SEM-LIKE XPS MICROPROBE

Unique Capabilities:

PHI’s scanning XPS microprobe instrument platform provides scanning X-ray induced secondary electron images (SXI) generated by scanning a focused sub-5 μm X-ray beam across the sample. Just like an SEM, SXI’s can be used to navigate to areas of interest and to select areas for analysis in real time. SXI images provide 100% confidence in locating small features of interest and in avoiding areas with contamination and inhomogeneities for analysis.

Smart Mosaic allows a user to set up a mosaic acquisition of SXI images from large areas. Stitched mosaic SXI images can be used to investigate the homogeneity of the sample across much larger areas
than available in a single SXI image.

HIGH-SENSITIVITY SPECTRAL AND IMAGING ANALYSIS

A typical XPS analysis on the PHI Genesis begins by  collecting an SXI image that is quickly generated using a sub-5 μm diameter raster scanned X-ray beam. Areas of interest for small or large spectral analysis or imaging are selected and used to guide the next steps which may include: obtaining high energy resolution spectra for chemical state analysis, chemical state images, or compositional sputter depth profiles.

Multispectral chemical maps can be acquired from areas of any size and stitched into a single large area chemical map. Overlays with a variety of color maps and transparency display options can be used to highlight areas that are spatially and chemically distinct.

SINGLE CRATER MULTI-POINT DEPTH PROFILING

A powerful capability enabled by PHI’s unique scanning XPS microprobe technology is the ability to define analysis points on an SXI image and then obtain sputter depth profiles from multiple locations in a single sputter crater. For samples where sputtering area should be minimized, this is a powerful tool for analysis of  neighboring features or on and off defect sites.

The image registration option is coupled to PHI’s unique SXI X-ray imaging capability to ensure XPS analysis is performed at the precise location of interest, even for very small features. Accurate positioning of very small features within a single sputter crater for analysis can be guaranteed.

OPTIMIZED CONFIGURATION

A focused X-ray beam, high sensitivity spectrometer, high performance floating column argon ion gun, automated dual beam charge neutralization, Zalar rotation, and advanced data reduction algorithms provides the highest performance XPS depth profiling capability available.

The standard monatomic argon ion gun can generate 5 eV to 5 keV Ar⁺ ion beams and is ideally suited for most inorganic depth  profiling applications.

It is well known that monatomic Ar ion guns commonly used for inorganic thin film analysis typically cause severe chemical damage when sputtering most polymer and organic materials. PHI has led the way in developing and  applying cluster source ion guns for the successful thin film analysis of polymer and organic materials. Our optional 20 kV Argon gas cluster ion beam (GCIB) and  optional C₆₀ ion gun have proven performance for depth  profiling many polymer and organic films while minimizing the potential for chemical damage.

C60 CLUSTER SOURCE ION GUN OPTION FOR MIXED MATRIX DEPTH PROFILING

With the introduction of cluster source ion guns for organic and polymer thin film depth profiling, interest has grown in applying these ion guns to inorganic structures that sustain chemical damage with monatomic Ar ion beam sputtering. Our experience has shown that some metalloids, oxides, and thin film structures that contain both organic and inorganic materials sustain less chemical damage and differential sputtering artifacts when depth profiled using a 20 kV C₆₀ cluster source ion gun.

MEASUREMENT AT THE SAME LOCATION FOR XPS, UPS, LEIPS AND REELS

In the PHI Genesis, LEIPS, UPS, Argon and GCIB ion beams, and neutralization beams are all aligned to the XPS measurement position. This allows for comprehensive evaluation of organic semiconductor materials.

ULTRAVIOLET PHOTOELECTRON SPECTROSCOPY (UPS) – VALENCE BAND

Design of complex electronic material systems for display panels, flexible circuitry, and photovoltaics require knowledge of the basic properties of each component’s band structure in order to achieve efficient charge transport.

The combination of ultraviolet photoelectron spectroscopy (UPS) and low energy inverse photoemission spectroscopy (LEIPS) provides a complete characterization of the valence and conduction bands, as well as useful parameters such as the band gap, ionization energy, work function, and electron affinity.

Samples provided by: Organic Optoelectronics Practical Development Center（i3-opera)

COMBINED MEASUREMENTS FROM UPS AND LEIPS

LEIPS provides accurate values of electron affinity (EA) which is required for designing organic light-emitting diode, understanding band structure at metal-semiconductor and heterojunctions and in studies of charge-transfer processes.semiconductor.

Low energy incident electrons (<5 eV) used in this technique are well-suited for analysis of organic materials with minimal damage.

The ionization energy can be obtained from the highest occupied molecular orbital (HOMO) of the UPS measurement. The electron affinity can be obtained from the lowest unoccupied molecular orbital (LUMO) of the LEIPS measurement. From the difference in those two values, the semiconductor bandgap energy can be calculated.

COMBINED MEASUREMENTS FROM UPS AND LEIPS

• LEIPS is the inverse process of XPS/UPS
• A sample is irradiated with low energy (< 5 eV) electrons. Photons are emitted from the sample as electrons fill unoccupied states in the conduction band. Photon flux at fixed energy is measured relative to incident electron energy.
• Information obtained from LEIPS:
  • Obtain information on the unoccupied electronic energy levels
  • Measurement of the electron affinity of the sample

LOW DAMAGE ANALYSIS OF ORGANIC MATTER

A comparison of the degree of electron beam damage on a thin film C60 sample using LEIPS electron energies and conventional IPES energies is shown. When the sample was irradiated with 10 eV electrons, equivalent to conventional IPES, the spectral shape changed, indicating that electronic damage had occurred. On the other hand, in the LEIPS measurement using 5 eV of electron energy, there is no change in the spectrum after extensive measurement time, suggesting that no sample damage has occurred.