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(a) XRD pattern of a film (sample A) on (111) substrate. The asterisk denotes a forbidden peak originating from substrate that appeared after the film growth. (b) Pole figures for and (311) diffractions showing six poles at and three poles at , respectively. (c) Reciprocal space contour map around diffraction. (d) XRD rocking curves for (0006) diffraction of films (Ref. 13; dotted lines). (e) Laue fringes around (0006) diffraction peak of sample B (samples A and B: solid lines; Ref. 13: dotted line).
Temperature dependence of the absorption spectra for thin films on (sample B; solid lines) and on -sapphire (Ref. 9; dotted lines) substrates. Inset shows a schematic energy diagram representing the exciton absorptions.
(a) Absorption spectrum of a film (sample B) at 20 K (black dotted curve) and its fit (green curve) with a modified Elliott model [Eq. (1)], which are composed of ground-state [ at , red curve] and first-excited-state [ at , blue curve] exciton resonances and exciton continuum (II starting from , violet curve). Values of and represent the exciton binding energy and broadening parameter. (b) Energies of and as well as the broadening parameters plotted as a function of temperature . The determined parameters using Eqs. (2) and (3) are , , , , and , respectively.
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