Showing papers on "Hydrofluoric acid published in 2009"

Silicon nanowire-based solar cells on glass: synthesis, optical properties, and cell parameters.

Abstract: Silicon nanowire (SiNW)-based solar cells on glass substrates have been fabricated by wet electroless chemical etching (using silver nitrate and hydrofluoric acid) of 2.7 μm multicrystalline p+nn+ doped silicon layers thereby creating the nanowire structure. Low reflectance ( 90% at 500 nm) have been measured. The highest open-circuit voltage (Voc) and short-circuit current density (Jsc) for AM1.5 illumination were 450 mV and 40 mA/cm2, respectively at a maximum power conversion efficiency of 4.4%.

Chemical Properties of Oxidized Silicon Carbide Surfaces upon Etching in Hydrofluoric Acid

Abstract: Hydrogen termination of oxidized silicon in hydrofluoric acid results from an etching process that is now well understood and accepted. This surface has become a standard for studies of surface science and an important component in silicon device processing for microelectronics, energy, and sensor applications. The present work shows that HF etching of oxidized silicon carbide (SiC) leads to a very different surface termination, whether the surface is carbon or silicon terminated. Specifically, the silicon carbide surfaces are hydrophilic with hydroxyl termination, resulting from the inability of HF to remove the last oxygen layer at the oxide/SiC interface. The final surface chemistry and stability critically depend on the crystal face and surface stoichiometry. These surface properties affect the ability to chemically functionalize the surface and therefore impact how SiC can be used for biomedical applications.

Anti-reflection etching of silicon surfaces catalyzed with ionic metal solutions

Abstract: A method (300) for etching a silicon surface (116) The method (300) includes positioning (310) a substrate (112) with a silicon surface (116) into a vessel (122) The vessel (122) is filled (330, 340) with a volume of an etching solution (124) so as to cover the silicon surface (116) The etching solution (124) includes a catalytic solution (140) and an oxidant-etchant solution (146), eg, an aqueous solution of hydrofluoric acid and hydrogen peroxide The catalytic solution (140) may be a solution that provides metal-containing molecules or ionic species of catalytic metals The silicon surface (116) is etched (350) by agitating the etching solution (124) in the vessel (122) such as with ultrasonic agitation, and the etching may include heating (360) the etching solution (124) and directing light (365) onto the silicon surface (116) During the etching, the catalytic solution (140), such as a dilute solution of chorauric acid, in the presence of the oxidant-etchant solution (146) may release metal particles such as gold or silver nanoparticles that speed or drive the etching process

Dealloying of Cu-Zr-Ti Bulk Metallic Glass in Hydrofluoric Acid Solution

Abstract: metallic glass was investigated under free corrosion conditions using hydrofluoric acid (HF)solutions at room temperature. After immersing in HF solutions with various concentrations (0.05, 0.1, 0.5 and 1M) for 300s, color of allsamples changed to be pinkish or peachy, which was ascribed to Cu based on the XRD patterns. According to the SEM-EDS study, HFimmersion selectively leached the Zr and Ti elements, leaving Cu behind. Increasing the HF concentration increased the dealloying rate.Moreover, the HF concentration strongly influenced the surface morphology of the resulting Cu. [doi:10.2320/matertrans.ME200823](Received December 15, 2008; Accepted March 18, 2009; Published May 13, 2009)Keywords: dealloying, bulk metallic glass, Cu

Structure of early actinides(V) in acidic solutions

Abstract: Protactinium occupies a key position in the actinide series between thorium and uranium. In aqueous acidic solution, it is stable at oxidation state (V), occurring either as an oxocation or as a naked ion, depending on the media. Very few structural information on the hydration sphere of Pa(V) in acidic medium is available, in particular in hydrofluoric acid. Combined EXAFS and theoretical calculations have been used in this work to characterize the protactinium coordination sphere at various HF concentrations. The correlation of the XAFS data with quantum chemical calculations provides complementary structural and electronic models from ab initio techniques. At HF concentrations from 0.5 to 0.05 M, both theoretical calculations and EXAFS data suggest that the protactinium coordination sphere is mainly composed of fluoride ions. At the lowest HF concentration, the occurrence of a monooxo bond is observed with EXAFS, in agreement with the literature. A comparison of these data with related neptunium(V) and plutonium(V) diooxocations in perchloric acid is also presented.

Method for preparing fluorescent nano material converted on NaYF4

Abstract: The invention relates to a method for preparing fluorescent nano material converted on NaYF4, comprising the steps: yttrium nitrate, ytterbium nitrate and erbium nitrate or yttrium chloride, ytterbium chloride, erbium chloride and thulium chloride are dissolved in de-ionized water according to the mixture radio that the mol ratio of rare earth ions which are yttrium ion, ytterbium ion and erbium ion is equal to (70-95): (1-25): (0.5-10), so that the mixed solution is prepared; water soluble polymer having the ligand radical with the rare earth ions is added into the mixed solution for stirring reaction to form complex compound; the pH value of the mixed solution is adjusted to be 2-6; sodium fluoride, ammonium fluoride or hydrofluoric acid can be added into the mixed solution and stirred until colloid solution that is approximately transparent is obtained; then, the colloid solution is put into a high pressure closed reactor and heated at the temperature of 140-200 DEG C; after that the obtained product is cooled to be the room temperature, centrifugated, separated, washed and dried, finally, the fluorescent nano material converted on NaYF4 is obtained. The method can be used for preparing the converted material at lower temperature, the particle size and the appearance can be controlled, and the water-solubility is good.

Method for cleaning polycrystalline silicon material

Abstract: The invention relates to a method for cleaning a polycrystalline silicon material, which comprises the following steps: placing the polycrystalline silicon material into a mixed acid liquid to soak for 1 to 10 minutes away from light, fishing the material, flushing the material by purified water, and drying the material after ultrasonic flushing and compressed air bubbling, wherein the mixed acid liquid is corrosive liquid which is prepared by nitric acid, hydrofluoric acid and glacial acetic acid according to a volume ratio of 57:18:25; the concentration of the nitric acid is 68 to 72 percent, the concentration of the hydrofluoric acid is 38 to 41 percent, and the concentration of the glacial acetic acid is 99.8 to 99.9 percent; and the purity level is MOS level or UP level. Before the polycrystalline silicon material is placed into the mixed acid liquid and soaked away from light, the polycrystalline silicon material can be presoaked in the hydrofluoric acid liquid away from light, and can also be presoaked away from light in a solvent dissolving an optical resistor. The polycrystalline silicon material cleaned by the method has a smooth surface and has no acid stain or water stain; and the method has the advantages that the method has good cleaning effect, low cleaning cost and low operation difficulty, is easy to control the cleaning quality, and improves the cleaning efficiency.

Enhanced and stable electron emission of carbon nanotube emitter arrays by post-growth hydrofluoric acid treatment

Abstract: Carbon nanotubes (CNT) have been highlighted as possible candidates for field-emission emitters and vacuum nanoelectronic devices. In this article, we studied the effect of acid treatment of CNTs on field emission from carbon nanotube field emitter arrays (FEAs), grown using the resist-assisted patterning process (RAP). The emission current densities of as grown CNT-FEAs and those which were later immersed in hydrofluoric acid (HF) for 20 s, were 19 μA/cm2 and 7.0 mA/cm2, respectively, when measured at an anode field of 9.2 V/μm. Hence, the emission current densities after HF treatment are 300 times larger than those of as grown CNT-FEAs. Also, it was observed that a very stable electron emission current was obtained after stressing the CNTs with an electric field of 9.2 V/μm for 800 min in dc-mode, where the emission current non-uniformity was 0.13%. The enhancement in electron emission after HF treatment appears to be due to the effect of fluorine bonding. Also, the electron emission characteristics and structural improvement of CNT-FEAs after HF treatment are discussed.

Dependence of wet etch rate on deposition, annealing conditions and etchants for PECVD silicon nitride film

Abstract: The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition (PECVD) silicon nitride thin film is studied. The deposition source gas flow rate and annealing temperature were varied to decrease the etch rate of SiNx:H by HF solution. A low etch rate was achieved by increasing the SiH4 gas flow rate or annealing temperature, or decreasing the NH3 and N2 gas flow rate. Concentrated, buffered, and dilute hydrofluoric acid were utilized as etchants for SiO2 and SiNx:H. A high etching selectivity of SiO2 over SiNx:H was obtained using highly concentrated buffered HF.

Hydrofluoric-acid-resistant and hydrophobic pure-silica-zeolite MEL low-dielectric-constant films.

Abstract: A new technique for the silylation of pure-silica-zeolite MEL low-k films has been developed in which the spin-on films are calcined directly in trimethylchlorosilane or 1,1,1,3,3,3-hexamethyldisilazane (HMDS) in order to protect the films against corrosive wet etch chemicals and ambient moisture adsorption. In an alternative procedure, HMDS is also added to the zeolite suspension before film preparation. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, water-soak tests, and HF etch tests are performed to characterize the films. The dielectric constant is as low as 1.51, and the films resist HF attack up to 5.5 min. These properties are highly desirable by the semiconductor industry for next-generation microprocessors.

Effect of stannous fluoride and dilute hydrofluoric acid on early enamel erosion over time in vivo.

Abstract: Recent experimental in vivo studies have shown that aqueous solutions of stannous fluoride (SnF2) and hydrofluoric acid (HF) can reduce enamel solubility after 5 min. The aim of this study was to evaluate the longer-term protective effect of SnF2 (0.78%, pH 2.9) and HF (0.2%, pH 2.0) (both ∼0.1 mol/l F) using the same experimental model. Labial surfaces of healthy anterior teeth (all four surfaces when possible, otherwise a pair of surfaces) in 103 subjects (n = 399 teeth) were exposed to citric acid (0.01 mol/l, pH 2.7). The acid was applied using a peristaltic pump (5 ml, 6 ml/min) and was collected in coded test tubes (etch I). The test solutions were then applied to the same surfaces of the teeth (1 min, 6 ml/min). After either 1, 7, 14 or 28 days, citric acid was again applied to the same surfaces and subsequently collected (etch II). Enamel solubility was examined by assessment of calcium concentration in etch I and etch II solutions using atom absorption spectroscopy. Median values were calculated for all time periods and statistical analysis was carried out using the Wilcoxon signed-ranks test. Results showed that HF reduced enamel solubility by 54 and 36% after 1 and 7 days, respectively. After 14 and 28 days, there was no longer any effect. SnF2 showed no protective effect after the first day. Given these results, repeated application of HF and especially SnF2 may be necessary to improve the protective effect of these fluorides, and this requires further testing.

Method for measuring calcium constituent in silicon aluminum calcium barium alloy

Abstract: The invention discloses a method that is used for measuring the calcium element in a silicon, aluminum, calcium and barium alloy and comprises the following steps: a test sample is placed in a beaker, and deionized water is added until the test sample is wet; 9.5 to 10.5 millimeter of nitric acid is added; 1 to 2 millimeter of hydrofluoric acid is titrated; the mixture solution is heated until completely dissolved; perchloric acid is added; the mixture solution is heated until the sample volume is reduced to 1 to 2 millimeter; the mixture solution is naturally cooled; the perchloric acid is further added, and the mixture solution is heated until the sample volume is reduced to 1 to 2 millimeter; the hydrochloric acid and the deionized water are further added; the mixture solution is heated until all salts are dissolved, and the mixture solution is naturally cooled until the temperature is lower than 40 DEG C; the test sample is placed into a volumetric flask with scales and diluted with the deionized water; a mother solution is placed into a trigonal cup, the deionized water, trolamine (1 added by 1), lemery, bitter salt and an calcon-carboxylic acid are added, and the mother solution is adjusted to be red with potassium hydroxide; the potassium hydroxide is further added; EDTA is titrated until an end point that the mother solution becomes blue; an analyzing result is computed. The method does not need precipitation separation and filtration, and has the acute end point without intermediate color and raised measuring accuracy.

Austenitic stainless steel metallographic etchant, preparing method and use thereof

Abstract: The invention discloses a metallographic-phase aggressive agent of an austenitic stainless steel, a preparation method thereof and the application thereof. The metallographic-phase aggressive agent comprises the mixed solution of hydrofluoric acid and nitric acid, calculated by volume ratio, the proportion of each component of which is that hydrofluoric acid: nitric acid: water is equal to 2: 1: 7. The preparation method thereof is carried out according to the following steps of: taking 70 ml of water first, then taking 10 ml of analytically pure nitric acid and finally taking 20 ml of analytically pure hydrofluoric acid, which are then evenly missed. The application method thereof comprises the following steps of: putting a simple of the austenitic stainless steel in the metallographic-phase aggressive agent of the austenitic stainless steel and observing the color change of the surface of the sample by time, taking out the sample of the austenitic stainless steel when metallographic-phase surface of the sample is corroded to darker silver gray, washing the sample with water which is then neutralized with alkaline solution and finally washing with water and absolute ethyl alcohol. The technical effects thereof are represented by good corrosion effect, clear austenite grain boundary, slow corrosion speed, easy control, no pollution and other aspects.

Method for preparing high-voltage diac

Abstract: The invention relates to a method for preparing a high-voltage diac. In the method, a raw material silicon chip is processed in sequence by the following steps: chemical polishing, boron diffusion, oxidation of a mask, double-sided primary photoetching, phosphorous diffusion, nickel plating and alloying, scribing, welding, acid washing, protection, and packaging to obtain a finished product of the high-voltage diac, wherein the chemical polishing step is that the raw material silicon chip is evenly corroded in corrosion solution at the normal temperature for 3 to 5 minutes, washed for multiple times and dried to obtain a silicon chip (1) with the matt surface, and the corrosion solution is formed by mixing hydrofluoric acid, glacial acetic acid and nitric acid according to the volume ratio of 1:1 to 3:25 to 30; and the acid washing step is that a corrosion layer (8) is formed on the periphery of the silicon chip (1) obtained by soaking by mixed acid liquor, corroding and welding so as to obtain the electric performance, and the mixed acid solution is formed by mixing the hydrofluoric acid, the nitric acid, acetic acid and sulfuric acid according to the volume ratio of 9: 9: 9 to 15:4. The method has the advantages of simplified working procedure, low cost, reliable performance and corrosion resistance.

Method of manufacture of tri-crystalline si solar cell with surfactant and acid texture

Abstract: A method for manufacturing a solar cell of tricrystal silicon by using an acid solution wet etching method and surfactant is provided to further reduce reflectance of light by adding the surfactant when texturing a surface structure of an acid solution. An acid solution is manufactured by adding water (H2O) for the etching speed regulation properly to a mixture solution where hydrofluoric acid(HF) and nitric acid(HNO3) are mixed with a ratio of 1:1~1:15. By adding 500~10000ppm of triton as surfactant to the acid solution, an etching solution for surface structure texture is manufactured. The silicon substrate(10) is dipped in the etching solution for 5 seconds ~2 minutes. Thereof the surface structure of the substrate is improved. N-type dopant(20) is doped in a front side of the silicon substrate after the surface structure improvement stage. A reflection barrier layer(30) is formed in a front side of the doped N-type dopant. Aluminium is deposited on the back of the silicon substrate. Thermal processing is performed to form a P+ layer(42) and a back metal electrode(40). A front side metal electrode(50) is formed by using silver(Ag) on the front surface of the silicon substrate.

Molecular polarizabilities in aqueous proton transfer reactions

Abstract: Dipole polarizabilities of individual ions and molecules are computed from first principles in three condensed-phase systems: pure water, pure hydrofluoric acid, and an equimolar mixture of water and hydrofluoric acid in which HF is mostly ionized. We find that the polarizability of fluorine and oxygen centers varies linearly with the value of the bond order, which measures the local degree of advancement of the ionization reaction F–H+H2O⇄[Fδ−⋅H⋅Oδ+H2]⇄F−+H3O+. This observation explains the validity of the Lorentz–Lorenz formula for mixtures of acids and water and could have important practical consequences concerning the construction of empirical polarizable reactive force fields. Our results are consistent with the Mulliken charge-transfer picture of proton transfer reactions. The present results also suggest that the average isotropic polarizability of a chemical entity changes substantially only when that entity is involved in charge-transfer processes.

Preparation of magnesium fluoride

Abstract: The invention relates to a manufacturing method of magnesium fluoride, which takes ammonium fluoride and magnesium chloride as raw materials and comprises the steps as follows: (1) an ammonium fluoride solution whose concentration is 30 to 45 percent and a magnesium chloride solution whose concentration is 25 to 36 percent are added in a reaction kettle at the same time for reaction, and a magnesium fluoride ground-paste is generated; (2) the obtained magnesium fluoride ground-paste is filtered to prepare a magnesium fluoride paste which is cleaned by using hot water the temperature of which ranges from 60 to 70 DEG C; the magnesium fluoride paste is dried for 1 to 2 hours at the temperature ranging from 250 to 400 DEG C after washing, and the finished product of the magnesium fluoride is obtained The manufacturing method adopts the ammonium fluoride instead of hydrofluoric acid, wherein, the ammonium fluoride can be obtained through the ammonolysis by adding ammonia water into fluosilicic acid that is a by-product in the phosphate fertilizer industry; the fluosilicic acid is the deleterious-waste which is the by-product during the phosphate fertilizer production process, has very little purpose, and badly influences the environmental protection; in the manufacturing method, the development and the utilization of the fluosilicic acid greatly relieve the environmental protection pressure of the phosphate fertilizer production and the influences on the surrounding environment; and the cost is lower and the material is easy to get because the fluosilicic acid is the by-product in a phosphate fertilizer factory, thereby lowering the manufacturing cost of the magnesium fluoride

Method for fabricating semiconductor device

Abstract: A method for removing a semiconductor device is provided to maintain a stable semiconductor production condition by preventing generation of errors in semiconductor manufacturing equipment. A silicon nitride layer is formed on a semiconductor substrate(100). A first wet-etch process is performed to etch the silicon nitride layer by using a phosphoric acid solution(120). A second wet-etch process is performed to etch the silicon nitride layer by using the phosphoric acid solution. A first cleaning process is performed to clean the semiconductor substrate by using a first cleaning solution(130) including deionized water. A second cleaning process is performed to clean the semiconductor substrate by using a second cleaning solution including hydrofluoric acid. A drying process is performed to dry the semiconductor substrate.

Method for preparing silicon solar battery pile face in magnetic field

Abstract: The invention discloses a method for preparing a texture of a silicon solar cell under a magnetic field. The method comprises the following technological steps: firstly, a polysilicon wafer is put into a texture preparation reactor with prepared acid reaction solution for reaction, and the texture preparation reactor is put in the magnetic field, wherein, the reaction solution is made from 0.05%-15% of nitric acid or chromic acid by mass, 1%-30% of hydrofluoric acid by mass and 1%-30% of phosphoric acid or acetic acid by mass; the temperature of the reaction solution is kept at 0-30 DEG C, and the polysilicon wafer is washed in 0.5%-3% sodium hydroxide solution for 1-5 minutes after reaction in the acid solution; secondly, the magnetic field is applied in the whole course of preparing the texture of the silicon solar cell, the magnetic field strength is kept at 0-10T, and the texture preparation time is 1-45 minutes. A compact and even texture can be grown on the surface of the polysilicon wafer by the method, thus realizing the high-efficiency and even production of the silicon solar cell texture by acid oxidants under the magnetic field.

Niobium, tantalum, and titanium fluoride solutions

Abstract: Parameters for the preparation of concentrated tantalum, niobium, and titanium fluoride solutions by dissolution of their oxides or hydroxides in hydrofluoric acid were studied. Anatase titania, niobium oxide, and tantalum oxide calcined to 900°C were found to have high dissolution rates. Solid phases separated upon the dissolution of niobium, tantalum, and titanium oxides in hydrofluoric acid were identified as NbO2F, TaO2F, Ta3O7F, and TiOF2. Niobium hydroxide dissolution in an autoclave at the atmospheric pressure gave various complex salts: NH4NbOF4 and (NH4)3Nb2OF11.

Method of manufacturing vertical-cavity surface emitting laser

Abstract: According to a method of manufacturing a vertical-cavity surface-emitting semiconductor laser element in accordance with the present invention, a process of wet etching is performed for a part that is oxidized in a layer of an AlGaAs ( 42 ) which configures a layer having an index of refraction as lower and in which a composition of aluminum is designed to be as higher comparing to the other pairs of layers in a DBR mirror at an upper side that are formed at an inner side of a mesa post ( 38 ). And then a process of filling up again is performed with making use of a layer of polyimide ( 26 ). Moreover, an etchant that includes such as a hydrofluoric acid or a buffered hydrofluoric acid or an aqueous ammonia or the like is made use in order to perform such the process of wet etching.

Method for producing alkali niobate perovskite crystal

Abstract: PROBLEM TO BE SOLVED: To stably produce an alkali niobate perovskite crystal having a uniform texture. SOLUTION: Niobium pentoxide is dissolved in hydrofluoric acid. A precipitate is formed through a pH adjusting step of adding an aqueous alkali solution to the resultant solution, and the precipitate is dissolved in an aqueous citric acid solution to prepare a niobium raw material solution containing a chelate compound of niobium. An alkali raw material solution containing alkali metal ions is prepared and mixed with the niobium raw material solution. A deposit is formed from the mixed solution by adding ethanol to the mixed solution, a crystallization step of firing the deposit at a relatively low temperature in an oxidizing atmosphere is carried out, and then the product of the crystallization step is crushed, molded and fired at a relatively high temperature to obtain the objective alkali niobate perovskite crystal. COPYRIGHT: (C)2010,JPO&INPIT