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New, remarkably dry parts of the Gamslöcher-Kolowrat Cave at 728 to 853 m depth have been explored in the Untersberg nearSalzburg in Austria. This region is called the Desert, its greatest cavity is called the White Hall. The new cave part is characterizedby various white speleothems. The predominant ones are snow-like calcite powder with an extremely low density, and finegypsum needles. Gypsum also occurs in the form of balls stuck to vertical walls. In addition, fluorescent hydromagnesite crusts,Mg5(CO3)4(OH)2·4H2O, as well as the sodium sulfate mineral mirabilite were identified in this part of the cave. Mirabilite and gypsumneedles differ from the gypsum balls in their isotopic sulfur signature (δ34S of -16.9‰ and -18.4‰ vs. +2.9‰). The unusually lowsulfur isotopic compositional values are tentatively explained by a source of bacteriogenetic sulfur from sulfides.

Oxidation is the main cause of degradation of many 2D materials, including transition metal dichalcogenides (TMDs), under ambient conditions. Some of the materials are more affected by oxidation than others. To elucidate the oxidation‐induced degradation mechanisms in TMDs, the chemical effects in single layer MoS2 and MoTe2 are studied in situ in an electron microscope under controlled low‐pressure oxygen environments at room temperature. MoTe2 is found to be reactive to oxygen, leading to significant degradation above a pressure of 1 × 10−7 torr. Curiously, the common hydrocarbon contamination found on practically all surfaces accelerates the damage rate significantly, by up to a factor of forty. In contrast to MoTe2, MoS2 is found to be inert under oxygen environment, with all observed structural changes being caused by electron irradiation only, leading to well‐defined pores with high proportion of molybdenum nanowire‐terminated edges. Using density functional theory calculations, a further atomic‐scale mechanism leading to the observed oxygen‐related degradation in MoTe2 is proposed, and the role of the carbon in the etching is explored. Together, the results provide an important insight into the oxygen‐related deterioration of 2D materials under ambient conditions relevant in many fields. [ABSTRACT FROM AUTHOR]

Many applications of 2D materials require deposition of non‐2D metals and metal‐oxides onto the 2D materials. Little is however known about the mechanisms of such non‐2D/2D interfacing, particularly at the atomic scale. Here, atomically resolved scanning transmission electron microscopy (STEM) is used to follow the entire physical vapor deposition (PVD) cycle of application‐relevant non‐2D In/In2O3 nanostructures on graphene. First, a "quasi‐in‐situ" approach with indium being in situ evaporated onto graphene in oxygen‐/water‐free ultra‐high‐vacuum (UHV) is employed, followed by STEM imaging without vacuum break and then repeated controlled ambient air exposures and reloading into STEM. This allows stepwise monitoring of the oxidation of specific In particles toward In2O3 on graphene. This is then compared with conventional, scalable ex situ In PVD onto graphene in high vacuum (HV) with significant residual oxygen/water traces. The data shows that the process pathway difference of oxygen/water feeding between UHV/ambient and HV fabrication drastically impacts not only non‐2D In/In2O3 phase evolution but also In2O3/graphene out‐of‐plane texture and in‐plane rotational van‐der‐Waals epitaxy. Since non‐2D/2D heterostructures' properties are intimately linked to their structure and since influences like oxygen/water traces are often hard to control in scalable fabrication, this is a key finding for non‐2D/2D integration process design. [ABSTRACT FROM AUTHOR]