What is XPS? XPS (x-ray photoelectron spectroscopy) is also known as ESCA (electron spectroscopy for chemical analysis). XPS provides chemical information via binding energy measurements. XPS is a surface analysis technique with an average analysis depth of 50Å. XPS has an average detection limit of 0.05 atom percent. XPS is highly quantitative. XPS provides spatial distribution information via mapping or depth profiling. Ejected Photoelectron X-ray Excitation

Electron Spectroscopy for Chemical Analysis ESCA is an analytical technique that obtains compositional information from the top few monolayers of a material by probing the sample with a mono-energetic X-ray beam. ESCA is also known as XPS (X-ray Photoelectron Spectroscopy). Detect: all elements above He Detection limits: 0.5 - 0.01 atomic % Analysis depth: 0.5-7.5 nm Spatial resolution: <10µm probe size

ESCA Provides Surface Sensitivity Detection of all Elements above He Quantification Chemical State Identification Chemical State Distributions Mapping Sputter Depth Profiling Angle Dependant Depth Profiling

Binding Energy = X-ray Energy - Photoelectron Kinetic Energy ESCA Process Photoelectron Efermi level 3/2 2p 1/2 X-ray (photon) Binding Energy 2s 1s Binding Energy = X-ray Energy - Photoelectron Kinetic Energy

ESCA System Schematic Energy Analyzer (SCA) Quartz Crystal Monochromator Electron Source Al ka x-rays 15-20 kv electrons Input Lens Multi-channel Detector Rowland Circle Photoelectrons Al Anode Sample

Application Areas for XPS Surface chemistry: Adhesion, corrosion, bio-compatibility, lubrication, catalysis, surface cleanliness, processing residues, composition of thin layers, migration of impurities or additives from the bulk, etc.. Interface chemistry: Contamination, migration of impurities or low level bulk components, interdiffusion of layers. Construction analysis: Thin film chemical analysis, imaging and cross-section analysis. Particle analysis: Micro analysis of small particulates, defects or features.

ESCA Spectra from Poly(ethylene terephthalate) Atom % C 70.9 O 29.1 PET -O1s C 1s O O -C1s O C C O CH2 CH2 % of C 1s CH 62.7 C-O 20.2 O=C-O 17.1 c/s c/s C-O=O C-O CH -O KLL -O2s 1000 800 600 400 200 300 295 290 285 280 Binding Energy (eV) Binding Energy (eV) ESCA survey spectra provide quantitative elemental information. High resolution ESCA spectra provide quantitative chemical state information.

ESCA Sputter Depth Profile 185 20 40 60 80 100 Sputter Depth (nm) Atomic Concentration (%) Si 2p O 1s Cr 2p Ni 2p The analysis of thin film structures to verify composition or search for impurities at interfaces is a routine task for PHI ESCA instruments.

SPS Photo of Paint System Cross-section Showing area defined for ESCA maps Polyethylene Mapping Area Substrate Adhesion Layer Base Coat Clear Coat 695 x 320µm 1072 x 812mm

ESCA Maps of an Automotive Paint Cross-section 695 x 320mm

Chemical State Maps for Carbon C 1s Chemical state maps are generated by examining the C 1s spectra stored at each pixel of the map.

Angle Resolved Analysis XPS ESCA/ Angle Resolved Analysis Sample is tilted with respect to x-ray source and analyzer Angle determines sampling depth (d) Analyzer Analyzer X-ray Source X-ray Source Q = 10o Q = 90o d1 L1 L2 d = lsinq = Sampling Depth d1 > d2 L1 = L2 d2 ECA-FP-06-01A

Plasma Treated Polymer, Angle Resolved Analysis XPS ESCA/ Plasma Treated Polymer, Angle Resolved Analysis High Sensitivity Mode 90º Take Off Angle C 1s Greater sampling depth More surface sensitive N (E)/E C AUGER O 1s O AUGER 1000.0 500.0 0.0 O 1s 10º Take Off Angle C AUGER N (E)/E O AUGER C 1s 1000.0 500.0 0.0 Binding Energy (eV) ECA-AP-08-01C

Ion Beam Depth Profiling XPS ESCA/ Ion Beam Depth Profiling Depth profiling features Energetic (1–4 keV) Ar+ ion beam 1–50 nm/min sputter rates Alternating sputter/spectral data acquisition High resolution elemental windows Zalar™ rotation for enhanced depth resolution Issues Energetic ion beam can change sample chemistry All organic information lost Preferential sputtering may change observed stoichiometry Ion Milling with XPS is fundamentally the same as milling with Auger. However, because of the larger spot size (in some cases) and the desire for chemical state information, there are some important differences. ECA-AP-18-08A

Quantification In contrast to other surface analysis techniques the mechanisms for quantification of XPS data are relatively well understood. PHI is a leader in applying current methodology and obtaining the empirical data needed to provide accurate quantification. PHI uses the following building blocks to provide accurate quantification: A standardized set of sensitivity factors based on PHI’s library of empirical data. Algorithms to model the transmission function of the spectrometer. Corrections for geometric asymmetry related to the angle between the X-ray source and the analyzer input lens Key information including transmission function parameters are stored with data files to allow accurate quantification at any data reduction station.

Application Areas for XPS Surface Sensitivity X-rays Escaping photoelectrons Application Areas for XPS X-rays penetrate deep into the sample surface, exciting photoelectrons. However, photoelectrons can travel only a short distance before their energy is modified due to interaction with another atom. Only photoelectrons that escape at their original energy contribute to a peak in a spectrum. This phenomena makes ESCA a very surface sensitive technique, with an average depth of analysis of 5 nm or less.

Which System Meets Your Needs? PHI 5800 MultiTechnique ESCA PHI Quantum 2000 Scanning ESCA Microprobe low medium high