Changes in optical properties of MnAs thin films on GaAs(001) induced by a- to B-phase transition
2008 (English)In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, Vol. 205, no 4, 859-862 p.Article in journal (Refereed) Published
MnAs layers with 45 nm thickness were grown epitaxially on GaAs(001) substrates. Ellipsometry measurements were made in the spectral range 0.045 eV to 6 eV as a function of temperature (between –10 °C and 50 °C) at 70° of incidence. In this way the transition from the hexagonal α-phase to the orthorhombic β-phase could be monitored. Non-zero off-diagonal elements of the Jones matrix for an azimuth of 38° off the  axis of the substrate indicate that the optical functions of MnAs are anisotropic in both phases. The optical conductivity exhibits low-energy interband transitions around 0.3 eV, more clearly seen in the α-phase than in the β-phase. Extrapolation of the optical conductivity to zero frequency confirms that the α-phase is about two times more conducting than the β-phase. A broad structure is observed in the visible range around 3 eV. The α-phase is characterised by an anisotropy induced energy difference of this structure with a maximum at 2.8 eV for the extraordinary index and at 3.15 eV for the ordinary index. This difference vanishes in the β-phase in which anisotropy mainly induces changes in amplitude of the 3 eV structure. The assignment of the structures will be discussed.
Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2008. Vol. 205, no 4, 859-862 p.
IdentifiersURN: urn:nbn:se:liu:diva-42729DOI: 10.1002/pssa.200777782ISI: 000255702600033Local ID: 68441OAI: oai:DiVA.org:liu-42729DiVA: diva2:263586
4th International Conference on Spectroscopic Ellipsometry (ICSE 4), Stockholm, Sweden, 11–15 June 2007