Photoluminescence properties of Eu-doped ZnO grown by radio frequency magnetron sputtering technique are
investigated. Under the UV light excitation, Eu3+-related red emissions are observed, which reveals that an energy
transfer exists from the ZnO host to the Eu3+ ions. By carrying out temperature dependent behavior of the time-resolved
photoluminescence, we confirm the lifetime is likely associated with transitions including both temperature insensitive
radiative decay and temperature sensitive non-radiative decay mechanisms. So a rate-equation model is used to analyze
the population dynamics and the transitions between different states and decay constants for the relaxation processes are
obtained. The study suggests that the energy transfer efficiency from the ZnO host to the Eu3+ ions is reduced above 80
In this work, a textured surface structure of Si substrate has been prepared using pyramid structure ZnO glass as
mask, and the structure of textured surface and reflection characteristics of Si substrate have been analyzed by scanning
electron microscope (SEM) and reflectivity spectra. The results show that U-shaped structure is formed on the surface of
photoresist after the incidence of ultraviolet light, and it is caused by the different decrement of light intensity in the ZnO
glass Mask Blank. The U-shaped structure which is same with the photoresist appears at the surface of Si substrate after
reactive ion etching (RIE) process, and the size of U-shaped structure is in the range of 0.5-1.5 μm. Needle-like
morphology caused by the RIE process appears on the U-shaped structure. The reflectivity of the U-shaped Si surface is
decreased by the needle-like morphology, and it is protected by the U-shaped structure. The textured structure etched at
different pressure is further investigated, and the results suggest that the reflectance of the sample reduces firstly and then
increases with the decrease of pressure, and a minimal average reflectance is obtained at 0.8 Pa. The ion damage of Si
surface is reduced in the second texturing process, which is useful for film deposition. The results suggest that low
reflectance and textured surface of Si substrate can be obtained by ZnO glass mask blank with natural pyramid structure,
which is meaningful for light trapping in solar cells.
The Si-rich SiNx:H films have been prepared by helicon wave plasma-enhanced chemical vapor deposition (HWP-CVD) technique. Parts of the samples have been post-annealed at 800 °C in the H2, FG (10%H2 in N2), and N2 ambient, respectively. Fourier transform infrared spectroscopy (FTIR) and the optical absorption spectroscopy have been used to investigate the influence of different annealing environment on the structural and optical properties of the films. After the thermal annealing process, there is a significant increase of Si-N bonding density. Meanwhile, the band related to hydrogen (N-H and Si-H) decreased which indicates that the hydrogen is effused out of the films during the annealing treatment. The Si-sH stretching vibrations can be divided into three components by Gaussian distribution; the Si-H absorption band at different wave numbers corresponds to different configurations. The changes of the three peaks contributions decreased indicate that the configurations of the Si-H stretching vibrations band occurs restructuring in the different annealing environments. Furthermore, the investigation of the optical absorption spectroscopy suggests that the band gap Eg decreased after the thermal annealing process. The decreased optical gap should be related to the loss of hydrogen and the slightly increase in the mean size of silicon nanoparticles, which is in good agreement with that of the hydrogen bonding structure.
Protocrystalline silicon/amorphous SiC multilayer films were fabricated by helicon wave plasma enhanced chemical vapour deposition (HW-PECVD). Atom force microscopy, Raman scattering and optical absorption measurements were used to analyze the microstructure and optical properties of the multilayer films. Experiment analyses reveal that through inserting transient a-SiC layer into film depositing process, well-controlled pc-Si:H films have been obtained in the growth condition of the μc-Si:H. The optical gap is observed being tuned from 2.15 to 2.43 eV by varying single pc-Si:H layer thickness. Such multilayer structure should have potential application in constructing high efficiency and stable Si-based solar cells.
Effect of Al-N codoping ratio on the conducting and optical properties of ZnO films deposited by helicon wave plasma
assisted radio frequency magnetron sputtering under various N2 gas flow is investigated. Hall measurements show that p-type
ZnO thin films have been achieved with proper N2 flow rate. X-ray diffraction patterns indicate that all the films are
highly c-axis oriented. Room temperature photoluminescence spectra show a strong near-band-edge emission. With
increasing N doping, the intensity of the emission behaves an increased and then decreased trend while the full width at
half maximum is narrowed and then widened. In addition, photoluminescence spectrum at 77 K in the p-type ZnO film
with the highest hole concentration show a much stronger peak near 3.32 eV (due to N related neutral acceptor bound
excitons), than at 3.36 eV (neutral donor bound excitons), and the acceptor energy level is estimated to be 186 meV.