Surface Analysis

Surface Analysis Techniques

Auger Electron Spectroscopy

Physical Electronics PHI 660

  • Elemental mapping with high spatial resolution and is capable of performing scanning electron microscopy (SEM)
  • Coaxial LaB6 Filament Electron Gun, ~100 nm Min. Spot Size for Auger Analysis, 0.5-20 KeV
  • Single Pass Cylindical Mirror Analyzer
  • Single Channel Electron Multiplier
  • Differentially Pumped 1-5 KeV Ar Ion Gun with Automatic Leak Valve
  • Attached UHV Chamber for Sample Fracture or Heating

Staff Contact

Rick Haasch
(217) 244-2967

Location

B06 Materials Research Laboratory
(217) 244-2963

Background

Auger electron spectroscopy (AES) is a surface sensitive analytical technique used mainly to determine elemental compositions of materials and, in certain cases to identify the chemical states of surface atoms. With AES, a primary electron beam is used to excite secondary and Auger electrons. If a scanning primary beam is used, the secondary electron images yield information related to surface topography. Auger electrons, when analyzed as a function of energy, are used to identify the elements and chemical states present. The information depth for Auger analysis is the top 2-20 atomic layers, and can be used in depth profiling applications in conjunction with ion beam sputtering.

Instrumentation

The Physical Electronics model PHI 660 Scanning Auger Microprobe (SAM) has elemental mapping with high spatial resolution and is capable of performing scanning electron microscopy (SEM). The instrument is equipped with an in situ impact fracture stage for analysis of grain boundaries and other internal surfaces. It also has an attached stage capable of heating samples to 1000 C in situ or during gas exposure, suitable for surface segregation studies. Auger point analysis and scanning analysis can be performed with a spatial resolution down to 250 nm, while SEM resolution is around 100 nm. The Auger has a sputter ion gun for depth profiling analysis.

Applications

This instrument is primarily used when high spatial resolution surface analysis is required, for example, failure analysis of integrated circuits, elemental mapping of fine particles, thin-film depth profiling, and studies of corrosion and oxidation scales and of fiber composites. Also of particular importance is the ability to perform in-vacuo fracture so that uncontaminated boundary surfaces can be analyzed.

Secondardy Ion Mass Spectrometry

Cameca ims 5f

  • The Cameca ims 5f is a dynamic SIMS which uses either cesium or oxygen for the incident primary ion beam, which maximizes sensitivity for both electronegative and electropositive elements. This allows for sensitivity in parts per billion for many elements and can perform depth profiles with 3-15 nm depth resolution. A normal incidence electron gun gives charge neutralization to facilitate the analysis of insulators. Mass resolution up to 20,000 is attainable. The mass range normally is 1-280 amu with extension to 1-500 amu under some conditions. Quantitation of dopant levels is possible with standards.

Physical Electronics PHI Trift III

  • The PHI TRIFT III is a Time of Flight SIMS which uses a gold liquid metal ion source as the analysis ion beam. The gold source can be run with Au+, Au2+, and Au3+ ions. The TRIFT III normally operates in static mode which allows for the analysis of both elemental and molecular species at the sample surface. The mass range can be set to 10,000 amu or more for large organic molecules. A dual ion source (Cs and O) is also available for elemental depth profiling work.

Staff Contact

Tim Spila
(217) 244-0298

Location

Cameca
B01 Materials Research Laboratory
(217) 244-2965

PHI Trift III
B04 Materials Research Laboratroy
(217) 244-2964

Background

In secondary ion mass spectrometry (SIMS) a focused ion beam is directed to a solid surface, removing material in the form of neutral and ionized atoms and molecules. The secondary ions are then accelerated into a mass spectrometer and separated according to their mass-to-charge ratio.

Instrumentation

The CMM has two secondary ion mass spectrometers, a Cameca ims 5f and a Physical Electronics PHI Trift III. The Cameca can be operated as a true ion microscope with a spatial resolution of 1 micron or as an ion microprobe with a lateral resolution on the order of 200 nm. It has a sensitivity in the parts per billion range for many elements and can perform depth profiles with 3-15 nm depth resolution.

Features

The SIMS is equipped with cesium and duoplasmatron sources for the incident primary ion beam, which maximizes sensitivity for both electronegative and electropositive elements. Each source can be used in the microbeam mode. The instrument is usually used for dynamic SIMS, but static SIMS can also be done. A normal incidence electron gun gives charge neutralization to facilitate the analysis of insulators. Mass resolution up to 20,000 is attainable. The mass range normally is 1-280 amu with extension to 1-500 amu under some conditions. Quantitation of dopant levels is possible with standards. The instrument is equipped for imaging in both the microscope and microprobe modes. With sputter depth profiling and successive 2-dimensional image collection, 3-dimensional analysis can be obtained.

Applications

The primary strengths of SIMS are surface/near surface analysis with low detection limits, isotopic analysis, imaging, and rapid depth profiling. Isotopic sensitivity has been exploited to determine diffusion rates and mechanisms. Hydrogen in metals, ceramics, semiconductors, and polymers has been studied. Semiconductor applications include the study of the redistribution of a dopant species and depth profiling modulated structures such as quantum well devices.

Surface Profilometry

Sloan Dektak3

Staff Contact

Steve Burdin
(217) 333-0386

Location

B67 Materials Research Laboratory
(217) 333-0386

General

Surface profilometry is a technique in which a diamond stylus, in contact with a sample, can measure minute physical surface variations as a function of position.

Instrumentation

The center operates a Sloan Dektak3 ST stylus surface profilometer for the measurement of surface topography. This instrument has the capability of measuring step height down to a few nm.

Features

The Dektak profilometer has two available stylii, 2.5 and 12.5 micrometer radius, and has a force variable between 1-40 mg allowing the capability to profile a wide variety of materials. The Dektak is controlled by a PC running Windows, making the system very easy to use. The software offers several data processing funtions as well as image capture and storage. The data can be easily converted to ASCII format and stored on a diskette for those requiring additional processing capabilities.

Applications

Surface profilometry is commonly used to measure film thickness in thin film deposition and processing. Another important application is the measurement of crater depths for those surface analysis methods such as secondary ion mass spectrometry (SIMS) that use ion sputtering for depth profiling.

X-ray Photoelectron Spectroscopy

Kratos Axis ULTRA

  • Excitation Sources
    Dual Anode X-ray Source: Mg, Al
    Monochromatic Xray Source: Al
  • Detection System
    Small Area Extraction Optics: Hybrid Spherical Capacitor Electron Energy Analyzer for Spectroscopy and 2-D Imaging
  • Sputtering System
    Differentially Pumped 1-5 KeV Ion Gun

Physical Electronics PHI 5400

  • Excitation Sources
    Dual Anode X-ray Source: Mg, Al
    Monochromatic Xray Source:Al
    Ultraviolet Source: He I, He II
  • Detection System
    Small Area Extraction Optics: 0.2, 0.5, 1.0, and 1 mm x 3.5 mm
    Spherical Capacitor Electron Energy Analyzer
    Dual Channel Plate Position Sensitive Detector
  • Sputtering System
    Differentially Pumped 1-5 KeV Ion Gun with Automatic Leak Valve

Staff Contact

Rick Haasch
(217) 244-2974

Location

Kratos
B81 Materials Research Laboratory
(217) 244-2974

PHI 5400 XPS
B08 Materials Research Laboratroy
(217) 244-2974

Background

In X-ray photoelectron spectroscopy (XPS)- also called electron spectroscopy for chemical analysis (ESCA)- X-rays excite photoelectrons, and the emitted electron signal is plotted as a spectrum of binding energies. Differing chemical states resulting from compound formation are reflected in the photoelectron peak positions and shapes. Spectral information is collected from a depth of 2-20 atomic layers, depending on the material studied.

Instrumentation

The Center for Microanalysis of Materials has two instruments for X-ray photoelectron spectroscopy: a Kratos Axis ULTRA and a Physical Electronics PHI 5400. Both instruments have monochromated X-ray sources for high-energy resolution analysis and are capable of small area detection. The Axis ULTRA and PHI 5400 are high-resolution analytical spectrometers which allow sample tilting for depth resolved analysis. The Axis ULTRA and PHI 5400 also have attached sample processing chambers for heating and thin film deposition.

Applications

The strength of XPS is its ability to identify different chemical states. This ability is useful in a range of physical studies, for example, oxidation/corrosion products, adsorbed species, and thin-film growth processes. Analysis of insulators is possible with the Kratos Axis ULTRA. XPS is also capable of semiquantitative analysis.