A comparative study of the growth processes, microstructures, and electrical characteristics of oxide/metal/oxide trilayer structures of different compositions synthesized at 50°C by rf magnetron sputtering in argon has been performed. The effect of subsequent annealing in an open atmosphere on the conductivity of the structures has been investigated. Transmission electron microscopy and energy-dispersive X-ray spectroscopy have been used to examine changes in the microstructure and profiles of distribution of chemical elements included in the structures under annealing. Based on the results obtained, mechanisms have been proposed for the transformation of interlayer interfaces and conditions of carrier transport in the structures, depending on the composition of the oxide and metallic layers comprising them.

The features of aluminum localization and the mechanism of donor center formation in ZnO:Al layers synthesized by high-frequency magnetron sputtering are studied. It is shown that aluminum predominantly localizes at grain boundaries of zinc oxide in its own oxide phase. The mechanism of aluminum oxidation at grain boundaries significantly depends on the oxygen content in the working chamber: during sputtering in an atmosphere of pure argon under conditions of oxygen deficiency, aluminum oxidation occurs as a result of interaction with oxygen from the surface layer of zinc oxide crystallites, forming surface donor centers at grain boundaries. With an increase in the partial pressure of oxygen, aluminum is predominantly oxidized by oxygen from the gas atmosphere, forming its own barrier phase at grain boundaries.

Исследована стабильность поверхностного сопротивления и оптического пропускания трехслойных структур ITO/Ag/ITO, GZO/Al/GZO, а также тонкопленочной периодической структуры IZO с модулированным по толщине содержанием кислорода при 1000-часовых испытаниях в условиях влажности 85% и температуры 85 °С. Проведен анализ механизмов деградации структур в зависимости от состава и свойств единичных слоев.

The specific features of aluminum localization and the mechanism of formation of donor centers in ZnO:Al layers synthesized by rf magnetron sputtering have been investigated. It is shown that aluminum is mainly localized on intergranular boundaries of zinc oxide in the intrinsic oxide phase. The mechanism of Al oxidation on grain boundaries depends strongly on the oxygen content in the working chamber: during sputtering in a pure argon atmosphere with oxygen deficit, aluminum oxidation occurs as a result of the interaction of the surface layer of zinc oxide crystallites with oxygen, which leads to the formation of surface donor centers on grain boundaries. With an increase in partial oxygen pressure aluminum is mainly oxidized by the oxygen from the gas atmosphere, forming an intrinsic barrier phase on grain boundaries.

It is common knowledge that using different oxygen contents in the working gas during sputtering deposition results in fabrication of indium zinc oxide (IZO) films with a wide range of optoelectronic properties. It is also important that high deposition temperature is not required to achieve excellent transparent electrode quality in the IZO films. Modulation of the oxygen content in the working gas during RF sputtering of IZO ceramic targets was used to deposit IZO-based multilayers in which the ultrathin IZO unit layers with high electron mobility (μ-IZO) alternate with ones characterized by high concentration of free electrons (n-IZO). As a result of optimizing the thicknesses of each type of unit layer, low-temperature 400 nm thick IZO multilayers with excellent transparent electrode quality, indicated by the low sheet resistance (R ≤ 8 Ω/sq.) with high transmittance in the visible range (T¯ > 83%) and a very flat multilayer surface, were obtained.

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Проанализированы процессы магнетронного синтеза нанокристаллических и аморфных слоев на основе оксида цинка. Изучено влияние легирующих компонентов и уровня легирования на степень аморфизации слоев. Рассмотрено влияние водорода в составе атмосферы на структурное совершенство синтезируемых слоев. Показана зависимость структуры слоев ZnO–SnO2 от соотношения компонентов в распыляемых мишенях. Обсуждены механизмы формирования аморфных слоев на основе ZnO при магнетронных методах синтеза.

АннотацияЦель.Изучение процессов формирования, электрических и оптических свойств многослойных тонкоплёночных периодических структур на основе чередующихся слоёв нелегированного и легированного алюминием оксида цинка в зависимости от толщины единичных слоёв и температуры синтеза

Тонкопленочные конвертеры нейтронов на основе карбида бора B4C, обогащенного изотопом 10В, наносимые на подложки из алюминия, алюминиевой фольги и полимерных пленок большой площади, являются перспективным материалом для создания новых детекторов нейтронов. Нанесение пленок B4C методом магнетронного распыления на такие основания сильно осложняется необходимостью нагрева подложек до температуры 400 °С и более, что может приводить к их деформации. В работе показано, что применение ионного ассистирования в процессе магнетронного осаждения B4C приводит к формированию пленок нанокристаллической структуры, обладающих высокой прочностью и гибкостью, даже при понижении температуры подложки до 50 °С, а использование подслоя алюминия повышает адгезию. Получены тонкие пленки B4C на подложках из алюминия 0,5 × 100 × 100 мм2 и 0,5 × 280 × 400 мм2 в атмосфере аргона при температуре 400, 200 и 50 °С. Исследованы структура, состав и показатель преломления по пленкам на пластинах из кремния. Гибкость получаемых пленок и низкая температура формирования дают возможность нанесения конвертера нейтронов из 10B4C на тонкие полимерные основания.

The synthesis process of aluminum-doped zinc-oxide ceramics (ZnO : Al) from an initial mixture of commercial powders of zinc and aluminum oxides with a low specific surface area (no more than 5 m 2 /g) which consists in the preliminary formation of a slip and subsequent high-temperature sintering in an open atmosphere is studied. It is found that the porosity of the slip blank, density of sintered ceramics, and degree of predominant stacking of grains in it depend on both the duration of grinding of the slip and its pH index. It is demonstrated that, by optimizing the conditions of slip casting, obtaining conducting ZnO : Al ceramics with a density of more than 97% relative to the standard density of ZnO is possible, which is acceptable in the synthesis of ceramic targets intended for the formation of energy-saving thermal control coatings.

На основе данных исследования процесса механоактивации и дериватографического анализа дисперных систем на основе оксида цинка изучены процессы термо- и механодесорбции цинка и кислорода в порошках чистого ZnO и смеси ZnO-Zn в замкнутом объеме при пониженном давлении кислорода.

The microstructure and functional properties of zinc oxide magnetron thin films depend on a number of factors: substrate temperature, mutual arrangement of the target and substrates, composition and pressure of residual and working gases, discharge power characteristics, target depletion rate, layer deposition rate, etc. At present, to study the influence of certain factors on the structure and properties of thin films, the method of successive deposition of a series of films with a stepwise change in one of the controlled parameters is used. At the same time, due to the large number of operating factors, as well as the complex nature of their impact, highlighting the contribution of each individual factor is a difficult and nontrivial task. The effect of the substrate temperature and the “target–substrate” distance on the structure and properties of zinc oxide films has been studied. At the same time, to minimize the influence of other factors with the help of an original system of heating and positioning of substrates, the concept of deposition of layers on substrates of the entire series with a change in only one controlled factor is implemented. This concept of deposition in a single vacuum cycle significantly lowers the requirements for the accuracy of controlling technological parameters of the process, reduces the impact on the final result of random unaccounted for factors, and also accelerates the preparation of the entire series of investigated thin-film samples.

The comparative deposition of ZnO:Ga layers by the magnetron sputtering of a ZnO:Ga (3 mol %) ceramic target and a composite ZnO:Ga(3 mol %)–Zn(20 wt %) cermet target is performed in the direct current mode at substrate temperatures of 50°С and 200°С. Studies of the formation processes, structure, and functional characteristics of the layers obtained by the sputtering of targets of both types in an atmosphere of argon showed that an increase in the zinc content in the reagent flux upon heating of the substrate to 200°С promotes improvement in the structural perfection of the layers and conductivity accompanied with the preservation of a high coefficient of optical transmittance.

The influence of oxygen in the working gas on the deposition process, microstructure, and functional properties of transparent conductive ZnO:Ga layers obtained by the magnetron sputtering of a composite ZnO:Ga–Zn cermet target is investigated. It is shown that a relative excess of the zinc content in the reagent flux decreases with an increase in the oxygen content and the observed changes in the microstructure and the electrical and optical properties of the ZnO:Ga layers are due to a decrease in the oxygen deficit in them. The efficiency of using atomized cermet target material generally increases as the oxygen content in the working chamber increases. However, transparent conductive ZnO:Ga layers with a specific conductivity of σ > 103 Ohm–1 cm–1 acceptable for practical use were obtained at an oxygen content of less than 3%.

The analysis the discharge processes in magnetron plasma, target sputtering processes, as well as nucleation and formation of oxide thin films during dc magnetron sputtering is carried out. Particular attention is paid to the phenomenon of instabilities of the current-voltage characteristics of magnetron plasma during the sputtering of oxide targets, the processes of structural transformations of the surface of metal oxide targets under ion bombardment impact, and the mechanisms of low-temperature magnetron deposition of metal oxide thin films. Based on the results of the analysis performed the optimal routes for improving technologies for the low-temperature formation of transparent conductive oxide thin films have been discussed.