Ilse Katz Institute for Nanoscale Science & Technology

XPS overview

Equipment Overview

X-ray photoelectron spectroscopy-Auger electron spectroscopy (XPS/AES) ESCALAB 250 Thermo Fisher Scientific

ESCALAB 250 is a multi-technique instrument including both XPS and AES surface sensitive methods of analysis.

In this system high-speed routine XPS analysis of large areas is optimized.

The X-ray source, data acquisition system and sample movement are all fully computer controlled, providing the user with unattended operation for the analysis of large numbers of samples.

An additional analytical capability is Angle Resolved XPS (ARXPS) with the programmed sample tilt.

The ESCALAB 250 provides the user with the most advanced parallel X-ray Photoelectron Imaging (XPI) capabilities for the analysis of small features at a spatial resolution approaching 1mm.

The system is equipped with two flood-guns for surface charge compensation.

Auger Electron Spectroscopy (AES), Scanning Auger Electron Mapping (SAM) is mounted on the system.

The FEG1000 electron gun is a high-resolution scanning electron source designed for use as a modular sub-system on multi-technique surface analysis systems. Its intended applications are SEM imaging, Auger spectroscopy, multi-point Auger analysis, Auger mapping.

The ESCALAB 250 is fitted with an EX05 inert ion gas gun. This allows the operator to remove surface contaminations from the sample and to etch away surface layers for composition analysis as a function of depth (Depth Profiling).

Two special issues are added to ESCALAB 250 system:

The gas-vessel system including three leak valves makes it possible to study in-situ the adsorption phenomena.

The glow-box is organized on the entrylock preparation chamber for sending the samples without expose to the air.

XPS specification

Equipment Specification:
X-ray photoelectron spectroscopy-Auger electron spectroscopy (XPS/AES) ESCALAB 250 Thermo Fisher Scientific

X-RAY PHOTOELECTRON SPECTROSCOPY:
Specimen viewing
Zoom microscope with field of view of approximately 500 ?m – 3 mm
Monochromatic X-ray Source:
Microfocused 0.5 m Rowland circle Al Ka source
Electron source operating voltage is 15 keV nominal
Aluminum-coated water cooled anode is mounted on linear drive mechanism to provide at least 20 operating positions before anode replacement is required.
Twin toroidal quartz crystals are used as monochromator, each independently adjustable with three degrees of freedom
Ultimate energy resolution < 0.45 eV
Ultimate spatial resolution < 20 microns
Electron energy analyser:
Hemispherical analyser of 150 mm mean radius full 180 degree
Continuously adjustable from 8 mm to less than 20 ?m analysis area

CHARGE NEUTRALISATION SOURCES:
Multi-mode electrostatic flood source:
Electron beam charge compensation
Argon ion flood compensation

AES SPECTROSCOPY
Electron source
Field emission electron FEG 1000 source with field replaceable Schottky emitter is used.
Scan modes
Point, line, raster, variable rate scan

ION SOURCE FOR SPECIMEN CLEANING AND DEPTH PROFILING
Differentially pumped electron impact EX05 ion gun with dual electrostatic lenses
Gas used is Ar Maximum Ar beam current >5 ?A at 4 keV

SPECIMEN STAGE MOVING
Motorised high precision specimen manipulator with X,Y, Z and tilt motions. Stage travel in X direction 50 mm, in Y 20 mm and in Z 12 mm, with 5 ?m resolutions.
The stage tilt may be obtained in the range -90° to +60° from horizontal.
Remote stage control is by operation of trackerball or joystick on control unit. Stage automation giving full automation of all four motions with provision for storage of multiple sets of specimen co-ordinates, and controlled by the Avantage datasystem.

VACUUM
In fully degassed, system the following ultimate pressures are achieved:
Analysis chamber with titanium sublimation pump 1*10^-9mbar
Fast entry chamber 2*10^-8 mbar

DATA PROCESSING
The Avantage data system allows processing and analysis of all types of data including spectra, linescans, profiles and images in the same processing document.

XPS application examples

Application Examples:

XPS analysis

EXAMPLE 1:

Surface composition and depth profile for Ti layer deposited on (PbCd)Se mono-crystal sample.

a) XPS spectra obtained from the corresponding depth of the sample - Oxygen is very low in the Ti layer and oxidized surface of the (PbCd)Se mono-crystal substrate was detected.

b) Depth profile of the elemental composition estimated from the XPS spectra (rate of sputtering 0.1nm/sec).

AES Analysis

EXAMPLE 1:

AES point analysis locally performed on a part of an electronic device showing gold wire contact lines on GaAs (SEM image -a).

AES spectra (1, 2-b) obtained from the corresponding points (shown in Fig.a) are given below:

XPS contact person

Dr. Natalya Froumin

Office :
Building 51 , Room 124
Tel : 972-8-6428664
Fax : 972-8-6428638

Lab :
Building 51 , Room 017
Tel : 972-8- 6428662

Email : nfrum@bgu.ac.il