Bulk Etch Research Articles

Bulk etch rates of CR-39 nuclear track detectors over a wide range of etchant (NaOH aqueous solution + ethanol) concentrations: measurements and modeling

Bulk etch rates for CR-39 detector were measured and studied over a wide range of NaOH aqueous solution concentrations (2–20 N) with different ethanol volumes. This wide range of etching concentration is divided into two major parts: soft etching part (2–8 N NaOH) and dense etching part (8–20 N NaOH). This classification will be explained and discussed. The etchant viscosity in the two parts was measured and compared. The effect of ethanol in both parts was deduced through a new parameter called ‘reduced bulk etch rate’. This new parameter helps in analyzing the dependence of bulk etching on the amount of ethanol in the etchant. It was found that conducting the etching process in the dense etching part reduces the etching time significantly. Etching in the dense part is not far away from equilibrium where Mushtaq, Multi-hit and Arrhenius fitting equations are applicable. The fitting of measured bulk etching data was carried out in the soft (low), dense (high) and the whole etching concentration ranges. Generally, a good agreement was found between physical data and model calculations.

The along-track etching structure of fission tracks in apatite: Observations and implications

Interpretation of apatite fission-track length data rests on the assumptions that etching fully reveals latent tracks, and that laboratory annealing of induced tracks constitutes a good proxy for geological annealing of spontaneous tracks. Recent work using improved step-etching procedures questions both of these assumptions. Step etching experiments interrogating the etching structure of tracks near and beyond their tips have shown that tracks are often not etched to their full extent of latent track damage in a standard single-step, 20-s etch, and that the etching structure in this outer region differs between fossil and induced tracks. In this study, we develop a more complete picture of track revelation for fossil and unannealed and annealed induced tracks in Durango apatite. Using first steps as early as 10 s after the beginning of etching, we discern differences in etching structure between various track types, and document a gradual fall-off in etching velocity from the track interior toward its tips. When effective etching time is constrained by selecting earlier-etching confined tracks for later analysis, mean lengths are longer, but length dispersion is not diminished. Although some proportion of unannealed tracks are under-etched after 20 s of etching, with increased levels of annealing the probability of an induced track being fully etched increases. We use an etch-anneal-etch procedure, consisting of partially etching tracks, annealing the apatite grains, and then continuing etching, to establish bulk etching rates at track tips. Bulk etching is effectively isotropic, as is etching velocity in the central portions of tracks, away from their tips. We use our data to compare two end-member possibilities for along-track etching structure, which provides a first step toward a deeper understanding of annealing and development of a more robust standard etching protocol.

Effects of He–Ne laser on etching parameters of lexan (polycarbonate) plastic track detector irradiated with fission fragments

This research work investigates the effects of He–Ne laser (115 and 287 J/cm2 fluence) radiation on the etching parameters like bulk etch rate VB, track etch rate VT, Sensitivity S, critical angle θC and efficiency η of Lexan plastic track detector, irradiated with fission fragments from 252Cf source. The changes in etching parameters due to He–Ne laser in the fluence range of 0, 115, and 287 J/cm2 at different temperatures (328–348 K) have been discussed in detail. Bulk and track etch rates are observed to vary with He–Ne laser fluence both in case of pre-exposed and post-exposed detectors as compared to un-exposed Lexan plastic detector. Both bulk and track etch rates follow Arrhenius equation. Based on these results, important inferences regarding activation energies associated with bulk and track etch rates have been made. Sensitivity, critical angles and efficiencies of detector material also reveal significant facts about the changes in properties due to He–Ne laser on the Lexan plastic detector. A comparative study is performed on the effects of coherent/in-coherent electromagnetic radiation on nuclear track detectors. The activation energies of bulk and tack etching for commonly used nuclear track detectors is also reported.

Impact of infrared radiation on track etching parameters of Lexan track detector to fission fragments from 252Cf source

In this research work, the impact of infrared (IR) radiation on the etching parameters like bulk etch rate VB, track etch rate VT, Sensitivity S, Critical angle of etching θC and track registration efficiency η of Lexan track detector, irradiated to fission fragments from 252Cf source, were investigated. The changes in etching parameters due to infrared radiation for 0, 12 and 24 h at different temperatures (328–348 K) are discussed based on chain scission and cross-linking mechanisms. Bulk and track etch rates increase with infrared radiation in case of post-exposed as compared to un-exposed while sensitivity slightly decreases for 12 h exposure with infrared radiation but slightly increases for 24 h exposure with infrared radiation as compared to un-exposed. On the other hand, bulk and track etch rates decrease with infrared radiation in case of pre-exposed as compared to un-exposed while sensitivity slightly increases. Critical angles increase and track registration efficiency decreases with etching temperatures. Activation energies for bulk and track etching rates have been determined by fitting Arrhenius equation to the experimental data of bulk and track etch rates which show a decrease in bulk activation energies in case of post-exposed but slightly increase in case of pre-exposed as compared to un-exposed Lexan track detectors. Track activation energies show the same trend as for bulk etch rate.

Strong etching investigation on PADC CR-39 as a thick track membrane with deep depth profile study

Shape and size of micro-tubes produced by high energy Au, Ni, Si and Fe ions on thick CR-39 polymer processed in strong etching solution were studied. Deep internal polymer track parameters of sensitivity (V); bulk (Vb) and track etch rates (Vt) were intensively investigated by measuring the track opening as well as the track cone length. Development of track envelope with etching was studied using track profile technique, TPT. Variations in Vb, Vt, and V with deep depth inside the polymer were studied down to ≈100 μm depth or more. CR-39 sensitivity was reduced to 60–70% at the first 25 μm inwards. Microphotographs for the developed track profile for each ion was shown. Fe and Si profiles show new and interesting track profile for the first time where their profiles deviate from the normal cone shape of the track. Ion's track membranes (TMs) for thick CR-39 polymer were produced and their properties were determined.

Fission-track evolution in Macusanite volcanic glass

Macusanite is a natural volcanic glass, which is produced by the rapid cooling of magma during a volcanic eruption. Since it typically contains concentrations of uranium, it can be used for fission-track dating. Understanding the fission-track formation process and its morphology in natural volcanic glass is of major importance in this dating method. Therefore, in this work the latent fission-track structure was investigated using the geometry evolution of etched tracks. This evolution was characterized as a function of the chemical etching time via optical microscopy and atomic force microscopy. In this way, measurements of track diameters and theoretical estimation of track depths of normal incident fission fragments were made in order to determine the bulk and track etch rates. As a result, both rates yield constant values, and therefore the defect density along the fission fragment trajectory can be considered constant.

Bulk etch rate for PADC CR-39 at extended concentration range of NaOH mixed with ethanol and etchant viscosity study

Bulk etch rate of PADC CR-39 detector in a mixture of NaOH and ethanol alcohol aqueous solution of (8 ml of NaOH + X ml of ethanol: X = 0, 1, 2, 3) at 70 °C was determined using fission track diameter method. Wide range of NaOH concentration, never covered before, from 2 to 30 N was studied. Higher NaOH concentrations and ethanol increase the detector etching rate dramatically leading to a reaction rate far from equilibrium. Arrhenius and multi hit equations are no longer hold and therefore a need for new equations is arise. Viscosity of (NaOH + ethanol) in such wide concentration range was also studied at different temperatures to explain the reaction rate. Many efforts and different fitting equations were used to manipulate the data. Some of these equations are statistically as well as chemically rejected and finally three equations seem to read the data quit well are suggested.

Effects of UV irradiation on Fission-fragment track parameters in Makrofol-E detector

This study gives information about the effects of UV (here, the wavelength is 160 nm) exposure on the bulk etch rate ([Formula: see text], track etch rate ([Formula: see text], the detector sensitivity ([Formula: see text], critical angle ([Formula: see text] and etching efficiency ([Formula: see text] of Makrofol-E Solid State Nuclear Track Detector. The effect of UV on the activation energy of Makrofol-E was also studied. Nine pieces of Makrofol-E Solid State Nuclear Track Detector were separated into three equal sets as set A, set B and set C. Set A, named as reference set (Fission fragment FF), was irradiated to [Formula: see text]Cf source. Set B, called as post-exposed ([Formula: see text]), was first irradiated to [Formula: see text]Cf and then exposed to UV. The process was reversed for set C named as pre-exposed ([Formula: see text]) at the same conditions. From the results, it is concluded that radiation produces small but significant effect on activation energy [Formula: see text] of bulk etch rate for pre-exposed and post-exposed samples. Also, the activation energies [Formula: see text] of track etch rate for post-exposed and Fission fragment samples are within experimental uncertainty. The energy carried by UV radiation may be responsible for cross networking processes occurring during the exposure which results small change in activation energies for both [Formula: see text] and [Formula: see text]. The [Formula: see text] can be increased by hardening detector material of the pre-exposed detector.

A new chemical etchant for the development of alpha tracks in CR-39 solid state nuclear track detector

Chemical etching is an important step for enlargement of latent tracks in solid state nuclear track detectors (SSNTD). In the etching process, bulk and track etch rates are determined by various parameters, which decide the sensitivity and efficiency of the track detector. Thus, determination of the etching parameters is essential in introducing a new chemical etchant. For the enlargement of latent tracks in CR-39, chemical etching is usually carried out at temperatures of 60–70 °C by using 6–6.5 N concentrations of alkali like NaOH or KOH. In the present work, a mixture of 8 g NaOH in 25 mL water and 25 mL ethanolamine as an etchant at 70 °C was found to be very effective in the enlargement of alpha tracks in CR-39 SSNTD. The diameters of alpha tracks resulting from this new etchant are found to be a quadratic function of the etching time, whereas those from the standard etchant are linear with respect to the etching time. This results in the reduction in the etching time by a factor of 4 with an increased etching efficiency.

IR radiation-induced changes in the optical and registration properties of a CR-39 nuclear track detector

The UV–Vis (ultraviolet–visible) spectra and etching characteristics have been studied of poly allyl diglycol carbonate (PADC, a form of the CR-39 polymer) detector films after exposure to 250 W IR-radiation lamp for various times ranging from 1 to 40 min. Etching experiments were carried out on the IR-exposed CR-39 detectors after alpha particle irradiation using a241Am source. The bulk and track etch rates were measured using the weight loss and alpha track diameter methods, respectively, as well as the sensitivity, the detection efficiency, and the critical angle, were also determined. The optical band gap for both indirect and direct transitions was calculated based on the absorption edge of the UV spectra of the pristine and variously IR-exposed detectors. UV–Vis spectra of pristine and IR irradiated PADC polymer films exhibit a decreasing trend in the optical band gap, direct and indirect transitions, ranging from 4.64 ± 0.23, 3.85 ± 0.20 to 3.40 ± 0.12 and 3.04 ± 0.11 eV, correspondent to IR exposure time from 0 to 40 min, respectively. This decline in the optical band gap with increasing IR exposure time has been discussed on the basis of IR irradiation-induced defects in PADC. Further etching measurements, of 3 and 9 h etching times, confirmed a decrease in sensitivity from 1.86 ± 0.06 to 1.05 ± 0.03 and from 1.78 ± 0.06 to 1.03 ± 0.03 as well as in detection efficiency from 46.2 ± 1.45 to 4.68 ± 0.12 and from 43.91 ± 1.50 to 2.98 ± 0.09 (%) correspondents to IR exposure time from 0 to 40 min, respectively, in IR irradiated CR-39 polymer detector.

Energy window of Makrofol for alpha particle detection

Abstract Detection energy window of Makrofol detector irradiated with alpha particles and chemically treated by PEW (potassium hydroxide, ethanol, water) solution was investigated. Detectors were exposed to 241 Am source through the cylindrical collimators in order to control incident alpha particle energies and angles. Alpha particles were detected in the wide energy range from 0.4 MeV to above 5 MeV. The dependence of track diameter on particle incident energy was also examined. Changes of etchant concentration and bulk etch rate ( V b ) during two-hour etching were investigated. A slight increase of etchant concentration was observed while V b was nearly constant during the whole etching process. Alpha particle passage through collimators with various dimensions and the corresponding energy distribution were also simulated theoretically using Monte Carlo Method and computer program written in Fortran90.

Microwave induced chemical etching of CR-39 with KOH etchant: Comparison with chemical etching

Abstract Microwave induced chemical etching (MICE) has been successfully employed in reducing the etching duration using NaOH etchant. In this work, the MICE technique has been studied with KOH etchant to investigate the effect on the track development. Chemical etching (CE) has also been performed at different temperatures for a comparison purpose. Neutron irradiated CR-39 track detectors were subjected to stepwise MICE at 4 microwave powers after generating the temperature profile with 200 ml of 6 N KOH. The rate of increase in temperature before attaining the saturation temperature was found to be 3.28, 5.78, 8.2 and 16°C/minute for 300, 450, 600 and 900 W respectively. The image analysis showed the increase in track size with the increase in etching duration in both MICE and CE. The rate of growth of track diameter in MICE was observed to be higher than that of CE. The bulk etch rate as determined by the gravimetric method was found to be higher in MICE than CE. The maximum bulk etch rate in CE at 90°C was 11.81 μ m h−1 which was lower than the minimum bulk etch rate 16.92 μ m h−1 in MICE at 300 W. The bulk etch rate was found to increase with microwave power in MICE and with temperature in CE. Study on the variation of bulk etch rate with microwave power (in MICE) has been carried out and an empirical relation was generated. From the variation of bulk etch rate with temperature, the activation energy of CE for 6 N KOH was found to be 0.70 eV.

GaN‐Based Nanorods/Graphene Heterostructures for Optoelectronic Applications

The insulating character of sapphire, meltback etching of Si, bulk and surface defects prevented the efficient integration of GaN nanostructures in optoelectronic devices. Here, it is demonstrated that graphene can simultaneously serve as an electrical bottom contact, a chemically inert buffer layer, and a superior lattice and thermal matched growth substrate. Vertically aligned, high crystal quality GaN nanorods (NRs) without bulk defects such as threading dislocations and with only a mild strain at the NRs’ base are grown by metal‐organic vapor‐phase epitaxy on defect‐free graphene using nanometer‐sized AlxGa1−xN nucleation islands. Here no influence of the supporting substrate on the GaN epitaxy is observed. However, at defects in graphene the effects of dangling bonds and the underlying substrate, presumably through nanoholes in graphene, on the properties of GaN NRs are visible. It is also shown that surface defects in InxGa1−xN/GaN NRs from planar films produced by etching of the defective material can be effectively passivated with only 10 nm alumina deposited by atomic layer deposition. This is confirmed by the increase in electroluminescence measured on finished devices with graphene top contact. These results can potentially lead to new material combinations including graphene, GaN, and other relevant semiconductors like Si toward yet unexplored device concepts.

Ion track etching in polyethylene-terephthalate studied by charge particle transmission technique

ABSTRACTIn the paper, thin films of polyethylene-terephthalate, pristine or irradiated with 170 MeV Xe+ ions to the fluence of 105 cm−2, were etched in the mild 1 M NaOH medium at 60°C for different times. The main aspects of the etching process (i.e. development of the pores, dependence of the foil thickness and transparency on the time of etching) were studied by the ion transmission technique (ion energy loss spectroscopy) that was previously introduced by the author’s team. It has been shown that the transmission method makes it possible to closely monitor the development of the polymeric porosity and to determine the important parameters of the etching process (e.g. etching rate along the latent tracks, bulk etching rate, radial etching rate, breakthrough, foil transparency). The measurement was carried out at the NPI Rez using the alpha particle microprobe on the Tandetron accelerator.

The Induced Changes in the Bulk Etch Rate and the Thermal Stability of PADC by the Effect of Long Storing Time at Room Temperature and Heat Treatment

The samples of poly allyl diglycol carbonate PADC (CR-39) (stored and fresh samples) polymer track detectors have been heated for different annealing temperatures and different annealing times. The thermal stability has been studied for different annealed samples; also it was examined as a function of storage time. The degree of crystallinity percentage has been studied for different annealed samples and stored samples. The samples were etched in 6 M KOH solution at 70°C for 3 h as etchant duration. The variation of bulk etch rate of isochronal annealed samples has been studied. The results indicate an improvement in the thermal stability of Poly allyl diglycol carbonate PADC; where the bulk etch rate increases with the increase in the annealing temperature and annealing time. The storage time has no noticeable effect on the bulk etch rate of un- annealed samples, though the thermal stability of PADC improved with increasing the storage time.

Fabrication of ZnO/Si lamb wave acoustic devices

Surface acoustic wave devices have widespread applications in various fields including in communication and wireless sensing devices. However some shortcomings like lower sensitivity and the corrosion of IDT’s limit their application as sensing devices. Lamb wave SAW devices have proved to be promising for sensing applications. In the present work effort has been made to find out the optimum etching temperature in order to get the sufficiently fast etch rate and smooth surface for the fabrication of SiO2/Si membrane for Lamb wave acoustic (LWA) devices. Piezoelectric ZnO thin film deposited using rf sputtering technique has been integrated with the SiO2/Si membrane. The bulk etching of Silicon has been carried out from back side of each LWA device using wet etching. The devices are packaged and frequency response is studied using a network analyzer. The antisymmetric and symmetric modes of the Lamb wave devices have been identified.

CR-39 nuclear track detector: An experimental guide

The influence of preservation period of CR-39 detectors, in refrigerator and in the laboratory atmosphere, on bulk etch rate is studied. The effect of etching solution usage time on the bulk etch rate is also investigated. Analyses and quantitative results in the said cases are presented. Finally, precision results on the use of CR-39 as a charged particle detector are presented in a systematic manner. These results are selected from our radiation detection and measurement experiments, ranged over last two decades. Selected results (unpublished and published) include CR-39 measurements of 5.9 MeV antiprotons, 6.12 MeV alpha particles and spontaneous fission fragments of 252Cf. Our published results, presented here, are further analyzed and presented in comparison with new results and discussion. Experimental procedures of exposures, chemical etching, track measurements using the optical microscopy are described, keeping in view the new users and research students. Computer codes TRACK_Vision and SRIM were employed to provide a comparison with measurements of track parameters, where possible.

Determination of the Bulk Etch Rate of the Nuclear Track Detector LR-115

Determination of the Bulk Etch Rate of the Nuclear Track Detector LR-115

Bulk Etch Rate and the Activation Energy of the CR-39 Detector using Thickness Difference Method

The aim of this paper is to determine the bulk etch rate Vb of the nuclear track detector CR-39 using the method based on measuring the thickness of the layer removed from the surface of the detector (the thickness difference) by the chemical etching, and then studying how to change it with the temperature of the etching solution to extract an empirical relationship between them. The detector samples were etched in a 6 N of NaOH solution at temperatures 80, 70, 60 and 501 oC, and the thickness of the removed layer was determined by successive measuring the detector thickness for etching times of 1-9 h increasing with 1 h intervals. The results showed that the values of Vb range between 2.351-0.605 μm/h for etching temperature 50-80 oC respectively. An exponential relationship was obtained between the bulk etch rate and the etching temperature. It was noted that the results were consistent with that obtained by other studies using the track Length-diameter- (Le-D) measurement method. The slight difference in Vb magnitudes between the compared results is due to the slight difference in the concentration of the etching solution in certain

Cu-assisted chemical etching of bulk c-Si: A rapid and novel method to obtain 45 μm ultrathin flexible c-Si solar cells with asymmetric front and back light trapping structures

Ultrathin c-Si solar cells (≤50 μm) are believed to be applied in military, aerospace and other special circumstances in the future due to their flexibility and high specific power density, and thus has attracted a great deal of research interest. However, until now, lacking fabrication means of high-quality ultrathin c-Si materials accompanied with their inefficient absorption of near-infrared light greatly limits their further application. In this work, we present a simple and novel method to realize rapid thinning and texturing of bulk c-Si at room temperature by varying the ρ ([HF]/([HF] + [H2O2])) values during the one-step Cu-assisted chemical etching process, followed by a systematic investigation of the formation mechanism of the surface structures. It is found that the sizes of surface structures accompanied with the etching rate increase with increasing the ρ values from 40% to 95% during the double sided etching process, and a high etching rate of 29.6 µm/min is obtained under the ρ value of 95%. For rapid thinning and efficient absorption of near-infrared light, 45 µm c-Si solar cell with asymmetric front and back light trapping structures is rapidly fabricated by directly immersing as-sawn bulk c-Si substrate into the thinning (ρ = 95%) and texturing (ρ = 60%) solution successively for only a few minutes. A high short-current density (Jsc) (36.12 mA/cm2) and energy-conversion efficiency (17.3%) are achieved, which are 1.09 mA/cm2 and 0.4% higher respectively than that in 45 µm c-Si with flat back surface. Based on the absorption spectra, it is demonstrated that the 45 µm c-Si cell with our asymmetric structures yields a high theoretical Jsc of 42.47 mA/cm2, which nearly approaches the Yablonovitch limit of 42.56 mA/cm2. All the findings offer additional insight into the structure formation mechanism and pave a rapid and novel way for exploration of next-generation flexible photovoltaics.