Ukrainian Journal of Physical Optics


2022, Volume 23, Issue 2


ISSN 1816-2002 (Online), ISSN 1609-1833 (Print)

Optical pseudogap of Ag7(Si1–xGex)S5I solid solutions

Pogodin A. I., Malakhovska T. O., Filep M. J., Kokhan O. P., Shender I. O., Studenyak Y. I., Zhukova Y. P.

Uzhhorod National University, 46 Pidhirna Street, 88000 Uzhhorod, Ukraine

ABSTRACT

Ag7(Si1–xGex)S5 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) solid solutions are obtained in the form of micro-crystalline powders by grinding the substance in agate mortar. Diffuse optical reflectance spectra of Ag7(Si1–xGex)S5 are studied at 293 K in the spectral range 220–1350 nm. They are analyzed using a Kubelka–Munk function. It is shown that increasing Si content in the solid solutions shifts the absorption edge towards higher photon energies. The optical pseudogap is estimated by a known Tauc method. It is demonstrated that the cationic substitution Si+4 → Ge+4 inside anionic sublattice decreases monotonically the optical pseudogap such that the corresponding compositional dependence is close to linear one.


Keywords: argyrodites, optical properties, diffuse reflection, solid solutions

UDC: 535.3

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    Одержано тверді розчини Ag7(Si1–xGex)S5 (x = 0, 0,2, 0,4, 0,6, 0,8 і 1,0) у вигляді мікрокристалічних порошків шляхом розтирання речовини в агатовій ступці. Досліджено спектри дифузного оптичного відбивання Ag7(Si1–xGex)S5 у діапазоні 220–1350 нм при 293 К. Аналіз цих спектрів виконано за допомогою функції Кубелки–Мунка. Показано, що збільшення вмісту Si у твердих розчинах зміщує край поглинання в бік вищих енергій фотонів. Оцінено оптичну псевдощілину за відомим методом Таука. Показано, що катіонне заміщення Si+4 → Ge+4 всередині аніонної підґратки монотонно зменшує оптичну псевдощілину так, що відповідна композиційна залежність близька до лінійної.

    Ключові слова: аргіродити, оптичні властивості, дифузне відбиття, тверді розчини.
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