银覆盖冠状硅柱阵列基底的制备、SERS特性分析及肿瘤标志物miRNA-106a的检测

以聚苯乙烯(PS)小球为模板,采用金属辅助刻蚀和湿法化学刻蚀技术,制备大面积冠状硅柱阵列,再原位生长银纳米粒子后得到银覆盖冠状硅柱阵列(Ag/Si CPA)基底。实验表明,制备的基底具有优良的表面增强拉曼散射(SERS)特性,电磁增强因子达到1.81×10~6。同时,将制备的罗丹明分子(R6G)标记的DNA发卡探针与基底链接,在与miRNA-106a互补杂交后进行SERS信号检测,获得相应的剂量-响应曲线。结果表明,基于(Ag/Si CPA)基底的SERS特性,开展miRNA-106a的检测,具有特异性好和灵敏度高的优势,检测范围为1 fmol·L~(-1)～100 pmol·L~(-1),检测极限为0.917 fmol·L~(-1)。此外,与实时荧光定量多聚核苷酸链式反应(RT-qPCR)方法相比,不仅检测结果一致,而且基于SERS光谱技术的检测方法具有更高的灵敏度。     

The study of the solution concentration influencing on laser-induced electrochemical etching silicon

The laser electrochemical etching process, which combines the laser direct etching process and the electrochemical etching process, is a compound etching technique. In order to further understand the solution concentration influencing on the laser-induced electrochemical etching of silicon; a 248 nm excimer laser as a light source and KOH solution as an electrolyte were adopted in this study. The experiments of micromachining silicon by laser-induced electrochemical etching were carried out. On the basis of the experiments results, the solution concentration influencing on the etching rates in the process of laser electrochemical etching of silicon was researched. The reasons of the etching phenomena were analyzed in detail. The experimental results indicate that the solution concentration influencing on the etching process is mainly rooted in the absorption of different concentration solutions to laser. In general, less absorption and low solution concentration are good for the etching role in the process of laser electrochemical etching.     

Nanostructural and photoluminescence features of nanoporous silicon prepared by anodic etching

The nanostructural and photoluminescence (PL) features of nanoporous Si (NPS) were investigated in terms of various process parameters such as current density, etching time and oxidation conditions. The NPS was prepared by electrochemical anodic etching of p-type (0 0 1) Si wafers of 4 Ω cm resistivity in HF solution. The pores are of polygon-type columns with 5, 6 and 7 side walls. The average diameter of the column-shaped pores is critically determined by the current density, while the etching time plays an important role on the pore depth; in particular, when the current densities of 30 and 100 mA/cm² were applied, the pore diameters were 9 nm and 3.3 μm, respectively. The variation in the PL characteristics of the NPS with oxidation condition and etching current density was measured and then related with their structural changes. The aging and thermal treatments produce oxidation and lattice distortion in the NPS. The degree of deviation from the as-prepared NPS during aging or thermal treatment seems to depend on the nanostructure as well as morphology of the NPS. It is found in this study that etching current density plays an important role on such structural features of the NPS.     

Fabrication of microrods and microtips of InP by electrochemical etching

Here we presented a simple approach to fabricate the microstructures of InP by electrochemical etching. Microrods were formed while InP etched in 7 M HCl solutions for 30 s, and microtips were obtained while InP etched for 120 s. In addition, with increasing applied potential the surface of the microrods became smoother. The formation mechanism was also discussed in this article.     

New detectors on the basis of copolymer of tetrafluoroethylene with ethylene (PTFE-E)

The registration properties of PTFE-E (F-40, Russia; Tefzel, DuPont, USA; Hostaflon ET, Germany) having exceptional chemical and thermal (about 300°C) resistance are considered. The polymer samples were irradiated with ions in a wide region of masses (from O up to Xe) and energies (from 1 to 6 MeV/amu). Alkaline KMnO₄ solutions at 100°C were used for etching. It is shown that the polymer registration properties depend on the hydrogen content in the polymer. For a copolymer with 2–3 wt% of hydrogen the registration threshold is about 8 MeVcm²/mg. The ion tracks were not found after chemical etching for a copolymer with 1 wt% of hydrogen. Track membranes were produced and examined.     

The pore opening process and its influence on conductivity measurements of irradiated polymer films by application of the electrochemical etching method

The technique of the electrochemical etching of irradiated polymer films is an useful method to investigate structures of the track cores.

The transversale etching rate as a function of the radius, derived from the time-dependence of the radius of the etching pore, can be interpreted as a corresponding magnitude of the degree of the damage within the track core.

In the case of polymer films irradiated by a high track density, the influence of the time distribution of the breakthroughs (pore opening process) of the etching microchannels on the conductivity changes during the etching process is to be discussed. First represented results lead to statements about the statistical nature of the pore opening process.     

Real-time monitoring of SiO2/Si(1 1 1) interlayer etching by Brewster-angle reflectometry

A transitory etching regime after SiO₂ dissolution and before bulk Si(1 1 1) etching in neutral NH₄F solutions was monitored by in situ Brewster-angle reflectometry (BAR). An observed intermediate increase of the BAR reflectance signal is attributed to a fast dissolution of a stressed/strained interlayer beneath the SiO₂/Si(1 1 1) interface. Similar effects were observed on thin thermal oxides (18.2 nm), grown on float zone silicon, as well as on ultra-thin native oxides (1.2 nm) on Czochralsky silicon. Native oxide covered samples showed an increased surface roughness in the course of interlayer dissolution while the surface is progressively covered with compounds of fluorinated silicon. The etch rate, determined by atomic force microscopy (AFM) and compared to the etch rate of bulk silicon, is increased by a factor of four. In the limit of extended etching, the known low etch rates for silicon in 40% NH₄F are observed. Structural and chemical properties of the interfacial layer were analyzed by synchrotron radiation photoelectron spectroscopy (SRPES) which confirmed the presence of Si^3+/4+ valence states throughout the interlayer and by near open-circuit potential (N-OCP) dark current measurements. As a result, oxide etch rates in NH₄F in the pH-range 7–8 as well as the silicon interlayer depth can be assessed by in situ BAR.     

On problem of ultrasensitive determination of man-made plutonium in living species

To improve the sensitivity of the method of Pu determination in specimens we applied two additional steps of chemical separation of Pu from U. After the usual chemical separation of Pu we used second step with ion-exchange column, where the ions of U⁴⁺ were absorbed by sorbent and Pu³⁺ ions remains in solution. For converting Plutonium to Pu³⁺ state the electrochemical procedure has been used. After the electrochemical separation procedure the solution was deposited onto quartz glass. Then the quartz glass plates were inserted into the gas mixture flow (SOCL₂+air) at the temperature 650°C. Such a procedure extracts ≥90% U from Pu layer. Now we provide the chemical separation of Pu from U by a factor ≥10⁷. It means that now we are able to perform the routine Pu analysis at the level of sensitivity 10⁻¹⁴–10⁻¹⁵ g/g.

By using combined n-γ activation technique we can determine the Pu content in the small fragments of tissues of living species with the weight as small as 0,05-0,1 gram. The new technique could be used in routine analysis of Pu in population of heavily Pu damaged regions (Chernobyl, Ural Region, Semipalatinsk).     

Performance of CR-39 with addition of DOP (dioctylphthalate) for fast neutron dosimetry

The ENEA fast neutron dosemeter is based on a planar poly allyl diglicol carbonate (PADC) placed in a polyethylene holder. The present paper reports the results of an experimental study of a CR-39^® material with the addition of 0.1% of dioctylphthalate (DOP) produced by the Italian company Intercast Europe S.p.A.

The etching procedure is: pre-etching with 40% KOH water solution 6.25 N and 60% ethyl alcohol at 70°C followed by 12 h of etching in 6.25 N KOH water solution. For the energy dependence of response, dosemeters have been irradiated with neutron sources (²⁴¹Am–Be, ²⁵²Cf, Pu–Li) and 14.9 MeV monoenergetic neutrons. The dosimetric performance of the material for fast neutrons is expressed in terms of sensitivity, background value, lowest detectable dose and energy dependence of response. Moreover, the results of a quality acceptance test of the material, performed on 11 sheets (980×980 mm², 1.4 mm thick) of the same production batch, are given. Therefore, the homogeneity of the neutron sensitivity and of the background signal within a sheet and the whole batch is considered. The results are compared with the acceptance test outcome for a CR39 standard material batch.     

基于电感耦合等离子体的InP基半导体材料干法刻蚀的研究

研究了基于电感耦合等离子体(ICP)刻蚀系统的InP基半导体材料的干法刻蚀.采用Cl2/Ar/H:混合刻蚀气体,分别研究了氯气体积分数和ICP功率与刻蚀速率之间的关系,及镍、二氧化硅和二者结合型掩膜版的适用范围.获得有效的刻蚀速率为450～1 200 nm/min,InP对金属镍的选择性刻蚀比值为175～190.掩膜版...     

Superconducting flux flow transistor fabricated by an inductively coupled plasma etching technique

Superconducting flux flow transistors (SFFT) was successfully fabricated by an inductively coupled plasma (ICP) etching technique. YBaCuO thin films on LaAlO₃ substrate were patterned as a three-terminal device by a conventional wet etching method and the ICP system. The characteristics of a fabricated device were investigated by examining the I–V curves under various applied currents. The control current dependence of the transresistance was also measured. The SFFT with a channel fabricated by the ICP system showed a transistor-like characteristic over the liquid nitrogen temperature.     

Applications of porous silicon formed by electrochemical etching using an electrolyte based on HF:formaldehyde

In this work, we report the experimental results on the formation of porous silicon (PSi) monolayers by electrochemical etching using a formaldehyde based electrolyte. The results were compared with PSi monolayers obtained with the traditional electrolyte (HF:ethanol). Both electrolytes facilitate the removal of H₂ generated as a subproduct during the electrochemical etching process in the surface of the c-Si substrate. Formaldehyde presents a good affinity to surfaces and interfaces and the excess of water in the electrolyte reduces the pore sizes of PSi samples. The porosity and etching rate values are similar than those obtained using HF:et solutions. The refractive index values are the same in both cases at the same porosity in the visible range. The results have shown that the chemical characteristics of the ethanol and formaldehyde can give some different advantages to the PSi process and its applications.     

Design of a multifoil electrolytically controlled etching cell

Irradiating polymer films with heavy ions and subsequent electrolytically controlled etching (ECE) produces nuclear track filters with desired pore dimensions and pore density. During ECE, an electric field with low field strength and a frequency in the audio range is applied across the irradiated polymer film, which is immersed in the etching solution. An ECE cell for the simultaneous etching of three irradiated samples has been designed and developed. The average pore diameter and break-through time for tracks due to ²³⁸U(11.4 and 14 MeV/u) and ²⁰⁹Bi(13 MeV/u) ions in polycarbonate and polyethylene terepthalate have been measured.     

High sensitive electrolytical conductivity measurements of irradiated polymer films of 1μm thickness measured by a modified experimental set-up

The interaction of heavy ions with solids produces a narrow radial core of primary damage. The actual nature of the damage and the mechanism of its formation is not yet fully understood.

The technique of the electrochemical etching of irradiated samples is an useful method to investigate these structures of the track cores. The transversale etching rate as a function of the radius, derived from the time-dependence of the radius of the etching pore, can be interpreted as the corresponding magnitude of the degree of the damage within the track core.

To carry through measurements of smallest radii of etching pores, their very high electric resistance respectively, a sophisticated experimental set-up is required.

An advanced set-up is performed, which enables, by application of a combined d.c.-a.c.-method, to measure the resistance of the sample during the whole etching process, associated with the origin of pore and its growth up to radii of 10 nm and more.     

Analysis of machining characteristics in electrochemical etching using laser masking

Electrochemical etching using laser masking (EELM), which is a combination of laser beam irradiation for masking and electrochemical etching, allows the micro fabrication of stainless steel without photolithography technology. The EELM process can produce various micro patterns and multilayered structures. In this study, the machining characteristics of EELM were investigated. Changes in characteristics of recast layer formation and the protective effect of the recast layer according to the laser masking conditions and electrochemical etching conditions were investigated by field emission scanning electron microscopy (FE-SEM), focused ion beam (FIB) and X-ray photoelectron spectroscopy (XPS). The oxidized recast layer with a thickness of 500 nm was verified to yield a superior protective effect during electrochemical etching and good form accuracy. Finally, micro patterns and structures were fabricated by EELM.     

Nanoporous silicon fabricated at different illumination and electrochemical conditions

The properties of porous silicon prepared at different illumination and electrochemical conditions were studied. The preparation procedure was based on the electrochemical etching in HF containing electrolyte. In the dissolution of n-type silicon, an external source of light is necessary to obtain a sufficient holes flux density. Here, illumination was applied from the backside of the wafer (the side not immersed in the electrolyte), from topside (the side immersed in the electrolyte), and for the highly doped silicon, etching proceeds without illumination. The electrolyte contains HF in the range 2–50 wt%. The highest current density flows with topside assisted illumination. Backside illumination and etching in the dark resulted in a reduction in the current density. In the dark the current density significantly increased at a higher anodic bias. These conditions gave rise to pores formation with a diameter from 20 nm up to 3 μm. The smallest pore size was obtained for highly doped n-Si (111) wafers, etched without illumination. The present paper confirms the possibility of porous silicon formation in the dark and with backside illumination, these being alternative methods for topside assisted illumination etching methods.     

Energy loss dependent transversal etching rates of heavy ion tracks in plastic

By the method of electrolytical etching track etching rates V_t and corresponding transversal track etching rates V_trans of single heavy ion tracks in thin Makrofol KG foils have been measured at ion energies from 10–480 MeV/u. Makrofol KG foils of 8 μm thickness were irradiated perpendicular to the surface with ⁷⁹Au and ⁵⁴Xe ions at specific energies with energy loss values of REL=(10–90) ^*10³ MeVcm²/g at GSI Darmstadt, Germany, and Lawrence Berkeley Lab., Cal., USA. Using the electrolytical etching method by measuring the resistance of the foil during the etching process (etching conditions: 6n NaOH, room temperature and controlled 50° C) the breakthrough time and track etching rates V_t, V_trans and V_m (bulk etching rate) were analysed. Response curves (V_t/V_m)-1 as a function of Restricted Energy Loss (REL), the maximum extension of the ion induced damage perpendicular to the ion path and the dimension of the ion track core depending on the deposited energy can be estimated.     

Increased surface roughness by oxygen plasma treatment of graphite/polymer composite

The technology of selective plasma etching was applied to increase the surface roughness of graphite/polymer composite. Etching was performed with a low pressure weakly ionised oxygen plasma created with a RF generator of the output power of 200 W and frequency of 27.12 MHz. The density of charged particles, density of neutral oxygen atoms and the electron temperature was about 1×10¹⁶ m⁻³, 4×10²¹ m⁻³, and 5 eV, respectively. The effects of plasma treatment were observed by scanning electron microscope (SEM), electron microprobe (EMPA) and Talysurf. It was found that the surface roughness was increased by approximately 15 times, from a virgin sample at the roughness of R_a=0.27 μm to a very rough surface with R_a=4 μm. The roughness increased with increasing plasma exposure time. The EMPA results showed that the amount of sulphur in the surface layer decreased with increasing etching time indicating that PPS polymer was the material etched preferentially.     

Fluorination of the silicon dioxide surface during reactive ion and plasma etching in halocarbon plasmas

Surface sensitive spectroscopies were employed to investigate the surface modifications which occur on SiO₂ during actual reactive ion and plasma etching in CF₄ and CF₄/O₂ plasmas. Photoemission and electron energy loss spectroscopies were used to characterize the composition and bonding in the modified layer. Core level photoemission measurements indicated a reaction layer 10–15 Å thick with a mean composition of SiOF₂. Photoemission and EELS studies of the valence bands identified several features due to Si---F bonding. Comparisons with the SiO₂ valence bands and implications for bonding are discussed. Electron energy loss spectra were also used to determine if ion induced “defect” species formed during reactive etching persist in the reaction layer. A comparison of reactive ion etching samples with those exposed to plasma etching conditions (negligible ion bombardment) indicated that the ion bombarded surfaces exhibit a reduced level of fluorination during steady state etching. Low energy ion scattering was used to determine the composition of the outermost atomic layer. These measurements indicated a fluorine terminated surface with virtually no remaining surface oxygen.     

Track sensitivity and the surface roughness measurements of CR-39 with atomic force microscope

Atomic Force Microscope (AFM) has been applied to evaluate the surface roughness and the track sensitivity of CR-39 track detector. We experimentally confirmed the inverse correlation between the track sensitivity and the roughness of the detector surface after etching. The surface of CR-39 (CR-39 doped with antioxidant (HARZLAS (TD-1)) and copolymer of CR-39/NIPAAm (TNF-1)) with high sensitivity becomes rough by the etching, while the pure CR-39 (BARYOTRAK) with low sensitivity keeps its original surface clarity even for the long etching.