Strain splitting of1syellow orthoexciton of epitaxial orthorhombicCu2Ofilms on MgO [110]

Abstract

We investigated the optical properties of epitaxial orthorhomic cuprous oxide films grown on MgO ͓110͔. Absorption measurements show clear excitonic peaks up to nϭ5p. Photoluminescence at 2 K shows several sharp emission peaks in the vicinity of 610 nm associated with a splitting of various 1s orthoexciton energy levels. The evolution of the peaks with temperature indicates that three peaks at higher energy are due to direct recombination of 1s yellow orthoexcitons and three corresponding peaks at lower energy are their phonon replicas. The symmetry of each level is identified by the polarization properties of their photoluminescence emissions. The observed splitting of the energy levels is used to calculate the coherency strain based on an earlier-parametrized theory for the level splitting by Waters et al. based on the known symmetry of the electronic states. This predicted strain is compared with that determined by x-ray diffraction measurements of the measured lattice parameters.

Photoluminescence spectra and biaxial stress effects of yellow 1S excitons in Cu2O thin films recrystallized epitaxially between paired MgO plates

“…In the previous studies [3,4], uniaxial stresses have been only investigated. However, we have to consider two kinds of biaxial stresses illustrated in Fig.…”

“…4(a) and (b). Stress dependences of the energy splittings on the D 4h and C 2v symmetries can be analyzed by the respective effective Hamiltonians that take into account deformation on the valence and conduction bands as perturbations [3,4]. By using such analyses, we estimate the strengths of the stresses in the Cu 2 O thin film from the splitting energies observed in Fig.…”

“…They derived an effective Hamiltonian including stress effects and studied stress dependence of the state splitting in the yellow 1S ortho excitons. A revised theory was developed by Sunet al They took into consideration the symmetries of the exciton-basis functions in the orthorhombic structure due to the deformation by the stresses [4].…”

Decay and coherence of two-photon excited yellow orthoexcitons inCu2O

“…The deviations observed at the onset of the emission are due to replica-like structures which presumably appear due to a small strain induced by the mounting of the sample on the cold finger of the cryostat. 24 In the final fitting of the data this was taken into account by adding a scaled down replica of the spectrum, shifted by about 3 meV to Eq. (1).…”

Наноразмерные пленки Cu-=SUB=-2-=/SUB=-O: формирование методом ВЧ-магнетронного распыления, исследование структурных и оптических свойств

“…Это относится, в частности, к кремнию, который потенци-ально может быть использован для изготовления двух-переходного солнечного элемента на основе Cu 2 O/Si. Отметим, что если объемные кристаллы Cu 2 O являются кубическими (группа симметрии O 4 h ), то пленки могут быть и орторомбическими [7].…”