Discover the new automatic method for combining two crystals into a low-strain interface

May 09 2018

Discover the new automatic low-strain interfaces via lattice matching method [1] in QuantumATK NanoLab (VNL-ATK 2017), developed in a collaboration between the Synopsys QuantumATK team and the Atomic-Scale Materials Design Group at Technical University of Denmark (DTU), lead by Prof. Karsten Wedel Jacobsen. The method combines two crystals into low-strain interfaces, based only on the materials bulk crystalline structure. As the size of electronic devices decreases, interfaces become an increasingly dominant part of the system. Avoiding large strain at the interface is important, as its presence could result in defects and reconstructions, limiting the electronic device performance.

geometric matching 4

How does the low-strain interfaces via lattice matching method work?

The method considers all possible/indicated crystal orientations and surfaces at the same time (by performing a single calculation) as shown in the figure above. The strength of this method is also that it is possible to apply the results obtained for two arbitrary crystals to all interfaces between materials of these crystal structures. 

The matching is based only on the materials bulk crystalline structure, not the atomic structure, so it is a very good starting point for determing stable interfaces between two materials. The chosen most appropriate (lowest-strain) interfaces (with specific crystal orientations and lattice parameters) can afterwards be built using the Interface Builder in NanoLab and optimized while the atomic structure is taken into account. Finally, one can obtain the electronic structure of the optimised interface and calculate (or measure) properties, such as contact resistance and Schottky barrier. 

Agreement with experiments

We have shown that the lowest-strain interface InAs(111)/Al(111), predicted by the lattice matching method, is in agreement with the experimentally measured structure reported in Ref. [2].

Application examples

The crystal matching method is very useful in the cases when we do not have much information about the interfaces. One example is the interface between semiconductor alloys (such as InAs1-xSbx and GaxIn1-xAs) and superconductors (such as Al or NbTinN) [1]. Changing the semiconductor alloy composition (mole fractions) allows for tuning the lattice constant of the semiconductor to obtain perfectly matched/low-strain interfaces between materials. Alloys are commonly used in the fabrication of core-shell nanowires that are promising candidates for applications in quantum computing using Majorana states, photodetectors, photoelectrodes, and thermoelectric devices, etc. It is expected that alloys will be used to design many more future devices.

Relevant resources

Have a look at the tutorial on how to use the low-strain interfaces via lattice matching method, i.e., create an input file and analyse results.

References

[1] L. Jelver, P. M. Larsen, D. Stradi, K. Stokbro and K. W. Jacobsen, "Determination of low-strain interfaces via geometric matching", Phys. Rev. B 96, 085306 (2017).

[2] P. Krogstrup, N. L. B. Ziino, W. Chang, S. M. Albrecht, M. H. Madsen, E. Johnson, J. Nygård, C. M. Marcus, and T. S. Jespersen, "Epitaxy of semiconductor–superconductor nanowires", Nature Materials 14, 400 (2015).  

 

 

 

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