Optical Properties of Epitaxial Chromium Sesquioxide Films
EMSL Project ID
1751
Abstract
The aim is to measure the optical properties of epitaxial films of Cr2O3 particularly the sharp 2E excitons in the near infrared. These should act as a sensitive probe of film strains and purity as well as providing a way to measure magnetic couplings in a multilayer configuration. The first step will be to see how thin a layer can be detected since these excitons have a low oscillator strength. We are developing a spectrometer to measure low absorption but it will also depend on the linewidth of the excitons which is a function of the inhomogeneity of lattice strains. I propose films of 2000A and 200A on sapphire 0001. It would be best to use substrates polished on both surfaces but since we will probably need to add diffusers in the optical path it would be also be of great interest for us to have films on substrates that are polished on one side. If we are able to measure exciton spectra for very thin films of the order of one or two monolayers there will be interesting experiments to do (e.g. effect of the breakdown of k-selection, structure induced by superlattices). Also of interest would be exchange coupling across the interface with a ferromagnet, (e.g. CoPt as a function of the orientation of the ferromagnetic moment).Summary: concentrate on the detectability of the weak exciton absortion, then expand results. The most important step in growth conditions will be to minimize inhomogeneous strains - if the dislocations can be localized near the interface with the substrate that would be very desirable and there is also the question of the use of buffer layers to reduce strain. Gallium oxide Ga2O3 is structurally well matched to Cr2O3 but I imagine that this substrate material is hard to obtain. Would it be possible or desirable to grow a Ga2O3 buffer layer on the sapphire substrate and then grow Cr2O3 on the Ga2O3?
Project Details
Project type
Exploratory Research
Start Date
2000-01-17
End Date
2001-09-01
Status
Closed
Released Data Link
Team
Principal Investigator