Standing waves of Fermi electrons in thin films between their two interfaces lead to a stabilization of films with certain thicknesses. Such Quantum Size Effects (QSE) were first reported for the growth of ultrathin lead layers on Cu(111). Initially, the preferred film thicknesses correspond to odd layers followed by a crossover to even layers around a 10 layers thick film. A beating pattern of the preference for odd and even layers is attributed to a non-perfect match of the Fermi wave length and the interlayer spacing. QSE’s can even be sufficiently strong to impose the crystalline structure of ultrathin films. The crystalline structure of ultrathin Bi-films on Ni(111) was found to be modified in order to establish a QSE-matched ratio of the Fermi wavelength and interlayer spacing leading quantum well driven allotropism of Bi.
Recently we found evidence for the importance of QSE in nanowires too. Ultra thin Ir-nanowires on Ge(001) show distinct length preferences imposed by QSE.
Bene Poelsema, "Consequences of quantum size effects in 2D and 1D nano-epitaxy (Presentation Recording)," Proc. SPIE 9553, Low-Dimensional Materials and Devices, 95530A (Presented at SPIE Nanoscience + Engineering: August 12, 2015; Published: 5 October 2015); https://doi.org/10.1117/12.2192837.4519371108001.
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