Hydrogen plasma treatment of silicon thin-film structures and nanostructured layers

The review concentrates on the analysis of the RF hydrogen plasma effect on thin-film metal-dioxide-silicon and silicon-dioxide silicon structures which are a modern basis of micro- and nanoelectronics. The especial attention is paid to athermic mechanisms of transformation of defects in dioxide, SiO₂-Si interface and SiO₂-Si nanocrystal ones and thin layers of silicon; atomic hydrogen influence on the annealing of vacancy defects and the implanted impurity activation in a subsurface implanted silicon layer; and the hydrogen plasma effect on luminescent properties of nanostructured light emitting materials

Influence of traps in gate oxide-Si film transition layers on FD MOSFET's characteristics at cryogenic emperatures

The results of experiments on the influence of recharging the electron traps in a Si-SiO₂ transition layer on the low-temperature characteristics of fully depleted silicon in insulator MOSFET devices are presented. It is shown that the low-dose gammaradiation improves electrophysical parameters of the transition layer

Scythian graves of barrow 14 of the “Sluiceway” group in the Lower Dniester region

The paper publishes for the first time the Scythian graves from barrow 14 of the “Sluiceway” (“Vodovod”) group, which was studied near the Glinoe village, Slobodzeya district, on the left bank of the Lower Dniester in 2018. The scientific data obtained during the study of this mound allow us to pay special attention to some elements of the funerary rite such as placing objects on the grave covering and under the body of the buried. The graves contained tools (a knife, an awl, needles, a whorl, a whetstone), a mirror and two toilet vessels (blackglazed and handmade), vessels (blackglazed kantharos and a saltcellar, a handmade pot), numerous adornments (necklace of beads, bracelets of beads, a bronze bracelet, mollusk shells, bronze finger rings, three chains of bronze rings), as well as cult objects (pieces of ocher, a dog's tooth, two pebbles, a stone slab with traces of soot and a large set of astragali). Barrow 14 of the "Sluiceway" group dates to the second quarter of the 4th c. BCE on the basis of blackglazed vessels

Photoconductivity mechanism in structures with Ge-nanoclusters grown on Si(100) surface

Interband optical transitions in the epitaxial Si/Ge heterostructures with Ge nanoislands grown on Si(100) surface were investigated using photocurrent spectroscopy. The mechanism of photoconductivity was discussed. It was shown that electron transitions from the ground state of the valence band in a quantum dot to the conduction band of Si surrounding make the main contribution into monopolar photoconductivity below the fundamental absorption edge of crystalline Si. Photoexcited holes were found to be localized in Ge nanoislands inducing the lateral conductivity changes in the near-surface depletion layer of p-Si substrate due to the field-effect

Characterization of charge trapping processes in fully-depleted UNIBOND SOI MOSFET subjected to γ-irradiation

An investigation of radiation effect on edgeless accumulation mode (AM) p-channel and fully-depleted enhancement mode (EM) n-channel MOSFETs, fabricated on UNIBOND silicon on insulatior wafers (SOI), is presented in the paper. Characterization of trapped charge in the gate and buried oxides of the devices was performed by measuring only the front-gate transistors. It was revealed that the irradiation effect on EM n-MOSFET is stronger than that on AM p-MOSFET. Radiation-induced positive charge in the buried oxide proved to invert back interface what causes back channel creation in EM n-MOSFET but no such effect in AM p-MOSFET has been not observed. The effect of improving the quality of both interfaces for small irradiation doses is demonstrated

Photoluminescent properties of oxidized stochiometric and carbon-rich amorphous Si₁₋xCx:H films

Near-stochiometric and carbon-rich a-Si₁₋xCx:H thin films were deposited using the magnetron sputtering of Si target in Ar/CH₄ gas mixture. As-deposited nearstochimetric (x = 0.5) sample showed weak blue photoluminescence (PL), while PL of as-deposited carbon-rich (x = 0.7) sample was 20 times stronger and white in color. The films were annealed in pure argon, wet argon, and dry oxygen at 450 °C for 30 min. The intensity of PL in a-Si₁₋xCx:H layers were enhanced by the factor from 2 to 12 after annealing in dependence on the annealing atmosphere. The strongest oxidation and strongest light emission were observed in carbon-rich series (x = 0.7) after annealing in oxidizing atmosphere. Structural properties of the films were characterized by infra-red absorption spectroscopy, ellipsometry and electron paramagnetic resonance. The effect of carbon enrichment of a-Si₁₋xCx:H films and annealing atmosphere on the evolution of photoluminescence and local interatomic bonding structure in annealed material were studied and analyzed. It has been found that main effects of thermal treatments is strong enhancement of photoluminescence accompanied by formation of Si:C–Hn and Si–OxCy bonding. The strongest oxidation effect as well as strongest hotoluminescence were observed in carbon-rich a-SiC:H films

Nano- and micro-scale morghological defects in oxidized a-SiC: H thin films

Amorphous carbon rich a-SiC:H films were deposited on silicon substrates by RF-magnetron sputtering of SiC target in argon/methane gas mixture. The principal focus of this study was investigation of the effect of thermal oxidation on structure and morphology reconstruction in a-SiC:H amorphous network. The density of the films was varied over the range 1.6-2.2 g/cm2 by varying the magnetron discharge power. The local nano- and micro-scale surface morphology and chemical composition distribution were examined by atomic force microscopy, scanning electron microscopy equipped with Auger electron scanning system and optical profilometry. It was found that partial oxidation leads to local structure reconstruction accompanied by transformation of mechanical stresses from compressive to tensile. Formation of carbon-enriched nano- and micro-scale regions was observed after oxidation in low density samples. We attrribute these morphological defects to migration and precipitation of carbon species released in the process of oxidation of the SiC amorphous network. The mechanism of tensile stresses generation is also discussed.Science and Technology Center of Ukraine, project No. 5513, National Academy of Science project No. 2-2-15-28 and Arts et Métiers ParisTech (invited professor

Multiband light emission and nanoscale chemical analyses of carbonized fumed silica

Fumed silica with a specific area of 295 m(2)/g was carbonized by successive phenyltrimethoxysilane treatments followed by annealing in inert atmosphere up to 650 degrees C. Emission, excitation, kinetics, and photo-induced bleaching effects were investigated by steady state and time-resolved photoluminescence spectroscopies. The local chemistry was also studied by infrared transmission spectroscopy. Strong ultraviolet and visible photoluminescence was observed in the samples after the chemical treatments/modifications and thermal annealing. It has been shown that ultraviolet photoluminescence in chemically modified fumed silica is associated with phenyl groups, while near ultraviolet and visible emission in annealed samples originated from inorganic pyrolytic carbon precipitates dispersed in the silica host matrix. Two types of emission bands were identified as a function of the annealing temperature: one is in the near UV and the other is in the visible range. Based on the emission/excitation analysis of these two bands, as well as on correlations with the synthesis conditions, a structural-energy concept of light-emitting centers has been proposed. According to this model, the light-emitting centers are associated with carbon clusters that can be bonded or adsorbed on the silica surface. This has been validated by a detailed (S)TEM-electron energy-loss spectroscopy study, confirming the inhomogeneous distribution of nanoscale carbon precipitates at the surface of the silica nanoparticles. These carbon precipitates are mostly amorphous although they possess some degree of graphitization and local order. Finally, the fraction of sp(2) carbon in these nanoclusters has been estimated to be close to 80%. Published by AIP Publishing

The spatial separation of electron-hole pairs in Si/Ge heterostructures

Photogeneration and transport of nonequilibrium charge carriers, and the determination of photoresponce mechanisms in semiconductor SiGe/Si and SiGe/SiO₂/p-Si heterostructures with nanoisland were investigated. The structures were grown by molecular beam epitaxy technique. The work generalizes the results of studies of morphological, structural, optical and electrical properties of heterostructures with nanoscale objects – quantum dots and quantum wells. It is shown that the photoconductivity of nanoheterostructures SiGe/Si in the infrared range depending on the component composition, size and magnitude of the mechanical stresses in nanoislands Si1-xGex is determined by interband and intraband transitions involving localized states of the valence band of the Ge nanoscale objects. The effects of long-decay photoconductivity and optical quenching of conductivity in SiGe/SiO₂/p-Si heterostructures with SiGe nanoclusters was found to be caused by variations of the electrostatic potential in the near-suraface region of p-Si substrate and optically-induced spatial redistribution of trapped positive charges between SiO₂/Si interface levels and localized states of Ge nanoislads. Adsorption complexes of germanium on the reconstructed Si(001)(4×2) surface have been simulated by the Si₉₆Ge₂Н₈₄ cluster. For Ge atoms located on the surface layer of the latter, DFT calculations (B3LYP, 6-31G**) of their 3d semicore-level energies have shown a clear-cut correlation between the chemical shifts and mutual arrangement of Ge atoms.Були досліджені фотогенерація і транспорт нерівноважних носіїв заряду і визначений механізмфотовідповіді в напівпровідникових SiGe/Si і SiGe/SiO2/Siр-гетероструктурах з наноострівцями. Зразки були вирощені методом молекулярно-променевої епітаксії. У роботі узагальнені результати досліджень морфологічних, структурних, оптичних та електричних властивостей гетероструктур з нанорозмірними об'єктами – квантовими точками і квантовими ямами. Показано, що фотопровідність наногетероструктури SiGe/Si в інфрачервоному діапазоні в залежності від компонентного складу, розмірів і величини механічних напружень в наноострівців Si1-xGex визначається міжзонними і внутрізонними переходами за участю локалізованих станів валентної зони Ge нанорозмірних об'єктів. Були встановлені ефекти фото- довгострокового розпаду і оптичного затухання провідності в SiGe/SiO₂/п-Si гетероструктур з SiGe нанокластерами, які викликані змінами електростатичного потенціалу в приповерхневій зоні р-Si підкладки і оптично-індукованого просторового перерозподілу захоплених позитивних зарядів між рівнями межі розділу SiO₂/Si і локалізованих станів Ge наноострівців. Були вивчені адсорбційні комплекси германію на реконструйованій грані Si (001) (4×2) на прикладі кластера Si₉₆Ge₂Н₈₄. Для атомів Ge, локалізованих в приповерхневому шарі кластера, результати розрахунків методом ТФГ (B3LYP, 6-31G**) положення їх 3d-остовних рівнів свідчить про кореляцію між хімічним зсувом Ge (3d) і хімічним оточенням атомів германію.Были исследованы фотогенерация и транспорт неравновесных носителей заряда и определен механизм фотопроводимости в полупроводниковых SiGe/Si и SiGe/SiO₂/Siр-гетероструктурах с наноостровками. Структуры были выращены методом молекулярно-лучевой эпитаксии. В работе обобщены результаты исследований морфологических, структурных, оптических и электрических свойств гетероструктур с наноразмерными объектами – квантовыми точками и квантовыми ямами. Показано, что фотопроводимость наногетероструктуры SiGe/Si в инфракрасном диапазоне в зависимости от компонентного состава, размеров и величины механических напряжений в наноостровках Si1-xGex определяется межзонными и внутризонными переходами с участием локализованных состояний валентной зоны Ge наноразмерных объектов. Были установлены эффекты фото долгосрочного распада и оптического затухания проводимости в SiGe/SiO₂/п-Si гетероструктур с SiGe нанокластерами, которые вызваны изменениями электростатического потенциала в приповерхностной зоне р-Si подложки и оптически индуцированного пространственного перераспределения захваченных положительных зарядов между уровнями границы раздела SiO₂/Si и локализованных состояний Ge наноостровков. Были изучены адсорбционные комплексы германия на реконструированной грани Si(001)(4×2) на примере кластера Si₉₆Ge₂Н₈₄. Для атомов Ge, локализованных в приповерхностном слое кластера, результаты расчетов методом ТФП (B3LYP, 6‑31G**) положения их 3d-остовных уровней свидетельствует о корреляции между химическим сдвигом Ge(3d) и химическим окружением атомов германия

High-temperature characteristics of zone-melting recrystallized silicon-on-insulator MOSFETs

The characteristics of enhancement-mode MOS transistors fabricated on zone-melting recrystallized (ZMR) silicon-on-insulator (SOI) films were systematically experimentally investigated in the temperature range 25–300°C. The main temperature-dependent parameters (the threshold voltage, the channel mobility, subthreshold slope, off-state leakage currents) of ZMR SOI MOSFETs are described and compared with both theory and SIMOX devices. It is shown that high carrier mobilities and low off-state leakage currents can be obtained in thin-film ZMR SOI MOSFETs at elevated temperatures. At T = 300°C, far beyond the operating range of bulk silicon devices, the off-state leakage current in ZMR SOI MOSFETs with a 0.15 mm-thick silicon film was only 0.5 nA/mm (for VD = 3 V), that is 3–4 orders of magnitude lower than typical values in bulk Si devices. The presented results demonstrate that CMOS devices fabricated on sufficiently thin ZMR SOI films are well suited for high-temperature applications.Проведені кропіткі експериментальні дослідження високотемпературних (25-300°С) характеристик МОН транзисторів на базі КНІ-структур, виготовлених методом зонної лазерної перекристалізації. Розглянута поведінка основних температрно-залежних параметрів КНІ МОН транзисторів (порогової напруги, рухливості носіїв, підпорогового нахилу та струму витоку). Проведено порівняння отриманих результатів з теорією та аналогічними параметрами приладів, створених за допомогою ЗІМОХ технології. Показано, що при підвищених температурах тонкоплівкові транзистори, отримані лазерною зонною перекристалізацією, виявляють високу рухливість носіїв і низькі струми витоку закритого транзистора. При Т = 300°С, що значно перевищує робочий діапазон приладів на об.ємному кремнії, струм витоку в КНІ транзисторах з плівкою Si товщиною 0,15 мкм ст всього лишу 0,5 nA/mm (при VD = ЗВ), що на 3-4 порядка нижче типових величин для приладів на об.ємному кремнії. Наведені результати свідчать, що тонкі плівки КНІ, створені методом лазерної зонної перекристалізації, можуть успішно використовуватись для створення КМОН ІС для високотемпературних застосувань.Проведено детальное экспериментальное исследование высокотемпературных (25-300°С) характеристик МОП транзисторов на основе КНИ-структур, изготовленных методом лазерной зонной перекристаллизации. Рассмотрено поведение основных температурно-зависимых параметров КНИ МОП транзисторов (порогового напряжения, подвижности носителей, подпорогового наклона и тока утечки). Проведено сравнение полученных результатов с теорией и аналогичными параметрами приборов, созданных SIМОХ технологией. Показано, что при повышенных температурах тонкопленочные транзисторы, полученные лазерной зонной перекристаллизацией, проявляют высокую подвижность носителей и низкие токи утечки закрытого транзистора. При Т = 300°С, значительно превышающей рабочий диапазон приборов на объемном кремнии, ток утечки в КНИ транзисторах с пленкой Si толщиной 0,15 мкм составляет всего лишь 0,5 nA/mm (при VD = ЗВ), что на 3-4 порядка ниже типичных величин для приборов на объемном кремнии. Приведенные результаты свидетельствуют, что тонкие пленки КНИ, полученные методом лазерной зонной перекристаллизации, могут успешно использоваться для создания КМОП ИС для высокотемпературных применений