Measuring Low Dimensional Schottky Barriers of Rare Earth Silicide-Silicon Interfaces

The focus of this study is the measurement of low dimensional Schottky barrier heights of metal silicide-silicon interfaces and the challenges of current-voltage (I/V) curve interpretation. Engineering the Schottky barrier to exploit the spin and charge of an electron and manipulate it through silicon requires careful control of the interface structure between the metal and the silicon substrate. In doing this the advantages of both magnetic materials and semiconductors can be combined in spintronics.

Current-voltage characteristics have been taken using contact probe techniques, and from these the Schottky barrier properties have been extracted using standard Schottky barrier models. Several ways of extracting the Schottky barrier height have been explored
concluding with the development of a new fitting program which utilises the whole data set and includes additional factors such as image force lowering and an oxide tunnel barrier. Nickel silicide thin films on silicon(111) have been used as a test system to develop the analysis for I/V measurements.

Rare earth silicides were grown on silicon(111) and silicon(001) forming ordered interface structures, which have been extensively studied in the group at York. The rare earth silicides on silicon have attractive low Schottky barrier heights (0.4 eV). Erbium silicide
islands of the order of 500 nm diameter were grown on silicon (111) and erbium silicide nanowires were grown on silicon (001) 4◦ offcut. Using an Omicron Nanoprobe contacts
were made with the nano structures enabling the measurement of the electrical properties of the silicide and the Schottky barrier between the silicide island and the substrate.

A new growth study of manganese on erbium silicide on silicon(111) is presented as a possible way to engineer the Schottky barrier between a ferromagnetic material and
silicon. Preliminary results of the I/V measurement are presented and the additional complication of an oxide layer highlighted. If engineering the Schottky barrier in this way is successful, the realisation of spintronics maybe a step closer.