A Cost-Effective Approach for Micro-Texturing of Silicon Using KOH for Solar Cell Devices

Purpose – In this research, we have prepared activated carbon (AC) from the waste of banana peels (Musa acuminate L.) using potassium hydroxide (KOH) for carbon monoxide (CO) adsorption from motorcycle gas emission. Design/Methodology/Approach – The activation was conducted using a chemical activator (KOH) at various concentrations of 1, 2, and 3 N for 1, 2, and 3 h, respectively. Characteristics of banana peels AC (BPAC) produced were analyzed using the Fourier-transform infra-red spectroscopy and scanning electron microscopy. Findings – Results showed that KOH concentration and activation time strongly affected the CO adsorption and opening of the AC surface pore. There was an increase in the CO sorption when the KOH concentration was increased up to 3 N concentration. The highest CO adsorption from the emission occurred at 70.95% under KOH concentration of 3 N during the 3-h preparation. Research Limitations/Implications – BPAC has been used as an adsorbent for only CO from motorcycle gas emission but not as an adsorbent for HC, NO, NOx, or H2S. Practical Implications – BPAC can be used as the potential adsorbent for the removal of CO from motorcycle gas emission, and it is an environmental friendly, low cost, and easy to make adsorbent. Originality/Value – In this study, the AC is made from biomass and is used in wastewater treatment, but limited studies are found on the removal of CO from motorcycle gas emission.

Microscale-pyramidal-structure-arrayed patterned silicon membranes are manufactured using semiconductor processes and potassium hydroxide (KOH) etching techniques for filter applications. The silicon nitride on silicon on the insulator wafer functions as a masking layer, and the roughness of the silicon (100) plane strongly depends on the etching temperature and KOH concentration. To fabricate the membrane filter, a series of dry and wet etching using 45 wt% KOH solutions at the constant temperature of 70 °C was performed. With the dry and wet etching, micro-pyramidal arrays with 300 μm top and 16-20 μm bottom opening sizes were created. The morphological structures were analyzed using scanning electron microscopy. The manufactured membranes were tested as optical directional filters and particle filters.

In this paper, silicon corrugated diaphragms with non‐compensated mask layout have been designed and realized using anisotropic etching process simulator. The corrugated diaphragms have been etched on silicon (100) wafer by using potassium hydroxide solutions (KOH). The influence of the KOH etching temperature and concentration on the convex corner undercutting of corrugated diaphragm were observed. The convex corner behavior has been analyzed based on the geometrical parameters and the new emergent high index silicon planes. It was found that the convex corner undercutting phenomena is significantly reduced at low etching temperature and high KOH concentration respectively. It can be concluded that the prominent facets contributing to the undercutting of the convex corners of the corrugated diaphragm for the given etching condition coincide with the {411} plane.

In this paper, silicon corrugated diaphragms with non-compensated and compensated mask layout have been fabricated on a single silicon (100) wafer by using potassium hydroxide (KOH) etching technique. Although, recently corrugated diaphragms have been used for a diaphragm structure due to its excellent properties, no theoretical and analytical studies on the fabrication process of these diaphragms have been performed. Therefore, the characterization of the KOH etching process with emphasized on convex corner behavior has been studied through both experiments and simulations in order to realize the perfect corrugated diaphragm. Details of the etching of corrugated diaphragms have been studied by using process simulation software of a three-dimensional anisotropic etching profile prior to fabrication process. The influence of the KOH etching temperature and concentration on the convex corner undercutting of corrugated diaphragm are observed. The convex corner behavior has been analyzed based on the geometrical parameters and the new emergent high index silicon planes. It was found that the convex corner undercutting phenomena is significantly reduced at low etching temperature and high KOH concentration respectively. It can be concluded that the prominent facets contributing to the undercutting of the convex corners of the corrugated diaphragm for the given etching condition coincide with the {411} plane. The introduction of the additional mask layout for the protection of convex corners at all convex-mask geometry of the corrugated diaphragm during the KOH etching process has been proved by simulation to produce almost perfect square corners. These simulation results have been confirmed by experiments.

Nanoholes integrated into microfluidic systems have been widely researched, due to their practical applications in biosensing fields. This paper is devoted to report a strategy for fabricating polygonal nanoholes by localized mask-free anisotropic etching. Underetching occurs at the pore mouth, causing shape modification of the original square nanohole prepared by wet etching. The influence of the etching under different etching temperatures, KOH concentrations, as well as KOH with isopropanol (IPA) addition, on the shape formation of nanoholes are carefully analyzed and verified by experiments. Under low etching temperature or low KOH concentration, the shape of nanohole turns to be dodecagonal. Under high etching temperature and high KOH concentration, the increase of etching rate of (331) planes promotes transition of the nanohole to an octagonal shaped. By adding IPA into KOH solution, the pore shape is limited to be dodecagonal, and it is irrelative to the etching temperature and KOH concentration.

Fabrication of silicon (Si) wafer microfilters via focus ion beam (FIB) sputtering (milling/drilling) is planned. However, due to limitations of FIB sputtering, the wafer has to be initially thinned to a certain thickness to ensure that micron-scale through holes can be successfully manufactured. This paper reports on thinning of a silicon wafer via wet chemical etching using 15, 20, and 25% w/w potassium hydroxide (KOH) at 3 different etchant temperatures (80oC, 90oC, and 100oC). The target is to achieve 100 μm with the lowest time taken and wafer surface roughness after etching. From the experiments conducted, it was determined that KOH solution at 15% w/w concentration at 100oC produced the best result with an etch rate of 5.43 μm/min, surface roughness (Ra) of 0.12μm and thickness of 123.00μm.

Wet etching of Si{100} in an alkaline solution result in pyramidal structures, mostly bounded by four {111} planes. Such geometrical structures work as excellent light trapping structures and potentially help in the efficiency increment of solar cells. In this work, the effect of very low concentration potassium hydroxide (KOH) on the etched surface morphology of Si{100} is systematically studied. KOH concentration is varied from 1.0 to 0.1 wt% KOH in a step of 0.5 wt% to investigate the effect of etching concentration. Wet etching is carried at a fixed temperature of 70°C for 5 to 40 min of etching time. Samples are taken for investigation after every 5 minutes of interval. The lowest reflectance of around 12 % is measured on the samples textured in 0.5 wt% KOH for 10 min.

Gallium nitride (GaN) nanowire (NW) light emitting diodes (LEDs) are promising candidates for microdisplay applications due to smaller dimensions and potential for novel integration approaches. For the commonly adopted top-down GaN NW fabrication, the required dry etching steps tend to result in surface states, leading to reduced radiative recombination rates in LEDs. To passivate the surface and tune the diameter of the NWs, hydroxyl-based chemicals such as potassium hydroxide (KOH) are widely used to treat the surface of these nanostructures. However, studies on the effects of temperature, concentration, and the damage recovery aspects of hydroxyl etching of GaN NWs are very scarce. These etching parameters are of great importance for device performance. Here, these effects are explored thoroughly with a focus on the correlation of InGaN/GaN NW LED performances to KOH etching temperature, concentration, and time, together with a fundamental crystallographic analysis. The KOH concentration resulting in total removal of the NW base tapering and a collimated etch profile for InGaN NW LEDs was found to be 0.8 wt. % at a temperature of 45 °C. A 20 min etch at 23 °C with a 0.1 wt. % KOH concentration will remove surface states from a top-down fabricated NW LED to recover up to 90% of the peak photoluminescence (PL) intensity lost by the dry etch step. The oscillation behavior in PL intensity with regard to the KOH etch time has been demonstrated in InGaN/GaN NW LEDs for the first time, which will shed light upon the design and passivation of these devices for microdisplays.

We evaluated the influence of the etching time and temperature of an acid solution (HCl/H2SO4) on the chemical and topographical superficial characteristics of cpTi grade IV. Samples were analyzed by electron microscopy, interferometry, and grazing incidence XRD. The surfaces kept the irregularity aspect when submitted to the same etching temperature. On the other hand, the irregularities increased in size and depth with increasing etching time. The etching treatments that produced higher values for roughness parameters showed a combination of high temperature for a longer etching time. Some treatments produced very large irregularities, with a brittle surface in some regions. According to statistical correlation, the temperature made the strongest contribution in the variance of the mean values of the surface roughness parameters when compared to the etching time. Titanium and oxygen were the only elements on the surface in all groups. All test group samples showed the presence of titanium hydride.

The influence of deposition temperature (TD) on thin film layers of high-k dielectrics used as insulators in embedded Metal-Insulator-Metal (MIM) decoupling capacitors is critical to their future behavior in terms of electrical properties and reliability. These layers are deposited via atomic layer deposition (ALD), which is known for its high uniformity in any type of structural topology. High-k dielectrics, such as Zr, inside high aspect ratio three-dimensional (3-D) structures are a challenging task even in the case of ALD processing. Al2O3 doping is often used within the high-k layer stack during ALD to optimize electrical performance of MIM structures with respect to leakage currents and reliability. In this context, appropriate atomic layer deposition temperature (TD) of the Al2O3-doped ZrO2 high-dielectric stack must be established to enable optimum electrical properties. Electrical data of decoupling capacitors must fulfill the industrial requirements, which demand that, for example, the leakage current density (J) must not exceed a certain level (<1µA/cm²) and that long-term lifetimes under different operating temperatures of a minimum of 10 years at accumulated fail rate of 10 ppm must be achieved.In this work, we report on a study of the influence of ALD TD on Al2O3-doped ZrO2 thin films fabricated on 300mm wafers. We evaluate the impact of TD on high aspect ratio substrates based on electrical properties and reliability parameters. To achieve this, we use 3 different deposition temperatures (293°C, 313°C, and 333°C) and two physical topologies (planar and 3-D capacitors with cavities-trenches) without compromising the chemical stability of the ALD precursors. For metal precursors, TEMAZ (Tetrakis-ethylmethylamino-zirconium) and TMA (Tri-methyl-aluminum) are used for Zr and Al, respectively. Ozone is used as reactant agent and argon as carrier/purge gas. The ZrO2 cycle consists of pulsing with TEMAZ, purging with Ar gas, oxidizing with O3, and purging with Ar gas. In a similar way, the dopant (TMA) is added, followed by purging steps with Ar, O3 and Ar again. After a few ZrO2 cycles, an Al2O3 cycle is followed, so that nano-laminate films of Al2O3 are formed on top of ZrO2 films. By repeating the ZrO2 and the Al2O3 cycles several times, the desired film thickness is achieved. For the MIM stacks, TiN is used as an electrode material on both sides. There was no post deposition anneal to maintain the amorphous state of the insulator with low defect density and high structural uniformity.The planar capacitors show minimal changes in terms of capacitance density with increasing TD. On the other hand, the 3-D samples show a 17% increase in capacitance density with a TD increase of 20°C from 293°C to 313°C. This increase becomes much smaller (2.3%) for a further TD increase of 20°C at 333°C. However, with increasing TD, the E-field linearity of 3-D samples, expressed by the quadratic E-field capacitor coefficient α, increases by 2% and 17% for TD=313°C and TD=333°C, respectively. The significant improvement in field linearity indicates the highest TD provides the best and most stable capacitance behavior. The J(E)-curves of planar and 3-D devices exhibit different behavior with respect to current density and dielectric breakdown. Specifically, planar devices show greater variation in J(E)-curves over temperature, with decreasing breakdown field (EBD) as TD increases. On the other hand, 3-D samples show little variation in EBD with temperature. Furthermore, planar devices show lower symmetry in their J(E)-curves over the field polarity compared to 3-D capacitors, which could be attributed to differences in conduction mechanisms. Despite having a lower EBD, planar devices reveal improved lifetime and reliability with increasing TD, possibly due to reduced carbon impurities during the insulator deposition. For instance, increasing TD from 293°C to 313°C leads to a 47% improvement in extrapolated lifetime, while a further increase in TD, improves lifetime by an additional 14%. A 10-year lifetime goal can only be achieved at 1MV/cm with TD=333°C and for samples exposed to any temperature conditions (25-150°C). In contrast, 3-D capacitors exhibit a better degradation slope at lower deposition temperatures but require the highest TD to achieve an 18% improvement in lifetime. However, due to their lower EBD, they cannot reach the 10-year lifetime goal at 1MV/cm, except at low applied temperatures (25°C-50°C).In conclusion, the highest TD of 333°C without any chemical decomposition of the metal precursor (TEMAZ) is the optimal deposition temperature for both planar and 3-D Al2O3-doped ZrO2 based MIM decoupling capacitors, providing auspicious results in terms of all relevant parameters. Figure 1

In this paper, membranes of 3C-SiC with dimensions up to 10 mm x 15 mm2 have been fabricated in epitaxial 3C-SiC/ Si wafers by the means of photolithography, reactive ion etching of 3C-SiC and wet etching of Si. Scanning electron microscope (SEM) micrographs were used to observe the structure of the membrane and the wall formed by the Si wet etching. The quality of the 3C-SiC membranes were observed using Raman Spectroscopy. The remains of &lt;111&gt; Si substrate which was unetched during the Si wet etching were presented with the formation of microstructure defects which showed distinct peaks in comparison to the high quality 3C-SiC membranes at different position. Here, the effect of the membrane fabrication procedures to the 3C-SiC membrane properties especially the morphological structure and its Raman characteristics is discussed in detail.

This paper presents the analysis effect of etching temperature and KOH concentration on convex corner undercutting of (MEMS) accelerometer structure. The Intellisuite CAD simulation software was used for the simulation analysis. From the analysis it was found that the optimum etching condition for this convex corner was at 25 wt% KOH concentration and 63 °C etching temperature. Different types of compensation mask corners were designed which are corner, square and triangle in order to study the undercutting phenomena. In this case, the square corner compensation mask was chosen as it shown the most suitable compensation mask for this design of accelerometer. The etching simulation was continued with square corner compensation mask etched in the optimized temperature and KOH concentration and it indicated that the square corner compensation mask is the most suitable mask to solve the convex corner undercutting for this accelerometer structure.

Abstract. Madung Z, Soloi S, Majid MHA, Sarjadi MS. 2022. Production and characterization of Imperata cylindrica paper using potassium hydroxide as pulping agent. Biodiversitas 23: 1490-1494. Non-woody plants have become an alternative fiber in paper production as woods, the primary sources of papers have become limited due to increasing demand of paper year by year. Imperata cylindrica or cogon grass as the source of fiber for the pulp and paper industry in replacing the wood fiber because it has high cellulose and low lignin content. In this study, cogon grasses were treated with various concentrations of potassium hydroxide, KOH (5%, 8%, 10% and 12%). The effects of alkali treatment on the properties of the papers were investigated in the present study. Scanning Electron Microscope (SEM) image of the paper sheet indicates that the amount of cellulose fiber and other materials were lessening toward a higher concentration of KOH treatment. This explained that most of the lignin was entirely removed and some cellulose probably degraded at higher KOH concentrations. Fourier Transform Infa-Red (FTIR) analysis showed that the peaks at range 1650 cm-1-1630 cm-1 attributed to the presence of v(C=C) aromatic ring of lignin disappeared at 10% and 12% of KOH. The mechanical strength of the papers decreased with an increasing concentration of KOH, while 5% of KOH produced the highest value of tensile strength.

KOH process simulation etching of corrugated diaphragm with bossed structure on silicon (100) is presented with emphasis on convex corner behavior. The influence of the KOH etching temperature and concentration on the convex corner undercutting of corrugated diaphragm are observed. The convex corner behavior is analyzed based on the geometrical parameters and the new emergent high index silicon planes. It was found that the convex corner undercutting phenomena is significantly reduced at low etching temperature and high KOH concentration respectively.

This research paper describes the synthesis of a heterogeneous catalyst (Potassium hydroxide (KOH)-impregnated eggshell) from waste chicken eggshell using the wet impregnation technique. In this experiment, the catalyst was derived from eggshell that was calcined at 800 °C for 5 h. It was impregnated with KOH at various KOH concentrations (10%, 15%, 20%, and 25%). The best catalyst was obtained by eggshell impregnated with 20% KOH concentration. This result was supported by the analysis of the catalyst characterization using Fourier-transform infrared spectrometry (FT-IR), which showed that the catalyst contained CaCO3 and CaOH groups. X-ray fluorescence analysis (XRF) was also used to analyze the types of mineral contained in the catalyst, including calcium, potassium, sulfur, and other impurities. It revealed that the optimum minerals were found in the KOH-impregnated eggshell (20%) catalyst of 94.42% calcium, 5.06% potassium, and a small amount of other impurities. These optimum minerals serve as active sites to increase the biodiesel yield. Scanning electron microscopy (SEM) showed that the catalyst samples appear as small, spherical, homogenous, and solid particles. The catalytic activity was investigated by the transesterification of Reutalism trisperma oil in various types of catalyst (KOH-impregnated eggshell, eggshell, and KOH-impregnated CaO), percentages of catalyst loading (weight of 1%, 3%, 5%, 7%, and 10%) and molar ratios (methanol to oil of 6:1, 8:1, 10:1, 12:1, and 15:1) for 60 min at 60 °C. The result indicated the optimum catalyst loading was 5 wt% with an 84.57% biodiesel yield. While the best molar ratio was 12:1 (methanol:oil) with a 97.95% biodiesel yield. The optimum condition was gained using a molar ratio of 12:1, 5 wt% catalyst loading, and KOH-impregnated eggshell with a 94% biodiesel yield.