iLab Name: Kratos AXIS Ultra DLD Imaging X-ray Photoelectron Spectrometer (XPS)
iLab Kiosk: BRK Metrology Core
Owner: Dmitry Zemlyanov
Location: BRK 1077
Maximum Wafer Size:  N/A

Overview

General Description

Imaging X-ray Photoelectron Spectroscopy (XPS) provides information about the element and chemical composition of a substrate with a lateral resolution of 5 μm. The technique can analyze any vacuum-compatible substrate. The Kratos AXIS ULTRA DLD incorporates quantitative, real-time parallel XPS imaging with high spatial resolution spectroscopy.

Specifications

The technique can analyze any vacuum-compatible substrate.

• A Kratos charge neutralization system allows to work with non-conducting samples.
• Magnetic immersion lens for efficient  photoelectron collection.
• Spherical mirror analyzers  for high resolution (over spectrometer-sample resolution is <0.35 eV).
• Monochromized Al and Ag anodes minimize a sample radioactive damage.
• Concentric hemispherical analyzers combined with a DLD detector for real time XPS imaging.
• Fast load lock with cryo/heating options, which can used for biological and organic samples.
• A catalytic cell to facilitate substrate treatment and preparation (6 bar, 1000).
• A glove box attached directly to the instrument to load/prepare a moisture– or air–sensitive samples.
• A corronene gun for non-destructive depth profiling.

Technology Overview

 The basic principle of XPS is fairly simple: the sample under investigation is irradiated by an X-ray beam and the photoelectrons generated are collected by an energy analyzer. The kinetic energy, E_KE, of the ejected photoelectrons is related to the energy of the incident X-ray photon, hν, the electron binding energy, E_BE, measured in respect to the Fermi level and the work function of the spectrometer, φ_sp:
                                                   E_KE=hν-E_BE-φ_sp. 
The binding energy correlates with the energy of an electron level, ε_i. Figure below shows the energy diagram of the photoemission process.
   

How to have your sample analyzed with XPS at the BNC Surface Analysis Facility

XPS data acquisition is performed by Dr. Dmitry Zemlyanov. No training is required to have samples analyzed by XPS, however an acquisition and data analysis fee will be accessed. In certain circumstance a user can be train to operate the XPS equipment alone without supervision and only be accessed the instrument acquisition fee. Please see “How to become an expert user in the Surface Analysis facility”.

The following steps should be followed to have your sample(s) analyzed by XPS:

1. If you’ve never used the XPS facility at Birck Nanotechnology Center, schedule a preliminary meeting Dr. Dmitry Zemlyanov (dzemlian@purdue.edu) is required. The meeting is essential for the proper evaluation of a project, time required to complete, sample handling/transportation, etc. Sample transportation is very critical to the quality and reliability of the XPS analysis therefore the user should discuss how to store and how to carry the sample(s) during the preliminary meeting.

2. Open iLab account (consult with your department Business Office how to do this).

3. Following your e-mail request, you are supposed to receive a confirmation from Dmitry Zemlyanov with 3 days with a date and time when samples can be delivered to the BNC for analysis. You have to confirm the date and time to ensure proper sample transfer.

4. Bring your samples at the scheduled date and time to (BRK 1274 or BRK 1077).

5. Receive the data in the desired format (x-y columns, vamas, etc.) and collect your samples. Samples not collected within 2 weeks will be disposed.

6. Please do not hesitate to check the status of the work and request your data.

Sample Requirements and Preparation

The recommended sample size is 3-12mm × 3-8mm × 0.1-3mm. It is not necessary to have a square sample, any shape in this range is acceptable. Power samples MUST be in GLASS vial in amount of 100-200 mg ( any leftover will be retuned).   

Helpful details:

1. Fee for Purdue users is $40 per hour for XPS data acquisition. Also, Kratos XPS Scientific Staff Time, $94 per hour, will be applied, which is 0.5-3 hours depending on the staff scientist involvement. By a rough estimation, it takes 2-4 hours ($80 to $160) per acquisition point. 

2. Preliminary data analysis and data interpretation can be performed by Dmitry Zemlyanov. The rate for the data analysis is $70 per hour for

Purdue users. It takes from 0.5 hour to 3 hours per sample/acquisition point depending on complexity and kind of analysis required.

In publications, an user is kindly asked to acknowledge the Birck facility using the template below:
'The XPS data was obtained at the Surface Analysis Facility of the Birck Nanotechnology Center, Purdue University.'

If XPS data was analyzed by Dr. Zemlyanov, it implies acknowledgement and/or co-authorship based on intellectual contribution in any related publications.

Standard Operating Procedure

There is no SOP for the Kratos XPS. Mainly, the acquisition is performed by the staff scientist, Dr. Dmitry Zemlyanov (dzemlian@purdue.edu). Please contact him by email if you want your samples to be analyzed by XPS. 

Data Analysis

CasaXPS is a standart software for the XPS data analysis. The Purdue University has a site license. Please contact for detail Dr. Dmitry Zemlyanov (dzemlian@purdue.edu). The XPS workshops training how to analyze the XPS data and how to understand the XPS results are typically performed by every year by Dr. Dmitry Zemlyanov.

References

Recommended web resources:

1. https://srdata.nist.gov/xps/main_search_menu.aspx - NIST database summarizing peak positions for different elements/transitions, chemical shifts, spin-orbital splitting, etc.
2. https://www.thermofisher.com/us/en/home/materials-science/learning-center/periodic-table.html - Thermofisher database demonstrating actual spectra, peak positions for  main chemical states, spin-orbital splitting, etc.

3. http://www.nottingham.ac.uk/~ppzpjm/amshome.htm