Photoluminescence Studies of ZnO Films Fabricated by Using a Combination of a Hydrothermal Method and Plasma-assisted Molecular Beam Epitaxy Regrowth

다국어 초록 (Multilingual Abstract)

ZnO films were deposited on Si (100) substrates by using a two-step growth process. In the firststep, ZnO nanorods were grown by using the hydrothermal method at 140 C for 5 min. In thesecond step, a ZnO amorphous layer was deposited on the ZnO nanorods by spin-coating. Aftercompletion of the growth process, the films were annealed at 800 C for 10 min, and a ZnO activelayer was deposited on top of the amorphous layer by using plasma-assisted molecular beam epitaxy.
Further, temperature-dependent photoluminescence (PL) measurement were conducted to study theoptical properties of the prepared films. In the low-temperature PL spectra, emission peaks in thenear-band-edge region were observed at 3.370, 3.362, 3.347, 3.329, 3.317, 3.288, 3.263, 3.219, 3.191,and 3.116 eV; these peaks were attributed to free excitons, neutral donor bound excitons, neutralacceptor donor excitons, two electron satellites, and donor acceptor pairs, respectively. Thesepeaks were red-shifted, and their intensity decreased with increasing temperature. The bindingenergy of the donor was calculated as 43.1 meV by using the Haynes rule. Further, the valueand , factors in the equation for the energy of localized excitons of donors and acceptors wereobtained as 0.73 meV and 750 K, respectively, by fitting the free exciton (FX) peak according toVarshni’s equation. The full width at half-maximum of PL for the films was about 95.1 meV atroom temperature; moreover, the following values were obtained for the films by using theoreticalequations: the background impurity broadening, I0 = 62 meV, the parameter describing exciton-LO phonon interaction, ΙLO = 80 meV, LO phonon energy, ~!LO = 72 meV, and, the couplingstrength of an exciton-acoustic phonon interaction,ph = 0.087 meV/K Furthermore, the activationenergy was about 60.1 meV.

다국어 초록 (Multilingual Abstract)

ZnO films were deposited on Si (100) substrates by using a two-step growth process. In the firststep, ZnO nanorods were grown by using the hydrothermal method at 140 C for 5 min. In thesecond step, a ZnO amorphous layer was deposited on the ZnO nanorods by spin-coating. Aftercompletion of the growth process, the films were annealed at 800 C for 10 min, and a ZnO activelayer was deposited on top of the amorphous layer by using plasma-assisted molecular beam epitaxy.
Further, temperature-dependent photoluminescence (PL) measurement were conducted to study theoptical properties of the prepared films. In the low-temperature PL spectra, emission peaks in thenear-band-edge region were observed at 3.370, 3.362, 3.347, 3.329, 3.317, 3.288, 3.263, 3.219, 3.191,and 3.116 eV; these peaks were attributed to free excitons, neutral donor bound excitons, neutralacceptor donor excitons, two electron satellites, and donor acceptor pairs, respectively. Thesepeaks were red-shifted, and their intensity decreased with increasing temperature. The bindingenergy of the donor was calculated as 43.1 meV by using the Haynes rule. Further, the valueand , factors in the equation for the energy of localized excitons of donors and acceptors wereobtained as 0.73 meV and 750 K, respectively, by fitting the free exciton (FX) peak according toVarshni’s equation. The full width at half-maximum of PL for the films was about 95.1 meV atroom temperature; moreover, the following values were obtained for the films by using theoreticalequations: the background impurity broadening, I0 = 62 meV, the parameter describing exciton-LO phonon interaction, ILO = 80 meV, LO phonon energy, ~!LO = 72 meV, and, the couplingstrength of an exciton-acoustic phonon interaction,ph = 0.087 meV/K Furthermore, the activationenergy was about 60.1 meV.

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