Seminarium Fizyki Ciała Stałego

Since the discovery of graphene two-dimensional (2D) atomic crystals characterized by strong in-plane covalent bonds and weak interlayer van der Waals forces became one of the leading topics in the condensed matter physics. Indium selenide is a semiconductor which occurs in different crystalline structures, the most of which belong to the family of 2D semiconductors. They attract the interest due to outstanding electronic and optical properties, which are prospective in view of applications in next generation electronic and photonic devices. In the first part of the seminar it will be demonstrated how to fabricate optically active indium selenide thin layers by molecular beam epitaxy and to control its crystalline phase by changing the growth conditions. An attempt to obtain optically active crystal phase heterostructures involving γ-InSe, γ-In2Se3 and β-In2Se3 crystal phases in a well-controlled manner will be described. The second part of the seminar will be devoted to the molecular beam epitaxy of antimony triselenide (Sb2Se3). This semiconductor belongs to the family of one dimensional (1D) van der Waals semiconductors which attract the research interest due to the possibility of downscaling semiconducting channels in transistors even down to the one atomic chain limit. It crystalizes in the stibnite (orthorhombic) crystalline structure consisting of 1D ribbons held together by weak Se-Se van der Waals interactions. It will be demonstrated that self-assembled, highly anisotropic nanostructures spontaneously form in the molecular beam epitaxy process of antimony triselenide on GaAs substrates. With increasing growth time all three dimensions: the length, the width and the height of these nanostructures increase simultaneously, with length being usually one order of magnitude larger than the two other parameters. These 1D nanostripes have all the orientation parallel to the substrate surface and preserve the epitaxial relation with the substrate. The fabrication of well-ordered arrays of horizontal nanostripes aligned in directions defined by the orientation of the substrate is perspective in view of the development of electronic circuits and networks composed of interconnected nanostructures.