SYNTHESIS AND RESEARCH OF ALUMINUM-SCANDIUM NITRIDE THIN FILMS AS A PART OF PIEZOELECTRIC LAYERED STRUCTURES BASED ON SYNTHETIC DIAMOND SINGLE CRYSTALLINE SUBSTRATES
Abstract
solution of substitution of aluminum-scandium nitride in a wide range of scandium concentrations are considered. Based on them, piezoelectric layered structures with substrates made of synthetic diamond single crystal are obtained. Such structures are suitable for implementing microwave high overtone bulk resonators operating on bulk acoustic waves up to 20 GHz. Physical and chemical properties of aluminum-scandium nitride were studied, including analysis of a crystalline structure by X-ray diffraction and scanning electron microscopy. The methods of probe force microscopy and optical profilometry were used to study the film’s roughness. The quality of the films obtained was analyzed by the data on the full width of the reflex (002) at half the maximum. It was shown that an increase in Sc concentration leads to an increase in the full width of the reflex (002) at half the maximum, which may be due to an increase in disordering the structure of the transitive phase from wurzite to ScN rock salt. An increase in Sc concentration also leads to a systematic decrease in the average size of crystallites. Starting with scandium concentrations above 25%, there is a noticeable downward trend in the degree of ASN films texturing. Therefore, the actual piezoelectric response will decrease despite an increase in the electromechanical coupling coefficient. Thus, the area of scandium concentration values at which the best combination of crystal structure quality, film texture and piezoelectric properties of aluminum-scandium nitride is achievable is below 25%. The criteria developed for the perfection of axisymmetric texture in the application of aluminum-scandium nitride films were convenient for analyzing changes in the quality of films and further improving the synthesis processes.
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