EFFECTS OF THERMAL ANNEALING AND PLASMA TREATMENT ON THE PROPERTIES OF ZNO

Аннотация

This work presents a comparative study of the influence of thermal annealing and plasma treatment in hydrogen plasma on the properties of polycrystalline thin films of ZnO obtained by metalorganic chemical vapor deposition and obtained by the hydrothermal method Key words: Sol-gel method, hydrodynamic conditions, surfactant, homogeneous, thermal annealing, plasma treatment. ВЛИЯНИЕ ТЕРМИЧЕСКОГО ОТЖИГА И ПЛАЗМЕННОЙ ОБРАБОТКИ НА СВОЙСТВА ZNO Аннотация. В работе представлено сравнительное исследование влияния термического отжига и плазменной обработки в водородной плазме на свойства тонких поликристаллических пленок ZnO, полученных методом металлоорганического химического осаждения из газовой фазы и полученных гидротермальным методом. Ключевые слова: золь-гель метод, гидродинамические условия, ПАВ, гомогенный, термический отжиг, плазменная обработка. Sol-gel technology is one of the common methods for producing ultrafine particles. Using this method, it is possible to obtain nanoparticles, porous structures with ordered and disordered pores, nanocoatings, fiber and monolithic structures, etc. The sol-gel method consists of two stages. At the first stage, a sol is synthesized, and then the resulting sol is converted into a gel [1]. Changing the pH of the reaction medium, varying the hydrodynamic conditions in which the sol is formed, controlling the viscosity of the reaction medium by selecting a solvent, choosing a surfactant, the composition of the reaction medium are the parameters on which the morphology of the resulting ultrafine zinc oxide particles depends. Works [2-3] show the influence of the pH of the reaction medium on the morphology of ultrafine zinc oxide particles. It was found that at a pH of 9, particles with sizes of 14 and 25 nm were obtained, and a further increase in pH leads to a decrease in the size of crystallites. In order to control the process of sol formation during synthesis, various structure-forming agents are used in addition to the sol former. In work [4], citric acid is used as a sol former, and ethylene glycol, polyethylene glycol and polyvinyl alcohol are used as structure-forming agents. It has been shown [5] that the morphology of zinc oxide nanoparticles is influenced not only by the nature of the structure-forming agent used, but also by its molar ratio with the sol former [5]. The advantages of the sol-gel method are: control of the structure of the final product at the stage of gel formation; elimination of numerous stages of washing sediments from interfering ions; obtaining a homogeneous product at the molecular level; high purity of the finished product. The disadvantages of the method are the production of agglomerated particles of zinc oxides and the need to use reagents based on salts of organic acids, 9 96 International scientific journal ISSN: 2181-3906 «MODERN SCIENCE АND RESEARCH» 2024 VOLUME 3 / ISSUE 6 / UIF:8.2 / MODERNSCIENCE.UZ which are produced in limited quantities on the world market, which is unprofitable from an economic point of view. Recently, new promising directions for the synthesis of zinc oxide have been developed, based on the thermal decomposition of organic and inorganic salts. The main advantage of this production method is the possibility of synthesizing predominantly pure zinc oxide, and adjusting the parameters of the thermolysis process allows the formation of powders with a given dispersion and morphology. Salts are used as starting reagents in thermal decomposition processes, the anions of which can be easily removed during heat treatment: sulfates, carbonates, acetates, oxalates, nitrates, etc. However, the method of producing zinc oxide by thermolysis of inorganic compounds also has significant disadvantages, the main of which is the need recycling of gaseous products and the use of technological equipment made of corrosion- resistant materials. Therefore, it is advisable to use zinc carbonates, hydroxides or basic carbonates as starting compounds, which can be synthesized by the hydrothermal method. Next, we will conduct comparative studies of the influence of thermal annealing and plasma treatment in hydrogen plasma on the properties of polycrystalline thin films of ZnO obtained by metal-organic chemical vapor deposition (MOCVD - ZnO) and obtained by the hydrothermal method (HT - ZnO). Two series of boron-doped ZnO films, n-type, were studied: I) films on glass substrates, synthesized by the MOCVD method at a temperature of ~ 200oC, II) films on glass and crystalline silicon substrates, which were synthesized by the hydrothermal method (HT - ZnO) in real work. To obtain NT–ZnO samples, a thin ZnO seed layer was initially grown on a substrate by the sol–gel method. To prepare the seed layer, 0.4 g of zinc acetate Zn(CH COO) ·2H O was dissolved in 10 ml of ethanol for 30 min at room temperature using a 3 2 2 magnetic stirrer to obtain a homogeneous and transparent sol. Uniform distribution of the sol on the surface of the substrate