Low-dimensional Main Group Element Semiconductors of the SnIP-type

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The proposed project will deal with the synthesis, characterization and usage of low-dimensional, inorganic double helix compounds of the SnIP type. SnIP consists of a hexagonal rod-packed arrangement of double helices, composed by an outer [SnI] and an inner [P] helix.Starting with microcrystalline SnIP we intend to fabricate double helical, single-chain nano fibers down to 1 nm in diameter (an large aspect ratios) by chemical and mechanical exfoliation. In the case of a successful preparation of such nano fibers, we expect extraordinary mechanical, optical and electronic properties. After suspending SnIP in suitable solvents we intend to fabricate and characterize thin-layer devices on various substrates. Possible applications for such devices are solar cells, sensors and field effect transistors.To evaluate the phase formation and growth of SnIP, an in situ neutron diffraction experiment is planned. We expect to derive the growth speed and mechanism from a set of D20 measurements at the ILL, Grenoble. The gained knowledge can be transferred to optimize the synthesis conditions to prepare thin-films of SnIP directly on substrates.In Analogy to SnIP we intend to prepare more double helical compounds with the general formula MXPn (with M = Ge, Sn, Pb; X = Cl, Br, I und Pn = P, As, Sb). Selected representatives will be used to fabricate devices like in the case of SnIP.For all MXPn phases, starting with SnIP, we will try to dope them with suitable elements to induce or increase n- and p-type conductivity. To improve the exfoliation tendency and to examine the chemistry of inorganic double helix compounds we will react MXPn with Lewis bases, in order to get acid-base adducts. First experiments show that functionalized borates can improve the suspension tendency drastically. Based on this aspect we intend to evaluate the reactivity of MXPn compounds with Lewis bases.In the case of a successful realization of this project MXPn compounds will define a new class of flexible, mechanically robust, low-dimensional semiconductors with a perspective in semiconductor applications.