e--flux
Mini Electron Beam Evaporator
with 50mm rod
feed, shutter, flux monitor and thermocouple option
New:
Multi-Pocket
Mini
E-Beam Evaporators
further information
on 2-pocket
and 4-pocket versions
Animation of the 2 evaporation modes: rod and crucible evaporation:
Step 1: filament gets glowing and electrons are emitted Step 2: high voltage is applied to the evaporation rod Step 3: rod gets hot and starts evaporating Step 4: due to electron collision some evaporated particles get ionised (illustrated blue) Step 5: evaporated material exits through front aperture Step 6: the negative biased flux electrode collects ions as means for the flux last sequence shows the change from rod to crucible mode
E-Beam
Evaporator
The
e--flux
Mini E-Beam Evaporator is an UHV evaporator for small and medium
quantities
of almost any material in the temperature range of 400K to 3100K.
Evaporation
is possible either directly from evaporant in rod form
(Ø2-6mm)
or out of a crucible. An integrated flux monitor allows maximum
deposition
control. Highly efficient watercooling ensures negligible outgassing
during
operation. The e--flux electron beam evaporator
is very compact
and mounted on a CF-40 flange (2.75"OD). It can easily be retrofitted
to
existing UHV or MBE systems as the mounting orientation is virtually
unlimited.
Main applications of the e--flux
Mini E-Beam Evaporator
are in surface science, thin film deposition and doping.
Most common evaporation materials are such as Mo, Ta, W, Au, Ag, Pt,
Al, Cu, Ni, Ti, C, Si, Cr and others.
Main
features of the e--flux
Electron Beam Evaporator:
Evaporation of
almost every material possible
Dual mode operation
from rod or out of crucible (e-beam heated effusion cell)
Simple rugged construction
using only standard feedthroughs
Cost effective
pricing
shutter,
flux monitor,
various control options, wide range of crucibles and many other options
Description:
In the evaporation zone of the e-beam evaporator a
coiled tungsten
filament (ground potential) is placed in the close vicinity of an
electrically
conducting crucible or target (high positive potential) and provides
electrons
which are accelerated towards the evaporant rod/crucible producing
extremely
high heating-power densities. The evaporation hearth is highly
efficient
watercooled to ensure negligible outgassing.
The construction
is rugged for long term trouble free operation. Only standard
feedthroughs
are used even for the
rodfeed
and even for the watercooling lines to minimise
downtime
and enabling the user to self-service at any time.
The filament can easily be replaced and can be self-made using standard
Tungsten wire.
The power supply of the e-beam evaporator
is a conventional, rugged design which delivers up to 600W to allow
even
medium quantities of material to be deposited (>1nm/s). However,
fine control
of the emission current makes evaporation of very low rates
(<0,01A/s)
easy and reproducibly possible.
The e--flux
electron beam evaporator can be tailored to almost any application
using a wide range of options
such as flux monitor, shutter, thermocouple, extended rod feed, many
crucible
materials and others.
Unique new features of the e-flux mini e-beam
evaporator:
emission
current stabilizer1
LED
to
alert rod feed2
direct
setting of desired emission current3
ion trap
option4
1The
emission
current stabilizer is a closed
loop control to
keep the emission
current constant
automatically with rod melting down or decrease of crucible content
2An
LED
alerts when the evaporation rod
has to be fed. Threshold can be customer set.
3The
emission current can now be set directly
on a linear scale for easy reproduction.
4The
ion trap
option allows to deflect all charged particles out of the beam.
Modes
of
Operation:
This
electron
beam evaporator can be used to evaporate material in 3 ways:
e-beam evaporator
mode: The material in rod form is directly bombarded by electrons and
rises
rapidly to evaporation temperature. Rod evaporation is generally
preferable
because it creates purest films (only evaporant is heated), no crucible
employed (no crucible cost, no alloying) and evaporation from all
direction
possible. However, some materials such as those with high thermal
conductivity
and low melting points need crucible evaporation (below). Rod
evaporation
is suitable for refractory metals and other materials which reach high
partial pressures e.g. 10-1 Torr before melting.
As material
is evaporated, more can be fed into the evaporation zone, using the
linear
motion feedthrough.
effusion cell mode:
The material is placed in a conducting, usually refractory metal
crucible
which is heated by electron bombardment causing the contents to
evaporate.
Optional temperature control of the evaporant via a thermocouple and
PID
controller make this mode identical to more conventional effusion
cells.
Effusion cell mode is intended for insulators or other poor electrical
conductors and low vapour pressure materials such as gold and aluminium
which melt before reaching useful vapour pressures.
'wetted
wire technique': The material in form of a thin wire is winded around a
rod, typically Tungsten. In a first step the material is melted onto
the Tungsten rod and afterwards evaporated by electron bombardment.
This method is especially suitable for materials which cannot be
evaporated from rod directly and are alloying with conventional
crucible materials. Typical evaporants for this technique are Platinum
and Aluminium.
e--flux
Mini Electron Beam Evaporator (with
all options) and controller
Application of the e--flux
Mini Electron Beam Evaporator:
Typical
applications of the e--flux electron beam
evaporator are in thin film
growth for surface science, MBE, doping, metalization, atomic layer
deposition, optical films, oxide films and others. Materials used are
e.g. Mo, Ta, W, Fe, Cr, Ti,
C from rod and Au, Ag, Al, Cu, Ni out of a crucible. Some
materials like Pt have been successfully evaporated by using a 'wetted
wire' technique.
Rod
evaporation is dome as standard
from Ø2mm rods. Due to the powerful power supply evaporation
from 3, 4, 5 and even Ø6mm is possible. As
the rod evaporates it has to be from time to time fed with a linear
motion drive. This can be done without breaking the vacuum, not even
discontinuing the evaporation.
Deposition
rates can be achieved from sub-monolayers per minute up to several nm
per second. Typical values are for refractory materials as W, Ta, Mo
max 3-5nm/min and Ag, Cu, Al max 1nm/sec.
Quad
Control:
The e-flux ebeam evaporator can be controlled:
manually
manually with PI control of emission
current
flux
controlled (flux controller
required)
thermocouple
controlled (thermocouple
option and crucible mode required)
New
Features of the e--flux
Mini Electron Beam Evaporator:
This
e-beam
evaporator / e-beam heated effusion cell provides a number of new
features
and advantages over previous designs:
The
power supply
is constructed using simple and rugged technology which permits high
electron
beam powers up to 600W standard to be generated without the use of
complex
failure-prone electronics.
The
filament is
a small coil consisting of several turns of tungsten wire as opposed to
‘hairpin’ and short-wire filaments. Because the
filament fully surrounds
the target, more uniform e-beam heating with consequently improved flux
distribution can be achieved. Replacement filaments are readily
fabricated
from tungsten wire and easily exchanged thereby minimising operating
costs.
A
built-in thermocouple
(optional) can be used to monitor and stabilise the target temperature.
The thermocouple can be used, as in any other K-Cell as part of a
closed
control loop comprising a PID controller and the optional control input
on the power supply.
Only
standard feedthroughs
are used to minimise servicing costs and downtime in case of
eventual
failures. The watercooling lines are flange mounted (CF16,
1.33"OD)
and can hence be disassembled easily. The rod feed driven by a
conventional
linear motion feedthrough found in most vacuum components catalogues.
A
flux monitor
is available. This is an additional electrode which intercepts
the
edge of the emerging vapour beam. As the vapour leaves the crucible/rod
it is partially ionised by the incoming electron beam. Some of the ions
will be collected by the flux monitor electrode, generating a small
positive
current which is related in magnitude to the vapour flux.
Besides
flux monitor a flux controller (PID) is available to keep the flux
automatically
constant.
The
large electron
emission surface provided by the tungsten coil filament
allows higher
e-beam powers to be used at lower filament temperatures than in
short
filament designs, with consequently extended filament lifetime. The
filament
is simple in form. Replacements may of course be purchased or be easily
fabricated by the user from tungsten wire.
The
higher e-beam
power of max. 600W allows rods with larger diameters (up to 6mm) to
be
evaporated or crucibles with larger volumes can be used (up to 400mm3).
This
in
turn means that higher evaporation rates can be obtained because of the
larger evaporation area and that more material may be evaporated before
refilling is required. Besides the increased evaporation rates this
also allows higher quality films. As the homogeneity of thin films is
improved with larger distance, the disadvantage of lower deposition
rates can therefore easily be compensated.
The
design of the
evaporator allows rods of up to 50mm in length to be fed into the
evaporation
zone.
Schematics
of e-flux Mini E-Beam Evaporator (with oüptions)
Specification
of the e-flux mini e-beam evaporator:
in-vacuum
length:
190mm
(without
options). Special length possible on request.
max
in vacuum
diameter:
34mm
mounting
flange:
NW40CF
(2.75"OD)
bakeout
temperature:
max.
200°C
rod
feed:
25mm,
optionally
50mm
crucible
volume:
0,3ccm
crucible
materials:
Mo,
Ta, W,
pyrol. Graphite, BN liner, Al2O3, Quartz
deposition
rate:
from
<0,01A/s
to >2nm/s
beam
divergence:
±15°
(±12° with flux monitor)
e-beam
power:
max.
600W
controller:
19" rack mount,
3U high,
230VAC/50Hz
or 115VAC/60Hz or 100VAC/50Hz
*Deposition
Controller: for many years the flux measurement of the e--flux
Mini E-Beam Evaporator has been established to indicate the deposition
growth rate. Besides flux monitoring a PID control was available to
keep
the flux/rate constant.
As a new
option for the electron beam evaporator we now a
Deposition Controller is offered. This extends the flux based
possibilities
by features as known from quartz microbalances. The Deposition
Controller
can automatically run a process only by input of the desired film
thickness
and the evaporation rate.
The
Deposition Controller
is an ideal tool for users who often want to evaporate different
thicknesses
or evaporation rates from known material. Parameters of up to 9
materials
and processes can be stored after an initial calibration. A user
friendly
software is provided. Via an RS232C interface the process can be
controlled
and monitored.
The
Deposition Controller
needs the flux electrode option and it’s recommendable to
have a motorised
shutter for automatic end point control.
reproducable
evaporation
stores
up to 9 materials/process
parameters
automatic
shutter control
RS232C
interface for control
and documentation
In the
interests of continuous
product development, specifications of the e--flux
Mini Electron Beam Evaporator are subject to change without
notice.
