Imprint lithography of pyramidal photonic pillars using hydrazine etching

An inexpensive method to produce a pyramidal-type 2D photonic structures in the silicon substrate was proposed. The method is based on the combination of imprint lithography and wet Si1 0 0 etching in water solution of hydrazine, which etches 1 1 1 faces much more slowly than others. Thermally grown SiO₂ mask for the hydrazine etching was used, because single Al mask cannot be well bonded to the substrate and tends to peel during the etching. It was revealed that transmittance in the infrared spectrum region of the patterned silicon decreases by about five times compared with that of flat silicon substrate and this decrease is almost independent of the angle of the incident beam. In the infrared region, decrease of transmittance of the patterned samples is directly proportional to the wave number. The shape of formed pyramids has strong influence on the transmittance. Decrease of the transmittance is much more rapid and larger in the case of sharpless pillars.     

电致发光色纯性增强的硅基有机微腔

报道了硅基有机微腔的电致发光（EL）.该微腔由上半透明金属膜、中心有源多层膜和多孔硅分布Bragg反射镜（PS DBR）组成.半透明金属膜由Ag（２０nm）构成，充当发光器件的负电极和微腔的上反射镜.有源多层膜由Al (1 nm) / LiF(05 nm) /Alq3/Alq3:DCJTB/NPB/CuPc/ITO/SiO2组成，其中的Al/LiF为电子注入层，ITO为正电极，SiO2为使正、负电极电隔离的介质层.该PS DBR是采用设备简单、成本低廉且非常省时的电化学腐蚀法用单晶Si来制备的；该PS 关键词： 电化学腐蚀 电致发光 窄峰发射 硅基有机微腔     

High-density plasma etching of indium-zinc oxide films in Ar/Cl2 and Ar/CH4/H2 chemistries

The dry etching characteristics of transparent and conductive indium-zinc oxide (IZO) films have been investigated using an inductively coupled high-density plasma. While the Cl₂-based plasma mixture showed little enhancement over physical sputtering in a pure argon atmosphere, the CH₄/H₂/Ar chemistry produced an increase of the IZO etch rate. On the other hand, the surface morphology of IZO films after etching in Ar and Ar/Cl₂ discharges is smooth, whereas that after etching in CH₄/H₂/Ar presents particle-like features resulting from the preferential desorption of In- and O-containing products. Etching in CH₄/H₂/Ar also produces formation of a Zn-rich surface layer, whose thickness (∼40 nm) is well-above the expected range of incident ions in the material (∼1 nm). Such alteration of the IZO layer after etching in CH₄/H₂/Ar plasmas is expected to have a significant impact on the transparent electrode properties in optoelectronic device fabrication.     

Microstructure effect on microtopography of chemically etched α + β Ti alloys

Microstructure effect on chemical etching behavior of the annealed Ti-6Al-4V and Ti-3Al-2.5V titanium (Ti) alloys was compared with that of unalloyed commercially pure titanium. The microstructural evolution of structure phases after annealing the titanium and its alloys at temperature near and above β transus and followed by furnace cooling to room temperature was studied using optical microscope, scanning electron microscope and X-ray diffraction techniques. The microstructure study illustrates that the heat treatment enhanced partitioning effect allows extensive formation of hemispherical and near spherical pits roughened surface to be readily acquired by chemically etching the annealed α + β titanium alloys. The kinetics of the chemical etching reaction process show a linear dependence on time. The annealed α + β titanium alloys that exhibit relatively lower weight loss and thickness reduction rate illustrate less chemical activity than the annealed unalloyed titanium.     

Microstructure array on Si and SiOx generated by micro-contact printing, wet chemical etching and reactive ion etching

A method, combining micro-contact printing (μCP), wet chemical etching and reactive ion etching (RIE), is reported to fabricate microstructures on Si and SiOx. Positive and negative structures were generated based on different stamps used for μCP. The reproducibility of the obtained microstructures shows the methodology reported herein could be useful in Micro-Electro-Mechanical Systems (MEMS), optical and biological sensing applications.     

Angular response characteristic of pyramid shape fast neutron dosimeter using CR-39 films

CR-39 is a highly sensitive etched track detector for neutron monitoring and dosimetry applications but its dose equivalent response is strongly direction dependent with respect to the incident neutrons. This is considered to be a major drawback for their use. In the present study, an attempt has been made to develop a pyramid shaped dosimeter, which consists of polyethylene material of thickness 1 mm with the provision to hold three CR-39 films at an angle of 35° to each other. The response of CR-39 in this configuration under optimum electrochemical etching at elevated temperature have been found nearly angular independent and therefore the dosimeter can be used for neutron monitoring, i.e. personnel as well as area monitoring.     

Fabricating blazing grating on NGD by photochemical etching

This paper tries to introduce the reader to the method of using photochemical re-action to copy holographic optical elements(HOEs)in relief.The holographic blazing gratingso copied is groove depth adjustable phase modulability enlarged through copying and 3.3times the diffraction efficiency(DE)of the original grating.It is expected that the newmethod will lead to the mass production of the light-weight HOEs at low cost.     

Use of CF3,Br/Al,discharges for reactive ion etching of III-V semiconductors

The reactive ion etching of GaAs, InP, InGaAs, and InAlAs in CF₃Br/Ar discharges was investigated as a function of both plasma power density (0.56-1.3 W - cm^–2) and total pressure (10-40 mTorr) The etch rate of GaAs in 19CF₃Br:1Ar discharges at 10 m Torr increases linearly with power density, from 600 Å min^–1 at 0.56 W · cm^–2, to 1550 Å · min at 1.3 W · cm^–2. The in-based materials show linear increases in etch rates only for power densities above – 1.0 W · cm^–2. These etch rates are comparable to those obtained with CCI₂F₂:O₂ mixtures under the same conditions. Smooth surface morphologies and vertical sidewalls are obtained over a wide range of plasma parameters. Reductions in the near-surface carrier concentration in n-type GaAs are evident for etching with power densities of >0.8 W cm^–2, due to the introduction of deep level trapping centers. At 1.3 W· cm^–2, the Schottky barrier height of TiPtAu contacts on GaAs is reduced from 0.74 to 0.53 eV as a result of this damage, and the photoluminescent intensity from the material is degraded. Alter RIE, we detect the presence of both F and Br on the surface of all of the semiconductors. This contamination is worse than with CCl₂F₂-based mixtures. High-power etching with CF₃Br/Ar together with Al-containing electrodes can lead to the presence of a substantial layer of aluminum oxide on the samples if the moisture content in the reactor is appreciable.     

Large-area microwave and radiofrequency plasma etching of polymers

We have investigated O₂/CF₄ plasma etching of five commercial polymers: polyimide, polyamide, polyethylene terephthalate, polycarbonate and cured epoxy resin. A new large-area microwave plasma apparatus has been used in this work, but the same apparatus can also be used as a capacitively coupled radiofrequency (13.56 MHz) discharge reactor. The effect of operating parameters such as pressure, etchant gas composition, excitation frequency and sample temperature upon etch kinetics has been examined. We have observed distinct maxima in the etch rate as functions of pressure and CF₄ concentration. Activation, energies evaluated from the Arrhenius plots fall in the range 0.04-0.2 eV, in agreement with data in the literature. Dry etch susceptibility of a given polymer correlates strongly with the degree of unsaturation in the polymer's structure     

Hybrid electron cyclotron resonance-radio-frequency plasma etching of III–V semiconductors in Cl2-based discharges. Part I: GaAs and related compounds

A systematic study has been performed of the dry etching characteristics of GaAs, Al_0.3Ga_0.7As, and GaSb in chlorine-based electron cyclotron resonance (ECR) discharges. The gas mixtures investigated were CCl₂F₂/O₂, CHCl₂F/O₂, and PCl₃. The etching rates of all three materials increase rapidly with applied RF power, while the addition of the microwave power at moderate levels (150 W) increases the etch rates by 20–80%. In the microwave discharges, the etch rates decrease with increasing pressure, but at 1 m Torr it is possible to obtain usable rates for self-bias voltages 100 V. Of the Freon-based mixtures, CHCl₂F provides the least degradation of optical (photoluminescence) and electrical (diode ideality factors and Schottky barrier heights) properties of GaAs as a result of dry etching. Smooth surface morphologies are obtained on all three materials provided the microwave power is limited to 200 W. Above this power, there is surface roughening evident with all of the gas mixtures investigated.