Browsing by Author "Haapalinna, Aino"

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Growth and characterization of lead selenide
(2024-01-12) Haapalinna, Aino
Perustieteiden korkeakoulu | Bachelor's thesis
Lead selenide is a IV-VI semiconductor, which principal property is its narrow band gap. The direct band gap of only 0.26 eV makes lead selenide sensitive to low-energy radiation, and thus it has been used widely, e.g., in infrared detectors. The use of lead selenide in the above-mentioned purpose, as well as in the study of its properties, require clean uniform samples, and thus manufacturing it in pure two-dimensional films is desirable. Molecular beam epitaxy offers a way of growing materials in a highly controlled manner in an ultra-high vacuum, and thus satisfies the demand. In this bachelor’s thesis, we optimized the growth of lead selenide on molecular beam epitaxy, in the pursuit of uniform monolayer islands that would exhibit the characteristic rectangular lattice structure of lead selenide. Samples grown with molecular beam epitaxy were characterized through scanning electron microscopy, which allowed examining the surface morphology of the sample on a nanoscale. Major challenges regarding the sample coverage complicated finding optimal growth parameters, and the acquired results show some unexpected growth formations, which contradict the known structure of lead selenide. This naturally prompts new questions about the growth of lead selenide concerning especially its structure and composition, which calls for further study on the topic.