Low Energy Electron Diffraction (LEED)
is one of the most powerful methods for the determination of
surface structure. To exploit the full power of the technique,
equally capable instrumentation is required.
SPECS LEED systems - and in particular the newer systems driven
by fully digital power supplies - provide the experimenter with
many unique advantages present in no other commercial unit.
Left, ErLEED 150 2-grid optics and right, ErLEED
100 4-grid optics with 50mm z-retraction.
All optics include zero length view-port. Both systems suitable
for digital drive.
Digital control unit with integrated 683232 micro processor
and memory
for storage and recall of complete parameter settings
Large screen dot matrix LC display
Menu driven manual operation or external PC control
Up to 9 HV-modules for independent supply of all voltages
Fully floating unit measures true beam current
Electron energy variable between 0-3000eV
Internal ramp generator and oscillator
RFA/AES detection energy variable between 0-2000eV
Noise reduction and preamplifier unit
Compatible with any commercially available LEED optics
ErLEED Digital - Introduction
The ErLEED Digital series is a new generation of LEED and
LEED/AES control units developed by Specs combining latest
digital and analogue technology and an innovative concept
of operation.
Microprocessor control coupled with a large screen dot
matrix display provides ease of use via menu driven displays.
Setup time is further reduced by recalling previously stored
parameter settings from the non-volatile memory. Remote
programming via an RS232 interface is provided as a standard
feature.
Operation of the control unit is performed by simply selecting
the required operating mode. Parameter values may be varied
by means of a rotary control knob, a numeric keypad or by
use of +/- keys. The displays are selectable at any point
of operation. Within each display, soft keys enable parameter
entry or selection of relevant functions. The large LC display,
with backlighting, offers excellent clarity and contrast.
The voltages at electron gun, screen, and grids are provided
by up to 9 independent, stabilized HV modules. All potentials
are strictly separated from each other which guarantees
the high voltage stability and reliability of the unit.
Voltages are set and read out in 18 bit resolution. The
unit is fully floating, facilitating measurement of true
beam currents.
ErLEED Digital Technical Features
Control Unit Details
68332 micro controller
18bit D/A converters for control and read-out of voltages
large screen dot-matrix LC display with backlight
manual operation by numeric keypad, Up-Down buttons,
and rotary control knob
operation by PC via RS 232 interface
non-volatile memory for store and recall of complete
parameter settings
up to 9 independent HV-modules
(filament, primary energy, Wehnelt, anode Einzel lens,
suppressor, screen, detection energy)
primary energy 0-1000eV (LEED), 0-3000eV (AES)
0-10 kV screen voltage
all gun voltages adjustable with offset and gain
internal and external measurement of beam current
internal ramp generator with 0-2000 eV detection energy
(AES)
variable energy sweep with variable scan time
0-500 V collector voltage
internal sine function generator with 750 Hz - 1.25
kHz oscillator frequency,
0-12 V p-p amplitude, 1f, 2f and reference output
external monitoring of primary energy preamplifier,
filter and matching unit
external 0-10 V control of primary and detection energy
Options
Version without front panel devices for exclusive operation
by PC
ErLEED 1000A analogue LEED power supply for standard
applications
AIDA-PC automatic data and image acquisition system
Software and Lock-In amplifier for AES and RFA applications
Additional Features
ErLEED Digital and ErLEED 1000A control units
operate any commercially available LEED optics not
only the Specs 4-grid ErLEED optics
