SPECTALEED

LEED / Auger

SpectaView

MCP-LEED

MBD-LEED

SPA-LEED

LEEDInstruments for

Low Energy Electron

Diffraction and AES

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Electron Spectroscopy (AES). In this case, the SPECTALEED is employed as a Retarding Field Analyser (RFA) in conjunction with the DATAuger software.

SPECTALEED delivers exceptionally sharp and bright LEED pat-terns with high resolution in k-space (typical transfer width of 300 Å at 100 eV), for easy observation even under condi-tions of high ambient light.

Non-magnetic gold plated molybdenum grids provide a high transmission (82 %) and

The SPECTALEED Control

Unit offers LEED and

AES with PC controlled

data acquisition in one

single compact unit

with integrated Lock-in

amplifi er.

Electron Spectroscopy (AES). In this case, the SPECTALEED is employed as a Retarding

terns with high resolution in k-space (typical transfer width

Electron Spectroscopy (AES). Electron Spectroscopy (AES). Electron Spectroscopy (AES). In this case, the SPECTALEED is In this case, the SPECTALEED is In this case, the SPECTALEED is employed as a Retarding

15 years experience

in the production and

development of LEED sys-

tems enables OMICRON

to offer a variety of LEED

instruments and support-

ing software with both

excellent performance

and reliability.

SPECTALEED

The SPECTALEED family ranges from basic instruments for crystal preparation with optional AES capability, to advanced applications. These include investigation of insulators or sensitive samples using beam currents down to 0.1 nA, dedicated Spot Profi le Analysis (SPA-LEED), I/V measurements, real-time Video LEED and MBD LEED.

Most commonly, LEED is used to determine the surface structure after its preparation during a multitechnique experiment involving other surface analysis methods.

2

Structural characteristics of the sample, for instance ter-race width, step height and facets may be investigated by the analysis of spot profi les and I/V curves.

In addition, dynamic proc-esses such as the structural phase transitions which take place during adsorption, can also be monitored and analysed in real-time using the SpectaView Video-LEED package.

Surface sensitive chemical analysis is made available through the use of Auger

Electron Spectroscopy (AES). The SPECTALEED Control Electron Spectroscopy (AES). Electron Spectroscopy (AES). Electron Spectroscopy (AES). Electron Spectroscopy (AES). Structural characteristics of

SPECTALEED

Control Unit

SPECTALEEDSPECTALEED PC

Versatility for

Structural and

Chemical Analysis

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W(100) at E = 144.7 eV C60 at E = 7.9 eV

3

a uniform work function. The wide viewing angle (102°) and minimal shadowing of the screen by the miniature electron gun give a maximum visible LEED pattern.The integral miniature electron source operates down to 5 eV, and is designed for minimised light emission - a very important feature for LEED I/V analysis.

The standard thoriated tungsten fi lament allows the operation at high background pressures and in aggressive atmospheres, e.g. oxygen. An optionally available LaB6 fi lament yields a perfectly circular spot with high beam current and extremely low stray light, due to the low emission temperature.

High brightness and perfect

geometry LEED patterns are

achieved with the SPECTALEED

even down to very low

energies.

The SPECTALEED Control Unit uses active HV modules for all elements of the electron gun to produce either a parallel beam (0-1000 eV) for LEED or a focused beam (250 µm spot size at 3 keV) for AES. Beam current and energy can be monitored without biasing the sample. Lens settings for a fi xed focus range from 20 - 500 eV beam energy are supplied as standard. The SPECTALEED Control Unit is used for all LEED instruments.

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MBD-LEED

The Molecular-Beam-Deposition-LEED is a new instrument for the in-situ observation of thin fi lm growth during the evaporation process. It combines 3 miniature Knudsen cells with the SPECTALEED for simultaneous and independent evaporation of up to three different materials. The Knudsen cells are integrated into the LEED optics so as to cause minimum reduction of the LEED viewing area and no disturbance of the LEED pattern.Low light emission is maintained even at the maximum evaporation temperature of approx. 700°C. The quartz glass crucibles are prealigned onto the sample and are easily exchanged and refi lled. The design geometry prevents contami-nation of the LEED grids by the evaporant.

- Temperature range 40 - 700 °C- Crucible capacity 15 mm3 (max. 50 mm3)- Evaporator control unit with up to 3 independent T-controllers, programmable via RS232

The MCP-LEED uses a

fringe-fi eld correction

plate to produce a

perfect LEED pattern

on the plane

channelplate.

MBD-LEED with

3 pre-aligned,

integrated miniature

evaporators.

1) Courtesy of: J. Vogt and H. Weiss, Univ. of Magdeburg2) Courtesy of: C. Seidel, H. Kopf and H. Fuchs, Univ. of Muenster

- Ultra low beam current 0.1 - 30 nA- Single or double channelplate- Viewing angle 70°- High stability/low noise channelplate control unit

O3(0001) at 232 eV,

beam current of 30 nA.

Al2O

beam current of 30 nA.

MCP-LEED

The highly sensitive channelplate version of the SPECTALEED reverse view LEED optics is specially designed for operation using low primary beam currents. Such low beam currents may be demanded in applications where the beam current levels experienced in standard LEED applications (typi-cally in the microampere range) may possibly lead to damage of delicate samples or cause rapid charging of insulator surfaces.With the MCP-LEED, the low beam current in the nanoampere range enables the structural study of inherently sensitive or prob-lematic samples, such as insulators or single crystals with weakly bound adsorbates, without complications caused by deterioration due to beam-induced effects.The primary beam current may be further reduced, down to the picoampere range, by means of a second channelplate.

NaCl(100) with 5nA

beam current 1)

Organic molecules (DCNQI) on

Ag(110) during deposition in UHV

at 340 K (electron energy: 14.6

eV). Spots produced by the restruc-

turing of molecules into a denser

packing are marked yellow 2).

4

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SpectaView

SpectaView is a user-friendly Video-LEED system for high-speed imaging and I(V)- and I(t)-meas-urements, consisting of software (Windows NT), frame grabber and low light CCD camera. The Video-LEED image is displayed in real-time. The high rate of data acquisition required for the study of dynamic processes is achieved by data storage rates in excess of 8 frames per second.Data analysis may be carried out either directly, or from the saved images. Up to 18 I(V) curves can be measured simultaneously in either auto-matic, template or manual spot-tracking modes. The enhanced image presentation includes on-line brightness and contrast control.

- I(V) and I(t)-measurements - Automatic/manual/template spot tracking - 25 fps real-time display (8 fps stored) - PCI Frame grabber, 512 x 512 pixel, 256 grey levels - Low light CCD (CCIR, analogue out, 400 - 650 nm) - 12 bit DAC/ADC for energy/beam current (PCI-board)

- Active cross-talk compensation for high sensitivity- Fully computer controlled spectra acquisition- Regulated high-stability fi lament supply- Easy adjustment with Fast Scan and Peak modes- Control unit with integrated Lock-in/oscillator- PCI interface board (Windows NT)

DATAuger Software

The DATAuger software makes full use of the multitasking ability of Windows NT. Easy to use routines for AES in analogue mode allow experi-ments consisting of up to 10 sequential scans with independent setting of all experimental parameters. Operating values of the oscillator and Lock-in amplifi er may be set individually for each scan. In addition to the normal data acquisition mode, Fast Scan enables rapid selection and setting of optimum sample position and focus. Peak Mode displays a bar graph and the signal value at a fi xed energy setting.Data processing routines include 3 and 5 point smoothing, Savitsky Golay smoothing, together with differentiation, integration, background sub-traction and addition or subtraction of scans.

Let's Talk About Software

Fully software controlled

AES data acquisition

with DATAuger. The

spectrum of silver was

acquired with the SPEC-

TALEED using a 3.5 keV/

30 µA primary beam

and a grid modulation of

5 Vpp (resolution 0.5%).

Frame grabber and DAC/ADC card allow full PC control of the LEED control unit

and fast acquisition of I(V), I(t) and image data.

CCD

5

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SPA-LEED

Conventional LEED is most com-monly used to judge surface perfection, identify adsorbate-induced superstructures and determine the surface structure as derived from I/V curves.Spot Profi le Analysis (SPA-LEED) was pioneered by Prof. Henzler and his group at the University of Hannover. The SPA-LEED is manufactured under exclusive licence by OMICRON.

Spot Profi le Analysis is a dedicated, high perform-ance LEED application which exploits detailed structural information contained in the width and shape of the LEED spots, to show any deviation from the ideal lattice. SPA-LEED is designed to give maximum resolution in k-space, thus extend-ing the detection limit to a typical average terrace width of about 50 nm and a mosaic angle of down to 0.01°.

Applications of SPA-LEED include the classifi cation and analysis of point defects, facets, terraces, islands, steps, horizontal and vertical roughness, thermal or static disorder, domains, and phase transitions. The technique enables precise

quantitative analysis of lateral and vertical lattice constants, terrace/island size and height distribu-tions, ordering parameters in phase transitions, and diffusion barriers at step edges.

SPA-LEED can be applied in-situ during epitaxial growth processes, chemical reactions, surface diffusion, ordering transitions, reconstruction, etc. Observation of intensity modulations and spot profi le allows precise character-isation of growth processes.

With SPA-LEED the conventional LEED pattern is only visible on a part of the LEED screen, since a section of the screen area is occupied by an elec-tron multiplier positioned behind a 100 µm aper-ture. Heart of the SPA-LEED is an octopole which is used to scan the diffracted electrons relative to the SPA-LEED detector. In this way individual LEED spots can be quantitatively analysed with excel-lent sensitivity and signal-to-noise ratio.

The dynamic range is 100 times higher than in conventional LEED, and resolution in k-space, determined by the transfer width of > 100 nm, is signifi cantly improved. Thus very low concentra-tions of defects can be detected and the nature of their structure can be investigated.

SPA-LEED achieves

excellent resolution

and high dynamic

range by scanning

the diffraction pat-

tern relative to the

detector by means of

a patented octopole

detector.

SPA-LEED: Au-induced

faceting of Si(001)3).

SPA-LEED pattern

measured during homo-

epitaxial growth of Si on

Si(111) in H2 at:

p = 5 x 10-7 mbar,

T = 520°C, E = 75.6 eV.4)

SPA-LEED pattern

measured during homo-

epitaxial growth of Si on

Si(111) in H

p = 5 x 10

T = 520°C, E = 75.6 eV.

6

Latest version of the

SPA-LEED, redesigned

in close collaboration

with the University

of Hannover.

3) Courtesy of: F. J. Meyer zu Heringdorf, H. Minoda and M. H. v. Hoegen, Univ. of Hannover4) Courtesy of: M. H. v. Hoegen and A. Golla, Univ. of Hannover

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The SPA-LEED data acquisition and evaluation soft-ware features an easy-to- handle setup routine. Rate meter and oscilloscope functions are dis-played on the monitor, thus enabling interactive optimisation of peak shape, peak intensity, scan range and scan area. The auto-scan menu allows individual measurement routines to be defi ned and run consecutively. Electron beam energy, beam current and frequency signal from a quartz micro balance can be recorded for the control of layer growth.

The software features many useful data analysis routines including calibration of the defl ection voltage in „Percentage of Brillouin-Zone“, linear or logarithmic count rate display with scaling to the primary current or user defi ned rescaling. Zoom, smoothing, line scans, coloured 3D view, contour plots, comparison facility for two or more scans, evaluation of integral and peak intensities and FWHM of individual spots are also available.

Operation is assisted by a comprehensive manual plus an electronic Help menu.

ring" which identifi es a regular distribution of islands on the surface.

- Transfer width > 1000 Å at 95.4 eV- Beam current range 500 pA - 10 µA, LaB6 fi lament- Angular resolution better than 0.1°- Defl ection Scan ± 30°, viewing angle ± 11°- Channeltron detector for > 8 x 106 cps- 16 bit DACs for defl ection, and 32 bit counter- Fixed focus range 40 - 300 eV- Fully software controlled (2 ISA PC slots, DOS)- Control unit for octopol defl ector, channeltron supply

Inte

nsity

Si/Si(111) (0,0) spot

Spot intensity oscillations and spot profi le measure-ments during epitaxial

growth processes give precise measures of the growing coverage and the

growth characteristics, e.g. increasing roughness.

The SPA-LEED is operated by the LEED control electronics in

combination with the SPA-LEED Control Unit.

SPA-LEED analysis of a diffraction spot of 5 ML Si on

H-terminated Si(111), revealing a „Henzler ring“ which

identifi es a regular distribution

of islands on the surface.

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Coverage [Bilayers]

301-V06/10.02

Technical alterations reserved Printed by Druckerei und Verlag Klaus Koch GmbH

How to contact us

UK:

Omicron Surface Science Ltd

Tel. 01342 331000 • Fax 01342 331003

France:

Omicron Eurl

Tel. 04 42 50 68 64 • Fax 04 42 50 68 65

Italy:

Omicron NanoTechnology GmbH, Roma

Tel. (06) 35 45 85 53 • Fax (06) 35 40 38 67

Switzerland:

Omicron NanoTechnology GmbH

Tel. 055 645 5232 • Fax 055 645 5230

Sweden:

Advanced Vacuum AB

Tel. 013 21 3200 • Fax 040 41 1318

Headquarters: Omicron NanoTechnology GmbHLimburger Str. 75 • D-65232 Taunusstein • GermanyTel. +49 (0) 61 28 / 987 - 0 • Fax +49 (0) 61 28 / 987 - 185www.omicron.de or www.omicron-instruments.com

Headquarters USA:

Omicron NanoTechnology USA

Tel. (952) 746-1316 • Fax (952) 952-1320

USA (East):

Omicron NanoTechnology, E. Regional Offi ce

Tel. (724) 942-9821 • Fax (724) 942-9822

USA (West):

Omicron NanoTechnology, W. Regional Offi ce

Tel. (303) 893 2388 • Fax (303) 893 2399

Japan:

ULVAC-PHI, Inc.

Tel. 0467 85 6522 • Fax 0467 85 4411

South Korea:

Woosin Cryovac Ltd

Tel. (031) 457 5615 • Fax (031) 457 5629

Taiwan:

Omega Scientifi c Taiwan Ltd

Tel. (02) 8780-5228 • Fax (02) 8780-5225

Singapore:

Research Instruments Pte Ltd

Tel. 775-7284 • Fax 775-9228

India:

Mack International

Tel. (022) 285 52 61 • Fax (022) 285 23 26

China:

Omicron China Offi ce

Tel. (010) 82073793 • Fax (010) 82070995

Australia:

Thomson Scientifi c Instruments Pty Ltd

Tel. (03) 9663 2738 • Fax (03) 9663 3680

BRAZIL:

BOC DO BRASIL LTDA

Tel. (011) 3952 5000 • Fax (011) 3965 2766

Specifi cations Mgax. beam current x x x > 10 µA for WTh, > 30 µA for LaB6

Transfer width x x x > 250 Å at E = 100 eV

Fixed focus range x x x 20 - 500 eV

Viewing angle x x 102°

x (70° for MCP-LEED)

AES resolution x x better than 0.5 % (FWHM)

Filament types x x x Thoriated tungsten; LaB6 crystal

Number of grids x x x 3 (AES with MCP-LEED)

x x 4 (AES with SPECTALEED)

Channelplates x single or double channelplate

Magnetic shielding x x x mu-metal (stainless steel cylinder for mu-metal chambers)

Bakeout temperature x x x 220°C

Standard length (mm)* x x x 203 (8”) or 254 (10”) fl ange-sample

Mounting fl ange type x x x NW 150 CF (8” OD), tapped holes

Optional lin. retraction x x x 45 mm (up to 140 mm on request)Note: SPA-LEED Specifi cations and technical details described inside * Special lengths on request

Power Supply NG LEEDBeam energy range 0-3500 eV

Retard energy range 0-2000 eV (for AES)

Filament supply emission regulated (switchable)

Monitor outputs (0-10 V) beam current (10 nA - 100 µA) / beam energy (full range)

Remote control (0-10 V) beam energy / retard energy

AES (optional) Integrated Lock-in with oscillator

MCP

-LEE

D

MBD

-LEE

D

SPEC

TALE

ED

View from vacuum side

All dimensions in [mm]

SPECTALEED, MCP-LEED, MBD-LEED

SPA-LEED

212

36°

36°

36°

54°

54°

CP

CC

CROctopoles

Screen H.V.

165

Rotary drive for

linear retraction

190 172

Sample

20315

Ø 1

42

View from vacuum side

All dimensions in [mm]

Gun & Grid

a= Optics to sample distance

3 grids: d=26 mm

4 grids: d=22mm

a

203 or 254 57

Ø 15

Ø 1

42.5

NW 150 CF 8" OD

Mounting Flange (tapped holes)

213

109

120

213

109

180

82

(MCP and MBD only)

mu-metal shield