Combinatorial materials screening
Fast materials composition screening
In materials science, one is often faced with the problem of optimizing a materials property by tuning its composition. Traditionally, composition-property relationships are investigated by sequential synthesis of multiple samples that each have a distinct composition, requiring a lot of time and effort.
In recent years COCOON research group has developed an efficient workflow for screening new materials systems. This consist of an efficient way of fabricating graded thin film libraries by means of physical vapor deposition, characterization of the created libraries using different mapping stages and typically followed by (in-situ) annealing of the whole wafer or selected individual samples from the deposited library.
Deposition and characterization of thin film material libraries
In our home-built combinatorial deposition systems, thin films can be deposited with a continuous compositional gradient. In this way, a single deposition results in the availability of a thin film combinatorial library, which is in fact a binary or ternary phase diagram that is printed as a thin film onto a planar substrate. Combining the substrate with a shadow mask, the printed gradient can be divided into smaller individual samples. The composition of each individual sample is close to uniform and a such detailed experiments can be performed either on selected individual samples with a discrete composition or on the fully graded printed substrate.
After deposition of such a thin film combinatorial library, the properties of interest can be evaluated as a function of position within the library, and hence as a function of composition of the deposited material. Through the availability of mapping stages on several characterization tools, our lab is well equipped for this task:
- Compositional analysis by mapping XRF or EDX
- Crystalline structure analysis by mapping XRD
- Morphology by mapping SEM or AFM
- Optical characterization by spectroscopic ellipsometry mapping
- Electrical characterisation by IV/CV and four-point probing
Quite often one is interested on the influence of temperature for the specific alloy system. Therefore either the full graded substrate can undergo a heat treatment under the desired atmosphere, followed by ex-situ characterization of the whole substrate by means of the different mapping tools described above. Or specific selected samples from the graded library can be cut out and undergo a heat treatment in combination with an a specific in-situ measuring technique. Read more about in situ characterization during thermal processing.
Publications:
Devulder, Wouter et al. “Combinatorial Study of Ag-Te Thin Films and Their Application as Cation Supply Layer in CBRAM Cells.” ACS COMBINATORIAL SCIENCE 17, 5 (2015): 334–340. DOI: 10.1021/acscombsci.5b00025