Back Scattered Detector

8/6/2019 Back Scattered Detector

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BSD Issue 4 dated 05/07/04

• EXCELLENT ATOMIC NUMBER

RESOLUTION 0.1Z at Z = 30

• HIGH BANDWIDTH-TV RATE

OPERATION

• LOW NOISE IN SLOW SCAN

MODE

• 4 QUADRANT DETECTOR FOR

COMPOSITION OR TOPOGRAHIC STUDIES.

• RANGE OF DETECTORS FOR,

0.4KeV, 1keV, 4keV, UHV, & STEM APPLICATIONS.

The Backscattered Electron Detectoruses a large area silicon diode specially

fabricated for electron detection. Itsdevelopment over the years has led to acompact highly sensitive device. Thefour quadrant annular constructionachieves almost perfect symmetryvirtually eliminating topographicinformation and producing a purecompositional signal.

The ability to select quadrants allows itto be used for topographical studies with

the compositional informationsuppressed.

State of the art electronic amplifiers andprocessing use surface mounttechnology in critical areas permittingthe highest possible gain and lowestpossible noise level.

SOLID STATEBACKSCATTEREDELECTRON DETECTOR

24mm Silicon Detector

Corrosion of Steel.Composition Image 15kv, x60

Corrosion of Steel.Topographic Image 15kv, x60

B A C K S C A T T E R

E D

E L E C T R O N

D E T E C T O R




The 4 Quadrant system offers thegreatest flexibility in imaging withbackscattered electrons, and is oftenspecified as standard by SEMmanufacturers.

THE SOLID STATE DETECTOR

The K.E.Developments BackscatteredDetector may be used routinely withmost types of SEM specimen. It givesexcellent atomic number contrast and isseldom affected by specimen chargingand edge effects normally associatedwith secondary electron images.

Due to its symmetrical designtopographic information is virtually

eliminated but by quadrant selection thetopographic information may beenhanced and the atomic numbercontrast completely suppressed.

DETECTOR TYPES

Detector elements are available in aselection of segmentations, sizes andsensitivities suitable for mostapplications.

The Standard detector is used for allgeneral applications. It has a thresholdsensitivity of around 4KeV. This is theideal detector for most systems and isespecially recommended for SEMs withWDX and EDX capabilities wheregeneral applications require high keV’sand large probe currents.

The Low Voltage detector was

developed for operation over a widerange of kV’s and is sensitive to signalsas low as 1keV.

The Ultra Low Voltage detector wasdeveloped with low vacuum operation inmind, and operates over a wide range ofkeVs from as low as 0.4keV.

Above 10keV Standard, Low Voltageand Ultra Low Voltage devices exhibitsimilar characteristics but the Low andUltra Low Voltage detectors are idealfor the more sensitive biological andsemiconductor specimens that could bedamaged by high acceleration voltages.

The Low and Ultra Low Voltagedetectors may however be affected byCathodoluminescence signals or otherstray light, particularly infra red which issometimes used for the stage positionsensors.

Polishing Block. Grit Embedded

Rubber. Composition Image.Uncoated Specimen

Topographic Image of Above




DETECTOR SIZES

The detector elements are available in avariety of internal diameters, externaldiameters and segmentations to suit theapplication. Standard sizes are 18mmand 24mm.

The 18mm element is ideal for generalapplications and is most sensitive atworking distances around 8mm. It isslightly less sensitive than the 24mmdevice due to its smaller area.

The 24mm are best for longer workingdistances and gives peak output at aworking distance of about 12mm.

Other sizes of detectors in the range6mm-35mm are available for specificapplications. In particular a 10mmelement can be used for very shortworking distances or for applicationswhere space is restricted due to the sizeof the stage.

18mm Detector in a typical holder

SPECIAL DETECTORS

Whilst it is feasible to undertakeCATHODOLUMINESCENCE detectionutilizing a light sensitive silicon detector,a semiconductor CL detector will neverbe as sensitive as a dedicatedphotomultiplier based system. Forregular CL applications at lower beamcurrents the K.E.DevelopmentsCENTAURUS detector offers far greaterperformance and flexibility.

A UHV version of the standard detectoris fully UHV compatible and allows thedetector to be baked at up to 200°Cwithout sustaining permanent damage.

The STEM detector uses a smallrectangular silicon device, which is builtinto a standard 12.7mm specimen stub.The 3.05mm grid is fitted above thedetector and held securely in positionduring analysis. It may be used for bothbright field and dark field studies. Whenthe STEM detector is used a systemwith a retractable arm an adaptorassembly be required.

STEM Detector




STEM Image of Microfossil 25kV,X4000

RETRACTION SYSTEMS

Retraction systems are provided to hold

the detector element and to accuratelyposition it just underneath the final lens.

Retraction enables the element to bemoved away from the final lens whennot in use and helps minimize the risk ofaccidental damage.

The system also allows the microscopeto be used at very short workingdistances and with fine mechanical

adjustment for high resolutionapplications.

As a low cost solution the detectorelement may be permanently attachedto the final lens cap. This type of Fixedsystem whilst allowing a very shortworking distance leaves the elementpermanently exposed to damage andmay restrict access for other detectionsystems unless a less than optimal

small element detector is used.

The Push Pull Arm is the most versatileretraction system and can be suppliedfor virtually any chamber. Because ittakes up less space internally it isparticularly suitable for the smallerchambers. As it uses a sliding vacuum

seal it can be prone to slight vacuumleakage so is less suitable for highvacuum and cold field emission SEM’s.

The Swing Arm is suitable for mostlarge SEM chambers and can be swungout of the way by means of an externalcontrol knob.

A Screw Retractable system can alsobe supplied for virtually any chamberand offers most of the advantages of thePush Pull system and can be fitted tohigh vacuum and field emission SEMs.With the recommended addition ofbellows sealing

Swing Arm

Push-Pull Arm




The chance of accidental damage to thedetector element can be minimized bythe use of a K.E.Developments InfraredChamberscope, which gives acontinuous overall view of the inside ofthe specimen chamber.

Brass showing ά and β Phases. Mean Atomic Differences 0.1Z.

Multiphase Metal Alloy

SPECIFICATIONS

DETECTOR ASSEMBLY

Annular 4 quadrant N-type diffused junction. Atomic Number resolutionbetter than 0.1Z when Z = 30.

DETECTOR TYPES

Standard. General purpose applicationsThreshold sensitivity approx. 4keV.Good immunity to stray light.

Low Voltage. Similar to Standarddetector but with increased sensitivity

below 10keV. Threshold sensitivity1keV. Poor immunity to straylight.

Ultra Low Voltage. Similar to LowVoltage detector but with Thresholdsensitivity below 400eV. Poor immunityto stray light.

STEM. Small single element deviceaccepts standard 3.05mm TEM grids.

UHV. High temperature version of thestandard detector made with UHVcompatible materials. Can be baked upto 200°c.

Various other detectors in themechanical range 6mm to 35mm andwith a variety of segmentations can besupplied to special order.




STEM Thin section of kidney

Sandstone Cathodoluminescence taken

with Centaurus CL detector

ORDERING DETAILSWhen ordering please state make andmodel of SEM and preferred port.The Backscattered Detector normallyfits into a specific port. Where this isalready in use it may be possible to offeran alternative position. Please inquirefor details.Please also state detector type and size

i.e.”Low Voltage 18mm”.Where a retractable arm isrequired we will normally supply the

most cost effective solution for theapplication. If a particular type is preferredplease specify.Where a retractable arm is not requesteda fixed lens mounting system and aseparate vacuum feedthrough will benecessary.K.E.Developments are continuously

improving its products. The productsupplied may therefore differ in detail tothat described in this brochure.

K.E.DEVELOPMENTS LIMITEDThe Mount, Toft, Cambridge, CB3 7RL, England

Telephone +44 1223 263532 Fax +44 1223 263948Web Site. WWW.KEDEV.CO.UK Email. [email protected]

SPECIFICATIONS

PREAMPLIFIER

High sensitivity, low noise design usingsurface mount components. Size;

144mm(L) x 92mm(H) x 25mm(W).

CONTROL UNITVideo output level configured for SEMQuadrant and gain switching using pushbutton controls with Led indication.Four gain ranges with noise filtering.Bandwidth Gain 1 & 2, 4MHz

Gain 3, 200kHzGain 4, 50kHz

Free standing case or compatible

modules for some SEMs.

Field Emission correction for some coldFE SEMsAuto Bandwidth control for some digitalSEMs

Power Supply 100, 120, 220 & 230Vac., 50/60Hz.

WARRANTY. Two years from date of

purchase.

http://www.kedev.co.uk/

mailto:[email protected]

mailto:[email protected]

http://www.kedev.co.uk/

Back Scattered Detector

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