Kratos AXIS Nova - Applications

Surface coatings and thin films are of great commercial importance in many industries and are used to enhance or provide required properties to bulk materials specific to their applications. Thin films can range from tens of Angstroms to several microns in thickness, making XPS an idea technique for their characterisation. In recent decades, rapid development in computational and theoretical tools for fabricating, simulating, and characterizing thin film material systems has been made. Combinatorial approaches have been widely used to discover new material phases allowing rapid exploration of compositional and structural properties in complex systems. The AXIS Nova, with its large 110 mm diameter sample platen and automated sample handling is ideally suited to this approach of novel materials discovery. Group array analysis functionality of the ESCApe software allows acquisition, processing and reporting of large matrices of data with relative ease. The strengths of this type of analysis are demonstrated in application note MO455, which details the characterisation of a ternary shape memory alloy, NiTiCo, deposited across a 3 inch silicon wafer.

The critical properties of thin films also extend to their composition as a function of distance from the surface. The ability to engineer the electronic and optical properties of thin films and grow multiple layers on top of each other (heterostructures) is key to many of their applications. Elemental or chemical state depth profiles can be generated by combining XPS analysis with Ar⁺ ion erosion of the sample. The AXIS Nova is equipped with either a monatomic Ar⁺ ion source or the more versatile Ar_n⁺ gas cluster ion source (GCIS). The use of massive Ar_n⁺ gas cluster ions as the projectile allows successful sputtering of ‘soft’ organic materials. The ability to tailor n, the cluster size, and acceleration energy of the cluster ion allows the partition energy (energy per atom in the cluster ion) to be selected appropriate to the thin film material being sputtered. This is vital for successful depth profiling of complex organic, inorganic or mixed multilayer thin film materials.

Suggested applications notes include:

Polymer materials find ever increasing application in numerous consumer products. Applications range from fields as diverse as organic electronics and food packaging to biomaterials and automotive body panels. The surface properties of these materials are often vital in determining performance of the polymer for its specific application, making XPS an ideal characterisation technique. A fundamental understanding of polymer surfaces is often vital for their intended application. None more so than when polymer components are used for bioengineering and clinical applications where the polymer must exhibit a specific surface chemical behaviour as well as the required bulk properties.

Qualitative information determined from chemical shifts provides the ability to identify the surface functionality of the polymer. XP spectra acquired from a polymer valence band may be used to provide isomeric information, particularly when compared to known standard reference materials.

Furthermore, XPS chemical state imaging using the AXIS Nova can also probe the lateral distribution of these chemistries across the surface. Quantitative analysis of the XPS data then allows concentration of elemental and functional groups to be determined from the outmost surface and, when combined with Ar_n⁺ cluster depth profiling, as a function of depth into the bulk.

Suggested applications notes include:

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