Etching Angle Research Articles

The growth of crossover structures of laser ablated YBCO or BSCCO thin films with different insulating materials

Trilayers of YBCO or BSCCO (2212) on SrTiO3 substrates were fabricated by laser ablation with different insulating materials like SrTiO3, CeO2 and MgO as intermediate layers. The growth of trilayer systems was investigated by SEM, RBS, XRD and electrical measurements for both in situ and ex situ ablation processes. For trilayers YBCO-SrTiO3-YBCO we found, at optimal conditions for the SrTiO3 growth chi min of 5% for in situ and 9% for ex situ fabricated samples. The TCO of both YBCO layers was higher than 89 K. The trilayers based on BSCCO showed a chi min of 45% and a TCO approximately=35 K. For crossover structures all three layers were patterned by ion beam etching. To solve the problem of growth of a top YBCO layer on a patterned bottom bilayer of YBCO and SrTiO3, the etching angles of the bottom system were modified by special choice of the parameters of the ion beam etching process. So we found TCO values of more than 89 K and a critical current density of jc (77 K)>105 A cm-2 for the top YBCO layer. The resistances of the SrTiO3 and CeO2 insulating films showed semiconducting behaviour and reached 107 Omega cm and 106 Omega cm, respectively. With the described technology the first YBCO thin film coils were fabricated.

Etching Behavior of Fission Fragment Tracks in Synthetic Quartz and Its Application to Neutron Detection

The etching behavior of fission fragment tracks in synthetic quartz plates concerning to +x, y and z planes was studied using NaOH solution as an etchant. Systematic experiments gave an optimum etching condition of 65% NaOH at 150°C suitable for track detection. Under this etching condition, following several properties were studied; the bulk etching rate, the etched track opening shape and its growth rate, the critical angle of track etching, and the irradiation effect of low LET radiation. All of three different cuts were demonstrated to be useful for plates as fission track detectors. An application to neutron detection was studied for the +x-plane of an x-cut plate. The detection sensitivity of the plane in close contact with a Th-radiator was 2.7×10−6 tracks/fluence for 14 MeV neutrons.

Etching Behavior of Fission Fragment Tracks in Synthetic Quartz and Its Application to Neutron Detection.

The etching behavior of fission fragment tracks in synthetic quartz plates concerning to +x, y and z planes was studied using NaOH solution as an etchant. Systematic experiments gave an optimum etching condition of 65% NaOH at 150°C suitable for track detection. Under this etching condition, following several properties were studied; the bulk etching rate, the etched track opening shape and its growth rate, the critical angle of track etching, and the irradiation effect of low LET radiation. All of three different cuts were demonstrated to be useful for plates as fission track detectors. An application to neutron detection was studied for the +x-plane of an x-cut plate. The detection sensitivity of the plane in close contact with a Th-radiator was 2.7×10−6 tracks/fluence for 14 MeV neutrons.

Low energy ion modification of thin films

This paper presents some of the uses of broad beams of low energy (< 500 eV) ions for modifying surfaces and thin films physically and chemically. We discuss bombardment-induced variation in the index of refraction of thin films with applications in integrated optics, variation of etch profiles using biased masks, and generation of heavy ion beams. ZrO x F y films were made by depositing ZrF 4 with a coincident oxygen ion flux. The index of refraction can be increased by 0.12 without increasing waveguide losses beyond 8 dB/cm, with ion energy being the primary determinant of index variation, and ion flux having the largest effect on losses. The second modification technique focuses on the use of local fields at the substrate to alter the path of incoming ions. Using voltage biased metal masks, we have been able to alter the sputter-etch profile of thin films. The experimental results are compared with calculated etch profiles; changes in the etch angle of up to 20° have been observed. We describe preliminary work on the generation and use of C 60 and metal ions as bombarding particles.

Etch Profile Development in Spray Etching Processes

An investigation to develop a better understanding of the fundamentals behind the operation of spray‐etching processes revealed several interesting phenomena that explain some of the difficulties encountered during operation. Higher spray pressures are required for the top sides than for the bottom sides in order to achieve equal amounts of etching on each side of the boards being processed. This is due to additional mass‐transfer limitations that are created when puddles of liquid collect on the top side of the boards. Another phenomenon observed was an increase in the etch angle, resulting in more vertical sidewalls, as the extent of etch undercut increases. Based on these experimental observations, a dynamic model for the spray‐etching process is developed.

Dry Etching of Indium Phosphide

ABSTRACTIndium Phosphide (InP) based multilayer structures are becoming increasingly important in the semiconductor industry with optoelectronic applications being the main growth area. Mesa type structures with finely controlled width and etch angle, often form the building blocks for many of these photonic devices. Traditional wet etching techniques have often proved to be inadequate for the required anisotropie removal of material. This paper presents the results of etching semi-insulating InP (100) using a combination of an Argon ion beam and a reactive gas, CCl2F2 (Freon 12). It was found that the etch rate was enhanced by increasing the ion energy and by the addition of CCl2F2. Auger electron spectroscopy revealed that the increased etch rate was accompanied by an increase in the surface indium concentration and at low ion beam energies carbon build-up retarded the etch rate. The optimum etch angle to fabricate 3μm waveguides was found to be 22° to the surface normal, however Schottky contacts to these structures were unsuccessful.

Low-threshold InGaAs/GaAs strained-layer surface emitting lasers with two 45 degrees angle etched total reflection mirrors

An InGaAs/GaAs strained-layer IPSEL (in-plane surface emitting laser) structure with two 45 degrees dry-etched mirrors and a highly reflecting bottom quarter-wavelength stack is reported. It has a record low continuous-wave (CW) threshold current at 10 mA. The laser structure consists of a conventional double-heterostructure single-quantum-well (80-AA In/sub 0.2/Ga/sub 0.8/As/100-AA GaAs) laser structure on top of a quarter-wave stack (25 pairs of 695-AA GaAs/830-AA AlAs), which serves as a distributed Bragg reflector ( approximately 99%) after 45 degrees angle etching.

Image formation in track-etch detectors—II. The space-dependent transfer function in thin detectors

A model of the imaging process in autoradiography with solid state nuclear track detectors has been employed to determine the space-dependent transfer function (optical density vs distance). The dependence of line-, plane- and edge-spread functions on the particle range, critical angle of etching, removed detector layer, track size and track density for thin detector foils was studied. Asymmetry of the edge-spread function at high exposure is revealed and explained.

Image formation in track-etch detectors—III. The space-dependent transfer function in thick detectors

Abstract A model of the imaging process in autoradiography with solid state nuclear track detectors has been employed to determine the space-dependent transfer function (optical density vs distance). The dependence of line-, plane- and edge-spread functions on the particle range, critical angle of etching, removed detector layer, track size and track density for thin detector foils was studied. Asymmetry of the edge-spread function at high exposure is revealed and explained.

Electrochemical etching of CR-39 detectors irradiated with alpha particles

Abstract The diameters of electrochemically etched alpha particle tracks of different energies were investigated as a function of etching and pre-etching time and angle of incidence. The measurements were carried out with Pershore Mouldings and MA-ND CR-39 nuclear track detectors. The mean track etching rate, at different particle energies, was determined as a function of pre-etching time. From the measurements of track diameters it is shown that electrochemical etching combined with chemical pre-etching is suitable for determining the energy and/or the incidence angle of alpha particles.

OMVPE growth of 660 nm AIGaAs double heterojunction LEDs

Organometallic vapor phase epitaxial (OMVPE) growth of 660 nm AIGaAs double heterojunction (DH) light emitting diodes (LEDs) is reported. Photoluminescent (PL) intensities from bare active layers are measured as a function of growth temperature, doping (undoped, Se and Mg) and emission wavelength. Maximum PL intensity results at 800° C growth temperature. PL intensity is nearly constant from 810 to 700 nm and then drops by one-half at 660 nm. DH LEDs are grown with a 660 nm Mg-doped active layer sandwiched between 90% AIGaAs cladding layers. Angle etching is used to study the active-cladding layer interface. Electroluminescentphotometric efficiency is measured as a function of active layer acceptor concentration, active layer width and interface grading. Our best encapsulated lamp shows a peakradiometric efficiency of 2.4% at 667 nm (1.5 lumens/amp) when forward biased to 10 mA.

Variable-angle dry etching with a hollow cathode

Previous experiments have shown that very high etch rates can be obtained with an rf hollow cathode reactive sputter etching apparatus. This letter shows that hollow cathode etching also permits profile control, without mask undercut or mask erosion. The angle of etching is here varied from 90° (i.e., normal to the etched surface) to 50°, at a constant pressure of CF4 and a constant applied rf voltage, by varying the etch conditions. The etch angle is largely independent of the etched material (SiO2 or Si).

High resolution alpha-particle spectroscopy using CR-39 plastic track detector

A technique has been developed for high resolution alpha particle spectroscopy from track length determination in CR-39 plastic. On individual tracks an energy resolution δE close to the range straggling limit is obtainable. For 6 MeV alpha-particles δE is ∼ 35 keV on individual particles and for groups of particles δE ∼ 20 keV can be achieved using certain data selection criteria. At 100 keV on individual particles δE is ∼ 20 keV. The analysis requires (1) a knowledge of the track-etch rate ( V T-range) relationship and (2) a theoretical understanding of alpha-particle track structure in CR-39 as a function of particle energy, dip angle and degree of etching. The structure of alpha-particle etched tracks in CR-39 is described and two methods of analysis discussed. Examples are given of the resolution attainable on tracks of alpha-particles as natural decay energy and from alpha-particles generated in laser driven deuterium and tritium fusion reactions which escape the fusion centre with energies in the range 50 keV-1 MeV.

Critical distances in geometry factor calculations using solid state nuclear track detectors (SSNTD)

It has been shown that the normally used geometry factor formulae have limitations when applied to systems using solid state nuclear track detectors (SSNTDs) instead of the conventional detectors. Critical distances (the distance below which the conventional geometry factor formulae need modification) for point and extended sources and track detectors of different sizes have been determined. The results indicate that for a fixed detector size, the critical distance increases with (a) increasing critical angle of etching, (b) decreasing effective charge of particle, and (c) increasing size of the extended source.

Determination of critical angles of etching and track registration efficiencies of track detectors

The critical angles of etching and the track registration efficiencies of different types of solid state nuclear track detectors (SSNTD) have been determined. An extensive use of the scanning electron microscope (SEM) has been made in this regard. From the pictorial observations, numerical values of track parameters such as (a) δ, the cone angles, (b) θ c , the critical angles of etching, and (c) η, the track registration efficiency (in 2π-geometry) were obtained. A decrease in the critical angles of etching and an increase in particle registration efficiency with the increasing value of (a) restricted energy loss (REL), and (b) ( Z eff/ β) 2 of the incident particles have been observed. The results are expected to be useful in experiments carried out for the quantitative study of the emission of charged particles in nuclear reactions and for the determination of reaction cross sections.

Critical angles of etching of CR-39 track detectors

The critical angles of etching of CR-39, the latest member of the SSNTD family have been determined for a number of light and heavy charged particles, having a wide spectrum of energies. It has been observed that the critical angles increase with the decreasing value of the parameter, Z eff 2/ β 2 of the charged particles. The results are expected to be useful in experiments carried out for the measurement of absolute emission of charged particles in nuclear reactions, and for the determination of reaction cross-sections.

Measurement of critical angle in SSTDs

A method of measurement of critical angles of etching is described, relying upon the distortion caused in the shape of the distribution in the number of etched tracks of ions emitted from a ‘point-like’ source. The method is applied to quartz and mica samples.

Light charged particle registration characteristics of CR-39 plastic track detectors

Abstract CR-39 plastic sheets have been tested for their response to protons, deuterons, and alpha particles. The enlargement of the latent damage trail has been studied (a) under varying experimental conditions, and (b) as a function of energy, restricted energy loss, and Z2 crr/β2 of the light charged particles. The critical angles of etching of CR-39 and its response curves have been obtained. Scanning-Electron-Microscopy (SEM) has been employed for studying the profiles of the etched channels.

Enlarging the fission fragment tracks in glass detectors by etching in weak solutions of HF—a safe etchant

The effect of etchant concentration and temperature on track revelation properties of soda glass detectors has been studied. Etch rate ratio, maximum observable diameter and the energy resolution of the fission fragment tracks of 252Cf in glasses are increased when the samples are etched in 1.25 vol% HF as compared to higher concentrations of HF and other etching solutions. The critical angle of etching is found to decrease with decrease in etchant concentration. The activation energies for bulk etching and track etching have also been estimated. Better results were obtained by using lower etching temperatures.

Scanning electron microscopic studies of etched track profiles

Abstract Most of the work, reported uptil now on etched tracks in insulating solids employed optical microscopy. We have made studies of etched track profiles in a variety of detectors with a view to have a better understanding of the process of etched track formation. Soda lime and phosphate glasses were exposed to various energy Kr-84, Xe-136, and U-238 ions from UNILAC (GSI, Darmstadt) and etched thereafter. The etch pits were broken up along the lengths/heights of the cones, and Scanning Electron Microscope (SEM) analysis of their side views was carried out. Detailed SEM studies indicate that the cone angle (θ) and, thus, the critical angle of etching (θ C ), decreases with increasing ‘Z’ of the incoming particle. On the other hand, there does not seem to be any significant dependence on the initial energy of the projectiles. Phosphate glass yields much smaller values of ‘θ’ and ‘θ C ’ as compared to that produced by soda lime glass for the same projectiles. Mica crystalline track detectors have almost always been etched in hydrofluoric acid. We have made some successful attempts to reveal the latent damage trails in Muscovite mica by etching it in boiling solution of 6N NaOH. The hexagonal etch pits so obtained have been found to go through interesting variations in their size, shape, and geometry with the change of the etching conditions.