A LEED analysis of the ()HNi(110) structure

Magnetic quantization in superlattices

“…The H atoms tend to form 'zig-zag' rows along the [ll-0]-direction (due to attractive interactions), while repulsive interactions act in [001]-direction and keep parallel rows apart from each other until at 0 = 1 all rows are equally occupied. In this 2 × l-structure the H-atoms occupy again three-fold coordinated sites (formed by two Ni atoms from the topmost and one atom from the second layer) with three equal Ni-H distances of 1.7 A [2]. Interestingly, the expansion of the spacing between the first and second Ni layer is reduced from 8.5 to 3.5 % in the presence of the chemisorbed overlayer.…”

“…For simple parabolic bands, like the conduction band, these levels are given by Eq. (2) and are therefore equidistant and linearly field dependent. In the perpendicular configuration for both the superlattice and the quantum well electrons orbit in the plane of the layers, and the bands are split by the field like in a bulk material as indeed is observed.…”

“…4a show the best fit of Eq. (2) to the data with a reduced mass of 0.069 mo. It can be seen that this fit is not bad except for the lowest energy transition which is shifted to lower energies due to excitonic effects, neglected in this scheme.…”

“…Together with the orbital quantization, the energy is also quantized by a field, in this case in Landau levels which for simple bands are given by: EN = (N + 1)hoot (2) with coc the cyclotron frequency, eB/m*. In a field of 20 T in GaAs hc~c~30 ineV which is of the order of the width of the minibands in a GaAs]GaAIAs superlattice.…”

“…Despite the fact that in 1970 the creation of such structures would "require considerable effort with the use of the most advanced technologies" [1] the initial progress was impressively rapid. In early 1974 Chang, Esaki, and Tsu [2] However, in some sense the experimental results by Esaki and Chang [3] on vertical transport in superlattices were somewhat disappointing, because their results showed a reproducible but very irregular behaviour of the conductance through the layers as a function of the voltage applied over the superlattice. This behaviour was explained by the formation of domains of high electric field where tunnelling between neighbouring layers took place, and the spiky structure they observed, was explained as the successive breakthrough of the individual layers.…”