K-Alpha, an exciting new concept in XPS

K-Alpha is an X-ray photoelectron spectrometer (XPS), designed to maximise the throughput and efficiency of the Surface Analysis Laboratory. Many of the repetitive, routine activities have been automated or simplified without compromising the performance or versatility demanded by the XPS expert. Since its launch at the Microscopy and Microanalysis exhibition in Chicago in July 2006, the instrument has proved to be very popular and has attracted a great deal of attention, picking up three awards.

Description

The high-performance K-Alpha is compact and fully integrated. Figure 1 shows the complete instrument, there is no additional electronics rack to add to the configuration, all of the electronics are built into the unit along with the spectrometer. A PC running Windows XP^TM, connected to K-Alpha via a single USB cable, controls all aspects of the instrument. See Figure 1 at the top right =  The new K-Alpha from Thermo Fisher Scientific.

The geometry of all of the analytical components has been given careful consideration in order to optimise performance; their arrangement can be seen in Figure 2. Some of the important features of this arrangement are:

1. The axis of the transfer lens is parallel to the sample surface normal, ensuring maximum collection efficiency.
2. There is always a live view of the analysis position via the patented Reflex Optics and this view is also parallel with the sample normal, providing the best possible conditions for identifying the analysis position with great accuracy.
3. The height setting camera ensures that the sample is in exactly the right position for small area analysis and at the right height for optimum sensitivity.
4. X-rays are delivered from a microfocusing monochromator. This allows the user to define the analysis area and ensures that maximum sensitivity is achieved during small area analysis.
5. The new ion gun will provide depth profiles with excellent depth resolution. It has been designed to deliver a beam of low energy ions into a small spot so that resolution is combined with speed of analysis.
6. The new flood gun is designed in such a way that the user only needs to switch it on when required for the analysis of insulators, no adjustment or optimisation is required
7. Sample illumination is as important as high quality live sample viewing. K-Alpha is equipped with two types of lighting. One is arranged so that the lighting is co-axial with the reflex optics, ideal for samples having a smooth surface. The other light source is off-axis which is ideal for rough samples.

Figure 2 The internal geometry of the analytical components in K-Alpha.

The analysis chamber is precision machined from a single billet of nickel/iron alloy. This provides excellent magnetic shielding and the precision of manufacture minimises the requirement for alignment of the components. It is pumped using a turbo molecular pump, backed by a ‘dry’ scroll pump, and a sublimation pump.

Sample navigation and alignment could not be easier, it is essential that the analyst can define the position and size of the area to be analysed with great confidence. This is facilitated by the unique arrangement of sample illumination and viewing optics.

The instrument is capable of extremely high quality analysis from both insulators and conducting samples:

1. High-resolution, high-sensitivity XPS spectroscopy
2. Small area XPS measurements with a minimum spot size of 30 µm
3. Sputter depth profiling
4. Chemical state mapping

Uniquely amongst XPS instruments, K-Alpha has a set of calibration and alignment standards built into the system. Automatic routines ensure that peak performance is constantly maintained and a calibration log is maintained for traceability purposes.

Auto-analysis

In addition to allowing the analyst full control over the analysis, for suitable samples there is an ‘Auto-analyse’ routine. Using this feature, the analyst simply loads the samples and indicates on the Platter View image the positions at which analysis is required. The instrument will then perform the following steps automatically:

1. Pump the loadlock and transfer the samples
2. Collect a survey spectrum
3. Identify the elements present in the survey spectrum
4. Quantify the spectrum
5. Collect high-resolution spectra from the elements identified
6. Perform a chemical state appraisal of the elements identified
7. Move to the next sample and repeat from 2, above
8. When all samples have been analysed a report is generated
9. Samples returned to loadlock so that K-Alpha can be loaded with a new set of samples.

Conclusion

K-Alpha is a new departure for XPS. Every aspect of the analysis process has been simplified or automated with a view to increasing both the throughput of the laboratory and the reliability of the data produced. It is a high-performance instrument that provides the tool you need to get the job done.

To know more on K-Alpha, click here.