lo8 Vlcm) applied to the end of the
wetted tip causes the liquid Ga to form a point source on the order
of 2-5 nm in diameter in the shape of a "Taylor cone." The conical shape
forms as a result of the electrostatic and surface tension force balance that is
set up due to the applied electric field.
(ii) Once force balance is achieved, the cone tip is small enough such that the
extraction voltage can pull Ga from the W tip and efficiently ionize it by field
evaporation of the metal at the end of the Taylor cone. The current density of ions
that may be extracted is on the order of - 1x10' ~ l cm*A. flow of Ga to the cone
continuously replaces the evaporated ions
c. coluna iônica
F = q.E + q.v x B
d. Stage
X,y,z,R,Θ
e. Detetores
Elétrons secundários
Elétrons retroepalhados
EDS
EBSD
CL
...
SDD
MEV
2. Interação íon-sólido
Regimes da cascata de colisões
i) knock on regime
MI << M2 ou E0 é baixo.
ii) linear cascade regime
FIB
M1 ~ M2
iii) dense cascade regime
M1 > M2
O mecanismo dominante de perda de energia no processamento com FIB
(e.g., 5-50 keV) é o de interações elásticas entre o íon e os núcleos blindados
(i.e., nuclear stopping).
Conservação E e p
Ziegler et al
ZBL, LSS
TRIM - SRIM
http://www.srim.org/
TRIM calculation - Ga+ – 25 keV - 00
Flux is defined as the time rate of flow of
energy; the radiant or luminous power in a beam. In the case of an ion beam
flux is measured as the number of particles flowing through a given area per
unit time and has units of ions/cm2/s.
Fluence is, the sum of energies, the number of particles or
photons incident during a given time interval on a small sphere centered at a
given point in space divided by the cross-sectional area of that sphere.
Fluence has units of ions/cm2
beam current is also a measure
of the time rate flow of energy or how many ions are delivered per unit time.
The beam current is measured in amperes, which is equivalent to units of
charge per unit time or Coulombs(C)/sec.
Current density is a measure of the energy intensity or
number of ions in a given area at any instant in time. Current density has
units of c/cm2 or in the case of a singly charged ion like ~ a t'hi s is
equivalent to ions/cm2
http://www.srim.org/
40 keV
5 keV
sputtering
3. Imageamento
Channeling contrast
4. Fontes de gás (deposição e remoção)
varying dwell times
5. Sistemas dual beam
6. Nanofabricação
Fabricação 3D
7. Preparação de amostras para TEM
0.5µm with a 13°taper angle
8. Tomografia
Focused Ion-Beam Tomography
A.J. KUBIS, G.J. SHIFLET, D.N. DUNN, and R. HULL
METALLURGICAL AND MATERIALS TRANSACTIONS A VOLUME 35A, JULY 2004—1935