KCl ultra-thin films with polar and non-polar surfaces grown on Si(111)7 × 7

Abstract

The growth of ultra-thin KCl films on the Si(111)7 × 7 reconstructed surface has been investigated as a function of KCl coverage and substrate temperature. The structure and morphology of the films were characterized by means of scanning tunneling microscopy (STM) under ultra-high vacuum (UHV) conditions. Detailed analysis of the atomically resolved STM images of islands grown at room and high temperatures (400 K–430 K) revealed the presence of KCl(001) and KCl(111) islands with the ratio between both structures depending on the growth temperature. At room temperature, the growth of the first layer, which covers the initial Si(111)7 × 7 surface, contains double/triple atomic layers of KCl(001) with a small fraction of KCl(111) islands. The high temperature growth promotes the appearance of large KCl(111) areas, which are built up by three atomic layers. At room and high temperatures, flat and atomically well-defined ultra-thin KCl films can be grown on the Si(111)7 × 7 substrate. The formation of the above mentioned (111) polar films is interpreted as a result of the thermally activated dissociative adsorption of KCl molecules on Si(111)7 × 7, which produces an excess of potassium on the Si surface.

Atomically Thin 1T-FeCl2 Grown by Molecular-Beam Epitaxy

“…Note that the apparent height of the second and third FeCl 2 layers is 3.8 Å, which is slightly larger than the height of the first layer but is still underestimated in comparison to the bulk interlayer spacing. Such a phenomenon is common in transition-metal chalcogenides − and alkali metal compounds − grown on metal substrates, owing to the large difference of DOS between the metal surface and the epitaxial layer. The growth of a few-layer FeCl 2 on Au(111) at elevated temperatures (120 °C) follows the layer-by-layer mode, resulting in similar morphology as that of the sample grown at room temperature followed by annealing at elevated temperatures.…”

Growth of NaCl on thin epitaxial KCl films on Ag(100) studied by SPA-LEED

“…For completeness we note that, up to today, the epitaxial growth of AH on metals has been investigated on a wide range of different fcc metals or semiconductors, e.g., on Cu [11][12][13], Ag [2,4,9,10,14,15], Au [16,17], Ni [12], Pd [18], Pt [18,19], Al [20,21], Si [22] and Ge [23,24]. In addition, heteroepitaxial growth of AH on AH bulk crystals was also studied for several examples [5,[25][26][27][28].…”

Core-Level Binding Energy Shifts in Ultrathin Alkali-Halide Films on Metals: KCl on Ag(100)

“…Alkali halides (AH) are naturally abundant ionic crystals, which are increasingly used as ultrathin insulating layers in nanoscience and nanotechnology. This is because, on the one hand, AH films as thin as two or three atomic layers already exhibit a wide, bulk-like electronic bandgap. , On the other hand, such films can be grown through simple techniques, such as thermal evaporation from a crucible, on a variety of metal − and semiconductor − surfaces. Ultrathin AH films epitaxially grown on metals have been key in recent breakthroughs in scanning probe microscopy experiments in nanophysics and nanooptics to probe and control the states of individual atoms and molecules electronically decoupled from their substrate. − AH thin films are also increasingly used as electronic buffer layers at the electrode/semiconductor interfaces of organic-based optoelectronic devices to engineer the band-bending effects at these interfaces and thus optimize the device performance. − In such applications, understanding the effects of the atomic-scale structure, low dimensionality, and interfacial interactions of the insulating layer on its electronic properties is crucial.…”