Стандартизация в сфере менеджмента информационной безопасности

Описано сучасний стан стандартизації в сфері менеджменту інформаційної безпеки. Розглянуто вимоги до стандартів, що розробляються, типи стандартів, принципи, яких слід дотримуватись під час розроблення стандартів. Робота грунтується на матеріалах, прийнятих в підкомітеті ПК 27 «Методи захисту» об’єднаного технічного комітету ІСО/ МЕК ОТК 1 «Інформаційні технології».The article describes state of the art of the standardization in information security area. The requirements to the standards being developed, the types of standards, the principles to which it is required to follow are discussed. The contents of the article is based on the documents adopted within subcommittee 27 ”Security techniques” of the joint technical committee ISO/IEC JTC 1 “Information technology”

Etching of wide-bandgap chemically resistant semiconductors : An electrochemical study

The wide-bandgap semiconductors, SiC and GaN, are important for a whole range of (opto)electronic and other applications. Etching of these chemically very resistant materials poses problems in device technology. This thesis describes an electrochemical approach to etching. In addition, the use of p-type SiC as a photocathode for water splitting is described. For the (photo)electrochemical dissolution of SiC two etching systems are considered: acidic fluoride and alkaline solutions. The anodic current-potential curve of SiC in KOH solution shows a typical active/passive transition. The kinetics of the dissolution reaction were elucidated and interesting applications were identified. These include defect-selective, anisotropic and material-selective etching. Anodic etching of SiC in acidic fluoride solution, as in KOH solution, occurs for the p-type semiconductor in the dark and for the n-type semiconductor under illumination. What is striking for acidic solution is the growth of a micron-thick porous silicon oxide at positive potential. Electropolishing of p-type SiC is possible, while porous etching is observed for n-type 4H and 6H-SiC under illumination. The (photo)electrochemistry of n-type epitaxial GaN in alkaline peroxy¬disulphate (S2O82-) is described. The results form the basis for a consideration of the photoetching of the semiconductor. Three approaches are discussed: (i) photoanodic etching in which the potential of the semiconductor is fixed by a voltage source, (ii) photogalvanic etching in which the semiconductor is short circuited to the counter electrode (no voltage source), (iii) electroless photoetching (without a counter electrode). By using a two compartment cell, we showed that GaN short-circuited to a noble metal, acts as a photogalvanic cell. The factors determining the etching kinetics and surface morphology have been elucidated. It is shown that SiC is an interesting cathode for the hydrogen evolution reaction. Illuminated p-type SiC short-circuited to a platinum electrode in alkaline solution, splits water: hydrogen is formed at the semiconductor and oxygen at the metal. Surprisingly, the hydrogen can be stored in the semiconductor. These results offer interesting perspectives for hydrogen production from solar energy

Photoelectrochemistry and Etching of SiC: a Comparison with Si

Contains fulltext : 71911.pdf (author's version ) (Open Access)211th meeting of the ECS, 6 mei 200

Electrochemical Growth of Micrometer-Thick Oxide on SiC in Acidic Fluoride Solution\ud

Anodic polarization of SiC at modest potential in dilute fluoride solution of pH 3 surprisingly gives rise to the growth of micrometer-thick surface layers, clearly revealed with scanning electron microscopy. The reaction occurs at p-type SiC in the dark and at n-type SiC under (supra)bandgap illumination. The surface layer was shown by Rutherford backscattering spectrometry (RBS) to consist of silicon dioxide and to contain excess oxygen. Elastic recoil detection (ERD) indicated only a low level of carbon and fluoride in the layer but a considerable content of hydrogen. The growth kinetics was characterized in situ by spectroscopic ellipsometry and electrical impedance spectroscopy. The results suggest the formation of a duplex layer: a thin inner dielectric oxide and a thick hydrated outer oxide. The latter must have a considerable degree of porosity to allow diffusion/migration of reactants and products during oxide growth.\u

Photoetching mechanisms of GaN in alkaline S2O2-8

A study of the electrochemistry of n-type GaN in an alkaline peroxydisulfate S2O8 2− solution was used to explain the mechanism of photoetching of the semiconductor under open-circuit conditions. The observed enhancement of the photoetch rate as a result of platinum either directly on or in electrical contact with the semiconductor is shown to be mainly a photogalvanic effect. The factors determining the etching kinetics and surface morphology are elucidated

Electrochemistry of anodic etching of 4H and 6H–SiC in fluoride solution of pH 3

Electrochemical etching of single-crystal SiC rotating disk electrodes in fluoride solution was studied at pH 3. Anodic dissolution and passivation are observed for p-type electrodes in the dark and for n-type electrodes under illumination. The dissolution of p-type (0 0 0 1) 4H–SiC is found to be under mixed transport/kinetic control; the diffusion current is first order in fluoride concentration. Polishing of p-type electrodes can be achieved at rates up to 5.8 μm/min. Porous etching was not observed in this case. The surface finish of n-type (0 0 0 1) 4H and 6H–SiC depends on the experimental conditions; both uniform and porous etching are observed. The results are compared with those of Si under comparable conditions

Electrochemistry and etching of wide bandgap chemically resistant semiconductors

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The K2S2O8-KOH photoetching system for GaN

A recently developed photoetching system for n-type GaN, a KOH solution containing the strong oxidizing agent potassium peroxydisulphate (K2S2O8), was studied in detail. By careful selection of the etching parameters, such as the ratio of components and the hydrodynamics, two distinct modes were defined: defect-selective etching (denoted by KSO-D) and polishing (KSO-P). Both photoetching methods can be used under open-circuit (electroless) conditions. Well-defined dislocation-related etch whiskers are formed during KSO-D etching. All types of dislocations are revealed, and this was confirmed by cross-sectional TEM examination of the etched samples. Extended electrically active defects are also clearly revealed. The known relationship between etch rate and carrier concentration for photoetching of GaN in KOH solutions was confirmed for KSO-D etch using Raman measurements. It is shown that during KSO-P etching diffusion is the rate-limiting step, i.e. this etch is suitable for polishing of GaN. Some constraints of the KSO etching system for GaN are discussed and peculiar etch features, so far not understood, are describe

Influence of electrochemical etching on electroluminescence from n-type 4H- and 6H-SiC

The influence of electrochemical etching on the electroluminescence properties of n-type 6H- and 4H-SiC was investigated. Luminescence was generated by forward-biasing the semiconductor in an electrolyte solution containing a hole-injecting species. The emission properties of unetched, uniformly etched, and porous-etched substrates are compared. It is shown that the spectral distribution of the luminescence and the emission intensity strongly depends on photoanodic treatment