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Improved galvanic porous silicon fabrication using patterned electrodes
摘要： On-chip porous silicon can be fabricated in a number of ways, but perhaps the simplest is a galvanic method that requires no external power supply. While this etch process is relatively simple, the etch is highly dependent on the surface area ratio (SAR) of a backside precious metal and frontside silicon surface, which respectively act as the cathode and the anode of an electrochemical cell. The SAR controls the etch current density, and therefore local variations can create high current densities that have detrimental effects on the quality of the final porous silicon film. The present study investigates the use of patterned backside platinum electrodes with the galvanic etch technique. The use of a patterned backside electrode that mimics the silicon pattern on the frontside, provides a more consistent etch current throughout the entire sample, and thus a more uniform porous silicon film. A triangular shape porous silicon film was tested in this work for comparison to a previous study utilizing an unpatterned electrode. With patterned electrodes, an etch depth variation percentage was observed throughout the length of the film of 8%. This is a considerable improvement over a 108% depth variation observed with a similar frontside silicon pattern and an unpatterned backside electrode.
关键词： porous silicon,electrochemical etching,mesoporous,galvanic etching
更新于2025-09-23 15:23:52
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Uniform position-sensitivity verification of novel electrochemically-etched panorama mega-size polymer ion image detectors
摘要： Recent novel applications of mega-size polycarbonate ion image detectors processed in mega-size electrochemical etching chambers have raised concerns on uniform position-sensitivity and consistency in ion energy responses of detectors with different effective areas. In this context, the uniform position-sensitivity, detection efficiency and track diameters of alpha particles over a broad energy range in detectors of different effective areas; i.e. small size (2 × 2 cm2), medium sizes (17 × 17 cm2) and (22.6 × 22.6 cm2), as well as large (33 × 33 cm2) were investigated in order to make them independent of the detector effective area. Alpha particles of 6 different energies from ~0.3 to ~3.0 MeV at a fluence of ~1.0 × 104 alphas·cm?2 were studied applying 50 Hz – HV field conditions. As an example, 36 positions on 6 rows and 6 columns of a 33 × 33 cm2 detector were studied. By having the same efficiency and mean track diameter only at ~0.8 MeV alpha energy in different detector effective areas under the conditions applied, it is concluded that: (1) position-sensitivity, efficiency and alpha energy responses are consistently uniform independent of the detector effective areas for particles with dE/dX)particle ≥ dE/dX)alpha at ~0.8 MeV, but (2) a "voltage compensation factor" (Vc) commensurate with each detector effective area and type of particle should be applied for particles with dE/dX)particle < dE/dX)alpha at ~0.8 MeV for efficient, consistent and uniform ion detection.
关键词： Electrochemical etching,Polycarbonate track detectors,Effective detector area,Position-sensitivity,Voltage compensation factor
更新于2025-09-23 15:23:52
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The effect of oxygen plasma treatment on the field emission properties of lanthanum hexaboride tip emitter
摘要： Polycrystal lanthanum hexaboride (LaB6) tip field emitter has been prepared using the electrochemical etching technique. The effects of oxygen plasma treatment on its morphology, structure and field emission properties are mainly discussed. The results reveal that the surface morphology of emitters did not change significantly after oxygen plasma treatment. The oxygen plasma treatment does not introduce any new phase into LaB6 emitter, but eliminates surface contaminants, which lead to lower work function. The cathode treated by 2 min shows the best emission performance during the field emission measurement. It obtains 8.2 μA at 2000 V, especially exhibiting strong ability of anti oxygen ion bombardment.
关键词： electrochemical etching,field emitter,lanthanum hexaboride
更新于2025-09-23 15:23:52
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Diamond nanofeathers
摘要： This paper reports a special diamond nanostructure which we call diamond nanofeathers (DNFs). The nanostructure was discovered after electrochemically etching doped nanocrystalline diamond (NCD) films. With high resolution SEM, we have repeatedly observed highly porous, fractal-like geometry with “shafts”, “barbs” and “barbules” of the DNFs. A DNF has very high aspect ratio, with a height comparable to the thickness of the etched diamond film and a lateral size as small as several nanometers. This diamond nanostructure seems not to belong to either conventionally defined NCD or ultrananocrystalline diamond (UNCD). The Raman spectra tell that after the electrochemical etch, the DNFs have lower signals from the grain boundaries, compared with the Raman spectra before the etch, which suggests the pores of the DNFs was related with mass loss from the grain boundaries. Preliminary electrochemical characterization has observed more than 300× capacitance increase after the DNFs are fabricated out of a NCD film. With the specific pore size and the ease of fabrication, the DNFs could be a great material choice for supercapacitors, batteries, sensors, and solar cells etc.
关键词： Diamond nanofeathers,Supercapacitors,Nanocrystalline diamond,Raman spectra,Electrochemical etching
更新于2025-09-23 15:21:21
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Thin-film flip-chip UVB LEDs realized by electrochemical etching
摘要： We demonstrate a thin-?lm ?ip-chip (TFFC) light-emitting diode (LED) emitting in the ultraviolet B (UVB) at 311 nm, where substrate removal has been achieved by electrochemical etching of a sacri?cial Al0:37Ga0:63N layer. The electroluminescence spectrum of the TFFC LED corresponds well to the as-grown LED structure, showing no sign of degradation of structural and optical properties by electrochemical etching. This is achieved by a proper epitaxial design of the sacri?cial layer and the etch stop layers in relation to the LED structure and the electrochemical etch conditions. Enabling a TFFC UV LED is an important step toward improving the light extraction ef?ciency that limits the power conversion ef?ciency in AlGaN-based LEDs.
关键词： Thin-film flip-chip,AlGaN,light extraction efficiency,UVB LEDs,electrochemical etching
更新于2025-09-23 15:19:57
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Selective seed layer patterning of PVD metal stacks by electrochemical screen printing for solar cell applications
摘要： A proof of principle for electrochemical screen printing (ESP) as a patterning process for thin metal stacks that can be employed, eg, in interdigitated back contact (IBC) or silicon heterojunction (SHJ) solar cells, is demonstrated. By using the ESP process, a 125 × 125‐mm2 interdigitated back contact grid was successfully patterned into a 100‐nm physical vapor deposited (PVD) aluminum layer. Optimizations of the ESP process were performed to improve the patterning resolution. Rectangular trenches with a mean width of 36 ± 5 μm could be demonstrated on a 100‐nm–thick aluminum layer. Up to now, ESP can be applied to PVD aluminum, copper, or stacks of both materials. Finally, metal stacks of aluminum and copper were structured, which allow a more homogeneous current distribution for the ESP process and additionally for the subsequent copper electroplating because of the second metal layer underneath the layer to be structured. The successful transfer from wafer substrate to polymer foils increases the application options of ESP technology enormously, where the topography of the surface to be structured affects the printing results.
关键词： silicon,screen printing,flexible circuit board,plating,interdigitated back contact (IBC) solar cell,electrochemical etching,water‐based printing paste,Al/Cu stack
更新于2025-09-16 10:30:52
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Single photon emission from top-down etched III-nitride quantum dots
摘要： We report the single photon emission properties of III-nitride quantum dots (QDs) fabricated by electrochemical etching method from an epitaxial wafer. Through such top-down fabrication, QDs with diameters of sub-10 nm are obtained, embedded in GaN nanoneedles. Owing to the size induced quantum con?nement effect, the photoluminescence of the QDs exhibits a 3.35 nm blueshift compared with that of the epitaxial wafer. At low temperature, a second order correlation value down to 0.123 is observed, indicating a high-purity single photon emission. Our QDs manifest single photon emission at a temperature up to 130 K with a high degree of polarization of 0.69, comparable to those QDs synthesized by epitaxial growth. Our work demonstrates single photon emission are viable in top-down QDs by electrochemical etching III-nitride wafers.
关键词： single photon emission,III-nitrides,quantum dot,electrochemical etching
更新于2025-09-16 10:30:52
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Efficient Modified Bimetallic Alloy Nanoparticles Porous Silicon Gas Sensors for CO Gas Detection Process
摘要： The influence of embedding Au, Pd monometallic and Au-Pd bimetallic nanoparticles on porous silicon-based gas sensor was investigated. Porous silicon layer P-si was prepared by photo electrochemical etching (PECE) with the laser wavelength of about 635 nm and 25 mW/cm2 laser power density. AuNPs/P-si, PdNPs/P-si and Au-PdNPs/P-si hetrostructures were prepared by ion reduction process, this made by dipping fresh P-si in the salt solution contain HAuCl4, PdCl2 and mixing solutions at ratio 1:1 for about (1.2, 5 and 2 min), respectively. Au NPs/P-si, Pd NPs/P-si and Au-Pd NPs/P-si were investigated by scanning electron microscopy (SEM), FTIR analysis, X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). Efficient gas sensing process was recorded for modified porous silicon P-si gas sensor with smallest bimetallic Au-Pd nanoparticles size. Considerable improvement in sensitivity and temporal response were obtained for modified bimetallic alloy nanoparticles porous silicon compared with bare P-si and monometallic nanoparticles gas sensors due to the high specific surface area.
关键词： Sensitivity,Ion reduction process,Monometallic,Photo Electrochemical Etching (PECE),Bimetallic,CO gas
更新于2025-09-09 09:28:46
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Electrochemical etching of lightweight nanotips for high quality-factor quartz tuning fork force sensor: atomic force microscopy applications
摘要： Commercially available quartz tuning forks (QTFs) can be transformed into self-sensing and actuating force sensors by micro-assembling a sharp tip on the apex of a tine. Mass of the tip is critical in determining the quality (Q)-factor of the sensor, therefore, fabrication of the lightweight nanotips is a precondition for high Q-factor QTF sensors. The work reports fabrication of very lightweight tungsten nanotips with a two-step electrochemical etching technique which can be used to develop high Q-factor QTF force sensor. First, a tungsten wire with protective coating at one end (1–2 mm) is etched with a trapezoidal waveform to form a lengthy (～2–5 mm) and slender (diameter ～10–40 μm) micro-needle. In the second step, sharp tip apex is fabricated with a direct current etching. High Q-factor (6600–8000) QTF force sensors have been developed with the fabricated nanotips. Atomic force microscope scanning of nano-grating and a triblock copolymer surface validates the scanning performance of the developed sensors.
关键词： quartz tuning fork,nanotips,atomic force microscopy,force sensor,electrochemical etching
更新于2025-09-04 15:30:14