XPS system specification requirements.pdf

Supply of a Complete Monochromated XPS Instrument.

A complete XPS system capable of high-resolution, monochromated XPS, small area XPS, XPS linescans, XPS chemical mapping, and depth profiling from conductors and insulators should be supplied and should have the following characteristics, as a minimum:

Analysis chamber: Single piece precision-machined from Ni-Fe alloy to combine optimum magnetic field shielding with precision component alignment. Analysis chamber base pressure after baking and cooling must be guaranteed at 5 x 10-9 mbar or better for ultra high vacuum (UHV) surface analysis. The analysis chamber should be fitted with a turbomolecular pump with a suitable backing pump and auxiliary titanium sublimation pump (TSP). The TSP should comprise of 3 filaments. The TSP control should allow for the following firing options: auto-degas, timed-fire (operator programmed firing during experiment sequences) and a mode in which it is disabled during data acquisition. A suitable pressure gauge should be included that is integrated into the spectrometer data system, and acts as a safety interlock for the instrument operation.

Sample manipulator: Should be fully automated and have at least 4 axes of movement, X, Y, Z and continuous azimuthal sample rotation. The sample holder and system configuration should allow for an analysis area of 60 mm x 60 mm and a maximum sample thickness of 20 mm.

Fast entry airlock (FEAL): This chamber should be made of aluminium and pumped using a turbomolecular pump and a suitable backing pump. The FEAL should be connected to the analysis chamber via an automated (low shock) gate valve. Transfer of the sample holder into the analysis chamber should be fully automated and integrated to the spectrometer’s vacuum control software to preserve UHV conditions. A combination gauge should be supplied to measure the chamber pressure, and used to control the automatic sample transfer via the data system. A non-out-gassing sample must be transferred from the FEAL to the analysis chamber in less than 10 minutes from the start of pumping.

X-ray monochromator: This is required for high energy resolution XPS. The instrument must have excellent energy resolution for chemical state analysis and a guaranteed full width at half-maximum energy resolution on Ag 3d5/2 peak of 0.50 eV or better. In order to avoid damage to areas of sample not being analysed the X-ray spot size should be variable in the range of 10µm to 400µm. The X-ray spot size selection should be adjustable in 5 µm steps from the smallest to the largest spot size to facilitate matching the analysis area to the feature of interest. The monochromator must not have a window through which the X-rays pass before reaching the sample, as such a window would reduce the sensitivity of the instrument. The monochromator should include an electron suppression device to reduce the number of unwanted high energy electrons reaching the sample analysis position. The quartz crystal monochromator goniometer should be motorised for automated or remote access X-ray spot alignment.

To minimise X-ray induced sample damage, the large area X-ray spot should have a power of less than 130 watts. The monochromator control electronics and software should include auto-degassing and filament conditioning routines.

Small Area XPS: A lateral resolution of 10 µm or better is required. In small area mode it must be possible to collect photoemission maps generated by continuous stage rastering, so that the image focus and pixel size is uniform across the image. XPS maps must be available within the software for feature identification, chemical state assignment and choosing analysis positions.

Electron Analyser: Should be of spherical sector type and fitted with a multi-channel detector with at least 128 channels for high sensitivity XPS. The detector should support a parallel 'snapshot' acquisition mode of operation for rapid data acquisition. Due to the need for high sensitivity at high spatial resolution, the instrument should be supplied with a large acceptance lens (> 60o), and have at least the following monochromated XPS performance:

1.0eV (FWHM) of the silver 3d5/2 with a peak height of ≥ 6,500,000 cps measured after removal of a linearly interpolated background using an X-ray spot size of 400 µm, and an X-ray power less than 130 W, on a horizontal silver specimen.

1.0eV (FWHM) of the silver 3d5/2 with a peak height of ≥ 450,000 cps measured after removal of a linearly interpolated background using an X-ray spot size of 30 µm on a horizontal silver specimen.

1.0eV (FWHM) of the silver 3d5/2 with a peak height of ≥ 74,000 cps measured after removal of a linearly interpolated background using an X-ray spot size of 10 µm on a horizontal silver specimen.

Both spot size and sensitivity should be determined with the sample normal parallel to the axis of the transfer lens. Specifications should be demonstrated using the anode power recommended for routine analysis at each spot size.

The system supports Grazing Angle XPS (GAXPS) on flat samples (for example Ag on SiO2). The guaranteed intensity at an energy resolution of 1.0 eV (FWHM) of the silver 3d5/2 peak is ≥ 10 Mcps (measured after removal of a linearly interpolated background using an X-ray spot size of 400 µm and an X-ray power less than 130 W).

Charge compensation: The system should provide excellent charge compensation on non-conductive samples even when analysing small areas. A system based on a combination of low energy ions and electrons is required. The ions and electrons should be produced from a single source. A single mode of operation should provide optimum neutralisation for all sample and experiment types. The flood control should include automated Ar gas handling. The spectrometer datasystem should include both automatic filament degas and conditioning routines.

Ion Gun: A high performance ion gun capable of operating in both monatomic and cluster ion modes must be supplied. In monatomic mode, this ion gun must offer high performance from 500 eV to 4 keV. In cluster mode, the ion gun must offer acceleration voltages from 2 keV to 8 keV, and average cluster sizes of up to 2000 atoms, allowing energy per atom values suitable for depth profiling polymers of 1 eV per atom and above.

The data system must control all of the parameters of the ion gun and the gas handling, including switching from monatomic to cluster ion mode. The system should include apertures and current measurement devices to support automated ion gun alignment routines. These apertures must be permanently mounted in the analysis chamber and always available to the user. The ion gun software should also support both automatic degas and filament conditioning procedures.

Sample Viewing and alignment: This is essential for small area XPS. The sample navigation tool should support several camera views to facilitate all sample navigation operations. To fulfil this requirement the following sample views are required.

• A full sample platter view for sample to sample translation.

• A real time magnified image of the sample giving a plan view of the sample. This view should have a maximum field of view of 4.8mm x 3.5mm. This camera should support digital zoom providing a magnification of x8.

• A higher magnification microscope camera for accurate sample height setting.

• A rapid mapping capability that can generate fast XPS images over areas of 0.1 mm2 – 3 mm2, which can be used to define analysis positions.

It should be possible to provide precise alignment between all three camera views. All camera outputs should provide direct feed into the spectrometer software allowing direct inclusion into data reports.

For best sample image contrast for all sample types both side and axial illumination should be provided.

The spectrometer software should provide full control of illumination levels from both sources.

Computer control: The data system must be capable of controlling and automatically recording the X-ray spot size, all settings of the analyser and transfer lens, all flood gun settings, and all settings of the ion gun. The datasystem must have full control of the sample stage for multi-point analysis, azimuthal and compucentric depth profiling, linescans and maps. Routines should also be included for full automatic spectrometer calibration, X-ray spot size measurement, ion gun alignment and source conditioning. To complement these routines, position indexed standards (Cu, Ag, Au) must be available at all times in the analysis chamber. The routines should have the capacity to align and prepare standard samples before acquiring data.

Data system: The data system should include a comprehensive package of data acquisition and processing software for XPS, including depth profiling, linescans and maps. A built-in database of XPS information and spectra should be included. The data system should include routines for automatic data acquisition and reporting. Simple pasting of data, tables, charts, and images from the data system into other applications must be facilitated.

Computer: This should be loaded with Microsoft Windows™ and the XPS data system software. It should include a network card for easy networking, remote control of the XPS instrument and XPS data file transfer. An additional data system licence for off-line data processing over the network must be included.

Calibration and alignment: XPS data precision and accuracy is dependent on the quality and frequency of the spectrometer alignment and calibration. For this reason a software controlled automated approach provides the most consistent and convenient approach. To achieve this, the instrument must include permanent standards and apertures as well as software to acquire and process the data. The instrument should offer auto calibration for the following functions:

• Energy scale linearity

• Transmission function

• X-ray spot size calibration

• Ion gun modes tuning and alignment

• Flood gun alignment

• Electron lens optimisation

• Detector optimisation

Automation: The supplied system must include automated features for sample handling, vacuum control and data acquisition allow a spectrometer to be operated in a multi user environment along with other analytical techniques. To meet these requirements the spectrometer should include the following functions.

• Automated sample transfer.

• Automated vacuum control and gas handling.

• Automatic sample height adjustment.

• Automatic data acquire for wide scan survey spectroscopy and high-resolution narrow scan data.

• Automatic data interpretation and quantification

• Automatic data reporting

• Automatic calibration.

System Form and Footprint: The overall footprint of the entire system (excluding chiller and data system) should be less than 1.80 m x 1.25 m. Electronic boards should designed for modular replacement and therefore be easily removed. All electronic boards should be mounted in fan-cooled, shielded enclosures.

To reduce mains noise interference all electronics boards should be powered from DC 24V / 48V power supplies. The bake-out shielding should be integrated into the system housing without the need for additional baking tents or panels. All cables connected to the main body of the system should be designed to withstand the bake out temperatures (>120ºC) allowing them to remain in place during the system bake out.

Ultra-Violet Photoelectron Spectroscopy: A gas discharge source capable of operating with noble gases must be supplied. All differential pumping, gas handling and source operation must be automated, so that it can be operated from the data system, and used within complex experiments such as depth profiles. The standard operation must be configured for use with helium, with the data system able to automatically start the lamp and operate in He(I) or He(II) modes. UPS performance must be demonstrated on a clean silver sample. Under identical spectroscopic conditions, a count rate of ≥ 2.0 Mcps must be demonstrated when the resolution at the Fermi edge is < 120 meV. Resolution is defined as the energy difference between the points at which the intensity is 20% and 80% of the maximum value below the Fermi level.

Installation and Warranty: The system shall include all installation labor and materials. The vendor will supply the facilities requirements prior to the system delivery to ensure that all electrical, HVAC, and other needs are met prior to personnel showing up to install the system. A warranty covering all parts and labor for at least 12 months must also be included.

Service Contract: A service contract that allows immediate response to issues by contacting the system must be included. The terms of this contract should cover basic parts servicing, software and troubleshooting with an option for on-site servicing for at least a 12 month period.

Supply of a Complete Monochromated XPS Instrument.