The NaYF4：Yb,Er nanocrystals were synthesized via the thermal decomposition ot metal oleate precursors, lhe nanocrys- tals in hexagonal structure were highly uniform and in size of 25 nm. The bright upconversion luminescence was observed under the excitation of 980 nm laser and the upeonversion emission spectra were investigated at different pump powers. The emission intensity ratio of red light to green light linearly increased with pump power increasing. This result indicated that there existed a large threshold power of saturation pump for the first excitation state in NaYFa：Yb,Er nanocrystals comparing to that in bulk material.
The Eu^3＋/Ag co-doped rare earth disilicate Y2Si2O7 microcrystal was synthesized by sol-gel method. Through controlling the thermal treatment process of YzSi2OT：EU3＋/Ag precursor, various phases （amorphous, α, β, γ, δ） were prepared. White light emis- sion was observed under UV light excitation in the samples heavily doped with Ag. The white light was realized by combining the intense red emission of Eu3＋, the green emission attributed to the very small molecule-like, non-plasmonic Ag particles （ML-Ag-particles）, and the blue emission due to Ag ions. Results demonstrated that Eu3＋/Ag co-doped Y2Si207 microcrystal could be potentially applied as white light emission phosphors for UV LED chips.
Raman and luminescence studies on the phase transition of europium orthoniobates （EuNbO4） under high pressure were performed. The pressure dependent Raman spectra revealed that an irreversible phase transition from monoclinic phase to M＇-fergusonite phase of EuNbO4 occurred at 7.3 GPa, and the two phases coexisted over a pressure range from 7.3 to 13.7 GPa. An obvious discontinuity on luminescence intensity ratio between 5D0 →7F2 and 5D0→7F1 transitions was observed with increasing pressure, in- dicating also that a phase transition occurred at 7.3 GPa, which was in agreement with the high pressure Raman spectra data. Mean- while, the Raman and luminescence spectra in the temperature range of 20--300 K showed the structure stability at low temperatures.
The temperature dependence of the photoluminescence（PL） from Mn S/Zn S core–shell quantum dots is investigated in a temperature range of 8 K–300 K. The orange emission from the ^4T1→^6A1transition of Mn^2＋ions and the blue emission related to the trapped surface state are observed in the Mn S/Zn S core–shell quantum dots. As the temperature increases, the orange emission is shifted toward a shorter wavelength while the blue emission is shifted towards the longer wavelength. Both the orange and blue emissions reduce their intensities with the increase of temperature but the blue emission is quenched faster. The temperature-dependent luminescence intensities of the two emissions are well explained by the thermal quenching theory.
Yb^3＋ and Er^3＋ co-doped BaBi4Ti4015 （BBT） ceramic samples showed brighter up-conversion photoluminescence （UC-PL） under excitation of 980 nm. The monotonous increase of fluorescence intensity ratio （FIR） from 525 to 550 nm with temperature showed that this material could be used for temperature sensing with the maximum sensitivity to be 0.0046 KI and the energy dif- ference was 700 cm-1. Moreover, the sudden change of red and green emissions around 400 ℃might imply a phase transition. With increasing pressure up to 4 GPa, the PL intensity decreased but was still strong enough. These results illustrated the wide applications of BBT in high temperature and high pressure conditions.
It has already been found that the round shape of holes can be changed into hexagonal shape during plasma etching processes.This work aims to understand the mechanism behind such a shape change using particle simulation method.The distribution of electric field produced by electrons was calculated for different heights from the mask surface.It is found that the field strength reaches its maximum around a hole edge and becomes the weakest between two holes. The field strength is weakened as moving away from the surface.The spatial distribution of this electric field shows obvious hexagonal shape around a hole edge at some distances from the surface. This charging distribution then affects the trajectories of ions that fall on a mask surface so that the round hole edge is etched to become a hexagonal hole edge.The changing of this hole shape will again alter the spatial distribution of electric field to enhance the charging effect dynamically.
Thin oxidized copper films in various thickness values are deposited onto quartz glass substrates by electron beam evaporation. The ellipsometry parameters and transmittance in a wavelength range of 300 nm-1000 nm are collected by a spectroscopic ellipsometer and a spectrophotometer respectively. The effective thickness and optical constants, i.e., refractive index n and extinction coefficient k, are accurately determined by using newly developed ellipsometry combined with transmittance iteration method. It is found that the effective thickness determined by this method is close to the physical thickness and has obvious difference from the mass thickness for very thin film due to variable density of film. Furthermore, the thickness dependence of optical constants of thin oxidized Cu films is analyzed.
