Development-free vapor photoetching effect of azide-type photopolymers

A new dry photoetching process that dose not required development step had been developed, utilizing the development-free vapor photoetching effect of cinnamate-type photopolymers.^1–3 In contrast to obtaining positive patterns with cinnamate-type photopolymers, this process with azide-type photopolymers, which consist of axide crosslinking agent and polymers, gives negative patterns. Some preliminary studies on the development-free vapor photoetching effect of azide-type photopolymers were made. The results indicate that the polymers in this process only play the role of forming a film on the surface of silicon dioxide; and the crosslinking agent is the most important factor, which leads the difference of etching rate between the exposed and unexposed areas.     

Anisotropic etching of silicon in hydrazine

This paper contains a detailed discussion of the practical issues related to the anisotropic etching of single crystal silicon using a 5050 hydrazinewater solution. Characteristics of the etchant, etching reactor design, etch procedures, safety precautions, etch rate data for typical samples and appropriate etch-masks are among the topic discussed. The etching process is carried out in a atmospheric reflux reactor, continuously purged with nitrogen. The etch rate of (100) silicon at 115°C in this hydrazine solution is nearly 3 μm/min, which is much higher than that of ethylenediaminepyrocatecholwater (EDP) solutions. Silicon dioxide, silicon nitride and most metallic thin films, except aluminium, can be used to mask the etching process. The etch rate is reduced significantly in highly-boron-doped silicon; a boron concentration of 1.5 × 10²⁰ cm⁻³ practically stops the etch. The use of the hydrazine solution for micromachining thin silicon diaphragms, cantilevers and fibers is demonstrated.     

In situ and Real-Time Monitoring of Plasma-Induced Etching of PET and Acrylic Films

Residual gas analysis (RGA) and optical emission spectroscopy have been evaluated as potential in situ techniques for the detection of plasma-induced polymer surface etching. The detection is based on the measurement of CO and CO₂ species formed in the gas phase following oxidation of the etching fragments released from the polymer surface. Experiments were performed on poly(ethylene terephthalate) and UV-cured acrylic (tripropylene glycol diacrylate) films exposed to O₂ RF (13.56 MHz) plasmas. A linear correlation is obtained between the formation of CO and the polymer etching rate over the entire experimental range, but discrepancies appear for the formation of CO₂ at high treatment powers (etching rate > 1.0 g/min.cm²). This behavior is attributed to a deficit of oxidizing agents relative to the generation of etching fragments. The results suggest that both RGA and optical emission spectroscopy can be used to monitor in situ and in real-time the etching of polymer surfaces during plasma treatment.     

Surface characterization and depth profiling of biological molecules by electrospray droplet impact/SIMS

Electrospray droplet impact (EDI) was applied to the analysis of peptides. The etching rate of bradykinin was estimated to be ~2 nm/min. This value is about one order of magnitude greater than the etching rate for SiO₂ (0.2 nm/min). Considering that the etching rate of argon cluster ions Ar₇₀₀⁺ for organic compounds is more than two orders of magnitude larger than that for inorganic materials, the rather small difference in etching rates of EDI for organic and inorganic materials is unique. When water/ethanol (1/1, vol%) solution of gramicidin S and arginine was dried in air, [gramicidin S + H]⁺ was observed as a predominant signal with little [Arg + H]⁺ right after the EDI irradiation, indicating that EDI is capable of detecting the analytes enriched on the sample surface. Copyright © 2011 John Wiley & Sons, Ltd.     

Photoelectrochemical behavior,XPS and Auger of n-In_2S_3

n-In_2S_3 has been prepared by CVT method.The photoelectrochemical behavior of n-In_2S_3 in a polysulfide redox solution was investigated.It was found that photoetching remarkablyincreased the fill factor.The maximum quantum efficiency of carrier collection reached 95% after 12hirradiation at 100 mW/cm~2 at an applied potential of+1.2V.XPS and Auger analysis were carriedout for examining surface and bulk concentration.The photoetching effect could be satisfactorilyexplained.     

Photoresponsive Nanosheets of Polyoxometalates Formed by Controlled Self‐Assembly Pathways

Anionic Keggin polyoxometalates (POMs) and ether linkage‐enriched ammonium ions spontaneously self‐assemble into rectangular ultrathin nanosheets in aqueous media. The structural flexibility of the cation is essential to form oriented nanosheets; as demonstrated by single‐crystal X‐ray diffraction measurements. The difference in initial conditions exerts significant influence on selecting for self‐assembly pathways in the energy landscape. Photoillumination of the POM sheets in pure water causes dissolution of reduced POMs, which allowed site‐specific etching of nanosheets using laser scanning microscopy. By contrast, photoetching was suppressed in aqueous AgNO₃ and site‐selective deposition of silver nanoparticles occurred as a consequence of electron transfer from the photoreduced POMs to Ag⁺ ions on the nanosheet surface.     

Fluorine‐Free Synthesis of High‐Purity Ti3C2Tx (T=OH,O) via Alkali Treatment

MXenes, 2D compounds generated from layered bulk materials, have attracted significant attention in energy‐related fields. However, most syntheses involve HF, which is highly corrosive and harmful to lithium‐ion battery and supercapacitor performance. Here an alkali‐assisted hydrothermal method is used to prepare a MXene Ti₃C₂T_x (T=OH, O). This route is inspired from a Bayer process used in bauxite refining. The process is free of fluorine and yields multilayer Ti₃C₂T_x with ca. 92 wt % in purity (using 27.5 m NaOH, 270 °C). Without the F terminations, the resulting Ti₃C₂T_x film electrode (ca. 52 μm in thickness, ca. 1.63 g cm^?3 in density) is 314 F g^?1 via gravimetric capacitance at 2 mV s^?1 in 1 m H₂SO₄. This surpasses (by ca. 214 %) that of the multilayer Ti₃C₂T_x prepared via HF treatments. This fluorine‐free method also provides an alkali‐etching strategy for exploring new MXenes for which the interlayer amphoteric/acidic atoms from the pristine MAX phase must be removed.     

Fluorine‐Free Synthesis of High‐Purity Ti3C2Tx (T=OH,O) via Alkali Treatment

MXenes, 2D compounds generated from layered bulk materials, have attracted significant attention in energy‐related fields. However, most syntheses involve HF, which is highly corrosive and harmful to lithium‐ion battery and supercapacitor performance. Here an alkali‐assisted hydrothermal method is used to prepare a MXene Ti₃C₂T_x (T=OH, O). This route is inspired from a Bayer process used in bauxite refining. The process is free of fluorine and yields multilayer Ti₃C₂T_x with ca. 92 wt % in purity (using 27.5 m NaOH, 270 °C). Without the F terminations, the resulting Ti₃C₂T_x film electrode (ca. 52 μm in thickness, ca. 1.63 g cm⁻³ in density) is 314 F g⁻¹ via gravimetric capacitance at 2 mV s⁻¹ in 1 m H₂SO₄. This surpasses (by ca. 214 %) that of the multilayer Ti₃C₂T_x prepared via HF treatments. This fluorine‐free method also provides an alkali‐etching strategy for exploring new MXenes for which the interlayer amphoteric/acidic atoms from the pristine MAX phase must be removed.     

Enriched Surface Oxygen Vacancies of Photoanodes by Photoetching with Enhanced Charge Separation

A facile photoetching approach is described that alleviates the negative effects from bulk defects by confining the oxygen vacancy (O_vac) at the surface of BiVO₄ photoanode, by 10‐minute photoetching. This strategy could induce enriched O_vac at the surface of BiVO₄, which avoids the formation of excessive bulk defects. A mechanism is proposed to explain the enhanced charge separation at the BiVO₄ /electrolyte interface, which is supported by density functional theory (DFT) calculations. The optimized BiVO₄ with enriched surface O_vac presents the highest photocurrent among undoped BiVO₄ photoanodes. Upon loading FeOOH/NiOOH cocatalysts, photoetched BiVO₄ photoanode reaches a considerable water oxidation photocurrent of 3.0 mA cm^?2 at 0.6 V vs. reversible hydrogen electrode. An unbiased solar‐to‐hydrogen conversion efficiency of 3.5 % is realized by this BiVO₄ photoanode and a Si photocathode under 1 sun illumination.     

Use of CF3,Br/Al,discharges for reactive ion etching of III-V semiconductors

The reactive ion etching of GaAs, InP, InGaAs, and InAlAs in CF₃Br/Ar discharges was investigated as a function of both plasma power density (0.56-1.3 W - cm^–2) and total pressure (10-40 mTorr) The etch rate of GaAs in 19CF₃Br:1Ar discharges at 10 m Torr increases linearly with power density, from 600 Å min^–1 at 0.56 W · cm^–2, to 1550 Å · min at 1.3 W · cm^–2. The in-based materials show linear increases in etch rates only for power densities above – 1.0 W · cm^–2. These etch rates are comparable to those obtained with CCI₂F₂:O₂ mixtures under the same conditions. Smooth surface morphologies and vertical sidewalls are obtained over a wide range of plasma parameters. Reductions in the near-surface carrier concentration in n-type GaAs are evident for etching with power densities of >0.8 W cm^–2, due to the introduction of deep level trapping centers. At 1.3 W· cm^–2, the Schottky barrier height of TiPtAu contacts on GaAs is reduced from 0.74 to 0.53 eV as a result of this damage, and the photoluminescent intensity from the material is degraded. Alter RIE, we detect the presence of both F and Br on the surface of all of the semiconductors. This contamination is worse than with CCl₂F₂-based mixtures. High-power etching with CF₃Br/Ar together with Al-containing electrodes can lead to the presence of a substantial layer of aluminum oxide on the samples if the moisture content in the reactor is appreciable.     

Alleviation of polyatomic ion interferences for determination of chlorine isotope ratios by inductively coupled plasma mass spectrometry

A simple variation in sample preparation and introduction allows the measurement of chlorine isotope ratios by inductively coupled plasma mass spectrometry (ICP/MS). Dissolution of the sample in D₂O rather than H₂O attenuates the major polyatomic ion ³⁶ArH⁺ and frees m/z 37 for determination of ³⁷Cl⁺. The isotope ratio ³⁵Cl/³⁷Cl in a 50 mg/L solution of Cl as LiCl is determined with a relative standard deviation of 0.21%. Sample memory is low, as the ³⁵Cl signal decays to less than 1% of its original value after ～2 min of cleanout with D_2O . The detection limit for Cl using this procedure is approximately 20 μg/L.     

Etching Characteristics and Mechanisms of Mo and Al2O3 Thin Films in O2/Cl2/Ar Inductively Coupled Plasmas: Effect of Gas Mixing Ratios

An investigation of etching behaviors for Mo and Al₂O₃ thin films in O₂/Cl₂/Ar inductively coupled plasmas at constant gas pressure (6 mTorr), input power (700 W) and bias power (200 W) was carried out. It was found that an increase in Ar mixing ratio for Cl₂/Ar plasma results in non-monotonic etching rates with the maximums of 160 nm/min at 60 % Ar for Mo and 27 nm/min at 20 % Ar for Al₂O₃. The addition of O₂ in the Cl₂/Ar plasma causes the non-monotonic Mo etching rate (max. 320 nm/min at 40–45 % O₂) while the Al₂O₃ etching rate decreases monotonically. The model-based analysis of etching kinetics allows one to relate the non-monotonic etching rates in Cl₂/Ar plasma to the change in the etching regime from the ion-flux-limited mode (at low Ar mixing ratios) to the neutral-flux-limited mode (for high Ar mixing ratios). In the Cl₂/O₂/Ar plasma, the non-monotonic Mo etching rate is probably due to the change in reaction probability.     

Plasma-induced chemical etching generating Ni3S2 for formaldehyde detection

In this paper,Ni₃S₂ nanosheet （NS） was generated by chemical etching with sodium sulfide directly on the nickel foam （NF）,which was induced by dielectric barrier discharge plasma in liquid.Compared with other chemical etching methods of nickel-based nanomaterials,this method was not only rapid （40 min）and mild （at room temperature and atmospheric pressure）,but also showed consistent stability and good reproducibility.The Ni₃S₂NS/NF electrode showed exc...     

Correlation of SiO x layer thickness and properties of BOPP/SiO x composite films with spin coating process parameters

The effects of the spin coating process parameters on the thickness of the SiOx layer of the BOPP/SiOx composite film were investigated. When the concentration of tetraethoxysilane (TEOS) increased from 12.5 vol% to 55% vol%, the SiOx thickness increased from about 80 nm to 470 nm. In the sol time range of 1.5 h to 5 h the SiOx layer thickness reached a maximum at about 4 h and the change of the thickness roughly matched the change of the silica colloidal sphere sizes in sol. When the spin-coating speed of the dispensing stage increased from 450 r/min to 500 r/min, the SiOx layer thickness drastically decreased from about 1.67 μm to 400 nm. While the spin-coating speed of the thinning and drying stage went up to 1200 r/min, the SiOx layer thickness was in the range of 330 nm to 390 nm. It was also found that the SiOx layer thickness was almost increased linearly from about 500 nm to 1.02 μm with the ratio of the commercial silica colloidal to the TEOS from 0.2 to 1.0. The water contact angles decreased to about 23.0° for the BOPP/Si-Sol composite film with 1.67 μm SiOx layer and about 4.0° for the BOPP/mixing Si-Sol composite film with 1.02 μm SiOx layer. Compared to BOPP, the light transparency of the BOPP/Si-Sol composite films decreased by about 5.5% with the SiOx layer from about 80 nm to 1.67 μm and by 7.0% for the BOPP/mixing Si-Sol composite film with the SiOx layer from about 350 nm to 1.02 μm respectively.     

Single DNA Condensation Induced by Hexammine Cobalt with Molecular Combing

We investigated the interaction between DNA and hexammine cobalt III [Co(NH₃)₆]³⁺ by a simple molecular combing method and dynamic light scattering. The average extension of ?λ-DNA-YOYO-1 complex is found to be 20.9 μm, about 30% longer than the contour length of the DNA in TE buffer (10 mmol/L Tris, 1 mmol/L EDTA, pH=8.0), due to bis-intercalation of YOYO-1. A multivalent cation, hexammine cobalt, is used for DNA condensation. We find that the length of DNA-[Co(NH₃)₆]³⁺ complexes decrease from 20.9 μm to 5.9 μm as the concentration of the [Co(NH₃)₆]³⁺ vary from 0 to 3 μmol/L. This observation provides a direct visualization of single DNA condensation induced by hexammine cobalt. The results from the molecular combing studies are supported by dynamic light scattering investigation, where the average hydrodynamic radius of the DNA complex decreases from 203.8 nm to 39.26 nm under the same conditions. It shows that the molecular combing method is feasible for quantitative conformation characterization of single bio-macromolecules.     

The synthesis and lithographic evaluation of a new organosilicon novolac-based resist

A novel material, bis(trimethylsilylmethoxy resorcinol) was synthesized by a phenoxide alkylation method. The new substituted resorcinol was then terpolymerized with 2-methyl resorcinol and formaldehyde. We evaluated the preparation of this new polymer in terms of feed ratio of the reactants, reaction time, and temperature; and prepared a series of materials with different silicon content. Polymers which retained base solubility at high silicon content were blended with a dissolution inhibitor, and studied for their lithographic capabilities as positive, photo- or electron-beam bilevel resists. When used in a photoresist formulation a dose of 120 mJ/cm² allowed formation of submicron features. When used in an electron-beam resist formulation 0.5 μm line/space patterns were obtained at a dose of 10 μC/cm². Furthermore, these materials displayed etching ratios relative to hardbaked HPR206 of ? 1 : 10. This value is believed to be large enough to allow these resists to withstand reactive ion etching conditions for pattern transfer in a bilevel scheme.     

Water‐Developable Poly(2‐oxazoline)‐Based Negative Photoresists

Copoly(2‐oxazoline)‐based photoresists are prepared from pEtOx₈₀Bu⁼Ox₂₀ and pPhOx₈₀Dc⁼Ox₂₀ , respectively, a tetrathiol, and a photosensitive initiator. It is possible to prepare copoly(2‐oxazoline)s bearing unsaturated side chains in a microwave reactor on a decagram scale in reaction times of 100 min or shorter. UV irradiation of dried polymer films through a quartz mask induces the thiol‐ene reaction in the illuminated areas. Subsequent development of the polymer films in halogen‐free solvents reproduces the negative pattern of the mask with a resolution of 2 μm. The pEtOx₈₀Bu⁼Ox₂₀ ‐derived photoresists can also be developed in water.     

Development of Process for Fast Plasma-Chemical Through Etching of Single-Crystal Quartz in SF<Subscript>6</Subscript>/O<Subscript>2</Subscript> Gas Mixture

Process for deep plasma-chemical etching of single-crystal quartz plates in a SF₆/O₂ gas mixture was developed. The method of scientific experiment design based on the Taguchi matrix technique was used to rank basic technological parameters (bias voltage applied to the substrate holder, output power of the high-frequency generator, oxygen flow rate, and position of the substrate holder relative to the lower edge of the discharge chamber) as regards their influence on the etching rate. The ranking results were used to optimize the plasma-chemical etching process and perform a control experiment on through etching of windows with large linear dimensions (3 × 10 mm) in a single-crystal quartz plate (z-cut) with thickness of 369 μm.     

Optical spectroscopy of low-phonon Ho3+ doped BaY2F8 single crystal

The Ho:BaY₂F₈ crystal was grown by Czochralski method. The crystal phase structure and absorption spectra were tested, the absorption peak exists near 899 nm, the absorption cross section was 1.27 × 10^?21 cm². The emission spectra of crystals in the vicinity of 2 and 3.9 μm were measured, the 2 μm near infrared light induced by ⁵I₇ → ⁵I₈ transition of Ho3+ ions was observed, as well as the fluorescence output at 3.9 μm (⁵I₅ → ⁵I₆), emission cross section at 3.9 μm was calculated to be 0.86 × 10^?21 cm². We suppose that the Ho:BaY₂F₈ crystal has a large application prospect for the 2–4 μm wavelength near infrared laser.     

Cold Plasma Processing and Plasma Chemistry of Metallic Cobalt Surface

Plasma processing of metallic cobalt was experimentally investigated with three fluorine-containing gases, CF₄–O₂, SF₆–O₂, and NF₃ to determine the surface decontamination rate and to examine the reaction mechanism. Results show that the maximum etching rate reaches 17.12 μm/min with NF₃ gas at 420°C, while the rates are 2.56 μm/min and 1.14 μm/min with CF₄–O₂ and SF₆–O₂ gas, respectively, at the same temperature. AES analysis identified the constituent elements of the reaction products to be oxygen, fluorine, and cobalt, and XPS analysis reveals that the reaction product with all three plasma gases is very likely to be CoF₂.