Method for manufacture of powerful shf transistor
SUBSTANCE: method for manufacture of powerful SHF transistor includes application of a solder layer to the flange, shaping of pedestal, application of a sublayer fixing the transistor crystal to the pedestal, formation of p-type conductivity oriented at the plane (111) at the base substrate of single-crystalline silicon and auxiliary epitaxial layers, application of the basic layer and buffer layer for growing of epitaxial structure of a semiconductor device based on wide-gap III-nitrides, application of heat conductive layer of CVD polycrystalline diamond to the basic layer, removal of the basic substrate with auxiliary epitaxial layers up to the basic layer, growing of heteroepitaxial structure based on wide-gap III-nitrides on the basic layer and formation of the source, gate and drain. The heat conductive layer of CVD polycrystalline diamond is used as a pedestal; nickel is implanted to its surficial region and annealed. Before formation of the source, gate and drain an additional layer of insulating polycrystalline diamond and additional layers of hafnium dioxide and aluminium oxide are deposited on top of the transistor crystal; the total thickness of the above layers is 1.0-4.0 nm.
EFFECT: invention allows increased heat removal from the active part of SHF-transistor and minimisation of gate current losses.
6 cl, 4 dwg
The invention relates to the field of semiconductor technology and can be used in the manufacture of such devices as, for example, heteroderidae field-effect transistors (HEMT), bipolar transistors (BJT), heterobipolar transistors (HBT), p-i-n diodes, diodes with barrier of a Schottky and many others.
The prior art method of manufacturing a semiconductor device in which layers HPP applied epitaxial methods such as a method of chemical vapor deposition of ORGANOMETALLIC compounds (MOCVD), molecular beam epitaxy (MBE), hydride method of epitaxy from the vapor phase (HVPE), and others. Unlike traditional semiconductor materials wide bandgap III-nitrides have a hexagonal type of crystal lattice and receive them in the form of thin heteroepitaxial structures on substrates with hexagonal lattice type. For this purpose, as a rule, use a substrate of sapphire (Al2O3), silicon carbide (SiC), bulk aluminum nitride (AlN) or gallium nitride (GaN), pseudo GaN substrate of silicon with an orientation plane (111) (Si(111)), and stocking GaN (or AlN) substrate, which can serve as one of the above (see Compound Semiconductor. October 2004, 27-31).
The disadvantages of this method are the low efficiency of semiconductor devices, high degradation is the situation, due to the low heat dissipation from the active part.
In addition, the prior art method of manufacturing a semiconductor device, comprising growing on the base substrate, the polycrystalline diamond epitaxial auxiliary layers and epitaxial structure of a semiconductor device based on wide-gap III-nitrides. On the surface of the base substrate to form an auxiliary epitaxial layers, one of which is the base for growing epitaxial structure of a semiconductor device based on wide-gap III-nitrides. Auxiliary epitaxial layers grown polycrystalline diamond, and after growing diamond base substrate is removed along with supporting the epitaxial layers to the base layer, on which is grown an epitaxial structure of a semiconductor device based on wide-gap III-nitrides (see RF patent №2368031, publ. 20.09.2009).
The disadvantages of this method are fast enough and high degradation of the semiconductor device, due to the low heat sink.
The present invention is to eliminate the above disadvantages.
The technical result is to increase heat removal from the active part of the microwave transistor and to minimize the leakage current of the gate.
T is khnicheskie the result is the fact, a method for manufacturing high-power microwave transistor comprises applying to the flange of the layer of solder, the formation of the pedestal, the underlayer coating for attachment of the transistor crystal to the pedestal, forming on a base substrate of monocrystalline silicon of p-type conductivity, oriented on a plane (111), a subsidiary of epitaxial layers, the application of the base layer and the buffer layer for growing epitaxial structure of a semiconductor device based on wide-gap III-nitrides, drawing on the base layer thermal CVD polycrystalline diamond, removing the base substrate, together with supporting the epitaxial layers to the base layer, building on the base layer heteroepitaxial structures based on wide-gap III-nitrides and forming source, gate and drain. As the pedestal use the heat-conducting layer of polycrystalline CVD diamond in the surface region which is implanted Nickel and annealed. Prior to forming the drain, gate and source on top of the transistor crystal sequentially precipitated an additional layer of insulating polycrystalline diamond and additional barrier layers of hafnium dioxide and aluminum oxide, with a total thickness of 1.0 to 4.0 nm.
In accordance with particular cases of execution of the invention ameeshaaeysha features.
A buffer layer made of AlN or HfN.
A base layer made of a solid solution of AlxGa1-xN, where 0≤x≤1.
On the base layer grow heteroepitaxial structure in the form of layers of undoped GaN, solid solution AlGaN, of the solid solution AlGaN n+type conductivity and of the solid solution AlGaN.
Cover the pedestal sublayer of the AuGe alloy.
The essence of the present invention is illustrated by the following illustrations:
Fig.1-4 shows the sequence of manufacturing a multilayer epitaxial structure.
On the surface of the base substrate 1 of monocrystalline silicon of p-type, oriented on a plane (III), precipitated epitaxial layers 2 (Fig.1), at least the base layer 3 (Fig.2) designed for growing epitaxial structure of III-nitrides. As the base layer 3, on which is grown polycrystalline diamond 4, either one of the auxiliary epitaxial layers above layer 3. After growing polycrystalline diamond base substrate 1, for example of silicon, remove the widely known methods of wet and dry etching together with the epitaxial layers to the base layer 3 (Fig.3)on which is grown an epitaxial structure 5 III-nitrides (Fig.4).
Powerful microwave transistor is manufactured as follows.
On LAF the CE mark MD-40 with a thickness of 1600 microns put a layer of solder of AuSn thickness of 25 microns, which sealed the pedestal of the heat-conducting layer CVD polycrystalline diamond with a thickness of about 0.15 μm. On top of the layer of polycrystalline diamond after implantation in its near-surface region of the Nickel and subsequent annealing precipitated the underlayer composition AuGe thickness of ~25 µm, which then serves as a basis for strengthening crystal transistor to the pedestal of CVD polycrystalline diamond. As the base substrate using monocrystalline silicon of p-type conductivity, is oriented according to the plane (111). On the surface of the base substrate with the epitaxial layer of AlN with a thickness of 0.1 μm are increasing the base layer of solid solution AlxGa1-xN, where 0≤x≤1, over which is deposited thermally conductive layer CVD polycrystalline diamond thickness ≥0,15 mm After deposition of a layer of polycrystalline CVD diamond on the base layer, the base substrate of silicon removed is widely known methods of wet and dry etching, and the free surface of the layer of polycrystalline CVD diamond prepared for mounting crystal transistor to the pedestal, are implanted in the surface region of the layer of polycrystalline diamond Nickel and carry out annealing. Further on the base layer build up a buffer layer of AlN (in another particular case, the run - HfN). On top of the buffer layer sequentially, naradeva the t multilayer heteroepitaxial layers of III-nitrides, consisting of undoped GaN buffer layer, a solid solution AlGaN (space), solid solution AlGaN n+type conductivity, a layer of solid solution AlGaN (roof).
After manufacturing in the area of the source and drain of the low resistance podkonicky plots of n+type conductivity over the transistor crystal precipitated layer of insulating polycrystalline diamond. Remove the layer of insulating polycrystalline diamond from the site of the future location of the shutter, precipitated additional barrier layers of hafnium dioxide and aluminum oxide. The barrier layers have a total thickness of 1.0 to 4.0 nm. In the field of the future shutter these layers are placed directly on the surface of the solid solution AlGaN. After etching Windows in the insulating layer of polycrystalline diamond and the optional barrier layer over pokontaktnuyu layers form the source, gate, and drain ohmic contacts to the source, the drain and the crystal microwave transistor connected to the pedestal.
In this method of manufacturing a transistor technology is used planarization layer CVD polycrystalline diamond suitable for technology thermoperiodicity layers further instruments manufacturing method of implantation of Nickel in the surface region of the layer of polycrystalline CVD diamond with subsequent annealing.
Dost is a sacrament of this method is the fact, all layers in the structures obtained using the well-known epitaxial techniques and does not require special processing technology and/or methods of joining layers. The semiconductor structure is formed almost on the surface of the substrate a large structural thickness, and the surface of the crystal and as a pedestal transistor of vysokoteploprovodnyh polycrystalline diamond. Eliminates the need for time-consuming polishing surface layer CVD polycrystalline diamond suitable for technology thermoperiodicity layers in the further manufacture of the devices.
The use of technical solutions provides additional heat dissipation and reduction of leakage current in the crystal microwave transistor through additional layers of thermally conductive polycrystalline diamond and hafnium dioxide and aluminum oxide deposited on the crystal surface between the source, gate and drain of high-power microwave GaN transistor. This embodiment reduces thermal resistance of the transistor structure is more than 1.5 times and significantly reduces the leakage current of the gate.
The use of an additional layer of thermally conductive polycrystalline diamond on the surface of the crystal of the transistor between the source, gate and drain of microwave implemented the torus increases the breakdown voltage of the transistor more than 30%. It is also provided by the manufacturer under the shutter (on the surface of the solid solution AlGaN n-type conductivity) additional barrier layers of hafnium dioxide and aluminum oxide (mask), which significantly reduce the leakage current.
1. A method of manufacturing a high-power microwave transistor, comprising coating the flange layer of solder, the formation of the pedestal, the underlayer coating for attachment of the transistor crystal to the pedestal, forming on a base substrate of monocrystalline silicon of p-type conductivity, oriented on a plane (111), a subsidiary of epitaxial layers, the application of the base layer and the buffer layer for growing epitaxial structure of a semiconductor device based on wide-gap III-nitrides, drawing on the base layer thermal CVD polycrystalline diamond, removing the base substrate, together with supporting the epitaxial layers to the base layer, building on the base layer heteroepitaxial structures based on wide-gap III-nitrides and forming source, gate and drain, characterized in that the pedestal use the heat-conducting layer of polycrystalline CVD diamond in the surface region which is implanted Nickel and annealed, and prior to forming the drain, gate and source on top of the transistor crystal pic is edutella precipitated an additional layer of insulating polycrystalline diamond and additional barrier layers of hafnium dioxide and aluminum oxide, with a total thickness of 1.0 to 4.0 nm.
2. The method according to p. 1, characterized in that a buffer layer made of AlN.
3. The method according to p. 1, characterized in that a buffer layer made of a HfN.
4. The method according to any of paragraphs.1-3, characterized in that the base layer made of a solid solution of AlxGa1-xN, where 0≤x≤1.
5. The method according to p. 4, characterized in that the base layer grow heteroepitaxial structure in the form of layers of undoped GaN, solid solution AlGaN, of the solid solution AlGaN n+type conductivity and of the solid solution AlGaN.
6. The method according to p. 1, characterized in that the cover pedestal sublayer of the AuGe alloy.
SUBSTANCE: invention relates to semiconductor technology. Proposed method comprises removal of photoresist from at least one surface of conducting layer with the help of the mix of chemical including first material of self-optimising monolayer and chemical to remove said photoresist. Thus self-optimising monolayer is deposited on at least one surface of said conducting ply. Semiconductor material is deposited on self-optimising monolayer applied on conducting layer without ozone cleaning of conducting layer.
EFFECT: simplified method.
15 cl, 4 dwg
SUBSTANCE: semiconductor device comprises a thinned substrate of single-crystal silicon of p-type conductivity, oriented according to the plane (111), with a buffer layer from AlN on it, above which there is a heat conducting substrate in the form of a deposited layer of polycrystalline diamond with thickness equal to at least 0.1 mm, on the other side of the substrate there is an epitaxial structure of the semiconducting device on the basis of wide-zone III-nitrides, a source from AlGaN, a gate, a drain from AlGaN, ohmic contacts to the source and drain, a solder in the form of a layer including AuSn, a copper pedestal and a flange. At the same time between the source, gate and drain there is a layer of an insulating polycrystalline diamond.
EFFECT: higher reliability of a semiconducting device and increased service life, makes it possible to simplify manufacturing of a device with high value of heat release from an active part.
3 cl, 7 dwg
FIELD: electrical engineering.
SUBSTANCE: method for manufacture of a powerful UHF transistor includes formation of the topology of at least one transistor crystal on the semiconductor substrate face side, formation of the transistor electrodes, formation of at least one protective dielectric layer along the whole of the transistor crystal topology by way of plasma chemical application, the layer total length being 0.15-0.25 mcm, formation of the transistor crystal size by way of lithography and chemical etching processes. Prior to formation of the transistor crystal size, within the choke electrode area one performs local plasma chemical etching of the protective dielectric layer to a depth equal to the layer thickness; immediately after that one performs formation of protectively passivating dielectric layers of silicon nitride and diozide with thickness equal to 0.045-0.050 mm; plasma chemical application of the latter layers and the protective dielectric layer is performed in the same technological modes with plasma power equal to 300-350 W, during 30-35 sec and at a temperature of 150-250°C; during formation of the transistor crystal size ne performs chemical etching of the protectively passivating dielectric layers and the protective dielectric layer within the same technological cycle.
EFFECT: increased power output and augmentation ratio or powerful transistors with their long-term stability preservation.
4 cl, 1 dwg, 1 tbl
SUBSTANCE: method for UHF high-power transistors manufacturing includes formation of transistor topology semiconductor substratum on the face side by electronic lithography and photolithography methods, metals spraying on, dielectrics application and etching, cathodic electrodeposition of gold, formation of preset size grooves on the face side outside the transistor topology, substrate thinning, formation of grounding through holes for the transistors source electrodes, formation of a common integrated heat sink, formation of a integrated heat sink for each transistor crystal, semiconductor substrate division into transistor crystals; one uses a semiconductor substrate with the preset structure of active layers having two stop layers with the preset distance between them, the stop layers ensuring minimum thermal resistance; the semiconductor substrate reverse side thinning is performed down to the stop-layer located close to such side; grounding through holes are formed immediately on the source electrodes with the common integrated heat sink thickness is set by the type of the transistor crystal subsequent mounting.
EFFECT: enhanced output capacity through reduction of thermal resistance, parasitic of the electric resistance in series and source electrodes grounding inductance; increased yield ratio, repeatability and functionalities extension.
4 cl, 1 dwg, 1 tbl
SUBSTANCE: field transistor manufacturing method includes creation of source and drain contacts, active area identification, application of a dielectric film onto the contact layer surface, formation of a submicron chink in the dielectric film for the needs of subsequent operations of contact layer etching and application of gate metal through the resistance mask; immediately after the dielectric film application one performs lithography for opening windows in the dielectric at least one edge whereof coincides with the Schottky gates location in the transistor being manufactured; after the window opening a second dielectric layer is applied onto the whole of the surface with the resistance removed; then, by way of repeated lithography, windows in the resistance are created, surrounding the chinks formed between the two dielectrics; selective etching of the contact layer is performed with metal films sprayed on to form the gates.
EFFECT: simplification of formation of under-gate chinks sized below 100 nm in the dielectric.
SUBSTANCE: manufacturing method of microwave transistor with control electrode of T-shaped configuration of submicron length involves formation on the front side of semi-insulating semi-conductor plate with active layer of the specified structure of a pair of electrodes of transistor, which form ohmic contacts by means of lithographic, etching method and method of sputtering of metal or system of metals, formation of transistor channel by means of electronic lithography and etching, application of masking dielectric layer, formation in masking dielectric layer of submicron slot by means of electronic lithography and etching; at that, submicron slot is formed with variable cross section decreasing as to height from wide upper part adjacent to the head of the above control electrode to narrow lower part adjacent to transistor channel, formation of topology of the above control electrode by means of electronic lithography method, formation of the above control electrode in submicron slot by means of sputtering of metal or system of metals; at that, configuration of its base repeats configuration of submicron slot. During formation of submicron slot with variable cross section in masking dielectric layer, which decreases throughout its height, by means of electronic lithography and etching, the latter of masking dielectric layer is performed in one common production process in high-frequency plasma of hexafluoride of sulphur, oxygen and helium and discharge power of 8-10 W.
EFFECT: increasing output power and amplification factor, increasing reproducibility of the above output parametres and therefore yield ratio, simplifying and decreasing labour input for manufacturing process.
2 cl, 1 dwg, 1 tbl, 5 ex
FIELD: electronic engineering; high-power microwave transistors and small-scale integrated circuits built around them.
SUBSTANCE: proposed method for producing high-power microwave transistors includes formation of transistor-layout semiconductor wafer on face side, evaporation of metals, application and etching of insulators, electrolytic deposition of gold, formation of grooves on wafer face side beyond transistor layout for specifying transistor chip dimensions, thinning of semiconductor wafer, formation of grooves on wafer underside just under those on face side, formation of through holes for grounding transistor leads, formation of integrated heat sinks for transistor chips around integrated heat sink followed by dividing semiconductor wafer into transistor chips by chemical etching using integrated heat sinks of transistor chips as mask.
EFFECT: enhanced power output due to reduced thermal resistance, enhanced yield, and facilitated manufacture.
2 cl, 1 dwg, 1 tbl
FIELD: technologies for making transistors.
SUBSTANCE: method includes following stages: precipitation of electric-conductive material on substrate of semiconductor material, forming of shape of first parallel band electrodes with step, determined by appropriate construction rules, while areas of substrate in form of stripes between first electrodes are left open, precipitation of barrier layer, covering first electrodes down to substrate, alloying of substrate in open areas, precipitation of electric-conductive material above alloyed areas of substrate with forming of second parallel band electrodes, removal of barrier layer, near which vertical channels are left, passing downwards to non-alloyed areas of substrate between first and second electrodes, alloying of substrate in open areas of lower portion of channels, filling channels with barrier material, removal of first electrodes, during which gaps between second electrodes are left and substrate areas are opened between them, alloying of open areas of substrate in gaps, from which first electrodes were removed, removal of electric-conductive material in said gaps for restoration of first electrodes and thus making an electrode layer, containing first and second parallel band electrodes of practically even width, which are adjacent to alloyed substrate and separated from each other only by thin layer of barrier material, while, dependent on alloying admixtures, used during alloying stages, first electrodes form source or discharge electrodes, and second electrodes - respectively discharge or source electrodes of transistor structures, precipitation of insulating barrier layer above electrodes and separating barrier layers. Precipitation of electric-conductive material above barrier layer and forming in said electric-conductive material of shape of parallel band valve electrodes, directed transversely to source and discharge electrodes, thus receiving structures matrix for field transistors with very short channel length and arbitrarily large width of channel, determined by width of valve electrode.
EFFECT: ultra-short channel length of produced transistors.
11 cl, 17 dwg
SUBSTANCE: invention relates to hydrometallurgy of lanthanides, particularly, to crystalline nanopowders of lanthanide oxides. Proposed method comprises deposition of lanthanide salts from nitric solutions of solid oxalic acid at continuous introduction of polyacrylamide, its separation, flushing, drying, heat treatment of produced sediment and subsequent treatment in weak alternating magnetic field at 20-50 Hz and with amplitude of 0.05-0.1 tesla.
EFFECT: nanosized particles with uniform grain sizes, higher water resistance.
1 dwg, 1 tbl, 1 ex
FIELD: measurement equipment.
SUBSTANCE: invention relates to nano-, microelectronics and analytical instrument making industry and can be used for development of technologies and for production of products of micro- and nanoelectronics, as well as for production of pure materials and for diagnostics and control of liquid process media. A method for determining atomic composition of active impurities in liquid media consists in preparation of an analysed object and its arrangement in vacuum. Then, irradiation of surface with a beam of charged particles and recording of secondary particles, as per which composition of surface atoms is determined, is performed. Preparation of the analysed object is performed by preparation of surface of a semiconductor plate by chemical etching, treatment in a peroxide alkali solution and by washing in deionised water. A drop of analysed liquid with the size of at least one micron is applied to the prepared surface of a clean semiconductor plate, then, it is removed, and for the purpose of analysis, the removed drop trace is irradiated with a beam of charged particles.
EFFECT: improvement of analysis rapidness, as well as improvement of a detection limit, and namely at least by 10-100 times.
SUBSTANCE: invention relates to nanotechnology and is designed to produce nitride structures of nano-thickness. According to the first embodiment, the nitride nanofilm or nanowire is obtained by depositing the silicon layer on a fluoroplastic fibre or a fluoroplastic film followed by exposure to the temperature of 800-1200°C in the atmosphere of nitrogen or ammonia. According to the second embodiment the nitride nanofilm or nanowire is obtained by exposure the corundum fibre or film to the temperature of 800-1200°C in the atmosphere of nitrogen or ammonia in the presence of a reducing agent. According to the third embodiment, the nitride nanofilm or nanowire is obtained by deposition of boron layer on corundum fibre or film followed by exposure to the temperature of 1360°C in the atmosphere of nitrogen or ammonia at a pressure of 60-70 t/cm2 to obtain borazon.
EFFECT: inventions enable to extend the range of means of obtaining nitride nanofilms or nanowires.
3 cl, 4 ex
SUBSTANCE: invention relates to methods for obtaining amorphous mesoporous aluminium hydroxide with a laminated fibrous microstructure. A method for obtaining amorphous mesoporous aerogel of aluminium hydroxide with a laminated fibrous oriented nanostructure involves the performance of a synthesis reaction of aluminium hydroxide aerogel in a tight container by the treatment of a binary melt with a steam-gas flow based on a mixture of inert and (or) low-active gases with a water vapour at the melt temperature of 280-1000°C. As the binary melt, bismuth with the aluminium content of 0.05-7.00 wt % is used.
EFFECT: invention allows improving technical and economic indices at the production of nanostructured aerogel AlOOH.
1 dwg, 1 tbl
SUBSTANCE: polyacryleamides are obtained by heterophase copolymerisation of vinyl monomers. First, n-dodecyclacrylamide is added to water solution of sodium dodecylsulfate, applied as stabiliser, with mixing. Then, water solution of acryleamide and acrylic acid is added to obtained dispersion. Reaction is carried out in alkaline medium at pH 9.5 with general concentration of copolymers from 3.0 to 3.8 mol/l. After that, particles of magnetic filler are added to obtained mixture with mixing in atmosphere of inert gas with gradual increase of reaction mass temperature from 20 to 55°C. Water solution of initiator, such as potassium persulphate or ammonium persulphate is added to obtained water dispersion to concentration 3.5-4.2 mmol/l. After that, obtained product is separated by known methods. As magnetic filler, applied is magnetite with particle size from 50 to 1000 nm or acicular particles of magnemite from 200 to 800 nm long with diameter from 20 to 50 nm. Magnetic liquid includes liquid phase - water or its mixture with organic solvents, such as ethanol methanol, and magnetic solid phase - upper said polyacryleamide.
EFFECT: invention makes it possible to obtain polyacryleamide by more technological economic method in absence of highly-toxic solvents and obtain magnetic liquid, which preserves sedimentation stability in magnetic field.
4 cl, 1 dwg, 1 tbl, 7 ex
SUBSTANCE: method of obtaining ultradisperse powders of alloys with particles sizes of 5-200 nm and specific surface area of 80-170 m2/g includes delivery of powder of initial mixture of primary and secondary metals with particles average size of 100-150 mcm by flow of inert plasma-supporting gas to reactor of gas-discharge plasma, evaporation of initial mixture of primary and secondary metals, cooling of thermal decomposition products by cooling inert gas and condensation of obtained ultradisperse powders of alloys in water-cooling inlet chamber. During cooling of thermal decomposition products they are mixed in flame cooling zone by electromagnetic field generated by electromagnetic mixer, located from outside of reactor cooling zone.
EFFECT: obtaining ultradisperse nanosized powders of alloys with uniform distribution of components.
6 cl, 6 ex
SUBSTANCE: method of obtaining a non-woven material consists in the following: initial components are mixed in an extruder and the catalytic synthesis of a polyamide-6 is carried out in a reaction zone of the extruder. After that fibres are obtained from the polyamide-6 melt by a method of electric formation. An initial mixture contains montmorillonite and ε-caprolactam as an initial monomer.
EFFECT: invention makes it possible to reduce energy consumption for the nanocomposite material obtaining, reduce the quantity of technological stages and makes it possible to regulate the structure of the finished material.
2 cl, 1 dwg, 1 tbl
SUBSTANCE: method for controlled growth of quantum dots from colloidal gold in a composite AFM/STM system comprises growing quantum dots with a negative voltage applied between the cantilever needle of the composite AFM/STM and a conducting substrate, wherein during growth of the quantum dots, the method includes periodically switching polarity of the external voltage from negative to positive and detecting a single peak at the tunnelling current-voltage curve at a certain value of the applied voltage from a range of values of 1 to 5 V. Growth of quantum dots is complete when the single peak is observed at the same value of the applied voltage as for a control quantum dot of a given size.
EFFECT: providing precision control of the size of quantum dots.
SUBSTANCE: invention can be used in inorganic chemistry. In order to obtain maghemite nanoparticles a water iron (III) chloride solution is prepared, an alkali is added to it to pH 6.5-8, heated to 60-70°C, washed until coloration of washing water starts. An agent, regulating the growth of iron oxide nanoparticles is added into the obtained suspension, and the alkali is re-introduced until the solution with pH 8-12 is obtained. After that, the suspension is heated to 130-190°C and exposed at the said temperature for 103 hours. Then, the obtained suspension is centrifuged, washed and dried until it starts crumbling. The iron (III) chloride solution is preliminarily filtered, centrifuged, and 25-38% hydrochloric acid is added to it until the solution pH value is 0.1-1.0. As the agent, regulating the growth of nanoparticles, phosphonic (oxyethylidenediphosphonic, nitrilotrimethylphosphonic, phosphonoacetic), hydroxypolycarboxylic (citric, tartaric), polycaboxylic (glutaric, adipinic, fumaric, maleinic) acids, or their amino acids (aminoacetic, 2-aminipropanic), or their mixtures are taken in an amount of 3·10-3-1.2·10-1 mole per a mole of iron. The supermagnetic powder composition contains maghemite and a protective coating, including the adsorbed agent, regulating the growth of nanoparticles.
EFFECT: invention makes it possible to simplify obtaining the maghemite nanoparticles, increase the chemical stability of the obtained supermagnetic nanoparticles of a spherical shape with the size less than 10 nm.
4 cl, 3 dwg, 10 ex
SUBSTANCE: in a method of forming nanowires from a colloidal natural material, based on a self-organised formation of linearly ordered nanosized current-conducting structures with a strictly specified orientation for the connection of separate micro- and nanoelectronic elements and/or formation of nanocomponents of an electronic element base, formation of structures and/or elements is carried out in one process for not more than 3 minutes under an impact of an electric constant field only with an intensity not higher than 5×103 V/m, configuration of which directly specifies both the dimensions and forms and the orientation of the nanosized current-conducting carbon structures, which are stably preserved without the application of any protective layers on a substrate from any material, including the one, containing separate micro- and nanoelectronic elements for their connection and/or for the formation of nanocomponents of the electronic element base.
EFFECT: invention makes it possible to simplify the process of control of the form and location of the synthesised particles.
FIELD: carbon materials.
SUBSTANCE: weighed quantity of diamonds with average particle size 4 nm are placed into press mold and compacted into tablet. Tablet is then placed into vacuum chamber as target. The latter is evacuated and after introduction of cushion gas, target is cooled to -100оС and kept until its mass increases by a factor of 2-4. Direct voltage is then applied to electrodes of vacuum chamber and target is exposed to pulse laser emission with power providing heating of particles not higher than 900оС. Atomized target material form microfibers between electrodes. In order to reduce fragility of microfibers, vapors of nonionic-type polymer, e.g. polyvinyl alcohol, polyvinylbutyral or polyacrylamide, are added into chamber to pressure 10-2 to 10-4 gauge atm immediately after laser irradiation. Resulting microfibers have diamond structure and content of non-diamond phase therein does not exceed 6.22%.
EFFECT: increased proportion of diamond structure in product and increased its storage stability.